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The common loon, a beloved symbol of the northern region, is experiencing a decline in its breeding range. This decline is attributed to climate change, specifically increased rainfall and temperature in July, which leads to decreased water clarity in lakes. The reduced water clarity hinders the feeding of loon chicks by their parents, resulting in fewer offspring and a shrinking population. The situation is predicted to worsen in the future with further increases in temperature and rainfall. [Extracted from the article]

Climate change has myriad impacts on ecosystems, but the mechanisms by which it affects individual species can be difficult to pinpoint. One strategy to discover such mechanisms is to identify a specific ecological factor related to survival or reproduction and determine how that factor is affected by climate. Here we used Landsat imagery to calculate water clarity for 127 lakes in northern Wisconsin from 1995 to 2021 and thus investigate the effect of clarity on the body condition of an aquatic visual predator, the common loon (Gavia immer). In addition, we examined rainfall and temperature as potential predictors of water clarity. Body mass tracked July water clarity strongly in loon chicks, which grow chiefly in that month, but weakly in adult males and females. Long‐term mean water clarity was negatively related to chick mass but positively related to adult male mass, suggesting that loons foraging in generally clear lakes enjoy good foraging conditions in the long run but might be sensitive to perturbations in clarity during chick‐rearing. Finally, chick mass was positively related to the density of docks, perhaps because angling removes large fishes and thus boosts the abundance of the small fishes on which chicks depend. Water clarity itself declined strongly from 1995 to 2021, was negatively related to July rainfall, and was positively related to July air temperature. Our findings identified both long‐term and short‐term water clarity as strong predictors of loon foraging efficiency, and suggest that climate change, through water clarity, impacts freshwater ecosystems profoundly. Moreover, our results identified the recent decrease in water clarity as a likely cause of population decline in common loons. [ABSTRACT FROM AUTHOR]

Age often indicates phenotypic quality, ecological experience or social status in animals. Consequently, behavioural signals in territorial animals that accurately convey age to potential mates or rivals might provide useful information for both signaller and receiver about the likelihood of aggression. We tested whether male territorial yodels convey information about age in the common loon, Gavia immer. Using a sample of male loons of known age, we found that the dominant frequency of Fintro3, a dominant syllable in the beginning sequence of a male yodel, increases strongly with age, but we were unable to replicate an earlier finding linking Fintro3 to body mass. We hypothesize that older male loons, which yodel more often than young males, might do so as a means to advertise their age and higher likelihood of aggression to potential rivals. • We tested whether male yodels convey information about age in common loons. • Dominant frequency of a dominant syllable (Fintro3) in male yodels increased with age. • Fintro3 was found previously to decrease with body mass, but not in our study. • Age may have a more significant effect on yodel acoustics than body mass. • Older males may yodel more often to advertise their age and likelihood of aggression. [ABSTRACT FROM AUTHOR]

Common loon (Gavia immer (Brünnich, 1764)) foraging patterns and the relative importance of cisco (Coregonus artedi Lesueur, 1818) in the diets of loons were evaluated for the Whitefish Chain of Lakes, a set of coldwater cisco refuge lakes in Minnesota, USA. Environmental DNA metabarcoding of loon fecal samples detected 15 fish species. Yellow perch (Perca flavescens (Mitchill, 1814)), mimic shiner (Notropis volucellus (Cope, 1865)), and cisco were the most prominent prey detected across the study lakes. We observed a shift in fish species consumed, with increases in detections of mimic shiner and cisco DNA among loon fecal samples collected in August and September. In some locations, suitable oxythermal habitat became restricted throughout the summer, forcing cisco into surface waters, which potentially increased their vulnerability to loon predation. Conversely, large foraging aggregations of loons were observed during late summer through fall at locations with ample oxythermal habitat and abundant cisco populations. We hypothesize that cisco were sought by loons as a high-calorie prey resource prior to migration. Conservation efforts directed at preserving water quality in important cisco refuge lakes are likely to benefit common loons through enhancement of both the forage base, for resident and migrating birds, and breeding habitat suitability. [ABSTRACT FROM AUTHOR]

Most studies of vertebrate breeding success have been unable to pinpoint the cause for a simple and almost universal pattern: its steady increase during an animal's lifetime. Yet potential causes of increased breeding success have profound implications for the evolution of reproductive behaviour. An age-related increase might come about through (1) higher breeding investment by older animals, (2) breeding improvement through learning, (3) better reproductive coordination between familiar mates or (4) accumulated benefits of site familiarity. We used mixed models to investigate age-related predictors of hatching and fledging success in a population of common loons, Gavia immer , that contained many known-age breeders and has been under continuous study for 30 years. Hatching success of breeding pairs increased between the female's first and second years on territory but did not increase with further female experience. In contrast, pair hatching success increased in proportion to the cube root of the males' residency on a territory, a pattern that persisted beyond 15 years. Hatching date was earlier for pairs that had spent at least 1 year together and in which the female was young but had spent at least one prior year on the territory. Fledging rate of hatched young was greater among pairs that nested early but decreased with female age, an apparent indication of female reproductive senescence. Overall, breeding pairs fledged more young when the breeding male had many years of experience on the territory and the breeding female had been on territory for at least 1 year and was of moderate age. Our findings highlight the persistent influence of both site familiarity and chronological age on reproductive fitness. • We examined attributes of male and female loons that affect reproductive success (RS). • Territory familiarity improved female RS only between the first and second years. • Age negatively affected RS in young and old females but made no difference in males. • Males showed increases in RS for over 15 years when they remained on familiar territory. • Mate familiarity had little impact on RS, but pairs with ≥1 year together nested earlier. [ABSTRACT FROM AUTHOR]

Understanding how risk factors affect populations across their annual cycle is a major challenge for conserving migratory birds. For example, disease outbreaks may happen on the breeding grounds, the wintering grounds, or during migration and are expected to accelerate under climate change. The ability to identify the geographic origins of impacted individuals, especially outside of breeding areas, might make it possible to predict demographic trends and inform conservation decision-making. However, such an effort is made more challenging by the degraded state of carcasses and resulting low quality of DNA available. Here, we describe a rapid and low-cost approach for identifying the origins of birds sampled across their annual cycle that is robust even when DNA quality is poor. We illustrate the approach in the common loon (Gavia immer), an iconic migratory aquatic bird that is under increasing threat on both its breeding and wintering areas. Using 300 samples collected from across the breeding range, we develop a panel of 158 single-nucleotide polymorphisms (SNP) loci with divergent allele frequencies across six genetic subpopulations. We use this SNP panel to identify the breeding grounds for 142 live nonbreeding individuals and carcasses. For example, genetic assignment of loons sampled during botulism outbreaks in parts of the Great Lakes provides evidence for the significant role the lakes play as migratory stopover areas for loons that breed across wide swaths of Canada, and highlights the vulnerability of a large segment of the breeding population to botulism outbreaks that are occurring in the Great Lakes with increasing frequency. Our results illustrate that the use of SNP panels to identify breeding origins of carcasses collected during the nonbreeding season can improve our understanding of the population-specific impacts of mortality from disease and anthropogenic stressors, ultimately allowing more effective management.

Monitoring species to better understand their status, ecology, and management needs is a major expense for agencies tasked with biodiversity conservation. Community science data have the potential to improve monitoring for minimal cost, given appropriate analytical frameworks. We describe a framework for integrating data from the eBird community science platform with agency‐collected monitoring data using a multistate occupancy model. Our model accounts for the structural differences across datasets and allows for estimation of both occupancy and breeding probabilities. The framework was applied to Common Loons (Gavia immer) in Washington State. A total of 766 sites had observation effort, of which 713 sites had only eBird effort, 26 sites had only Washington Department of Fish and Wildlife (WDFW) effort, and 27 sites had both. We predicted that the probability of occupancy was only 0.07 (95% Bayesian credible interval, BCI = 0.02–0.51) at the 2324 sites in our sampling frame, though the probability that Common Loons were breeding at occupied sites was 0.95 (95% BCI = 0.71–1.00). We found that probability of occupancy was positively related to waterbody size (probability of a positive effect = 0.88) and negatively related to an index of human influence (probability of a negative effect = 0.94). We found that probability of breeding at occupied sites was positively related to tree canopy cover (0.86), negatively related to elevation (0.99), and negatively related to barren, scrub/shrub, and herbaceous land cover (0.98). We found that state agency biologists were 16 times more likely to detect breeding Common Loons at a site than were eBird users (0.94, 95% BCI = 0.78–0.99 for agency biologists vs. 0.08, 95% BCI = 0.06–0.10 for eBird users). However, the amount of effort expended by eBird users meant that they confirmed Common Loons at 94 sites while agency biologists confirmed them at just 24 sites, although evidence of reproduction was only contributed by agency biologists. Our results provide a better understanding of the distribution of Common Loons in Washington, while further demonstrating that community science data can be a valuable complement to agency‐collected data, if appropriate frameworks are developed to integrate these data sources. [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.)

COVER PHOTO: In this photograph, a male common loon carries his four‐day‐old chick on Muskellunge Lake in northern Wisconsin, USA during a moment of repose. As described in Piper et al. in the related Ecology article (https://doi.org/10.1002/ecy.4291), higher rainfall over the past quarter century has caused a reduction in water clarity in the region. Low water clarity, in turn, hinders foraging by loons, which are visual predators, and has resulted in a substantial loss of chick mass and higher chick mortality. Photo taken by Linda Grenzer on June 17, 2014. Additional images appear in this issue of the Bulletin's Photo Gallery.. [Extracted from the article]

Abstract Understanding how risk factors affect populations across their annual cycle is a major challenge for conserving migratory birds. For example, disease outbreaks may happen on the breeding grounds, the wintering grounds, or during migration and are expected to accelerate under climate change. The ability to identify the geographic origins of impacted individuals, especially outside of breeding areas, might make it possible to predict demographic trends and inform conservation decision‐making. However, such an effort is made more challenging by the degraded state of carcasses and resulting low quality of DNA available. Here, we describe a rapid and low‐cost approach for identifying the origins of birds sampled across their annual cycle that is robust even when DNA quality is poor. We illustrate the approach in the common loon (Gavia immer), an iconic migratory aquatic bird that is under increasing threat on both its breeding and wintering areas. Using 300 samples collected from across the breeding range, we develop a panel of 158 single‐nucleotide polymorphisms (SNP) loci with divergent allele frequencies across six genetic subpopulations. We use this SNP panel to identify the breeding grounds for 142 live nonbreeding individuals and carcasses. For example, genetic assignment of loons sampled during botulism outbreaks in parts of the Great Lakes provides evidence for the significant role the lakes play as migratory stopover areas for loons that breed across wide swaths of Canada, and highlights the vulnerability of a large segment of the breeding population to botulism outbreaks that are occurring in the Great Lakes with increasing frequency. Our results illustrate that the use of SNP panels to identify breeding origins of carcasses collected during the nonbreeding season can improve our understanding of the population‐specific impacts of mortality from disease and anthropogenic stressors, ultimately allowing more effective management.

Common Loons (Gavia immer) winter primarily in marine coastal areas and utilize a forage base that is poorly defined, especially for offshore areas. Information on dive activity is needed for describing foraging strategies and for inferring prey distribution. Archival geolocator tags were used to determine the wintering locations and dive characteristics of adult Common Loons captured and marked on breeding lakes in Minnesota, Wisconsin, and the Upper Peninsula of Michigan. Among loons that completed fall migration, most wintered in the Gulf of Mexico, with smaller proportions wintering off the southern Atlantic Coast or impoundments in the southeastern United States. Adult Common Loons tended to occupy offshore areas of the Gulf of Mexico and the Atlantic Ocean and, on average, spent about 60% of daylight hours foraging. Dive depths were as deep as 50 m (Gulf of Mexico) and dive characteristics indicated that loons were primarily foraging on benthic prey. Total dive duration, time at maximum depth, and post-dive surface intervals increased with dive depths among wintering Common Loons. Our results are expected to contribute to the understanding of the wintering ecology of Common Loons and be useful in informing regional and national conservation planning efforts.

Aggression between adult Common Loons (Gavia immer) occurs frequently during the breeding season. In the past, it was suspected that most instances of intraspecific aggression took place between adult males. However, recent reports from the field suggest that female adult loons also participate in these battles. Postmortem investigation has shown that the damage incurred during these battles can range from incidental to fatal injuries. Sternal punctures are the most lasting evidence of this trauma and can serve as long-term records. Nearly half (46%, n = 268/574) of the loons received at Tufts Wildlife Clinic for postmortem from 2007 to 2015 were found to have sternal punctures. We conducted a focused analysis of the sternal punctures of 102 of these adult loons (49 female and 53 male) and found no significant difference in the number, distribution, or severity of sternal punctures between male and female loons. This suggests that the frequency and intensity of aggressive physical contests are remarkably similar between sexes and that there is no gender difference in the severity of these battles. Female Common Loons participate in lethal combats as often as their male counterparts. These findings provide an opportunity to better understand and study the biological or behavioral drivers of this aggression that is prevalent among both male and female Common Loons. [ABSTRACT FROM AUTHOR]

Common Loons (Gavia immer) wintering in watercourses of Barataria Bay, in coastal Louisiana were sampled in 2011–2014 following the Deepwater Horizon oil spill of 2010. Blood samples were analyzed for stable isotope ratios of carbon, nitrogen and sulfur as proxies for habitat use and diet in order to expand our understanding of the trophic position of wintering loons. The δ13C and δ34S values indicated that these Common Loons feed in coastal estuarine habitats. Trophic position was estimated indirectly by comparing loon stable isotope ratios with those of Brown Pelicans (Pelecanus occidentalis), a known piscivore, sampled concurrently in 2014. The isotopic signatures of the two species were not significantly different; this is consistent with the hypothesis that both species foraged primarily in coastal estuarine habitats and mainly as piscivores. No significant differences were found between subadult and adult Common Loons with respect to isotopic signatures, suggesting similar habitat usage and diet. Adults weighed more and were in better body condition than subadults. Stable isotope composition and body condition were not significantly related. Using a parallel data set of polycyclic aromatic hydrocarbons (PAH, an indicator or oil contamination) in the blood of the same loons, there was no significant relationship between PAH contamination and stable isotopic composition. Therefore, PAH-contamination could not be linked to a distinctive foraging habitat or diet. [ABSTRACT FROM AUTHOR]

Animals that show aggression often risk injury and incur steep energetic costs. Thus, aggression should occur at such times and towards such opponents as to maximize fitness. We tested hypotheses predicting adaptive territorial aggression in the common loon, a species in which ease of observation of territory owners and floaters (prebreeders) seeking to evict them provide a rare window onto owner-floater competition. As predicted, older, more competitive floaters (4-year-olds and upwards) tended to intrude into territories that had produced chicks the previous year (and, hence, were of high quality). Older floaters also showed predicted increases in aggression and territorial yodeling, and a lower rate of submissive behaviors than younger floaters. Floaters of all ages intruded more often than neighboring territory owners, as predicted, but tended to avoid territories with chicks. For their part, owners yodeled more often and behaved more aggressively during chick-rearing, although yodels peaked in frequency 2 weeks before aggression, suggesting that males with young chicks yodel to discourage intrusions, but employ aggression to protect older chicks. Territory owners showed the predicted higher rates of aggression and yodeling towards older, more dangerous floaters than towards young, submissive ones. However, territorial pairs did not treat floaters more aggressively than neighbors, overall. Moreover, owners showed no spike in aggression nor yodeling following a year with chicks, perhaps to avoid providing social information to floaters that use chicks as social information to target territories for eviction. Significance statement: Floaters are young nonbreeding individuals that compete with territory owners and are future breeders. Yet floaters are difficult to study because they are mostly unmarked, nomadic individuals. Owing to extensive efforts to capture juvenile common loons, we have established a large population of marked floaters in this species. Hence, loons offer a rare window to investigate efforts of floaters to settle on breeding territories. We found that older floaters (4 to 8 years), which are capable of evicting owners from their territories, target high-quality territories for their intrusions, show more aggression, and show less submissiveness during intrusions than do young floaters. We further discovered that territory owners are more aggressive towards older, more dangerous floaters. Our findings show that territory owners recognize the degree of threat posed by each floater and treat each floater differently on that basis. [ABSTRACT FROM AUTHOR]

Little is known about the behaviour of Common Loon (Gavia immer) during the critical overwintering period, let alone the behaviour of the small, but increasing number of loons that overwinter on freshwater lakes in North America. We examined the diurnal time-activity budgets of Common Loon overwintering on a large reservoir in northwest South Carolina between 2018 and 2020. Similar to previous studies of breeding individuals and individuals that overwinter in marine waters, loons (n = 132) overwintering on this reservoir spent most of their time (52%) foraging. However, we found distinct differences in the activity budgets of individuals associated with their degree of sociality. Solitary birds (individuals spending 0-20% of time within 20 m of conspecifics) spent significantly more time foraging than did those that were either loosely-social (>20-<70% of time within 20 m of conspecifics) or strongly-social (70-100% of time). Although solitary loons made as many foraging dives as social birds, their dives were much longer, likely reflecting dives for larger predatory fish. In contrast, social individuals made much shorter, shallower dives, often foraging on shallower baitfish that they appear to pursue to the water surface and consume collectively. Such findings add to our understanding of loon winter behaviour and raise interesting questions regarding social behaviour and the short- and long-term trade-offs associated with social foraging in this species. [ABSTRACT FROM AUTHOR]

Common Loons (Gavia immer) are migratory, piscivorous waterbirds that exhibit high wintering site fidelity. Forty-three immature loons were captured in 2013, 2015–2017, in southwest coastal Louisiana, an area moderately to heavily exposed to oil from the Deepwater Horizon oil spill of 2010. We analyzed blood from loons to examine associations between exposure to polycyclic aromatic hydrocarbons (PAH) and 25 blood analytes. Overall, 60% (26/43) of the loons had detectable concentrations of PAHs, with an average concentration of 55.3 ± 10.3 ng/g. After controlling for body weight, loons with detectable blood PAHs had higher concentrations of absolute eosinophils, lymphocytes, or monocytes compared to loons without PAH exposure. This study provides evidence of subclinical inflammation in Common Loons wintering in coastal Louisiana and identifies exposure to PAHs as a stressor, raising concern for potential impaired fitness in this population resulting from low-level exposure to PAHs. [ABSTRACT FROM AUTHOR]

Identification of geographic linkages among breeding, migratory and wintering common loon Gavia immer populations is needed to inform regional and national conservation planning efforts and compensation of loons lost during marine oil spill events. Satellite telemetry and archival geolocator tags were used to determine the migration patterns and wintering locations of breeding adult and young of the year juvenile common loons captured and marked on lakes in Minnesota, Wisconsin and Michigan. Adult loons typically traveled from breeding lakes, often via larger staging lakes, to the Great Lakes (primarily Lake Michigan) and then on to wintering areas. Most radiomarked juvenile common loons utilized natal lakes or local lakes through mid‐November. Subsequently, the first fall migration of juvenile loons was generally initiated later, and more direct and quicker to wintering areas relative to adults. Among adult (n = 103) and juvenile (n = 23) loons that completed fall migration, most wintered in the Gulf of Mexico (GOM), with smaller proportions wintering off the southern Atlantic Coast or impoundments in the southeastern United States. Spring migration of adults to breeding lakes was less prolonged than fall migration, with adult male loons tending to depart wintering areas earlier than adult females. Juvenile common loons migrated during their first spring from wintering sites in the GOM to summer in the Gulf of St Lawrence/Nova Scotia Coastal region. Juvenile mortality was largely linked to parasitic infection and emaciation; spring appeared to be a survival bottleneck among juvenile loons monitored in our study. Our results identify several areas where common loon conservation efforts could be directed to protect key habitats and minimize stressors during the non‐breeding period. [ABSTRACT FROM AUTHOR]

The article presents a summary of the activities of the Kansas Bird Record Committee for the year 2020 including the number of reports evaluated, resolution of previous year records, and records that were not accepted.

We investigated both social and foraging plasticity in a population of Common Loons (Gavia immer) that overwinter inland on Lake Jocassee Reservoir, South Carolina, using transects and time-activity budgets from 4 January to 10 March 2017. Loons were observed as either solitary individuals (65%) or in groups (35%, i.e., within ≤5 body lengths of another loon). Loons were more social (i.e., in groups) on transects with a river mouth (40.9% ± 7.1) than on transects without a river mouth (24.2% ± 5.4). The mean (± SE) dive duration for solitary loons was 71.3 ± 7.7 s (n = 46, range 15–219 s) and several dives exceeded 2 min (22.2%, 10/46). In contrast, 15 foraging flocks were characterized by numerous shallow dives of <20 s. The mean group size (± SE) was 6.9 ± 0.8 individuals and group foraging bouts lasted 8.3 ± 1.2 min. In addition, Horned Grebes (Podiceps auritus) and Ring-billed Gulls (Larus delawarensis) joined loons forming multispecies foraging flocks, 26.7% and 13.3% of the time, respectively. These data indicate Common Loons wintering at Lake Jocassee are social and exhibit foraging plasticity. [ABSTRACT FROM AUTHOR]

Together climate and land‐use change play a crucial role in determining species distribution and abundance, but measuring the simultaneous impacts of these processes on current and future population trajectories is challenging due to time lags, interactive effects and data limitations. Most approaches that relate multiple global change drivers to population changes have been based on occurrence or count data alone.We leveraged three long‐term (1995–2019) datasets to develop a coupled integrated population model‐Bayesian population viability analysis (IPM‐BPVA) to project future survival and reproductive success for common loons Gavia immer in northern Wisconsin, USA, by explicitly linking vital rates to changes in climate and land use.The winter North Atlantic Oscillation (NAO), a broad‐scale climate index, immediately preceding the breeding season and annual changes in developed land cover within breeding areas both had strongly negative influences on adult survival. Local summer rainfall was negatively related to fecundity, though this relationship was mediated by a lagged interaction with the winter NAO, suggesting a compensatory population‐level response to climate variability.We compared population viability under 12 future scenarios of annual land‐use change, precipitation and NAO conditions. Under all scenarios, the loon population was expected to decline, yet the steepest declines were projected under positive NAO trends, as anticipated with ongoing climate change. Thus, loons breeding in the northern United States are likely to remain affected by climatic processes occurring thousands of miles away in the North Atlantic during the non‐breeding period of the annual cycle.Our results reveal that climate and land‐use changes are differentially contributing to loon population declines along the southern edge of their breeding range and will continue to do so despite natural compensatory responses. We also demonstrate that concurrent analysis of multiple data types facilitates deeper understanding of the ecological implications of anthropogenic‐induced change occurring at multiple spatial scales. Our modelling approach can be used to project demographic responses of populations to varying environmental conditions while accounting for multiple sources of uncertainty, an increasingly pressing need in the face of unprecedented global change. [ABSTRACT FROM AUTHOR]

Many species show natal habitat preference induction (NHPI), a behavior in which young adults select habitats similar to those in which they were raised. However, we know little about how NHPI develops in natural systems. Here, we tested for NHPI in juvenile common loons (Gavia immer) that foraged on lakes in the vicinity of their natal lake after fledging. Juveniles visited lakes similar in pH to their natal lakes, and this significant effect persisted after controlling for spatial autocorrelation. On the other hand, juveniles showed no preference for foraging lakes of similar size to their natal one. When lakes were assigned to discrete classes based on size, depth, visibility, and trophic complexity, both juveniles from large lakes and small lakes preferred to visit large, trophically diverse lakes, which contained abundant food. Our results contrast with earlier findings, which show strict preference for lakes similar in size to the natal lake among young adults seeking to settle on a breeding lake. We suggest that NHPI is relaxed for juveniles, presumably because they select lakes that optimize short‐term survival and growth. By characterizing NHPI during a poorly studied life stage, this study illustrates that NHPI can take different forms at different life stages. [ABSTRACT FROM AUTHOR]

9 8 Vermilion Flycatcher (9 lists 38 points) This species is another solid choice to show up in Connecticut. Common Ringed Plover and Violet-green Swallow appeared on but one list each previously. C 44 *~ r 21- 10*4*Qi = i «~4 Nick Bonomo photo Reddish Egret CONNECTICUT'S NEXT BIRDS 13 Violet-green Swallow (4 lists) This swallow is undoubtedly missed due to its similarity to Tree Swallow, which is abundant. By Jory Teltser and Aidan Kiley With an introduction by Nick Bonomo, author Of the last Next Birds project Back in the summer of 2007 several active Connecticut birders attempted to predict (AKA "guess") those species we thought most likely to be added to the state's official list of avifauna, as kept by the Avian Records Committee of Connecticut. [Extracted from the article]

Early studies (1976-1982) of the Drizzle Lake Ecological Reserve on Haida Gwaii, British Columbia focussed on the endemic Giant Threespine Stickleback (Gasterosteus aculeatus) and their predators. These surveys showed daily visits to the small lake (110 ha) by up to 59 adult non-breeding Common Loon (Gavia immer), an important stickleback predator and up to 19 breeding and non-breeding adult Red-throated Loon (Gavia stellata), which leave daily to forage in nearby marine waters. We continued loon surveys for 17 additional years (1983-1989, 2011-2020) and found that aggregations of nonbreeding Common Loons occurred annually on the lake during July with maximum daily numbers of 78-83 individuals in 1987, 2018, and 2020 and a large increase from 2011 to 2020. We did not detect any relationship of these differences with the Pacific Decadal Oscillation but a significant inverse correlation with average wind speed. Average yearly numbers of Redthroated Loons declined by 50% from 1976 to 1989 and have remained low, with lowest numbers (<2) occurring in 2017. Two Red-throated Loon nesting territories on the lake were occupied from 1976 to 1995, with chicks occurring in 24 of 36 nests, but no successful nesting was observed on the lake over the last decade. The relative decline of Red-throated Loon in this reserve is similar to that reported in Arctic and Subarctic surveys of the species in the north Pacific and northern Europe. We discuss the implications for the evolutionary ecology of the sticklebacks and the conservation of the ecological reserve. [ABSTRACT FROM AUTHOR]

Populations of many vertebrates are declining and geographic ranges contracting, largely as a consequence of anthropogenic threats. Many reports of such decline, however, lack the breadth and detail to narrow down its causes. Here we describe population decline in the Common Loon (Gavia immer), a charismatic aquatic bird, based on systematic resighting and measurement of a marked population. During our 27-year investigation, age-adjusted chick mass has fallen by 11%, mortality among young and old chicks has increased by 31% and 82%, respectively, and fledging success has declined by 26%. Meanwhile, the return rate of marked nonbreeders ("floaters") has plunged by 53%, and the adult population overall has declined by 22%. Consistent with the thinning ranks of floaters, the rate of territory eviction has decreased by 52% during the study. Despite the decline in floaters, territory occupancy remains unchanged. However, a matrix model, updated with recent estimates for breeding success, juvenile survival, and senescence, yields a recalculated deterministic population growth rate (λ) of 0.94 for our study population, which suggests that declines in vital rates could lead to a loss of 52% of the current population and a decline of 37% in territory occupancy by 2031. Lack of data on floaters in other upper Midwest and New England loon populations leaves their status in doubt. LAY SUMMARY The adult loon population in northern Wisconsin has declined by 22% over the past 27 years. Numbers of chicks and chick mass have declined significantly. The population of young nonbreeders (floaters) has plummeted by 46%. Despite these steep declines, there has been no measurable drop in the number of territorial pairs. The hidden nature of the Wisconsin decline points out that floater populations can mask major drops in breeding populations and throws into question population trends in other loon populations, whose floater populations are largely unknown. [ABSTRACT FROM AUTHOR]

The common loon (Gavia immer), a top predator in the freshwater food web, has been recognized as an important bioindicator of aquatic mercury (Hg) pollution. Because capturing loons can be difficult, statistical approaches are needed to evaluate the efficiency of Hg monitoring. Using data from 1998 to 2016 collected in New York's Adirondack Park, we calculated the power to detect temporal changes in loon Hg concentrations and fledging success as a function of sampling intensity. There is a tradeoff between the number of lakes per year and the number of years needed to detect a particular rate of change. For example, a 5% year−1 change in Hg concentration could be detected with a sampling effort of either 15 lakes per year for 10 years, or 5 lakes per year for 15 years, given two loons sampled per lake per year. A 2% year−1 change in fledging success could be detected with a sampling effort of either 40 lakes per year for 15 years, or 30 lakes per year for 20 years. We found that more acidic lakes required greater sampling intensity than less acidic lakes for monitoring Hg concentrations but not for fledging success. Power analysis provides a means to optimize the sampling designs for monitoring loon Hg concentrations and reproductive success. This approach is applicable to other monitoring schemes where cost is an issue. [ABSTRACT FROM AUTHOR]

Habitat degradation resulting from anthropogenic activities can threaten wildlife populations. Even wildlife existing in seemingly pristine areas are at risk of airborne pollutants and urban development. The common loon (Gavia immer), a top-trophic level predator in freshwater aquatic ecosystems, has previously experienced detrimental changes in reproductive success as a result of anthropogenic activities. However, long-term studies and large sample sizes are necessary to ascertain the impacts of various anthropogenic activities on this long-lived species. Using a multi-year dataset, we investigated the effects of multiple biotic and abiotic factors on the probability of adult male and female common loon hatching and fledging success. From 1998–2017, we banded individual loons, collected blood samples to assess mercury (Hg) exposure of the birds, and monitored their reproductive success. Adult female loon hatching success was negatively associated with the amount of rainfall received in a given year while fledging success was positively associated with the amount of shoreline development. Adult male loon hatching success was positively associated with the amount of shoreline development and fledging success was negatively associated with the number of other loon pairs on a lake. [ABSTRACT FROM AUTHOR]

Mercury (Hg), a neurotoxic pollutant, can be transported long distances through the atmosphere and deposited in remote areas, threatening aquatic wildlife through methylation and bioaccumulation. Over the last two decades, air quality management has resulted in decreases in Hg emissions from waste incinerators and coal-fired power plants across North America. The common loon (Gavia immer) is an apex predator of the aquatic food web. Long-term monitoring of Hg in loons can help track biological recovery in response to the declines in atmospheric Hg that have been documented in the northeastern USA. To assess spatial patterns and temporal trends in Hg exposure of the common loon in the Adirondack Park of New York State, we analyzed Hg concentrations in loon blood and egg samples from 116 lakes between 1998 and 2016. We found spatially variable Hg concentrations in adult loon blood and feathers across the Park. Loon Hg concentrations (converted to female loon units) increased 5.7% yr−1 from 1998 to 2010 (p = 0.04), and then stabilized at 1.70 mg kg−1 from 2010 to 2016 (p = 0.91), based on 760 observations. Concentrations of Hg in juvenile loons also increased in the early part of the record, stabilizing 2 years before Hg concentrations stabilized in adults. For 52 individual lakes with samples from at least 4 different years, loon Hg increased in 34 lakes and decreased in 18 lakes. Overall, we found a delayed recovery of Hg concentrations in loons, despite recent declines in atmospheric Hg. [ABSTRACT FROM AUTHOR]

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Another report of the Czech Rarities Committee, working under the Czech Society for Ornithology (CSO), includes records of rare bird species in the Czech Republic submitted for assessment to the Committee in the year 2018 and early 2019. During this period, the Committee resolved altogether 85 records – 68 of them (82%) were accepted, 14 were rejected, and one was withdrawn by the author. Besides that, the report also includes 190 records of species which are subject to registration. In 2018, the Committee was composed of the following members: Jiří Horáček (chair), Jiří Šírek (secretary), Martin Vavřík, David Heyrovský, Jaroslav Šimek, and Michal Šindel. In 2018, the first occurrence of the Canvasback (Aythya valisineria) in the Czech Republic was confirmed – however, the observation was classified in the category D. Furthermore, the second record of the American Wigeon (Mareca americana), eighth record of the Ruddy Duck (Oxyura jamaicensis), eighth and ninth records of the Arctic Redpoll (Acanthis hornemanni), 11th record of the Glaucous Gull (Larus hyperboreus), 13th records of the Sociable Lapwing (Vanellus gregarius) and Terek Sandpiper (Xenus cinereus), and 14th record of the Pectoral Sandpiper (Calidris melanotos) were made. Third to eighth records of the Rosy Starling (Pastor roseus), eighth record of the Greater Spotted Eagle (Clanga clanga), and ninth to 11th records of the Common Loon (Gavia immer) since 1989 were accepted. Eight Yellow-browed Warblers (Phylloscopus inornatus) and 24 Long-legged Buzzards (Buteo rufinus) were recorded. Breeding of the Whooper Swan (Cygnus cygnus) was proved for the second time. In the following list, numbers in brackets in each species show the number of accepted records before 1988, in the years 1989–2017, and in 2018. Where provided, compound numbers such as n+2 indicate that, beside the accepted records, there is an uncertain number of reports not yet considered by the Committee. A dash (–) instead of a number means that records from the particular period were not collected. An asterisk (*) in front of the species name marks a new species for the fauna of the Czech Republic, “(r)” in front of the species name marks species whose records are only subject to registration. In the species registered since 2008, the number of records in the years 2008–2017 and in 2018 is given in brackets. The cases when the bird was first found already in the year 2017 and stayed till 2018, and added records from earlier years are shown in italics. We applied the nomenclature of the IOC World Bird List (version 8.2; IOC 2018). The Czech Rarities Committee is a member of the Association of European Records and Rarities Committees (AERC). See http://fkcso.cz and http://www.aerc.eu. [ABSTRACT FROM AUTHOR]

The article lists several references to common names, genera, species, and authors including Anthus spragueii; Barraga´n-Far´ıas KA; and P´erez-Casanova RA.

The Natural Resource Damage Assessment and Restoration Trustees for the Deepwater Horizon oil spill assessed the external oiling of migratory bird species dependent on open water in the Gulf of Mexico following the aforementioned spill. The assessment was designed to evaluate birds that use open water during the winter within 40 km of the Gulf shoreline. We focused on the American white pelican (Pelecanus erythrorhynchos), common loon (Gavia immer), and northern gannet (Morus bassanus). Point counts (pelican, loon) or strip transects (gannet) were used and each target species was assessed for oiling (unoiled, trace, light, moderate, or heavy amounts) and photographed. Due to distance at sighting and/or poor visibility, not all visible birds were assessed. The percentage of birds oiled varied by species, with the common loon being the highest (23.6%), followed by American white pelican (16.9%), and northern gannet (6.9%). Most of the American white pelicans and common loons had trace (83% and 72%, respectively) or light levels (11% and 24%, respectively) of oiling. The northern gannet had just trace levels of oiling. Some pelicans (6%) and loons (4%) had moderate amounts of oiling. Based on expert derived-mortality estimates and our estimates of oil exposure, we used Monte Carlo simulations to predict expected decreases of 2.5%, 4%, and 11% in the observed population for the northern gannet, American white pelican, and common loon, respectively. While these values are underestimates of the true values given the long time lag (10-12 months) between the oil spill and the assessment, these data represent some of the few estimates of exposure for these species and describe minimum risk estimates to these species. [ABSTRACT FROM AUTHOR]