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Long-distance migrants must optimise their timing of breeding to capitalise on resources at both breeding and over-wintering sites. In species with protracted breeding seasons, departing earlier on migration might be advantageous, but is constrained by the ongoing breeding attempt. Here we investigated how breeding timing affects migratory strategies in the Manx shearwater (Puffinus puffinus), a trans-hemispheric migratory seabird with large temporal variation in the onset of breeding. Using a geolocator tracking dataset, we found that that later-laying shearwaters had shorter overall breeding periods, yet still departed later for autumn migration. Earlier laying birds had increased migratory duration, stopped with greater frequency and at sites of higher chlorophyll concentration. Meanwhile, later departing birds flew more at night during migratory stints, and night flight generally increased with moon illumination, which could reflect moonlight providing the light conditions required for visually guided flight. Accordingly, birds that experienced higher levels of moon illumination whilst migrating had shorter migration durations. Here we provide an example of migratory behaviour being adjustable with breeding timing, allowing birds to both complete breeding and capitalise on resource availability at the wintering site. [ABSTRACT FROM AUTHOR]

Climate change can influence populations of monogamous species by affecting pair‐bond dynamics. This study examined the impact of climate on widowhood and divorce, and the subsequent effects on individual vital rates and life‐history outcomes over 54 years in a snow petrel (Pagodroma nivea) population. We found that environmental conditions can affect pair‐bond dynamics both directly and indirectly. Divorce was adaptive, occurring more frequently after breeding failure and leading to improved breeding success. Divorce probabilities also increased under severe climatic conditions, regardless of prior breeding success, supporting the 'Habitat‐mediated' mechanisms. Overall, pair‐bond disruptions reduced subsequent vital rates and lifetime outcomes. Climate forecasts from an Atmosphere–Ocean General Circulation Model projected increased male widowhood rates due to decreased sea ice negatively affecting female survival, despite considerable uncertainty. These findings highlight the importance of environmentally induced changes in demographic and pair‐bond disruption rates as crucial factors shaping demographic responses to climate change. [ABSTRACT FROM AUTHOR]

Every year in Newfoundland, young Atlantic puffins, Fratercula arctica , departing their nests at night for the first time become stranded in towns near their breeding colonies, a phenomenon thought to be caused by attraction towards artificial light. To test this hypothesis, we conducted three behavioural experiments. First, we illuminated beaches near a breeding colony to determine whether more fledglings would become stranded in illuminated versus dark conditions. Next, we conducted a Y-maze experiment to test stranded fledglings for phototactic behaviour in general and for preferences among high-pressure sodium (HPS), Warm white light-emitting diode (LED), Cool white LED, Blue LED and Orange LED light. Lastly, we quantified activity levels of stranded fledglings in an open field test during exposure to several different light types. We found significantly more fledglings stranded when beaches were illuminated, and fledglings significantly preferred light over darkness in the Y-maze, supporting our hypothesis that Atlantic puffin fledglings become stranded due to light attraction. Fledglings displayed no preferences for certain light types over others in the Y-maze, potentially suggesting that strandings in this species may not be mitigable by changing the streetlight type in stranding-prone towns. Interestingly, fledglings exhibited higher activity levels in darkness and HPS light than in LED light, potentially holding implications for rescue, rehabilitation and husbandry programmes. Overall, our findings demonstrate that the only evidence-based strategy for the reduction of Atlantic puffin strandings is the reduction of coastal artificial lighting; however, further research is needed to determine whether aspects of artificial light besides bulb type may be altered to effectively reduce light attraction in this species. • Atlantic puffin fledglings become stranded in towns near their breeding colonies. • More fledglings became stranded at experimentally lit beaches than at dark ones. • Fledglings preferred light over darkness in a choice experiment. • Light spectrum had no effect on fledgling preferences. • Fledglings were less active under LED light than under darkness or other light types. [ABSTRACT FROM AUTHOR]

Pulsed resources resulting from animal migrations represent important, transient influxes of high resource availability into recipient communities. The ability of predators to respond and exploit these large increases in background resource availability, however, may be constrained when the timing and magnitude of the resource pulse vary across years. In coastal Newfoundland, Canada, we studied aggregative responses of multiple seabird predators to the annual inshore pulse of a key forage fish species, capelin (Mallotus villosus). Seabird aggregative responses to fish biomass were quantified from weekly hydroacoustic and seabird surveys during July–August within an annually persistent foraging area (10 km2) associated with a cluster of capelin spawning sites across 10 years (2009–2010, 2012, 2014–2020). Seabird predators included breeding members of the families Alcidae (Common Murres Uria aalge, Razorbills Alca torda, Atlantic Puffins Fratercula arctica) and Laridae (Great Black‐backed Gulls Larus marinus, American Herring Gulls L. argentatus smithsonianus) and Northern Gannets Morus bassanus, along with non‐breeding, moulting members of the Family Procellariidae (Sooty Shearwaters Ardenna griseus, Great Shearwaters A. gravis). The inshore migration of spawning capelin resulted in 5–619 times (mean ± SE, 146 ± 59 times) increase in coastal fish biomass along with a shift towards more, larger and denser fish shoals. Within years, seabird abundance did not increase with inshore fish biomass but rather peaked near the first day of spawning, suggesting that seabirds primarily respond to the seasonal resource influx rather than short‐term variation in fish biomass. Across years, the magnitude of the seabird aggregative response was lower during low‐magnitude resource pulse years, suggesting that predators are unable to perceive low‐magnitude pulses, avoid foraging under high competitor densities, and/or shift dietary reliance away from capelin under these conditions. The seabird response magnitude, however, was higher when the resource pulse was delayed relative to the long‐term average, suggesting that predators increase exploitation during years of minimal overlap between the resource pulse and energetically demanding periods (e.g. breeding, moulting). This long‐term study quantifying responses of multiple predators to a pulsed resource illustrates the ability of natural systems to tolerate natural and human‐induced disturbance events. [ABSTRACT FROM AUTHOR]

Coloniality is strongly shaped by aspects of social foraging behaviour. For example, colonies may be important sources of information, while food competition may increase foraging efforts and limit colony size. Understanding foraging ecology considering these apparent trade‐offs is required to develop a better understanding of colonial living. We combined animal‐borne GPS, cameras and dive recorders to study social foraging in breeding adult northern gannets Morus bassanus—a wide‐ranging colonial seabird. We first tested for indirect evidence of prey depletion around the colony by estimating dive location, depth and duration. Next, we tested for sociality during different behaviours (commuting, foraging and resting) and distance from the colony. Finally, we quantified flocks of inbound and outbound birds to compare social foraging between outbound and inbound legs of the commute. Dive probability and depth (n = 46 individuals; n = 1590 dives) increased with distance from the colony, creating dive clusters at ~100 and 180 km consistent with conspecific prey depletion. Camera stills (n = 8 individuals; n = 7495 images) show gannets are highly social, but this varied among behaviours. Sociality was highest during foraging and commuting; especially inbound and social foraging was more likely far from the colony. Gannets were equally likely to be solitary or social when leaving the colony but returning birds were more likely in larger flocks. In summary, despite experiencing intraspecific competition for food, gannets engage in dynamic, context‐dependent social foraging associations. Conspecifics aggregated far from the colony possibly because of a prey depletion halo closer to home, but this provided potential benefits via local enhancement and by returning to the colony in flocks. Our results therefore illustrate how competition may, paradoxically, facilitate some aspects of group foraging in colonial animals. [ABSTRACT FROM AUTHOR]

Seasonal variation in food availability or adverse weather patterns can create challenging conditions for year-round survival. Birds experiencing such fluctuations may migrate to locations with better food availability in the non-breeding period. While some species are obligate migrants, others are facultative migrants where various post-breeding strategies exist within populations. Several cormorant and shag species are facultative migrants with a range of post-breeding movement strategies within populations. Currently, most of the information available on cormorant post-breeding strategies originates from banding studies and little is known about their movements, time budget or habitat use during the non-breeding period. In the present study, Australian endemic black-faced cormorants (Phalacrocorax fuscescens), breeding on Notch Island, Victoria, were tracked with GPS data loggers during the non-breeding period. Different post-breeding strategies were observed. Individuals were either resident (N = 36, 69%), remaining within a short distance of the colony (16.7 ± 2.2 km) or migratory (N = 16, 31%), travelling greater distances (250.7 ± 24.4 km) to establish a new central place foraging location. Data from individuals which covered the entire non-breeding period indicated that, across strategies, individual birds had one area of residency during the non-breeding period. Migratory individuals were found to have lower daily activity levels, spending less time flying and foraging, than resident individuals during the early non-breeding period, possibly indicating that they had access to greater prey resources. Regardless of the post-breeding strategy, individuals utilised foraging locations that were of similar seabed depths year-round suggesting individual specialisation in prey resources or foraging habitats. [ABSTRACT FROM AUTHOR]

Simple Summary: Black skimmers are state-threatened, colonial nesting seabirds that face numerous conservation health challenges. Through regular nest colony surveys, we observed a concerning pattern of annual fatalities among black skimmer juveniles that had grossly swollen joints at several nest colonies. This joint disease affected their mobility and ability to thrive and led to severe wasting and death in some individuals. Clinical and postmortem examinations of skimmers for four sequential years revealed that the joints were infected with a bacterium, Staphylococcus aureus, which normally cohabits the skin of many species (including humans) without causing disease. However, in this case, S. aureus likely gained entry to joints via skin injuries from sandspurs, which arise from vegetation that is common to many Florida beaches. S. aureus is also commonly detected as a sand and water contaminant in popular recreational beaches, which may also serve as a source of exposure in the skimmers. We recommend continued monitoring of black skimmer nest colonies for arthritic disease and other health-related challenges, with consideration of management techniques to reduce the risk of sandspur–skimmer interactions at nesting sites. The black skimmer (Rynchops niger) is a state-threatened, colonially nesting seabird in Florida, USA. Conservation threats include habitat alteration, human disturbances, severe weather, and predation. During nest monitoring (May–September, 2020–2022), black skimmer juveniles at colonies on Fort Myers Beach and Marco Island, Florida, had polyarthritis and died or were euthanized due to severe illness. Similarly-aged skimmers from geographically distant (considered unaffected) colonies were evaluated for comparison (2021–2023). We documented field, clinical, radiographical, and pathological findings to characterize disease and purported pathogenesis. The majority were lame and lethargic, in poor nutritional condition, and dehydrated. Additionally, 8/23 of the skimmers with dermatitis and arthritis from affected colonies also had penetrating sandspurs associated with skin ulceration, scabbing, and/or hemorrhage. The affected joints were often in limbs (interphalangeal and hock; less commonly stifle, elbow, carpus). A postmortem evaluation and bacteriology revealed Staphylococcal aureus-associated dermatitis, arthritis, tenosynovitis, and/or osteomyelitis in 21/22 of the juvenile skimmers from southwestern nest colonies. Staphylococcus aureus dissemination to internal organs occurred in 10/13 of the skimmers tested. Among skimmers evaluated from distant colonies, 5/10 that were examined histologically had skin crusting and inflammation but lacked arthritis. Occasional coinfections were documented (e.g., West Nile virus, Gram-negative bacilli). The results suggest that staphylococcal joint disease originated from sandspur-induced skin damage, followed by hematogenous dissemination to the joints and, occasionally, the internal organs. Additional nest sites should be tested to evaluate disease risk and potentially contributing environmental factors. We recommend that site managers employ techniques that reduce the risk of skimmer interactions with sandspurs. [ABSTRACT FROM AUTHOR]

Systematic surveys of marine birds from ships were first conducted by the Canadian Wildlife Service in Atlantic Canada in 1965, and then expanded to the Canadian Arctic in 1969 under PIROP (Programme intégré de recherches sur les oiseaux pélagiques). PIROP surveys ended in 1992, then resumed in 2006 under the Eastern Canada Seabirds at Sea program with an updated survey protocol. Surveys under both monitoring programs were conducted from a variety of ship types engaged in scientific, transport, and supply activities, totalling over 120 000 km within sub-Arctic and Arctic Canada waters and over a million marine birds observed, primarily northern fulmar (Fulmarus glacialis), black-legged kittiwake (Rissa tridactyla), thick-billed murre (Uria lomvia), and dovekie (Alle alle). The data collected inform offshore ecological inquiries, environmental impact reviews, mortality estimates from accidental oil releases, and define areas in need of protection. Although surveys were designed to quantify seabird distribution within the waters of eastern Canada, the data also include sightings of non-avian taxa that are made publicly available. Long-term and large-scale monitoring programs will remain essential for assessing the status and health of Canada's marine birds, including surveys that take place at sea where these species spend most of their time.

A small colony of black-browed albatrosses (Thalassarche melanophris, 21–65 breeding pairs) was discovered in 2003 on Albatross Islet, Tierra del Fuego, Chile. The formation of new breeding sites is important from an ecological and evolutionary perspective. This colony is particularly significant because it is the only one recorded for the species in a land-locked area. As its population dynamics could be shaped by stochastic and other factors affecting small populations, understanding the variables influencing its persistence, such as source of breeders, is crucial. Here, we used genetic markers (mitochondrial control region) to determine the origin of individuals at this new breeding site. Our results show that the new colony is an even mix of birds from Chilean colonies to the south and west (52%) and Falklands/Malvinas birds to the east (48%). Understanding the unique characteristics of this colony provides valuable insights for the conservation of black-browed albatrosses given increasing anthropogenic and environmental changes. [ABSTRACT FROM AUTHOR]

Abstract Seabird colonies with long-term monitoring records, i.e., > 50 years, are rare. The population data for northern gannets (Morus bassanus) in Cape St. Mary’s (CSM) Ecological Reserve (Newfoundland and Labrador, Canada) is robust, extending back to 1883 when the colony was presumed established. We inferred the colony’s historical population shifts by measuring ornithogenic proxies in a dated sediment record collected from a nearby pond. Our record extended to the early eighteenth century, but the proxy data only began to show significant signs of seabird presence between ca. 1832 and 1910, aligning with the period gannets were first observed at CSM. Through the twentieth century, we observed significant increases in δ15N, P, Zn, Cd, and chlorophyll a, coeval with a shift in the dominant diatom species, indicating rapid colony growth. The proxies were overall highest in ca. 2005, corresponding to the reported historical maximum of the gannet colony in 2009. Our results validate that paleo-reconstructions using ornithogenic proxies can accurately reflect population trends and provide a stronger understanding of the colony’s establishment and growth. This study highlights the value of applying paleolimnological methods in seabird population studies to frame the history of a colony’s dynamics and inform conservation efforts.

Abstract The warming of the Arctic had lead to a diverse range of impacts on local biota, including northward shifts of some species range. Here, we report past and present distribution and abundance of an Arctic zooplanktivorous seabird, the little auk Alle alle in West Greenland south of 74° N, and examine the changes in sea surface temperature (SST) and sea ice concentration (SIC) in the birds foraging areas in 1850–2007. We estimated the little auk population in the studied region to be 5,200 pairs in the 1930s, 6,000–6,500 pairs in the 1940-1970s and 70–80 pairs by the 2000s. We found that periods with increased SST and reduced SIC, especially in the last few decades, coincided with little auk population declines. Besides, years with little auk presence in breeding sites were characterized by either low SST and low to moderate SIC or higher SST but moderate to high SIC. Observed contraction of the breeding range and a decrease in abundance of the little auk may be attributed to more complex climate-driven changes in the marine ecosystem at finer spatial and temporal scales and/or cannot be easily detected given the coarseness of data used. It is possible that the population in this region has never been very numerous being subjected to local impacts such as disease, bycatch, predation, etc. The climate warming that is currently being observed, along with corresponding shifts in zooplankton communities, may lead to extirpation of the studied little auk populations.

Coral atoll islands are important breeding sites for tropical seabird species, but on many of these islands, disturbances from humans and introduced mammals have extirpated breeding colonies. In the Republic of the Maldives (Indian Ocean), little published information exists on the location and extent of seabird breeding colonies. Here, we document what appears to be a regionally significant breeding site for White-tailed Tropicbirds Phaethon lepturus on Kurehdhoo, the northern-most inhabited island of Lhaviyani Atoll in the central Maldives. We systematically surveyed the entire island on two separate occasions, six months apart, to count the number of White-tailed Tropicbird nests, their breeding stage, and habitat. We counted 128 and 202 nests at all breeding stages, indicating year-round breeding and an estimated population size of about 800 adults. This population is most likely the outcome of 14 y of sustained rat control across the entire island in the presence of native atoll vegetation. The effort has allowed White-tailed Tropicbirds to rapidly increase in numbers and a small population of Tropical Shearwaters Puffinus bailloni to establish on the island. These discoveries demonstrate that land-based seabird conservation opportunities exist in association with island resort land use in the Republic of the Maldives. [ABSTRACT FROM AUTHOR]

Climate change is a major concern for the future of marine Arctic food webs. Diet shifts of seabirds can be used as indicators of environmental changes such as species compositions of food webs. However, studies on diets are often laborious and costly, while research in vulnerable Arctic environments benefits from short visits for data collection that minimize disturbance to Arctic wildlife and the environment. DNA-metabarcoding techniques are rapidly developing and could be used as an effective method of monitoring diet choice of seabirds. We tested DNA-metabarcoding on seabird faeces collected during short visits of typically around 30 min at breeding colonies of black-legged kittiwake Rissa tridactyla (3 colonies), Brünnich's guillemot Uria lomvia (2 colonies) and little auk Alle alle (3 colonies). DNA metabarcoding based on COI and 18S of a limited number of faeces samples revealed a wide spectrum of fish species and crustaceans in the diets of these species, comparable with or even exceeding diversity in diet composition found in conventional, more invasive techniques where birds are shot or caught and handled to obtain samples. While previous studies on diet choice of little auk, a crustacean specialist, mainly report small fractions of unidentified fish remains, DNA metabarcoding of faeces revealed a large variety of pelagic and benthic fish species supplementing its diet. We conclude that DNA metabarcoding of seabird faeces can be an effective attribute to diet studies supporting our understanding of changes in numbers and distribution of Arctic seabirds and their marine environment. [ABSTRACT FROM AUTHOR]

Offshore windfarms are a potential threat to seabirds, partly due to collision risk with turbine blades. Wind influences the mode, height and speed of seabird flight, and therefore the risk of collision with turbines. We investigated how wind influences the flight of black-legged kittiwakes Rissa tridactyla, a gull of conservation concern, in order to incorporate these findings into collision risk estimates and identify mitigation measures. We used GPS telemetry data (23rd June to 10th August 2021) from 20 kittiwakes breeding in Aberdeenshire, UK (57.385°N, 1.868°W) to estimate the effect of wind on behavioural state, proportion of flight at collision risk height, probability of collision when within the rotor-swept zone, and overall collision risk. We found that as windspeed increased, kittiwakes commuted less and rested more. With increasing windspeed, kittiwakes spent a considerably smaller proportion of their flight time in the rotor-swept zone, but had a slightly higher probability of collision while in it. Uncertainty was high for most relationships between windspeed and kittiwake flight metrics. The overall effect of increasing windspeed on collision risk was negative, although we did not model avoidance rate. Effects of windspeed on collision risk were largely mediated through effects on commuting flight, and contingent on wind direction. Collision risk estimates incorporating the effects of windspeed may have greater precision and accuracy, but considerable uncertainty in windspeed-flight parameter relationships remains. Therefore although kittiwake collision risk may be mitigated by raising the 'cut-in' windspeed above which wind turbines generate power, the magnitude of this effect is uncertain. [ABSTRACT FROM AUTHOR]

Many industries are required to perform population viability analysis (PVA) during the consenting process for new developments to establish potential impacts on protected populations. However, these assessments rarely account for density‐dependent regulation of demographic rates. Excluding density‐dependent regulation from PVA‐based impact assessments is often assumed to provide a maximum estimate of impact and therefore offer a precautionary approach to assessment. However, there is also concern that this practice may unnecessarily impede the development of important industries, such as offshore renewable energy.In this study, we assess density‐dependent regulation of breeding success in 31 populations of seabird. We then quantify the strength and form of this regulation using eight different formulations. Finally, we use PVA to examine how each formulation influences the recreation of observed dynamics (i.e. model validation), as well as the predicted absolute and relative population response to an extrinsic threat (i.e. model projection).We found evidence of both negative (n = 3) and positive (n = 5) regulation of seabird breeding success. In populations exhibiting negative regulation, excluding density‐dependent regulation from PVA‐based impact assessment allowed uncontrolled population growth, such that model outcomes became biologically implausible. By contrast, in populations exhibiting positive regulation, excluding density‐dependent regulation provided an appropriate reconstruction of observed dynamics, but population decline was underestimated in some populations. We find that multiple formulations of density dependence perform comparably at the detection, validation and projection stages of analysis. However, we tentatively recommend using a log‐linear or Weibull distribution to describe density‐dependent regulation of seabird breeding success in impact assessments to balance accuracy with caution. Finally, we show that relative PVA metrics of impact assessment cannot necessarily be used to overcome PVA misspecification by assuming density independence in positively regulated populations.Synthesis and applications: We suggest that a density‐dependent approach when performing PVA‐based assessments for seabird populations will prevent biologically unrealistic, unconstrained population growth and therefore ensure meaningful PVA metrics in populations experiencing negative regulation. It will also maintain a precautionary approach for populations experiencing positive regulation, crucial when estimating impacts for these more vulnerable populations. These conclusions have immediate international application within the consenting processes for marine industries. [ABSTRACT FROM AUTHOR]

Scheduling between mates in species with long-term pair bonds can be essential for positive fitness. The annual cycle in photoperiod is the primary environmental cue used by many animals to synchronize behavior and physiology among members of a population, and animals that migrate must have similar annual schedules to ensure successful breeding. However, we know little about whether members of mated pairs in migratory species experience similar photic environments across the year, which could allow for synchronization in annual phenology. Here, we used light-based geolocation to estimate positions of mated pairs of Thick-billed Murres (Uria lomvia, a seabird a.k.a. Brünnich's Guillemot) which bred above the northern polar circle in Greenland. We tested the hypothesis that individuals in mated pairs occur in more similar locations and photic environments than randomly matched females and males. We found no difference in the amount of spatial separation or in the photic environment between mates and randomized heterosexual pairings. In general, the distance between females and males ranged from 1,198.5 km during August to 737.4 km during January. The sexes remained in photic environments with highly correlated photoperiods and moderately correlated times of solar noon in UTC. The spatial separation of, but similar photic environments experienced by, female and male murres regardless of pair status is probably adaptive by facilitating the synchronization of annual schedules between sexes, while allowing individuals in mated pairs the freedom to pursue the best foraging opportunities during migration and overwintering independent of their mate. [ABSTRACT FROM AUTHOR]

Seabird colonies with long-term monitoring records, i.e., > 50 years, are rare. The population data for northern gannets (Morus bassanus) in Cape St. Mary's (CSM) Ecological Reserve (Newfoundland and Labrador, Canada) is robust, extending back to 1883 when the colony was presumed established. We inferred the colony's historical population shifts by measuring ornithogenic proxies in a dated sediment record collected from a nearby pond. Our record extended to the early eighteenth century, but the proxy data only began to show significant signs of seabird presence between ca. 1832 and 1910, aligning with the period gannets were first observed at CSM. Through the twentieth century, we observed significant increases in δ15N, P, Zn, Cd, and chlorophyll a, coeval with a shift in the dominant diatom species, indicating rapid colony growth. The proxies were overall highest in ca. 2005, corresponding to the reported historical maximum of the gannet colony in 2009. Our results validate that paleo-reconstructions using ornithogenic proxies can accurately reflect population trends and provide a stronger understanding of the colony's establishment and growth. This study highlights the value of applying paleolimnological methods in seabird population studies to frame the history of a colony's dynamics and inform conservation efforts. [ABSTRACT FROM AUTHOR]

In seasonal environments, the fitness of animals depends upon the successful integration of life‐history stages throughout their annual cycle. Failing to do so can lead to negative carry‐over effects where individuals are transitioning into the next season in different states, consequently affecting their future performance. However, carry‐over effects can be masked by individual quality when individuals vary in their efficiency at acquiring resources year after year (i.e. 'quality'), leading to cross‐seasonal consistency in individual performance.Here we investigated the relative importance of carry‐over effects and individual quality in determining cross‐seasonal interactions and consequences for breeding success over the full annual cycle of a migratory seabird (black‐legged kittiwake Rissa tridactyla).We monitored the reproduction and annual movement of kittiwakes over 13 years using geolocators to estimate their breeding success, distribution and winter energy expenditure. We combined this with an experimental approach (clutch removal experiment, 2 years) to manipulate the reproductive effort irrespective of individual quality.Piecewise path analyses showed that successful breeders reproduced earlier and were more likely to breed successfully again the following year. This positive interaction among consecutive breeding stages disappeared after controlling for individual quality, suggesting that quality was dominant in determining seasonal interactions. Moreover, controlling experimentally for individual quality revealed underlying carry‐over effects that were otherwise masked by quality, with breeding costs paid in higher energy expenditure and delayed onset of reproduction.We highlight the need to combine an experimental approach along with long‐term data while assessing apparent carry‐over effects in wild animals, and their potential impact on fitness and population demography. [ABSTRACT FROM AUTHOR]

Bio‐logging has revealed much about high‐latitude seabird migratory strategies, but migratory behaviour in tropical species may differ, with implications for understanding nutrient deposition. Here we use combined light‐level and saltwater immersion loggers to study the year‐round movement behaviour of adult red‐footed boobies Sula sula rubripes from the Chagos Archipelago, tropical Indian Ocean, to assess migratory movements and estimate nutrient deposition rates based on the number of days they spent ashore. Light levels suggest that red‐footed boobies are resident in the Chagos Archipelago year‐round, although there are large latitudinal errors this close to the equator. Immersion data also indicate residency with tracked birds returning to land every one or two days. Spending an average of 79.86 ± 2.80 days and 280.84 ± 2.64 nights per year on land allows us to estimate that the 21 670 pairs of red‐footed boobies deposit 37.34 ± 0.56 tonnes year−1 of guano‐derived nitrogen throughout the archipelago. Our findings have implications for tropical seabird conservation and phylogenetics, as well as for assessing the impact of seabird nutrients on coral reef ecosystems. [ABSTRACT FROM AUTHOR]

The common murre (Uria aalge) is a species of seabird particularly vulnerable to several environmental stressors, including parasitic infection and oil contamination. However, the molecular response to these stressors is severely understudied. This study investigated the common murre's transcriptomic responses to these stressors. Blood samples were collected from common murres undergoing rehabilitation at International Bird Rescue in Fairfield, CA. Total RNA was extracted from these samples, followed by library preparation and Illumina sequencing to generate whole transcriptome data. Differential gene expression analysis was conducted using DeSeq2 to identify genes significantly altered in response to oil contamination and parasitic infection. Differential gene expression analysis revealed 194 genes shared between oil-contaminated and infected birds, including key immune-related genes, such as ANXA2, LY96, and LY86. These genes play vital roles inmediating the production of pro-inflammatory cytokines. Gene Set Enrichment Analysis indicated significant alterations in stress, immune, and inflammatory responses, with additional lipid metabolism changes in contaminated birds. Our findings highlight the detrimental effects that these stressors have on wild birds. These findings suggest a generalized stress response and specific metabolic adaptations to oil exposure, providing insights for seabird conservation. [ABSTRACT FROM AUTHOR]

As global heating and other anthropogenic influences alter tropical marine environments, it is unclear how marine bird populations will be impacted and whether their current roles in tropical marine ecosystems will change. Although marine birds roost and breed on tropical islands in large numbers, the direct trophic interactions between these birds and their prey across the tropics are poorly documented. We present a first framework for evaluating the dependence on and contributions of marine birds to tropical coral reef ecosystems and use it to examine the evidence for different kinds of interaction, focusing primarily on avian diets. We found 34 publications between 1967 and 2023 that presented a total of 111 data sets with enough detail for quantitative dietary analysis of tropical marine birds. Only two bird species out of 37 (5.4%) had diets of >50% coral reef fishes and only one, the Pacific Reef Egret, appeared to depend almost entirely on reef‐based production. Marine birds are also prey for other marine organisms, but insufficient data are available for quantitative analysis. Evidence for indirect effects of birds in tropical marine environments is stronger than for direct dependence on coral reefs, particularly in relation to nutrient concentration and the fertilisation impacts of guano on corals. Dispersal of propagules (e.g. seeds, spores, invertebrate eggs) by bathing, drinking, resting or foraging birds is under‐studied and poorly documented. Although the degradation of coral reefs appears unlikely to have a significant direct impact on food availability for most marine bird populations, indirect effects involving marine birds may be disrupted by global environmental change. [ABSTRACT FROM AUTHOR]

Offspring provisioning can act as a proxy of resource acquisition and vary with parental sex and age. Age-related variation can arise from individual experience and senescence, but also from selective disappearance of poor-quality parents. Distinguishing between these processes and quantifying their effect on the resource acquisition and fate of individual chicks requires longitudinal monitoring of known-age individuals, which is still rare. In our longitudinal study, we observed offspring provisioning of common terns, Sterna hirundo , across a 6-year period and analysed provisioning behaviour from both a parental and offspring perspective. Using repeated measures of provisioning of individual parents, our analyses showed that provisioning did not increase with age, but that parents that were observed at older ages provisioned more, suggesting selective disappearance of parents that provisioned less. Parental provisioning was higher in males than females and increased with brood size in both sexes. For offspring, energetic acquisition declined with hatching order and increased with age. Acquisition from the mother increased faster with chick age than that from the father, and mothers distributed their provisioning more evenly across chicks of different hatching order. Parental age, however, did not affect the energetic acquisition of the offspring. The early energetic acquisition rate of chicks predicted their fledging success, but not fledging mass. When decomposing effects on energetic provisioning and acquisition rate into effects on feeding rate, prey energetic density and prey size, we found that all arose from variation in feeding rate. Overall, these results therefore show that both parents and offspring vary in quality, which is reflected in their feeding rate. • Resource acquisition levels can reflect parental and/or offspring quality. • We studied offspring provisioning in common terns across 6 years. • We found selective disappearance with age of parents that provisioned at low levels. • For offspring, energetic acquisition rate predicted fledging success. • Both parents and offspring vary in quality, which is reflected in their feeding rate. [ABSTRACT FROM AUTHOR]

Maintaining a pair bond year after year (perennial monogamy) often enhances reproductive success, but what familiar pairs are doing differently to improve success is unknown. We tested the hypothesis that endocrine changes mediate improvements in parental attendance in known-age Cassin’s auklets Ptychoramphus aleuticus, for which we found limited evidence. Instead, we found sex-specific parental roles in familiar pairs. Males modulated their nest attendance depending on the attendance of their mate, but the direction depended on mate familiarity. We suggest his flexibility may be mediated by prolactin. In a historical dataset, females with a familiar mate laid larger eggs that hatched into more robust chicks, but larger eggs correlated with lower female body condition. In study birds, attendance by males and females in good condition predicted chick weight, but attendance by females in poor condition did not, suggesting female-specific energetic constraint. Our findings suggest that males and females contribute differently to their joint reproductive fortunes, and that improvements in their respective roles may result in the benefits of mate familiarity. Since improved reproductive success is presumed to be a main benefit of maintaining a long-term pair bond, these results suggest a new avenue of research in the evolution of monogamy.

ABSTRACT Coloniality is strongly shaped by aspects of social foraging behaviour. For example, colonies may be important sources of information, while food competition may increase foraging efforts and limit colony size. Understanding foraging ecology considering these apparent trade‐offs is required to develop a better understanding of colonial living. We combined animal‐borne GPS, cameras and dive recorders to study social foraging in breeding adult northern gannets Morus bassanus—a wide‐ranging colonial seabird. We first tested for indirect evidence of prey depletion around the colony by estimating dive location, depth and duration. Next, we tested for sociality during different behaviours (commuting, foraging and resting) and distance from the colony. Finally, we quantified flocks of inbound and outbound birds to compare social foraging between outbound and inbound legs of the commute. Dive probability and depth (n = 46 individuals; n = 1590 dives) increased with distance from the colony, creating dive clusters at ~100 and 180 km consistent with conspecific prey depletion. Camera stills (n = 8 individuals; n = 7495 images) show gannets are highly social, but this varied among behaviours. Sociality was highest during foraging and commuting; especially inbound and social foraging was more likely far from the colony. Gannets were equally likely to be solitary or social when leaving the colony but returning birds were more likely in larger flocks. In summary, despite experiencing intraspecific competition for food, gannets engage in dynamic, context‐dependent social foraging associations. Conspecifics aggregated far from the colony possibly because of a prey depletion halo closer to home, but this provided potential benefits via local enhancement and by returning to the colony in flocks. Our results therefore illustrate how competition may, paradoxically, facilitate some aspects of group foraging in colonial animals.

Abstract Background Parent-offspring conflict represents the sensitive balance of resource allocation between self-maintenance and reproduction. Two strategies have been proposed to better understand how species manage this conflict. In fixed-level feeding behavior, parents feed offspring consistent quantities of food; while flexible feeding shows plasticity in parental allocation based on offspring need. Life-history theory predicts that parents of long-lived species prioritize their survival and may favor the fixed-level hypothesis to maximize lifetime reproductive success. In this study, we highlight the natural variation of parent-offspring allocation strategies within a unique population of Leach’s storm-petrels (Hydrobates leucorhous), and through month-long food supplementation and restriction manipulations, we investigate how chick condition affects parental provisioning during the chick-rearing period of reproduction. Results We show that the parents upregulated chick feeding frequency of nutritionally deprived chicks, resulting in a larger total amount of food delivered during the study period. Additionally, the proportion of nights when both parents fed was highest in restricted chicks, and the proportion of nights when neither parents fed was lowest in restricted chicks, suggesting that storm-petrel parents shorten their foraging bouts to deliver food more often when their chicks are in relatively poor condition. Conclusions Our results support that Leach’s storm-petrels use a flexible-level feeding strategy, suggesting that parents can assess offspring condition, and respond by feeding chicks at higher frequencies. These data provide insight on how a long-lived seabird balances its own energetic demands with that of their offspring during the reproductive period.

Migratory birds must fit three costly life‐history events within the annual cycle, reproduction, moult and migration, to minimize their overlap and maximize survival and breeding success. However, some seabirds, such as Cory's Shearwater Calonectris borealis, overlap body moult and breeding, with flight feather renewal occurring in late chick‐rearing. In contrast, the moult patterns of non‐breeding adult (sabbatical) and immature Cory's Shearwaters, which also attend the colony during the breeding season, remain poorly understood. Furthermore, the potential implications of life‐stage and breeding status trade‐offs on moult status and colony attendance in non‐breeders has rarely been investigated. Surveying different areas within one colony between June and September 2013 and 2014, we studied the age and breeding status composition of birds attending the breeding colony and scored moult of their body (breast and upper‐neck), wing and tail feathers. We found that in addition to breeders (n = 165), 57.6% of the birds (n = 389) attending the colony were 4‐ to 10‐year‐old immatures (n = 132) and adult sabbatical shearwaters (n = 92). Sabbaticals and 8‐ to 10‐year‐old immatures (n = 28) were present at the colony during incubation, whereas only three sabbatical birds and no 8‐ to 10‐year‐old immatures were captured in late chick‐rearing. Conversely, 4‐ to 7‐year‐old immatures arrived later in the season but were still present in late chick‐rearing. Sabbatical and 8‐ to 10‐year‐old immatures were moulting body feathers at the same time as adult breeders, whereas, among 4‐ to 7‐year‐old immatures, older birds moulted earlier than younger birds. A larger proportion of sabbatical birds were replacing tail feathers compared with adult breeders. However, there was no evidence that sabbaticals or 8‐ to 10‐year‐old immatures differed in wing moult from adult breeders until August. Overall, our study shows that colony attendance by non‐breeding adults and immatures is widespread in this population. The synchronous moult schedule of flight and body feathers across age groups at different life‐history stages may suggest that this aspect of moult is controlled by environmental conditions. [ABSTRACT FROM AUTHOR]

The New Zealand fairy tern/tara iti (Sternula nereis davisae; NZFT) is New Zealand's most endangered bird, with approximately 40 individuals remaining. Due to previous poor breeding success, this species is on the brink of extinction. Nest failures occur because of adverse weather, predation, and potentially nest disturbance. We observed parental behaviour of 11 nesting pairs from November 2020 to January 2021 at three sites: Mangawhai, Waipu and Pakiri. Overall, avian predator disturbance was low at all nests, and most disturbance events were by interactions between conspecifics. Responses to conspecific disturbances were lowest for the three closely nesting pairs and highest for the three solitary nests. We measured the frequency of chick feeding and found feeding rates varied considerably between nests. Defensive response rates and feeding rates varied between nests but we found no relationship between the proportion of responses to disturbance and feeding rates. We found no relationship between feeding rate and tidal state. This could be due to our small sample size and the duration of our observation period (30 min). We urge future researchers to increase observation period time. With an understanding of feeding rates and disturbance, informed decisions can be made to support the conservation of NZFT. [ABSTRACT FROM AUTHOR]

Roseate Tern Sterna dougallii is a rare to uncommon resident and migrant species in Greater Sundas, with only a handful records in Java. On 24 May 2021, a nest containing a single egg of the species was found in Karang Ketel islet, Karimunjawa Islands and constitute the first breeding record of Roseate Tern in the area, filling the breeding information gap of the species in Java for about 80 years since it first reported. Follow up surveys after the findings carried out for three consecutive years from May 2021--June 2023, reveals the species regularly breed in three locations, i.e., Karang Ketel islet, Karang Kapal islet, and Krakal Besar I. Breeding recorded from May to August, with only small colony of 2-20 birds present. [ABSTRACT FROM AUTHOR]

The New Zealand storm petrel (NZSP; Fregetta maoriana), thought to be extinct for over 150 years, was rediscovered in 2003. In 2013, a single NZSP breeding population was identified on Te Hauturu-o-Toi (Little Barrier Island) in the Hauraki Gulf off the east coast of Aotearoa New Zealand's North Island. Expeditions in 2021 to the Far North of New Zealand identified numerous NZSP at-sea over 300 km from Te Hauturu-o-Toi, suggesting that another breeding colony may exist. Blood samples collected from NZSP in the Hauraki Gulf and the Far North were used to generate genomic data. These data were analysed to investigate if individuals from the Far North are genetically differentiated from NZSP from the Hauraki Gulf, and if any individuals from the two locations are close relatives. Analyses revealed that NZSP from the Far North and Hauraki Gulf are not genetically distinct, and possible second-degree relatives were identified between the locations. Genetic diversity estimates indicated low population diversity levels and low effective population size estimates. These results suggest that Te Hauturu-o-Toi may be the only NZSP breeding colony, and the Far North represents a foraging location for NZSP. Sex bias fluctuates through the year but is similar in the two locations, also supporting a lack of population structure and indicating little foraging location bias between the sexes. Further research is needed to confirm whether highly connected or recently established colonies exist. These results highlight the extinction risk for NZSP and the importance of conservation efforts on Te Hauturu-o-Toi. [ABSTRACT FROM AUTHOR]

This study investigated the feathers' composition of South polar skua (Stercorarius maccormicki) using WDXRF, evaluating the concentration of essential and non-essential elements in the feathers, and dividing it into rachis and barb parts. We collected South polar skuas feathers from Hennequin Point, King George Island, South Shetland, Antarctic Peninsula in January of 2013. Our results show that 18 elements were observed in the composition of the feathers, with a different concentration between the rachis and barbs, qualitatively and quantitatively. Only 3 elements observed were classified as non-essentials but still mostly elements do not have a function described in the literature to the feathers. According to our knowledge, this is the first study that uses this technique to evaluate the concentration of different elements in the feathers. The findings of this study highlight the use of alternative techniques to biomonitoring elements in the ecosystem and bring baseline information for future studies. [ABSTRACT FROM AUTHOR]

Density-dependent competition for food influences the foraging behaviour and demography of colonial animals, but how this influence varies across a species’ latitudinal range is poorly understood. Here we used satellite tracking from 21 Northern Gannet Morus bassanus colonies (39% of colonies worldwide, supporting 73% of the global population) during chick-rearing to test how foraging trip characteristics (distance and duration) covary with colony size (138–60 953 breeding pairs) and latitude across 89% of their latitudinal range (46.81–71.23° N). Tracking data for 1118 individuals showed that foraging trip duration and maximum distance both increased with square-root colony size. Foraging effort also varied between years for the same colony, consistent with a link to environmental variability. Trip duration and maximum distance also decreased with latitude, after controlling for colony size. Our results are consistent with density-dependent reduction in prey availability influencing colony size and reveal reduced competition at the poleward range margin. This provides a mechanism for rapid population growth at northern colonies and, therefore, a poleward shift in response to environmental change. Further work is required to understand when and how colonial animals deplete nearby prey, along with the positive and negative effects of social foraging behaviour.

Bio‐logging has revealed much about high‐latitude seabird migratory strategies, but migratory behaviour in tropical species may differ, with implications for understanding nutrient deposition. Here we use combined light‐level and saltwater immersion loggers to study the year‐round movement behaviour of adult red‐footed boobies Sula sula rubripes from the Chagos Archipelago, tropical Indian Ocean, to assess migratory movements and estimate nutrient deposition rates based on the number of days they spent ashore. Light levels suggest that red‐footed boobies are resident in the Chagos Archipelago year‐round, although there are large latitudinal errors this close to the equator. Immersion data also indicate residency with tracked birds returning to land every one or two days. Spending an average of 79.86 ± 2.80 days and 280.84 ± 2.64 nights per year on land allows us to estimate that the 21 670 pairs of red‐footed boobies deposit 37.34 ± 0.56 tonnes year−1 of guano‐derived nitrogen throughout the archipelago. Our findings have implications for tropical seabird conservation and phylogenetics, as well as for assessing the impact of seabird nutrients on coral reef ecosystems.

Abstract As global heating and other anthropogenic influences alter tropical marine environments, it is unclear how marine bird populations will be impacted and whether their current roles in tropical marine ecosystems will change. Although marine birds roost and breed on tropical islands in large numbers, the direct trophic interactions between these birds and their prey across the tropics are poorly documented. We present a first framework for evaluating the dependence on and contributions of marine birds to tropical coral reef ecosystems and use it to examine the evidence for different kinds of interaction, focusing primarily on avian diets. We found 34 publications between 1967 and 2023 that presented a total of 111 data sets with enough detail for quantitative dietary analysis of tropical marine birds. Only two bird species out of 37 (5.4%) had diets of >50% coral reef fishes and only one, the Pacific Reef Egret, appeared to depend almost entirely on reef‐based production. Marine birds are also prey for other marine organisms, but insufficient data are available for quantitative analysis. Evidence for indirect effects of birds in tropical marine environments is stronger than for direct dependence on coral reefs, particularly in relation to nutrient concentration and the fertilisation impacts of guano on corals. Dispersal of propagules (e.g. seeds, spores, invertebrate eggs) by bathing, drinking, resting or foraging birds is under‐studied and poorly documented. Although the degradation of coral reefs appears unlikely to have a significant direct impact on food availability for most marine bird populations, indirect effects involving marine birds may be disrupted by global environmental change.

The common murre (Uria aalge) is a species of seabird particularly vulnerable to several environmental stressors, including parasitic infection and oil contamination. However, the molecular response to these stressors is severely understudied. This study investigated the common murre’s transcriptomic responses to these stressors. Blood samples were collected from common murres undergoing rehabilitation at International Bird Rescue in Fairfield, CA. Total RNA was extracted from these samples, followed by library preparation and Illumina sequencing to generate whole transcriptome data. Differential gene expression analysis was conducted using DeSeq2 to identify genes significantly altered in response to oil contamination and parasitic infection. Differential gene expression analysis revealed 194 genes shared between oil-contaminated and infected birds, including key immune-related genes, such as ANXA2, LY96, and LY86. These genes play vital roles in mediating the production of pro-inflammatory cytokines. Gene Set Enrichment Analysis indicated significant alterations in stress, immune, and inflammatory responses, with additional lipid metabolism changes in contaminated birds. Our findings highlight the detrimental effects that these stressors have on wild birds. These findings suggest a generalized stress response and specific metabolic adaptations to oil exposure, providing insights for seabird conservation.

Abstract Background Ecological segregation allows populations to reduce competition and coexist in sympatry. Using as model organisms two closely related gadfly petrels endemic to the Madeira archipelago and breeding with a two month allochrony, we investigated how movement and foraging preferences shape ecological segregation in sympatric species. We tested the hypothesis that the breeding allochrony is underpinned by foraging niche segregation. Additionally, we investigated whether our data supported the hypothesis that allochrony is driven by species-specific adaptations to different windscapes. Methods We present contemporaneous tracking and stable isotopes datasets for Zino’s (Pterodroma madeira) and Desertas (Pterodroma deserta) petrels. We quantified the year-round distribution of the petrels, characterised their isotopic niches and quantified their habitat preferences using machine learning (boosted regression trees). Hidden-Markov-models were used to investigate the effect of wind on the central-place movement speed, and a simulation framework was developed to investigate whether each species breeds at times when the windscape is most favourable to sustain their trips. Results Despite substantial spatial overlap throughout the year, the petrels exhibited diverging isotopic niches and habitat preferences during breeding. Both species used a vast pelagic region in the North Atlantic, but targeted two different mesopelagic ecoregions and showed a preference for habitats mostly differing in sea surface temperature values. Based on our simulation framework, we found that both species would perform trips of similar speed during the other species’ breeding season. Conclusions The different breeding schedules between the species are underpinned by differences in foraging habitat preferences and adaptation to the local environment, rather than to the windscape. Nevertheless, the larger Desertas petrels exploited significantly windier conditions, potentially unsustainable for the smaller Zino’s petrels. Furthermore, due to larger mass and likely higher fasting endurance, Desertas petrels engaged in central-place-foraging movements that covered more ground and lasted longer than those of Zino’s petrels. Ultimately, patterns of ecological segregation in sympatric seabirds are shaped by a complex interplay between foraging and movement ecology, where morphology, foraging trip regulation and fasting endurance have an important– yet poorly understood– role.

The black skimmer (Rynchops niger) is a state-threatened, colonially nesting seabird in Florida, USA. Conservation threats include habitat alteration, human disturbances, severe weather, and predation. During nest monitoring (May–September, 2020–2022), black skimmer juveniles at colonies on Fort Myers Beach and Marco Island, Florida, had polyarthritis and died or were euthanized due to severe illness. Similarly-aged skimmers from geographically distant (considered unaffected) colonies were evaluated for comparison (2021–2023). We documented field, clinical, radiographical, and pathological findings to characterize disease and purported pathogenesis. The majority were lame and lethargic, in poor nutritional condition, and dehydrated. Additionally, 8/23 of the skimmers with dermatitis and arthritis from affected colonies also had penetrating sandspurs associated with skin ulceration, scabbing, and/or hemorrhage. The affected joints were often in limbs (interphalangeal and hock; less commonly stifle, elbow, carpus). A postmortem evaluation and bacteriology revealed Staphylococcal aureus-associated dermatitis, arthritis, tenosynovitis, and/or osteomyelitis in 21/22 of the juvenile skimmers from southwestern nest colonies. Staphylococcus aureus dissemination to internal organs occurred in 10/13 of the skimmers tested. Among skimmers evaluated from distant colonies, 5/10 that were examined histologically had skin crusting and inflammation but lacked arthritis. Occasional coinfections were documented (e.g., West Nile virus, Gram-negative bacilli). The results suggest that staphylococcal joint disease originated from sandspur-induced skin damage, followed by hematogenous dissemination to the joints and, occasionally, the internal organs. Additional nest sites should be tested to evaluate disease risk and potentially contributing environmental factors. We recommend that site managers employ techniques that reduce the risk of skimmer interactions with sandspurs.

Animals that co‐occur in a region (sympatry) may share the same environment (syntopy), and niche differentiation is expected among closely related species competing for resources. The masked booby (Sula dactylatra) and smaller congeneric red‐footed booby (Sula sula) share breeding grounds. In addition to the inter‐specific size difference, females of both species are also larger than the respective males (reversed sexual size dimorphism). Although both boobies consume similar prey, sometimes in mixed‐species flocks, each species and sex may specialize in terms of their diet or foraging habitats. We examined inter‐ and intra‐specific differences in isotopic values (δ13C and δ15N) in these pelagically feeding booby species during the incubation period at Clarion Island, Mexico, to quantify the degrees of inter‐ and intra‐specific niche partitioning throughout the annual cycle. During incubation, both species preyed mainly on flyingfish and squid, but masked boobies had heavier food loads than red‐footed boobies. There was no overlap in isotopic niches between masked and red‐footed boobies during breeding (determined from whole blood), but there was slight overlap during the non‐breeding period (determined from body feathers). Female masked boobies had a higher trophic position than conspecific males during breeding; however, no such pattern was detected in red‐footed boobies. These results provide evidence of inter‐ and intra‐specific niche partitioning in these tropical seabird species, particularly during the breeding period and in the more‐dimorphic species. Our results suggest that these closely related species use different strategies to cope with the same tropical marine environment. [ABSTRACT FROM AUTHOR]

In this study, Little Tern (Sternula albifrons) populations in Taiwan are examined based on two different types of data: mitochondrial control region DNA sequences and double digest restriction-site associated DNA (ddRAD) sequencing data. Feather samples were collected from 59 chicks across four known breeding colonies located on the eastern (Yilan and Hualien) and western (Penghu and Changhua) coasts of Taiwan. The results obtained are consistent in analyses and do not cluster into two geographical groups with respect to the eastern and western Taiwan. Furthermore, AMOVA analyses and pairwise ΦST/FST estimations based on both types of data reveal little to no differentiation among populations and between groups. The findings of this study suggest high population connectivity among Taiwan's breeding colonies. Additionally, control region sequences of Taiwan's Little Terns are compiled with those from Japan deposited in GenBank to compare genetic diversity and examine for phylogeographic breaks that could shape the diversity pattern of the species in eastern Asia. The resulting haplotype network does not clearly separate Taiwanese and Japanese populations, but the three most common haplotypes are prevalent for mainland Japan, Okinawa, and Taiwan. Little Tern populations may be frequently connected, but with some restrictions on gene flow causing moderate to great differentiation among the three. This is further supported by AMOVA analyses, pairwise ΦST estimations, and pattern of positive yet significant isolation by distance. [ABSTRACT FROM AUTHOR]

In the tuna purse seine fishery, seiners spend a considerable amount of time detecting objects such as seabirds, for which radar is a very efficient method. In this study, we present a radar image seabird identification method that can calculate the number of clusters, the area of seabird clusters, and the activity level of seabird clusters. We used a fishing vessel's radar to collect information on seabird groups within 29,632 km of the vessel and calculated a spatial clustering of the seabird-echoes. Generalized additive mixed models (GAMM) were used to investigate the relationship between drifting fish aggregating devices (FADs) and seabird dynamics in the Republic of Kiribati. The findings indicate that FAD variables affected seabird behavior. The random effects on cluster number, cluster area, and cluster ability were 3.27, 17.41, and −0.17, respectively. Then, we compared the radar image information that was calculated. The bird cluster around drifting FADs was found to be more concentrated and denser than in areas without FADs, with a lower level of activity observed. The longitude of 165°E had the highest number of bird clusters and the greatest area inhabited by birds, but these decreased to the east. However, model 3 showed that the minimum value of seabird cluster activity level occurred around 165°E and increased to the east. [ABSTRACT FROM AUTHOR]

Repeated use of a winning foraging strategy can be profitable when individuals use memory to return to successful food patches. However, in environments where patches are unpredictable, variable foraging behaviour may be more profitable. To test this idea, we explored how individual variation in foraging trip characteristics impacts breeding success in black-legged kittiwakes, Rissa tridactyla , on Middleton Island, Alaska, U.S.A., during a period of highly variable environmental conditions, the largest recorded marine heatwave. As anticipated, foraging trip characteristics were highly variable, within and between years and individuals. While characteristics of foraging trips alone did not influence annual breeding success, both age and variance in those trip characteristics explained variation in breeding success. Specifically, individuals with smaller variance in foraging trip characteristics among trips were more likely to fledge a chick. There was a maximum distance threshold in foraging implying that individuals searched within a restricted area, increasing foraging time rather than distance when searching was not profitable, and providing additional support for the idea that kittiwakes are most successful when foraging in known areas rather than exploring new areas. The Pacific Decadal Oscillation, which is associated with large scale shifts between cold and warm ocean climate and ecosystem regimes in the region, impacted breeding success but did not change foraging behaviour. However, mean breeding success decreased as mean time spent resting and in area-restricted search (intensive search) on foraging trips during incubation increased. Based on nearly a decade of data, we conclude that smaller variability in behaviour, even during challenging foraging conditions, enhances breeding success. As climate change and marine heatwaves continue to increase in intensity, individuals more variable in foraging behaviour may be unable to compensate. • Individuals with less variation in foraging behaviour were more likely to fledge a chick. • There was evidence of a maximum distance threshold in foraging. • Pacific Decadal Oscillation impacted breeding success but not foraging behaviour. [ABSTRACT FROM AUTHOR]