Search

Migratory birds excel in phenotypic flexibility, adapting physiologically as their life histories and environments require. Discerning the metabolic processes underlying migrants' physiology, an emergent property of multiple continuous and dynamic organism–environment interactions, is therefore challenging, particularly under natural conditions. Accordingly, analyses of snapshot‐sampled serum‐circulating metabolites, versatile and readily applicable for migrating birds, have increasingly become the method of choice for such physiologic inference. However, the atemporal nature of single sampling might obscure the links between observed metabolite concentrations and the processes producing them, necessitating an analytical decoupling of focal processes from their broader biochemical background.In the present study, we examined how variation in combined fat and muscle fuel stores, traits pivotal in migratory context, relates to the serum‐circulating metabolomes of spring‐migrating Eurasian blackcaps stopping‐over. Our analyses accounted for potential spatiotemporal influences in the form of time past night's fasting and random local conditions across three sites within the Negev Desert. We shifted the focus from compound‐level analysis of preselected metabolites towards the level of inclusive metabolome, quantifying serum‐circulating lipophilic and polar molecules via UHPLC–MS/MS untargeted metabolomic technique.Our results indicated a general relationship between fuel stores and the metabolome, comprising 16 326 lipophilic and 6923 polar compounds, among which 918 and 44 were annotated, respectively. By applying generalized latent‐variable linear modeling (GLLVM) upon concentrations of annotated metabolites, we identified several candidate biomarkers, some novel in migratory context, notably the fuel‐associated increase in serum ceramides likely derived from circulating very low‐density lipoproteins (VLDLs). Relying on estimated metabolite links with fuel and foraging time and on modeled residual covariations among metabolites, we demonstrate fuel–metabolite associations generally consistent with higher fat‐ and lower protein mobilization in birds having greater stores and with decreased fuel utilization as ingested nutrients accumulate over time, thus introducing a novel approach for the physiological study of migrating birds. [ABSTRACT FROM AUTHOR]

We recorded the diet of Amur Falcons (Falco amurensis) during their autumn passage at stopover sites across in Northeast India. We collected and examined 1200 pellets to identify prey remains in the diet of Amur Falcons from three major stopover sites in Nagaland State in the years 2017 and 2018. Additionally, in 2019, we examined 200 pellets each at two other sites in the neighboring states of Assam and Manipur. We only recorded insect prey belonging to five taxonomic orders: Orthoptera, Isoptera, Hemiptera, Coleoptera, and Hymenoptera, with Isoptera being dominant in the diet of Amur Falcons. The frequency of occurrence of Isoptera (termites) was the highest (87%) across years and across all stopover sites in Nagaland; diets were similar at the two other sites in Assam and Manipur. We identified the species of termites in the diet of Amur Falcons as Odontotermes feae and O. horni, the mass emergence of which coincided with the falcons' arrival in the region. We further estimated that 1,000,000 Amur Falcons stopping over for an average of 15 d in the region consumed approximately 67–134 metric tons of alates (approximately 1 to 2 billion individual alates). We concluded that Amur Falcons stop over in Northeast India primarily to refuel. Our study highlights the importance of availability of abundant termite prey for the success of Amur Falcons' onward migration, which includes oceanic crossings en route to Africa. [ABSTRACT FROM AUTHOR]

Every night during spring and autumn, the mass movement of migratory birds redistributes bird abundances found on the ground during the day. However, the connection between the magnitude of nocturnal migration and the resulting change in diurnal abundance remains poorly quantified. If departures and landings at the same location are balanced throughout the night, we expect high bird turnover but little change in diurnal abundance (stream‐like migration). Alternatively, migrants may move simultaneously in spatial pulses, with well‐separated areas of departure and landing that cause significant changes in the abundance of birds on the ground during the day (wave‐like migration). Here, we apply a flow model to data from weather surveillance radars (WSR) to quantify the daily fluxes of nocturnally migrating birds landing and departing from the ground, characterizing the movement and stopover of birds in a comprehensive synoptic scale framework. We corroborate our results with independent observations of the diurnal abundances of birds on the ground from eBird. Furthermore, we estimate the abundance turnover, defined as the proportion of birds replaced overnight. We find that seasonal bird migration chiefly resembles a stream where bird populations on the ground are continuously replaced by new individuals. Large areas show similar magnitudes of take‐off and landing, coupled with relatively small distances flown by birds each night, resulting in little change in bird densities on the ground. We further show that WSR‐inferred landing and take‐off fluxes predict changes in eBird‐derived abundance turnover rate and turnover in species composition. We find that the daily turnover rate of birds is 13% on average but can reach up to 50% on peak migration nights. Our results highlight that WSR networks can provide real‐time information on rapidly changing bird distributions on the ground. The flow model applied to WSR data can be a valuable tool for real‐time conservation and public engagement focused on migratory birds' daytime stopovers. [ABSTRACT FROM AUTHOR]

Optimal migration theory prescribes adaptive strategies of energy, time or mortality minimization. To test alternative hypotheses of energy- and time-minimization migration we used multisensory data loggers that record time-resolved flight activity and light for positioning by geolocation in a long-distance migratory shorebird, the little ringed plover, Charadrius dubius. We could reject the hypothesis of energy minimization based on a relationship between stopover duration and subsequent flight time as predicted for a time minimizer. We found seasonally diverging slopes between stopover and flight durations in relation to the progress (time) of migration, which follows a time-minimizing policy if resource gradients along the migration route increase in autumn and decrease in spring. Total flight duration did not differ significantly between autumn and spring migration, although spring migration was 6% shorter. Overall duration of autumn migration was longer than that in spring, mainly owing to a mid-migration stop in most birds, when they likely initiated moult. Overall migration speed was significantly different between autumn and spring. Migratory flights often occurred as runs of two to seven nocturnal flights on adjacent days, which may be countering a time-minimization strategy. Other factors may influence a preference for nocturnal migration, such as avoiding flight in turbulent conditions, heat stress and diurnal predators. [ABSTRACT FROM AUTHOR]

BackgroundMigrating passerines in North America have shown sharp declines. Understanding habitat selection and threats along migration paths are critical research needs, but details about migrations have been limited due to the difficulty of tracking small birds. Recent technological advances of tiny GPS-tags provide new opportunities to delineate fine-scale movements in small passerines during a life stage that has previously been inherently difficult to study.MethodsWe investigated habitat selection along migration routes for a temperate-zone migratory passerine, the Golden-crowned Sparrow (Zonotrichia atricapilla), given GPS tags on California wintering grounds. We used a resource selection function combined with conditional logistic regression to compare matched sets of known stopover locations and available but unused locations to determine how land cover class, vegetation greenness and climate variables influence habitat selection during migration. We also provide general migration descriptions for this understudied species including migration distance, duration, and elevation, and repeated use of stopover areas.ResultsWe acquired 22 tracks across 19 individuals, with a total of 541 valid spring and fall migration locations. Birds traveled to breeding grounds in Alaska and British Columbia along coastal routes, selecting for shrubland and higher vegetation greenness in both migration seasons as well as grasslands during fall migration. However, model interactions showed they selected sites with lower levels of greenness when in forest (both seasons) and shrubland (fall only), which may reflect their preference for more open habitats or represent a trade-off in selection between habitat type and productivity. Birds also selected for locations with higher daily maximum temperature during spring migration. Routes during spring migration were lower in elevation on average, shorter in duration, and had fewer long stopovers than in fall migration. For two birds, we found repeated use of the same stopover areas in spring and fall migration.ConclusionsUsing miniaturized GPS, this study provides new insight into habitat selection along migration routes for a common temperate-zone migrating songbird, contributing to a better understanding of full annual cycle models, and informing conservation efforts. Golden-crowned Sparrows selected for specific habitats along migration routes, and we found previously unknown behaviors such as repeated use of the same stopover areas by individuals across different migratory seasons.

Background: GPS-transmitters enable detailed study of animal behaviour but may impact the animals. Impacts vary from short-term stress and habituation to longer-term effects on e.g., migration and reproduction. To study impacts, ideally, true controls (i.e., uncaptured or untagged animals) are used, but unbiased assessments of their migration timing and breeding performance are challenging, especially in remote areas. Alternatively, quasi-controls can be used: individuals tagged longer ago, or the same tagged individuals but in later years. Quasi-controls reveal tagging effects that differ between the first and following years. Results: We captured Pink-footed geese (Anser brachyrhynchus) in spring and summer and deployed GPS-transmitter neckbands. In spring, geese were caught with cannon or clap nets on stopovers in Norway and Finland, 2 weeks before departure to breeding areas in Svalbard and Novaya Zemlya. In summer, geese were rounded up during wing moult in Svalbard. First, we compared geese tagged recently in spring with geese tagged in spring or summer 1–4 years prior. Newly tagged geese migrated significantly later, by 2 days, than previously tagged geese, both at departure from the spring stopover and arrival to the breeding grounds, while migration duration did not differ. Breeding propensity and laying date did not differ, but nesting success tended to be lowered, resulting in a significantly lower annual probability to produce hatchlings in recently tagged geese than in previously tagged geese. Second, within individuals tagged in spring, spring migration advanced in their next year, suggesting delay in their first spring. This was likely not an ageing effect, as geese tagged in summer showed no advancing spring migration timing over the years. Third, in Svalbard, observed brood sizes of geese tagged in summer and untagged geese did not differ 1 year after tagging. Conclusions: The capture and GPS-tagging of geese 2 weeks before spring departure delayed their spring migration and lowered their probability to produce hatchlings in that year. These effects lasted longer than previously reported week-long effects of GPS-tagging on time budgets in summer and of neck-banding on spring body condition. Additional study is needed to evaluate longer-term or permanent effects which remain undetected with quasi-controls. [ABSTRACT FROM AUTHOR]

Habitat selection theory suggests that environmental features selected at coarse scales reveal fundamental factors affecting animal fitness. When these factors vary across seasons, they may lead to large-scale movements, including long-distance seasonal migrations. We analyzed the seasonal habitat selection of 25 satellite-tracked Arctic hares from a population on Ellesmere Island (Nunavut, Canada) that relocated over 100 km in the fall. Since no other lagomorph is known to perform such extensive movements, this population offered an ideal setting to test animal movement and habitat selection theory. On summer grounds hares selected low elevation areas, while on winter grounds they selected high vegetation biomass, high elevation, and steep slopes. During fall relocation, they alternated between stopover and traveling behavioral states (ratio 2:1). Stopover locations were characterized by higher vegetation heterogeneity and lower rugosity than traveling locations, while vegetation biomass and elevation interacted to explain stopover locations in a more complex way. The selected combination of environmental features thus varied across seasons and behavioral states, in a way broadly consistent with predictions based on the changing food and safety needs of hares. Although causality was not demonstrated, our results improve our understanding of long-distance movements and habitat selection in Arctic hares, as well as herbivore ecology in the polar desert. Results also provide strong support to animal movement and habitat selection theory, by showing how some important hypotheses hold when tested in a species phylogenetically distinct from most animal models used in this research field. [ABSTRACT FROM AUTHOR]

Migration is an energetically challenging and risky life history stage for many animals, but could be supported by dietary choices en route, which may create opportunities to improve body and physiological condition. However, proposed benefits of diet shifts, such as between seasonally available invertebrates and fruits, have received limited investigation in free-living animals. We quantified diet composition and magnitude of autumn diet shifts over two time periods in two closely-related species of migratory songbirds on stopover in the northeastern U.S. (Swainson's thrush [Catharus ustulatus], long-distance migrant, N = 83; hermit thrush [C. guttatus], short-distance migrant, N = 79) and used piecewise structural equation models to evaluate the relationships among (1) migration timing, (2) dietary behavior, and (3) morphometric and physiological condition indices. Tissue isotope composition indicated that both species shifted towards greater fruit consumption. Larger shifts in recent weeks corresponded to higher body condition in Swainson's, but not hermit thrushes, and condition was more heavily influenced by capture date in Swainson's thrushes. Presence of "high-antioxidant" fruits in fecal samples was unrelated to condition in Swainson's thrushes and negatively related to multiple condition indices in hermit thrushes, possibly indicating the value of fruits during migration is related more to their energy and/or macronutrient content than antioxidant content. Our results suggest that increased frugivory during autumn migration can support condition, but those benefits might depend on migration strategy: a longer-distance, more capital-dependent migration strategy could require stricter regulation of body condition aided by increased fruit consumption. [ABSTRACT FROM AUTHOR]

Although miniaturized data loggers allow new insights into avian migration, incomplete knowledge of basic patterns persists, especially for nightjars. Using GPS data loggers, this study examined migration ecology of the eastern whip‐poor‐will Antrostomus vociferus, across three migration strategies: flyover, short‐stay, and long‐stay. We documented migration movements, conducted hotspot analyses, quantified land cover within 1 and 5 km buffers at used and available locations, and modeled habitat selection during migration. From 2018–2020 we captured breeding whip‐poor‐wills from three study sites in Massachusetts and programmed GPS tags to collect data during fall and spring migration periods. Across 19 individual males (nine of them with repeated years of data), GPS tags collected 479 locations, where 30% were classified as flyover points, 33% as short‐stays, and 37% as long‐stay locations. We documented seasonal flexibility in migration duration, routes, and stopover locations among individuals and between years. Analyses identified hotspot clusters in fall and spring migration in the Sierra de Tamaulipas in Mexico. Land cover at used locations differed across location types at the 5 km scale, where closed forest cover increased and crop cover decreased for flyover, short‐stay, and long‐stay locations, and urban cover was lowest at long‐stay locations. Discrete choice modeling indicated that habitat selection by migrating whip‐poor‐wills differs depending on the scale and migration strategy. For example, at the 5 km scale birds avoided urban cover at long‐stay locations and selected closed forest cover at short‐stay locations. We suggest that whip‐poor‐wills may use land cover cues at large spatial scales, like 5 km, to influence rush or stay tactics during migration. [ABSTRACT FROM AUTHOR]

In response to climate warming, migratory animals can alter their migration so that different events in the annual cycle are better aligned in space and time with suitable environmental conditions. Although such responses have been studied extensively during spring migration and the breeding season, much less is known about the influence of temperature on movements throughout autumn migration and how those movements result in a winter range and shifts therein. We use multi‐year GPS tracking data to quantify how daily autumn movement and annual winter distance from the breeding grounds are related to temperature in the Western Palearctic Bewick's swan, a long‐lived migratory waterbird whose winter range has shifted more than 350 km closer to the breeding grounds since 1970 due to individuals increasingly 'short‐stopping' their autumn migration. We show that the migratory movement of swans is driven by lower temperatures throughout the autumn season, with individuals during late autumn moving only substantially when temperatures drop below freezing. As a result, there is large flexibility in their annual winter distance as a response to winter temperature. On average, individuals overwinter 118 km closer to the breeding grounds per 1°C increase in mean December–January temperature. Given the observed temperature increase in the Bewick's swan winter range during the last decades, our results imply that the observed range shift is for a substantial part driven by individual responses to a warming climate. We thus present an example of individual flexibility towards climatic conditions driving the range shift of a migratory species. Our study adds to the understanding of the processes that shape autumn migration decisions, winter ranges and shifts therein, which is crucial to be able to predict how climate change may impact these processes in the future. [ABSTRACT FROM AUTHOR]

Environmental and climatic variation drive animal migration. Animals must adjust their behavioral strategies, for example, habitat selection, to match best variation in resources whose value likely varies with conditions such as weather. For example, climate change makes processes such as snowmelt and the emergence of vegetation less predictable at the scale of months or weeks. Furthermore, climate change makes meteorological conditions unpredictable—or dynamic—at the scale of days and hours. The profitability of selecting any particular resource may vary according to local meteorological condition. We studied the impact of dynamic weather conditions on fine-scale movement strategies and resource selection during spring migration of adult female Woodland Caribou (Rangifer tarandus). We assessed the role played by static resources such as open, lichen, and closed forest habitats and their role in a context-dependent of dynamic weather conditions, including temperature, precipitation, and changing snow water equivalent. We tested the role of static resources and dynamic conditions in three contexts: (1) whether caribou were encamped or moving using hidden Markov models; state-specific habitat selection for, and the interaction between, resources and conditions while (2) encamped and (3) moving. Weather conditions influenced the probability of moving or staying encamped, and the probability of selecting for a resource, which likely reflects the profitability of a given resource in a particular condition. The probability of staying encamped in the forest increases as temperature increases, and the probability of selecting an open area is higher when precipitation is lower. We highlight how meteorological conditions modify the selection of a static resource and likely the profitability of a given resource. The resource utility to a consumer is increasingly susceptible to climate change-induced effects. [ABSTRACT FROM AUTHOR]

Aims: Understanding the suite of environmental changes impacting migration and disentangling these from the dependencies between migratory stages is fundamental to understanding the drivers and mechanisms causing spatial shifts to migratory bird distributions. In this review, our objectives are to: (i) provide evidence of spatial change at all migratory stages, (ii) identify the key mechanisms driving change, (iii) discuss how anthropogenic change influences migratory patterns, (iv) highlight interdependencies between migratory stages and (v) offer a framework for understanding migratory pattern changes. Location: Migratory land birds globally. Methods: We defined a literature search to find examples of spatial changes in avian migrations and their underlying mechanisms. From the top 1000 search results, sorted by relevance, we retained 81 papers published between 1991 and 2020. Results: Spatial shifts in migratory bird distributions occur throughout the annual cycle, but patterns vary across taxa and migratory stages. Since avian migrants occupy multiple sites across the annual cycle, environmental change has particularly complex repercussions for their distributions. Multiple environmental changes can affect distributions at each migratory stage due to fitness asymmetries between migratory strategies and individuals responding flexibly to environmental changes within and across generations. Spatial changes at one stage (e.g. breeding) can also trigger further indirect spatial changes at other stages (e.g. stopovers) due to dependencies between stages. Conclusions: To understand the drivers and mechanisms underpinning spatial changes, comprehensive year‐round distributional data are crucial for observing change across multiple migratory stages and disentangling competing drivers. Biologging technology could elucidate the mechanisms causing changes to individual‐level strategies and uncover fitness asymmetries between strategies. Ultimately, gaining a clearer understanding of spatial changes will aid in predicting distributional responses to anthropogenic change in migratory birds. This is paramount for mitigating the effects of anthropogenic change and assessing future population viability within this vulnerable and extensive taxonomic group. [ABSTRACT FROM AUTHOR]

Copyright of Avian Conservation & Ecology is the property of Resilience Alliance and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

American woodcock (Scolopax minor; woodcock) are monitored, in part, by counts of displaying male woodcock collected via the American Woodcock Singing Ground Survey (SGS), which suggests long‐term, range‐wide declines in woodcock populations. Data from the SGS have been used extensively to develop conservation plans, direct management actions, and understand causes of decline. To avoid bias, the SGS should be timed to avoid spring migration, and the distribution of survey routes should coincide with woodcock breeding distribution. Our objectives for this research were to evaluate SGS timing with the phenology of male woodcock migration, relate the spatial coverage of the SGS to male woodcock breeding distributions, and explore other sources of variation in woodcock migration timing. We marked 133 male woodcock captured throughout eastern North America with global positioning system (GPS) transmitters during 2019–2022, and compared the timing of their spring migration with the spatiotemporal stratification of the SGS. Most woodcock (74%) completed migration prior to the onset of the SGS. In the northernmost SGS zone, a greater percentage of males (34%) continued migration during the survey window; however, the influence of this mismatch is offset because SGS routes were run more frequently during the second half of the window. Young woodcock completing their first spring migration took 8.6 days longer to do so, on average, compared to adults, and so were more likely to migrate during the SGS window. We found little evidence that timing of migration varied among years. Existing SGS routes cover the majority of male woodcock post‐migratory breeding distribution, with 90% of male woodcock establishing final breeding sites within the spatial coverage of the SGS. Our results confirm the SGS includes some migrating males, with the proportion relative to resident breeding males increasing in more northern survey strata. Our data suggests these errors are unlikely to bias trend estimates at large scales (e.g., within woodcock management regions), but there may be potential for bias at more local scales (e.g., state or provincial population indices). [ABSTRACT FROM AUTHOR]

For an avian migrant, refueling capacity attainable during stopovers governs the entire migration schedule and, ultimately, its fitness. Specifically, timely replenishing energy stores is critical when migration involves crossing ecological barriers, within which refueling may be limited. Here, we tested the hypothesis that fuel deposition rates (FDRs) of migratory passerines within barrier‐edge stopover sites are constrained by the density of potential competitors, irrespective of migration season, phenology, and local environmental conditions. We also evaluated diverse intra‐ and inter‐specific competition scenarios and explored a potential mediation of density‐dependence by environmental factors. The analyzed data, collected by us over 13 consecutive years (2009–2022), contain information on seven species of long‐distance migratory insectivorous passerines measured within eight desert‐edge habitats throughout autumn and spring migrations. As predicted, our analyses revealed negative density‐dependence regulation of FDRs, consistent across species and migration seasons. Notably, bird density exerted its effect above and beyond the other factors known to influence FDR, such as relative ambient temperature, phenology, temporal progress of stopover, and body mass next to landfall. As expected, FDR increased at higher relative ambient temperatures and with the stopover's progress. In spring, FDR also rose as the season advanced. These findings signify the substantial impact of competition on the refueling performance of migratory passerines during their stopover on an ecological barrier's edge, acting over and above the other environmental factors. The detected importance of competition and its interrelation with other predictors provides an insight into stopover's functioning; environmentally imposed and inescapable interspecific interference is thus a significant limiting factor of FDR, a deleterious relationship potentially remediable by informed habitat restoration and planning. [ABSTRACT FROM AUTHOR]

For an avian migrant, refueling capacity attainable during stopovers governs the entire migration schedule and, ultimately, its fitness. Specifically, timely replenishing energy stores is critical when migration involves crossing ecological barriers, within which refueling may be limited. Here, we tested the hypothesis that fuel deposition rates (FDRs) of migratory passerines within barrier‐edge stopover sites are constrained by the density of potential competitors, irrespective of migration season, phenology, and local environmental conditions. We also evaluated diverse intra‐ and inter‐specific competition scenarios and explored a potential mediation of density‐dependence by environmental factors. The analyzed data, collected by us over 13 consecutive years (2009–2022), contain information on seven species of long‐distance migratory insectivorous passerines measured within eight desert‐edge habitats throughout autumn and spring migrations. As predicted, our analyses revealed negative density‐dependence regulation of FDRs, consistent across species and migration seasons. Notably, bird density exerted its effect above and beyond the other factors known to influence FDR, such as relative ambient temperature, phenology, temporal progress of stopover, and body mass next to landfall. As expected, FDR increased at higher relative ambient temperatures and with the stopover's progress. In spring, FDR also rose as the season advanced. These findings signify the substantial impact of competition on the refueling performance of migratory passerines during their stopover on an ecological barrier's edge, acting over and above the other environmental factors. The detected importance of competition and its interrelation with other predictors provides an insight into stopover's functioning; environmentally imposed and inescapable interspecific interference is thus a significant limiting factor of FDR, a deleterious relationship potentially remediable by informed habitat restoration and planning.

Migration patterns are fundamentally linked to the spatio-temporal distributions of prey. How migrating animals can respond to changes in their prey's distribution and abundance remains largely unclear. During the last decade, humpback whales (Megaptera novaeangliae) used specific winter foraging sites in fjords of northern Norway, outside of their main summer foraging season, to feed on herring that started overwintering in the area. We used photographic matching to show that whales sighted during summer in the Barents Sea foraged in northern Norway from late October to February, staying up to three months and showing high inter-annual return rates (up to 82%). The number of identified whales in northern Norway totalled 866 individuals by 2019. Genetic sexing and hormone profiling in both areas demonstrate a female bias in northern Norway and suggest higher proportions of pregnancy in northern Norway. This may indicate that the fjord-based winter feeding is important for pregnant females before migration. Our results suggest that humpback whales can respond to foraging opportunities along their migration pathways, in some cases by continuing their feeding season well into winter. This provides an important reminder to implement dynamic ecosystem management that can account for changes in the spatio-temporal distribution of migrating marine mammals.

Canada geese (Branta canadensis) migrating along coastal flyways are reliant on natural coastal ecosystems. Within these stopover sites, eelgrass (Zostera marina), the most common and widespread seagrass species in North America, is an important food resource for migrating waterfowl. Given the growing anthropogenic pressure on coastal ecosystems, geese migrating along coastal regions may find it increasingly difficult to access suitable stopover sites where food is abundant and human disturbance is low. We assessed the influence of hunting and eelgrass on the spatiotemporal distribution of Canada geese in the Tabusintac Bay, New Brunswick, Canada, a wetland of international importance. We surveyed Canada geese at 6 stations from mid‐September to late October, 2016 and 2017. We used 2‐part hurdle models consisting of generalized linear mixed models with binomial and negative binomial response distributions to model Canada geese presence and abundance, respectively, in relation to eelgrass abundance, distance to the mainland coastline, water depth, and tidal conditions in 3 different hunting intensity periods. Eelgrass abundance is a significant predictor of Canada geese presence early in the season, when hunting activity is low. At the onset of the hunting period, geese shifted diurnal distribution to areas farther offshore, indicating a response to avoid disturbance, and the abundance of Canada geese increased with increasing eelgrass availability, emphasizing the importance of eelgrass as a food source during fall migration in that region. Thus, our results highlight the effects of human disturbance and eelgrass abundance in influencing stopover behavior of Canada geese during fall migration in eastern Canada. [ABSTRACT FROM AUTHOR]

During migration, landbirds normally need to stop-over in order to rest and/or acquire fuel stores that power their flight. Refuelling strategies become particularly evolutionarily relevant when birds must cross broad geographic barriers, where the chance to land and get food is nil, such as when crossing oceans. Our objective was to learn more about the use of the small islands located close to the mainland coast as stopover areas by small migratory birds that cross the Bay of Biscay. Using data collected in a constant-effort mist-netting programme conducted on Izaro Island (northern Spain) during autumn migration (years 2018 to 2021), we aimed to determine (1) which species land on the island and for how long they stay there, and (2) their fuel load and fuel deposition rate. Structurally, the assemblage was dominated by Willow Warblers Phylloscopus trochilus, which on average accounted for 84% of the abundance. Clustering analyses reveal that the assemblage was rather homogeneous across the four study years. Most birds probably stayed on the island for less than 24 hours, with fewer than 5% being recaptured one or more days after their first capture. The first-capture-event body mass of Willow Warblers captured only once (8.0g, 95%CI 7.8-8.4g) did not differ from the initial body mass of those captured two or more times within a season (8.0g, 95% CI 7.0-9.0g), and those stopping over on Izaro had a negative mean fuel deposition rate of –0.2g/day (SE = 0.1g/d). Overall, Izaro was used as an emergency stopover site during the course of this study, where exhausted birds landed after sea-crossings. From a conservation standpoint, and as compared to other stopover sites used as 'emergency' stopover sites, results suggest that Izaro is of little value for replenishing the fuel stores of these small birds during autumn migration.—Betanzos-Lejarraga, L., Guzmán, I., Escandell, R., Unamuno, E. & Arizaga, J. (2023). Stopover ecology of passerine birds on an islet in the Bay of Biscay in autumn reveals a pattern similar to their use of small Mediterranean islands in spring. Ardeola, 70: 241-255. Durante la migración, las aves terrestres normalmente necesitan detenerse para descansar o adquirir las reservas que después consumirán durante el vuelo. Las estrategias para ganar estas reservas se vuelven particularmente relevantes desde el punto de vista evolutivo cuando las aves han de cruzar grandes barreras geográficas en las que la posibilidad de aterrizar y alimentarse es nula, como ocurre al atravesar océanos. El objetivo de este artículo es profundizar en el uso de las pequeñas islas situadas cerca de la costa por las pequeñas aves migratorias que cruzan el golfo de Vizcaya. Utilizando los datos que fueron recolectados mediante un programa de anillamiento científico desarrollado en la isla de Izaro (norte de España) durante el periodo de paso posnupcial (años 2018 a 2021), se pretendió identificar (1) cuáles son las especies que usan la isla y cuánto tiempo permanecen allí, y (2) cuál es su cantidad y tasa de deposición de reservas. Estructuralmente, el ensamblado estuvo dominado por el mosquitero musical Phylloscopus trochilus, que en promedio representó el 84% de la abundancia. Los análisis de clusters revelaron un ensamblado muy homogéneo a lo largo de todo el periodo de estudio. En general el periodo de estancia en la isla fue de un día para la mayoría de los ejemplares capturados para anillamiento, y de ellos menos del 5% fueron recapturados uno o más días después de su primera captura. La masa corporal de la primera captura no varió entre mosquiteros musicales capturados una sola vez en la isla (8,0 g, IC 95 % 7,8-8,4 g) y capturados dos o más veces en la temporada (8,0 g, IC 95 % 7,0-9,0 g). La tasa de ganancia de reservas de los recapturados fue negativa (–0,2 g/d; SE = 0,1 g/d). En general, nuestros resultados sugieren que Izaro es usada como punto de parada migratoria de emergencia por las aves que, tras cruzar el Cantábrico, llegan exhaustas a la costa del norte de España. Desde el punto de vista de la conservación, y en comparación con otros sitios de parada migratoria utilizados, Izaro parece tener poco valor como punto de ganancia de reservas durante el periodo de paso posnupcial. —Betanzos-Lejarraga, L., Guzmán, I., Escandell, R., Unamuno, E. y Arizaga, J. (2023). La ecología de parada de descanso migratorio de las aves paseriformes en un islote del golfo de Vizcaya en otoño revela un patrón similar al uso de las pequeñas islas mediterráneas en primavera. Ardeola, 70: 241-255. [ABSTRACT FROM AUTHOR]

The Northern shoveler, Spatula clypeata, makes several migratory stopovers to reach its breeding site in the best conditions. These stopovers allow the species to replenish their reserves. Therefore, feeding efficiency at such sites is essential. Despite its importance, few studies have been conducted on the spring ecology of the shoveler, particularly on its diet at stopover sites. Therefore, this study focused on the Northern shoveler's feeding habit during its spring migratory stopover in the Marais breton (MB), a wetland situated in Vendée (France, Atlantic coast). The shoveler's plasma and potential food resources were studied using a stable carbon and nitrogen isotope analysis. The study showed that the shoveler feeds primarily on microcrustaceans, especially Cladocera and Copepoda; Chironomidae larvae, Corixidae, Hydrophilidae larvae, and particulate organic matter. This last food source, the POM, had never been highlighted before. [ABSTRACT FROM AUTHOR]

Natural variation in migratory strategies across the range of the American Kestrel (Falco sparverius) creates a unique opportunity for comparative research of annual cycles. However, it can be logistically and technically challenging to track such a small but highly mobile species. We tagged American Kestrels with light-level geolocators or satellite transmitters with the aim of estimating migration timing and connectivity, and we monitored a subset of satellite-tagged individuals during the breeding season to assess transmitter function and wear. We recovered geolocators from six of 49 (12%) tagged individuals. One geolocator-tagged individual migrated approximately 1235 km from its Idaho breeding grounds to New Mexico near the Arizona border for the winter and returned to Idaho the following spring. The other five recaptured individuals remained near (<200 km) the breeding grounds year-round. The low reliability of recovery and low precision of locations suggested major limitations of using geolocators to track this species. Most satellite transmitters (18 of 22, 82%) failed prior to migration, but one satellite-tagged individual migrated approximately 5945 km from Canada to Nicaragua, and three others transmitted ≥1 location during migration. Transmitters stopped functioning while on live individuals despite showing no visible damage and maintaining adequate battery levels. These results suggest further testing and development are needed before these recently developed tags are deployed again on American Kestrels. Both individuals with complete migration tracks showed evidence of short distance (250–350 km) post-breeding movements to southern stopover sites where they stayed 1–3 mo before migrating onward. Although sample sizes were small, migration patterns were consistent with latitudinal leap-frog patterns described in previous studies and revealed an interesting pattern of a prolonged post-breeding stopover before longer migration. Further, the migration track from Canada to Nicaragua represents the longest recorded migration path for this species. [ABSTRACT FROM AUTHOR]

Migratory landbirds are in decline across North America as factors like habitat loss and climate change pose significant challenges across the annual cycle. Migration is a period of especially high mortality as birds must navigate new landscapes to find suitable foraging habitat and deal with ecological barriers, predation, and competition along the way. Stopover sites where birds can rest and refuel are crucial for successful migration. Refueling performance is linked to a variety of factors including season, migratory distance, habitat quality, and body condition upon arrival. Here, we used plasma triglyceride to investigate how season, progression of season (ordinal day), and breeding latitude influenced the stopover refueling performance of 7 migratory songbird species during fall and spring migration at an inland site in the Connecticut River Valley in western Massachusetts. We found that Swainson's Thrushes (Catharus ustulatus) and White-throated Sparrows (Zonotrichia albicollis) had greater refueling performance in spring, while Gray Catbirds (Dumetella carolinensis) showed increased refueling performance in fall, suggesting that birds refuel differently at the same site and experience different pressures between seasons during migration. Progression of season did not influence refueling performance for most species in either season, but in fall the refueling performance of Gray Catbirds increased as the season progressed, while the refueling performance declined as the fall season progressed for Yellow-rumped Warblers (Setophaga coronata). We used stable isotopes to examine how breeding latitude influenced refueling performance for a subset of Gray Catbirds and found that, contrary to our expectations, Gray Catbirds nearer to their breeding destination in spring had greater refueling performance, suggesting that birds may try to improve their body condition directly before arriving at their breeding grounds to increase their reproductive competitiveness. Our results show that refueling performance of songbirds passing through inland stopover sites varies across species and can be influenced by a variety of factors including season and breeding latitude. En América del Norte, las aves migratorias terrestres están declinando ya que factores como la pérdida de hábitat y el cambio climático representan desafíos significativos a lo largo del ciclo anual. La migración es un período de mortalidad elevada debido a que las aves deben navegar nuevos paisajes para encontrar hábitats de forrajeo y a la vez lidiar con barreras ecológicas, depredación y competencia. Los sitios de parada, donde las aves descansan y se reabastecen, son cruciales para una migración exitosa. La efectividad del reabastecimiento está vinculada con varios factores, incluyendo la temporada, la distancia de migratoción, la calidad del hábitat y la condición corporal al llegar. Usamos triglicéridos del plasma para investigar la influencia de la temporada, la progresión de la temporada (día ordinal), y la latitud de reproducción sobre la efectividad de reabastecimiento durante paradas para 7 especies de aves migratorias terrestres durante la migración de otoño y primavera en un sitio de parada interior en el valle del río Connecticut en el oeste de Massachusetts. Encontramos que Catharus ustulatus y Zonotrichia albicollis tuvieron mejor efectividad de reabastecimiento en la primavera, mientras que Dumetella carolinensis tuvo mejor efectividad en el otoño, sugiriendo que en un mismo sitio las aves se reabastecen de manera diferente y están sujetas a diferentes presiones entre temporadas de migración. La progresión de la temporada no influyó en la efectividad de reabastecimiento para la mayoría de las especies en ninguna de las temporadas, pero en otoño la efectividad de reabastecimiento de Dumetella carolinensis aumentó con el avance de la temporada, mientras que para Setophaga coronata disminuyó con el avance de la temporada. Utilizamos isótopos estables para examinar la influencia de latitud de reproducción sobre la efectividad de reabastecimiento para un subconjunto de Dumetella carolinensis y encontramos que, contrario a nuestras expectativas, los individuos más cercanos a sus destinos reproductivos en primavera tuvieron mayor efectividad de reabastecimiento, sugiriendo que las aves posiblemente mejoran condición corporal antes de llegar a sus áreas de reproducción para aumentar su competencia reproductiva. Nuestros resultados muestran que la efectividad de abastecimiento en aves terrestres que pasan a través de áreas de paradas interiores varia por especie y puede ser influenciada por una variedad de factores incluyendo temporada y latitud de reproducción. Palabras clave: deuterio, isótopos estables, migración de aves terrestres, sitios de parada, triglicéridos en plasma. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Field Ornithology is the property of Resilience Alliance and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Abstract Background Birds have extremely elevated metabolic rates during migratory endurance flight and consequently can become physiologically exhausted. One feature of exhaustion is oxidative damage, which occurs when the antioxidant defense system is overwhelmed by the production of damaging reactive oxygen species (ROS). Migrating birds have been shown to decrease the amount of oxidative lipid damage during stopovers, relatively stationary periods in between migratory flights. It has therefore been argued that, in addition to accumulating fuel, one of the functions of stopover is to restore the oxidative balance. If this is so, we would expect that migrating birds are unlikely to resume migration from stopover when they still have high amounts of lipid damage. Methods To test this hypothesis, we measured parameters of the oxidative balance and related these to stopover departure decisions of song thrushes (Turdus philomelos) and northern wheatears (Oenanthe oenanthe), a medium- and long-distance songbird migrant, respectively. We measured malondialdehyde (MDA) concentration, a biomarker for oxidative lipid damage, and total non-enzymatic antioxidant capacity (AOX), an overall biomarker of protection against ROS. Stopover departure decisions were determined using a fully automated telemetry system set-up on our small island study site. Results The decision to resume migration was not related with MDA concentration in either study species, also not when this was corrected for circulating fatty acid concentrations. Similarly, AOX did not affect this decision, also not when corrected for uric-acid concentration. The time within the night when birds departed also was not affected by MDA concentration or AOX. However, confirming earlier observations, we found that in both species, fat individuals were more likely to depart than lean individuals, and fat northern wheatears departed earlier within the night than lean conspecifics. Northern wheatears additionally departed earlier in spring with more southerly winds. Conclusions We found no support for the idea that stopovers departure decisions are influenced by parameters of the oxidative balance. We discuss possible reasons for this unexpected finding.

Abstract Background Migrating passerines in North America have shown sharp declines. Understanding habitat selection and threats along migration paths are critical research needs, but details about migrations have been limited due to the difficulty of tracking small birds. Recent technological advances of tiny GPS-tags provide new opportunities to delineate fine-scale movements in small passerines during a life stage that has previously been inherently difficult to study. Methods We investigated habitat selection along migration routes for a temperate-zone migratory passerine, the Golden-crowned Sparrow (Zonotrichia atricapilla), given GPS tags on California wintering grounds. We used a resource selection function combined with conditional logistic regression to compare matched sets of known stopover locations and available but unused locations to determine how land cover class, vegetation greenness and climate variables influence habitat selection during migration. We also provide general migration descriptions for this understudied species including migration distance, duration, and elevation, and repeated use of stopover areas. Results We acquired 22 tracks across 19 individuals, with a total of 541 valid spring and fall migration locations. Birds traveled to breeding grounds in Alaska and British Columbia along coastal routes, selecting for shrubland and higher vegetation greenness in both migration seasons as well as grasslands during fall migration. However, model interactions showed they selected sites with lower levels of greenness when in forest (both seasons) and shrubland (fall only), which may reflect their preference for more open habitats or represent a trade-off in selection between habitat type and productivity. Birds also selected for locations with higher daily maximum temperature during spring migration. Routes during spring migration were lower in elevation on average, shorter in duration, and had fewer long stopovers than in fall migration. For two birds, we found repeated use of the same stopover areas in spring and fall migration. Conclusions Using miniaturized GPS, this study provides new insight into habitat selection along migration routes for a common temperate-zone migrating songbird, contributing to a better understanding of full annual cycle models, and informing conservation efforts. Golden-crowned Sparrows selected for specific habitats along migration routes, and we found previously unknown behaviors such as repeated use of the same stopover areas by individuals across different migratory seasons.

Wild waterbirds, and especially wild waterfowl, are considered to be a reservoir for avian influenza viruses, with transmission likely occurring at the agricultural-wildlife interface. In the past few decades, avian influenza has repeatedly emerged in China along the East Asian-Australasian Flyway (EAAF), where extensive habitat conversion has occurred. Rapid environmental changes in the EAAF, especially distributional changes in rice paddy agriculture, have the potential to affect both the movements of wild migratory birds and the likelihood of spillover at the agricultural-wildlife interface. To begin to understand the potential implications such changes may have on waterfowl and disease transmission risk, we created dynamic Brownian Bridge Movement Models (dBBMM) based on waterfowl telemetry data. We used these dBBMM models to create hypothetical scenarios that would predict likely changes in waterfowl distribution relative to recent changes in rice distribution quantified through remote sensing. Our models examined a range of responses in which increased availability of rice paddies would drive increased use by waterfowl and decreased availability would result in decreased use, predicted from empirical data. Results from our scenarios suggested that in southeast China, relatively small decreases in rice agriculture could lead to dramatic loss of stopover habitat, and in northeast China, increases in rice paddies should provide new areas that can be used by waterfowl. Finally, we explored the implications of how such scenarios of changing waterfowl distribution may affect the potential for avian influenza transmission. Our results provide advance understanding of changing disease transmission threats by incorporating real-world data that predicts differences in habitat utilization by migratory birds over time. [ABSTRACT FROM AUTHOR]

Migratory species are changing their timing of departure from wintering areas and arrival to breeding sites (i.e. migration phenology) in response to climate change to exploit maximum food availability at higher latitudes and improve their fitness. Despite the impact of changing migration phenology at population and community level, the extent to which individual and species-specific response affects associations among co-migrating species has been seldom explored. By applying temporal co-occurrence network models on 15 years of standardized bird ringing data at a spring stopover site, we show that African–European migratory landbirds tend to migrate in well-defined groups of species with high temporal overlap. Such ‘co-migration fidelity’ significantly increased over the years and was higher in long-distance (trans-Saharan) than in short-distance (North African) migrants. Our findings suggest non-random patterns of associations in co-migrating species, possibly related to the existence of regulatory mechanisms associated with changing climate conditions and different uses of stopover sites, ultimately influencing the global economy of migration of landbirds in the Palearctic–African migration system.

Nearctic Neotropical migratory songbirds incur the highest mortality during migration. En-route, songbirds rely on a network of stopover sites to rest, refuel, and/or seek refuge during poor weather. Conservation strategies prioritize protection of sites that best meet these needs. However, the specific function of a stopover site is expected to vary in relation to factors, such as geographic location, surrounding landscape, and weather. To identify sites with the highest conservation value for migratory songbirds, a conceptual framework was independently developed to classify sites into three functional categories based on their geographic and landscape features: fire escapes, convenience stores, and full-service hotels. The few attempts to empirically validate this framework have focused on temperate stopover sites. We evaluated the framework by testing the hypothesis that a site’s geographic and landscape characteristics can predict its function. We used capture and radio-tracking data at an island and mainland site in the Yucatan Peninsula, Mexico to quantify mean and variance in daily capture rate, body condition, stopover duration, and departure behavior during autumn, with a focus on four species: Swainson’s Thrush ( Catharus ustulatus ), Red-eyed Vireo ( Vireo olivaceus ), Gray Catbird ( Dumetella carolinensis ), and Prothonotary Warbler ( Protonotaria citrea ). Our results supported our predictions that the island functions as a fire escape, providing refuge for very high numbers of birds after encountering crosswinds or headwinds over the Gulf of Mexico, and the mainland forest site serves as a full-service hotel. The framework provides valuable insight for strategic conservation planning and management of stopover sites for songbirds. We suggest future studies evaluate the framework’s application to non-forest bird species. Additionally, we encourage collaborative efforts to consolidate and integrate tracking data, capture data from migration banding stations, and radar-based bird density estimates across a broad geography to test the framework’s ability to inform conservation planning across species’ full migratory range.

This study on stopovers, defined as consisting of a one to three-night transition to a destination featuring value-based experiences, uses a multi-site data collection approach of focus groups in six cities to examine stopovers during long-haul air travel in Dubai and Abu Dhabi, Singapore and Hong Kong. It contributes to the literature on stopovers by defining and conceptualizing the term and identifying the key influences of stopover choice and value experiences of travelers from distant geographic areas, namely, the United Kingdom, France, Australia, and New Zealand. The proposal of the conceptual model on stopovers offers a basis for destination marketers a greater understanding of stopover travelers and facilitates the destination's promotion from a practical perspective.

Background: Birds have extremely elevated metabolic rates during migratory endurance flight and consequently can become physiologically exhausted. One feature of exhaustion is oxidative damage, which occurs when the antioxidant defense system is overwhelmed by the production of damaging reactive oxygen species (ROS). Migrating birds have been shown to decrease the amount of oxidative lipid damage during stopovers, relatively stationary periods in between migratory flights. It has therefore been argued that, in addition to accumulating fuel, one of the functions of stopover is to restore the oxidative balance. If this is so, we would expect that migrating birds are unlikely to resume migration from stopover when they still have high amounts of lipid damage. Methods: To test this hypothesis, we measured parameters of the oxidative balance and related these to stopover departure decisions of song thrushes (Turdus philomelos) and northern wheatears (Oenanthe oenanthe), a medium- and long-distance songbird migrant, respectively. We measured malondialdehyde (MDA) concentration, a biomarker for oxidative lipid damage, and total non-enzymatic antioxidant capacity (AOX), an overall biomarker of protection against ROS. Stopover departure decisions were determined using a fully automated telemetry system set-up on our small island study site. Results: The decision to resume migration was not related with MDA concentration in either study species, also not when this was corrected for circulating fatty acid concentrations. Similarly, AOX did not affect this decision, also not when corrected for uric-acid concentration. The time within the night when birds departed also was not affected by MDA concentration or AOX. However, confirming earlier observations, we found that in both species, fat individuals were more likely to depart than lean individuals, and fat northern wheatears departed earlier within the night than lean conspecifics. Northern wheatears additionally departed earlier in spring with more southerly winds. Conclusions: We found no support for the idea that stopovers departure decisions are influenced by parameters of the oxidative balance. We discuss possible reasons for this unexpected finding. [ABSTRACT FROM AUTHOR]

Arctic-nesting geese face energetic challenges during spring migration, including ecological barriers and weather conditions (e.g., precipitation and temperature), which in long-lived species can lead to a trade-off to defer reproduction in favor of greater survival. We used GPS location and acceleration data collected from 35 greater white-fronted geese of the North American midcontinent and Greenland populations at spring migration stopovers, and novel applications of Bayesian dynamic linear models to test daily effects of minimum temperature and precipitation on energy expenditure (i.e., overall dynamic body acceleration, ODBA) and proportion of time spent feeding (PTF), then examined the daily and additive importance of ODBA and PTF on probability of breeding deferral using stochastic antecedent models. We expected distinct responses in behavior and probability of breeding deferral between and within populations due to differences in stopover area availability. Time-varying coefficients of weather conditions were variable between ODBA and PTF, and often did not show consistent patterns among birds, indicating plasticity in how individuals respond to conditions. An increase in antecedent ODBA was associated with a slightly increased probability of deferral in midcontinent geese but not Greenland geese. Probability of deferral decreased with increased PTF in both populations. We did not detect any differentially important time periods. These results suggest either that movements and behavior throughout spring migration do not explain breeding deferral or that ecological linkages between bird decisions during spring and subsequent breeding deferral were different between populations and across migration but occurred at different time scales than those we examined. [ABSTRACT FROM AUTHOR]

Technological advances in migratory tracking tools have revealed a remarkable diversity in migratory patterns. One such pattern is leapfrog migration, where individuals that breed further north migrate to locations further south. Here, we analyzed migration patterns in the Painted Bunting (Passerina ciris) using a genetic‐based approach. We started by mapping patterns of genetic variation across geographic space (called a genoscape) using 386 individuals from 25 populations across the breeding range. We then genotyped an additional 230 samples from 31 migration stopover locations and 178 samples from 16 wintering locations to map patterns of migratory connectivity. Our analyses of genetic variation across the breeding range show the existence of four genetically distinct groups within the species: Eastern, Southwestern, Louisiana, and Central groups. Subsequent assignment of migrating and wintering birds to genetic groups illustrated that birds from the Central group migrated during the fall via western Mexico or southern Texas, spent the winter from northeastern Mexico to Panama, and migrated north via the Gulf Coast of Mexico. While Louisiana birds overlapped with Central birds on their spring migratory routes along the Gulf Coast, we found that Louisiana birds had a more restricted wintering distribution in the Yucatan Peninsula and Central America. Further estimation of the straight‐line distance from the predicted breeding location to the wintering location revealed that individuals sampled at lower winter latitudes traveled to greater distances (i.e., the predicted breeding area was further north; p >.001), confirming that these species exhibit a leapfrog migration pattern. Overall, these results demonstrate the utility of a genoscape‐based approach for identifying range‐wide patterns of migratory connectivity such as leapfrog migration with a high degree of clarity. [ABSTRACT FROM AUTHOR]

Songbirds on migration spend a greater share of their travelling time at stopover sites in order to rest, recover and refuel compared to actively flying. In the German Bight of the North Sea, two subspecies of the northern wheatear split travelling routes, with Greenlandic/Icelandic breeders (subspecies leucorhoa) facing a long over‐sea flight and Scandinavian breeding birds (subspecies oenanthe) travelling further roughly along the coast. We used automated radio‐telemetry in spring to show that leucorhoa birds stayed significantly longer at a coastal stopover site and clearly selected for favourable weather, especially easterly winds, when resuming flights. Conditions for departures of individuals from the subspecies oenanthe were less obvious. They were more likely to depart on nights with southerly winds, often along with rising air temperatures, while air pressure dropped. Individuals of subspecies leucorhoa thus wait for optimal flying conditions to resume for longer flights, while oenanthe birds, with shorter distances ahead, seem to optimise time by leaving the stopover site more quickly. Our dataset thus confirms that songbirds optimise stopover based on their (sub)species‐specific migration patterns. [ABSTRACT FROM AUTHOR]

Introduction: Migration is a natural phenomenon that includes annual movements of many bird species in response to seasonal cycles. With approximately one third of all living bird species, South America has an important avifauna, and many migrants land in Brazil at stopping points and wintering sites. Objective: To identify associations between migrant birds and coastal vegetation, and environmental influence of on migration. Methods: At 10 points along the coast of Piauí State, Brazil, we made visual censuses and mist net captures, between April 2009 and February 2016. Results: We identified 82 migrant bird species (13 orders; 28 families) that represented 41 intracontinental migrating species, 26 northern visiting species, 14 nomad species and one vagrant species. The richness peaks were at the beginning and end of both dry and rainy seasons, matching insolation and atmospheric pressure. There were spatial pattern differences among vegetation complexes. Chrysolampis mosquitus is an indicator of caatinga vegetation, Numenius phaeopus of wetland, Charadrius collaris of non-flooding fields, Rostrhamus sociabilis of forest-grassland transition, and Columbina picui of orchards. Despite differences in number and species composition within vegetation types, the temporal pattern in species richness was similar among flooded fields, non-flooded fields, and transition grassland categories. Conclusions: Migrant birds occupy specific environments during their permanence along the coast of Piauí State, with richness matching insolation and atmospheric pressure. [ABSTRACT FROM AUTHOR]

Weather conditions experienced by birds can influence their migration decision‐making and strategy both within and across seasons. Additionally, decision‐making during migration may influence subsequent fitness (reproductive success and/or survival). Examining the effects of fine‐scale weather variables on individuals throughout the year could help identify stages of the annual cycle when species may be most affected by weather. In this study, we captured 24 black‐bellied plovers (gray plovers; Pluvialis squatarola) on nonbreeding areas along the western Gulf of Mexico coast and tracked their locations once every 2 h through their breeding season in the Alaskan and Canadian Arctic. We quantified migration strategies and weather conditions experienced by each individual throughout the nonbreeding, northward migration, and breeding seasons. We used a Bayesian hierarchical model which connected regressions linking weather with migration metrics, and migration metrics and breeding season weather with reproductive success. We found strong negative relationships between two migration metrics (migration duration and number of stopovers) and reproductive success, but no substantial relationships between breeding season weather variables and reproductive success. We found negative relationships between nonbreeding season temperature, migration temperature, and migration NDVI and both migration duration and number of stopovers, in addition to positive relationships between the number of stopovers and storms during migration, migration duration, and nonbreeding season precipitation. These results suggest that reproductive success is influenced by weather throughout the annual cycle and migration strategy is a key mechanism through which these effects operate. Our findings suggest that environmental factors throughout the year influence shorebird fitness, and, because black‐bellied plovers are often associated with mixed‐species flocks, many species likely experience similar constraints. [ABSTRACT FROM AUTHOR]

During the long‐distance migratory flights of birds, lean mass breakdown occurs in concert with fat catabolism and is expected to have repercussions on total stopover duration because birds require time to rebuild lean tissue before accumulating fat reserves. Despite this, little is known about the role of in‐flight lean mass breakdown on stopover duration because direct measurements are restricted by the destructive nature of traditional body composition analysis and the technological limitations of tracking small birds over large expanses.We used non‐lethal, non‐invasive Quantitative Magnetic Resonance technology and plasma metabolite profiling to measure the body composition and physiological state of free‐living birds captured at a migratory stopover site after flight across the Gulf of Mexico, and an automated radiotelemetry array covering ~5000 km2 to track stopover duration and regional movements. We tested whether stopover duration is prolonged in individuals arriving with lower lean mass and investigated how lean mass affects regional movements.Stopover duration decreased by 22% for each additional gram of lean mass in Northern Waterthrush (Parkesia noveboracensis), but this relationship was not apparent in Swainson's Thrush (Catharus ustulatus), Grey‐cheeked Thrush (Catharus minimus) or Yellow‐billed Cuckoo (Coccyzus americanus), even though these species also arrived with depleted lean mass. Stopover duration increased for Swainson's Thrush with higher plasma uric acid, a marker of protein catabolism. Northern Waterthrush with higher plasma triglycerides had longer stopover duration.Our findings suggest that migratory birds may compensate for substantial lean mass losses by increasing refuelling rate or moving to a different stopover site, and highlights species‐level differences in lean mass breakdown and the associated impacts on physiological function. Our results highlight the strategies used by different species to recover from a trans‐Gulf of Mexico flight and resume migration, which improves our understanding of the annual cycle of migratory birds. Read the free Plain Language Summary for this article on the Journal blog. [ABSTRACT FROM AUTHOR]

Many songbirds migrate twice a year to exploit seasonally available resources. These journeys are energetically demanding and energy reserves of these small birds are limited. Accordingly, most of the time migrating is spent during stopovers that serve to rest, replenish resources and recover. While external influences, like prevailing weather conditions and resource availability, are well studied with regard to stopover behaviour and departure decisions, studies on how birds' individual physiological condition and stopover decisions may be linked are scarce.We used a large‐scale radio‐telemetry network covering the German Bight (SE North Sea) to study how birds' immunological constitution at stopover may correlate with departure and flight behaviour in five species of short‐ to medium‐distance migratory songbirds. We measured markers of the innate (bacterial killing activity, lysozyme concentration, natural antibodies and complement titres) and acquired immune function (immunoglobulin Y) in the birds' plasma. After sampling, we tracked the birds' behaviour in terms of stopover duration as well as flight routes and flight distances within the telemetry network after departure.We found that stopover durations were positively related to natural antibodies and immunoglobulin Y across species and to the bacterial killing activity solely in song thrushes in spring, while no relations became apparent in fall. Flight distances were linked positively to immunoglobulin Y concentrations in both spring and fall, though not in all of the investigated species. Coastal and offshore‐oriented routes were taken independent of the birds' immune status.Our study for the first time shows that migratory behaviour of songbirds in the wild is correlated with their immune status, not only during but also beyond stopover. Furthermore, birds with increased complement titres and Immunoglobulin Y concentrations, either due to recent infection or greater investment in their immune function, took additional time at their stopover sites, probably to reach their breeding grounds in good condition. During the less time‐constrained fall season, stopovers were generally prolonged, independent from the birds' immune status and any delays taken to improve immune status are most likely not detrimental in terms of fitness. Read the free Plain Language Summary for this article on the Journal blog. [ABSTRACT FROM AUTHOR]

Tree Swallows (Tachycineta bicolor) are migratory aerial insectivores that breed across North America and have experienced long-term population declines. Although the mechanisms behind these declines have proved difficult to identify, emerging methods for studying migration staging areas could provide new insights. Tree Swallows congregate in staging roosts during fall migration, gathering at sunset to roost overnight, then leaving at sunrise to feed or continue their migration south. Using a particularly large roost site in Connecticut, USA, we used NEXRAD Level III data to calculate metrics of reflectivity corresponding to snapshots of morning roost size each day. Using these metrics as measures of relative abundance, we tested predictions about the effects of wind and date on daily roost size and day-to-day changes in relative abundance. We found that radar reflectivity around the roost decreased with higher wind speeds during the morning emergence and when wind speeds were high the previous day. In addition, we found a temporal pattern of roost abundance corresponding to a peak of migration around the end of August for this stopover site. Our results provide insight into the sensitivity of Tree Swallow responses to wind conditions and lay the groundwork for future studies using NEXRAD to examine links between migratory behavior and declines in swallow populations. [ABSTRACT FROM AUTHOR]

Abstract Technological advances in migratory tracking tools have revealed a remarkable diversity in migratory patterns. One such pattern is leapfrog migration, where individuals that breed further north migrate to locations further south. Here, we analyzed migration patterns in the Painted Bunting (Passerina ciris) using a genetic‐based approach. We started by mapping patterns of genetic variation across geographic space (called a genoscape) using 386 individuals from 25 populations across the breeding range. We then genotyped an additional 230 samples from 31 migration stopover locations and 178 samples from 16 wintering locations to map patterns of migratory connectivity. Our analyses of genetic variation across the breeding range show the existence of four genetically distinct groups within the species: Eastern, Southwestern, Louisiana, and Central groups. Subsequent assignment of migrating and wintering birds to genetic groups illustrated that birds from the Central group migrated during the fall via western Mexico or southern Texas, spent the winter from northeastern Mexico to Panama, and migrated north via the Gulf Coast of Mexico. While Louisiana birds overlapped with Central birds on their spring migratory routes along the Gulf Coast, we found that Louisiana birds had a more restricted wintering distribution in the Yucatan Peninsula and Central America. Further estimation of the straight‐line distance from the predicted breeding location to the wintering location revealed that individuals sampled at lower winter latitudes traveled to greater distances (i.e., the predicted breeding area was further north; p > .001), confirming that these species exhibit a leapfrog migration pattern. Overall, these results demonstrate the utility of a genoscape‐based approach for identifying range‐wide patterns of migratory connectivity such as leapfrog migration with a high degree of clarity.

Migrating birds flexibly adjust their individual migratory decisions, i.e. departing, routing and landing, based on intrinsic (e.g. energy stores) and extrinsic (e.g. landscape features and weather) factors modulating the endogenous stimuli. So far, these decisions have mostly been studied separately. Notably, we lack information on which factors landing decisions during active flight are based on. Therefore, we simultaneously recorded all three decisions in free-flying long-distance migratory songbirds in a coastal stopover area via regional-scale radio-telemetry and related them to the prevailing weather. Birds departed under favourable weather conditions resulting in specific nights with increased departure probability. Once departed, birds could either fly offshore or take a route along the coast, which was predicted by wind support. Radio-tracking revealed that departed individuals more likely interrupted their migratory endurance flight under overcast or headwind conditions. Studying departure, routing and landing decisions in concert, we highlight the importance of weather as a common driver across all migratory decisions. By radio-tracking individuals between stopovers, we provide evidence that avoidance of adverse weather conditions is an important function of stopover. Understanding how birds adjust migratory decisions and how they affect the timing of migration and survival is key to link migration performance to individual fitness.

Songbirds on migration spend a greater share of their travelling time at stopover sites in order to rest, recover and refuel compared to actively flying. In the German Bight of the North Sea, two subspecies of the northern wheatear split travelling routes, with Greenlandic/Icelandic breeders (subspecies leucorhoa) facing a long over‐sea flight and Scandinavian breeding birds (subspecies oenanthe) travelling further roughly along the coast. We used automated radio‐telemetry in spring to show that leucorhoa birds stayed significantly longer at a coastal stopover site and clearly selected for favourable weather, especially easterly winds, when resuming flights. Conditions for departures of individuals from the subspecies oenanthe were less obvious. They were more likely to depart on nights with southerly winds, often along with rising air temperatures, while air pressure dropped. Individuals of subspecies leucorhoa thus wait for optimal flying conditions to resume for longer flights, while oenanthe birds, with shorter distances ahead, seem to optimise time by leaving the stopover site more quickly. Our dataset thus confirms that songbirds optimise stopover based on their (sub)species‐specific migration patterns.

Many populations of long‐distance migrant shorebirds are declining rapidly. Since the 1970s, the lesser yellowlegs (Tringa flavipes) has experienced a pronounced reduction in abundance of ~63%. The potential causes of the species' decline are complex and interrelated. Understanding the timing of migration, seasonal routes, and important stopover and non‐breeding locations used by this species will aid in directing conservation planning to address potential threats. During 2018–2022, we tracked 118 adult lesser yellowlegs using GPS satellite tags deployed on birds from five breeding and two migratory stopover locations spanning the boreal forest of North America from Alaska to Eastern Canada. Our objectives were to identify migratory routes, quantify migratory connectivity, and describe key stopover and non‐breeding locations. We also evaluated predictors of southbound migratory departure date and migration distance. Individuals tagged in Alaska and Central Canada followed similar southbound migratory routes, stopping to refuel in the Prairie Pothole Region of North America, whereas birds tagged in Eastern Canada completed multi‐day transoceanic flights covering distances of >4000 km across the Atlantic between North and South America. Upon reaching their non‐breeding locations, lesser yellowlegs populations overlapped, resulting in weak migratory connectivity. Sex and population origin were significantly associated with the timing of migratory departure from breeding locations, and body mass at the time of GPS‐tag deployment was the best predictor of southbound migratory distance. Our findings suggest that lesser yellowlegs travel long distances and traverse numerous political boundaries each year, and breeding location likely has the greatest influence on migratory routes and therefore the threats birds experience during migration. Further, the species' dependence on wetlands in agricultural landscapes during migration and the non‐breeding period may make them vulnerable to threats related to agricultural practices, such as pesticide exposure. [ABSTRACT FROM AUTHOR]

Migration patterns in birds vary in space and time. Spatial patterns include chain, leapfrog and telescopic migration. Temporal patterns such as migration duration, number, and duration of stopovers may vary according to breeding latitude, sex, and season. This study aimed to verify these patterns in a long‐distance migrant, the Eurasian curlew Numenius arquata arquata, and to provide a synopsis of spatio‐temporal migration patterns in this species of concern throughout the East Atlantic Flyway. We tagged 85 adults with GPS‐data loggers in Germany, Poland, France and Estonia between 2013 and 2019. We computed the distance flown, linear loxodromic distance, duration, stopover number, total stopover duration, mean stopover duration, departure time and arrival time for 177 out of 187 tracks. On average (± standard deviation), spring migration occurred from 4 to 14 April (10.2 ± 8.4 days), curlews flew 3.623 ± 1.366 km, and had 5.8 ± 3.6 stopovers, with a duration of 29.4 ± 38.2 h per stopover, while autumn migration occurred from 18 to 29 June (10.9 ± 9.9 days), curlews flew 3.362 ± 1.351 km, and had 5.4 ± 4.0 stopovers, with 31.8 ± 32.3 h per stopover. Curlews displayed chain migration because wintering curlews maintained the latitudinal sequence to their breeding sites. Southern curlews had a longer nesting period due to their earlier arrivals. While spring arrival at breeding sites did not differ between the sexes, in autumn females departed earlier than males. Migration duration and distance, as well as stopover number and duration, showed a significant increase with breeding site latitude but did not differ between the sexes or between spring and autumn migrations, suggesting that curlews took a comparable amount of time migrating during both seasons. The high site faithfulness in curlews suggests that rapid autumn migration allows them to return to defend their winter foraging areas. [ABSTRACT FROM AUTHOR]

Abstract Background Long-term ringing and telemetry studies show that the Osprey (Pandion haliaetus) is a broad-front migrant following different migratory flyways, depending on the geographical location of their breeding populations. We have investigated two distinct and declining populations of Osprey in Poland, separated by only a few hundred kilometres, and hypothesised they may exhibit two different migration routes. We followed mortality causes, comparing them between migration and stationary phases of annual cycle, as well as between two distinct populations. Methods Nineteen Ospreys, both juveniles and adults, were equipped with GPS loggers in 2017–2020 in two populations in western and eastern Poland and followed on their autumn migration. We calculated the distance they covered on the migration, number of stopover days, migration duration, daily distances covered and departure dates to compare them between age and sex classes and between the eastern and western populations. Results Ospreys from the western and eastern populations showed a partial migratory divide. While the first migrated through a western flyway, the second followed a central flyway, resulting in crossing the Mediterranean Sea in distant passes that affected the distance covered. Annual mortality reached at least 67% in juveniles and at least 57% in adults. Conclusions We showed that two distinct Osprey populations in Poland revealed a partial migratory divide, with one covering greater distances over sea and deserts over the central flyway. This might affect individual survival rates and contribute to a steeper decline in one of the populations. In order for this to be confirmed, more individuals still have to be followed.

Abstract Many populations of long‐distance migrant shorebirds are declining rapidly. Since the 1970s, the lesser yellowlegs (Tringa flavipes) has experienced a pronounced reduction in abundance of ~63%. The potential causes of the species' decline are complex and interrelated. Understanding the timing of migration, seasonal routes, and important stopover and non‐breeding locations used by this species will aid in directing conservation planning to address potential threats. During 2018–2022, we tracked 118 adult lesser yellowlegs using GPS satellite tags deployed on birds from five breeding and two migratory stopover locations spanning the boreal forest of North America from Alaska to Eastern Canada. Our objectives were to identify migratory routes, quantify migratory connectivity, and describe key stopover and non‐breeding locations. We also evaluated predictors of southbound migratory departure date and migration distance. Individuals tagged in Alaska and Central Canada followed similar southbound migratory routes, stopping to refuel in the Prairie Pothole Region of North America, whereas birds tagged in Eastern Canada completed multi‐day transoceanic flights covering distances of >4000 km across the Atlantic between North and South America. Upon reaching their non‐breeding locations, lesser yellowlegs populations overlapped, resulting in weak migratory connectivity. Sex and population origin were significantly associated with the timing of migratory departure from breeding locations, and body mass at the time of GPS‐tag deployment was the best predictor of southbound migratory distance. Our findings suggest that lesser yellowlegs travel long distances and traverse numerous political boundaries each year, and breeding location likely has the greatest influence on migratory routes and therefore the threats birds experience during migration. Further, the species' dependence on wetlands in agricultural landscapes during migration and the non‐breeding period may make them vulnerable to threats related to agricultural practices, such as pesticide exposure.

Migration patterns in birds vary in space and time. Spatial patterns include chain, leapfrog and telescopic migration. Temporal patterns such as migration duration, number, and duration of stopovers may vary according to breeding latitude, sex, and season. This study aimed to verify these patterns in a long‐distance migrant, the Eurasian curlew Numenius arquata arquata, and to provide a synopsis of spatio‐temporal migration patterns in this species of concern throughout the East Atlantic Flyway. We tagged 85 adults with GPS‐data loggers in Germany, Poland, France and Estonia between 2013 and 2019. We computed the distance flown, linear loxodromic distance, duration, stopover number, total stopover duration, mean stopover duration, departure time and arrival time for 177 out of 187 tracks. On average (± standard deviation), spring migration occurred from 4 to 14 April (10.2 ± 8.4 days), curlews flew 3.623 ± 1.366 km, and had 5.8 ± 3.6 stopovers, with a duration of 29.4 ± 38.2 h per stopover, while autumn migration occurred from 18 to 29 June (10.9 ± 9.9 days), curlews flew 3.362 ± 1.351 km, and had 5.4 ± 4.0 stopovers, with 31.8 ± 32.3 h per stopover. Curlews displayed chain migration because wintering curlews maintained the latitudinal sequence to their breeding sites. Southern curlews had a longer nesting period due to their earlier arrivals. While spring arrival at breeding sites did not differ between the sexes, in autumn females departed earlier than males. Migration duration and distance, as well as stopover number and duration, showed a significant increase with breeding site latitude but did not differ between the sexes or between spring and autumn migrations, suggesting that curlews took a comparable amount of time migrating during both seasons. The high site faithfulness in curlews suggests that rapid autumn migration allows them to return to defend their winter foraging areas.

Migratory stopover sites are of high conservation concern especially those sites where shorebirds concentrate in large numbers to acquire fat reserves to fuel continued flight to breeding grounds. Many shorebirds use only a few stopover sites during northward migration to Arctic breeding grounds, thus identifying important locations, migration chronology, and flight routes are priority research topics to inform effective management strategies. We examined Ruddy Turnstones (Arenaria interpres) route and timing to Arctic breeding grounds from an island in South Carolina in the heart of the South Atlantic Bight using the Motus Wildlife Tracking System. Ruddy Turnstones leaving South Carolina did not migrate northward up the Atlantic coast but migrated inland through the Great Lakes Basin. Most Ruddy Turnstones did not make a stop in the Great Lakes Basin, thus making South Carolina the last presumed stopover before reaching Arctic habitats. Like other shorebird migration studies, most of the Ruddy Turnstones made use of tailwinds at departure and ground speeds were positively correlated with tailwind support. Future conservation planning for Ruddy Turnstones must consider the varied migratory routes and strategies of this declining shorebird species. This research also demonstrates the usefulness of Motus for tracking the movement of smaller shorebirds and the potential for strategic expansion of the Motus network to understand their full life cycle.