Effects of Fish Populations on Pacific Loon (Gavia pacifica) and Yellow-billed Loon (G. adamsii) Lake Occupancy and Chick Production in Northern Alaska

  Predator populations are vulnerable to changes in prey distribution or availability. With warming temperatures, lake ecosystems in the Arctic are predicted to change in terms of hydrologic flow, water levels, and connectivity with other lakes. We surveyed lakes in northern Alaska to understand how shifts in the distribution or availability of fish may affect the occupancy and breeding success of Pacific (Gavia pacifica) and Yellow-billed Loons (G. adamsii). We then modeled the influence of the presence and abundance of five fish species and the physical characteristics of lakes (e.g., hydrologic connectivity) on loon lake occupancy and chick production. The presence of Alaska blackfish (Dallia pectoralis) had a positive influence on Pacific Loon occupancy and chick production, which suggests that small-bodied fish species provide important prey for loon chicks. No characteristics of fish species abundance affected Yellow-billed Loon lake occupancy. Instead, Yellow-billed Loon occupancy was influenced by the physical characteristics of lakes that contribute to persistent fish populations, such as the size of the lake and the proportion of the lake that remained unfrozen over winter. Neither of these variables, however, influenced chick production. The probability of an unoccupied territory becoming occupied in a subsequent year by Yellow-billed Loons was low, and no loon chicks were successfully raised in territories that were previously unoccupied. In contrast, unoccupied territories had a much higher probability of becoming occupied by Pacific Loons, which suggests that Yellow-billed Loons have strict habitat requirements and suitable breeding lakes may be limited. Territories that were occupied had high probabilities of remaining occupied for both loon species.  Les populations de prédateurs sont vulnérables aux changements de répartition ou de disponibilité des proies. En raison du réchauffement des températures, on prévoit que les écosystèmes lacustres de l’Arctique changeront pour ce qui est du régime hydrologique, des niveaux d’eau et de la connectivité avec d’autres lacs. Nous avons examiné des lacs du nord de l’Alaska pour comprendre comment les changements en matière de répartition ou de disponibilité des poissons peuvent avoir des incidences sur le taux d’occupation et sur le succès de reproduction du huart du Pacifique (Gavia pacifica) et du huart à bec blanc (G. adamsii). Ensuite, nous avons modélisé l’influence de la présence et de l’abondance de cinq espèces de poissons de même que les caractéristiques physiques de lacs (comme la connectivité hydrologique) par rapport au taux d’occupation lacustre des huarts et à la production d’oisillons. La présence du dallia (Dallia pectoralis) avait une influence positive sur l’occupation et la production d’oisillons chez le huart du Pacifique, ce qui suggère que les espèces de poissons au petit corps constituent une proie importante pour les oisillons. Aucune caractéristique de l’abondance des espèces de poissons n’a eu d’influence sur l’occupation lacustre du huart à bec blanc. L’occupation du huart à bec blanc a plutôt été influencée par les caractéristiques physiques des lacs qui contribuent aux populations de poissons persistantes, comme la taille du lac et la proportion du lac qui ne gelait pas en hiver. Toutefois, aucune de ces variables n’a exercé d’influence sur la production d’oisillons. La probabilité qu’un territoire inoccupé devienne occupé par le huart au bec blanc au cours d’une année subséquente était faible, et aucun oisillon huart n’a été élevé avec succès dans des territoires d’oisillons anciennement inoccupés. En revanche, les territoires inoccupés avaient une beaucoup plus grande probabilité de devenir occupés par les huarts du Pacifique, ce qui suggère que les huarts à bec blanc ont des exigences strictes en matière d’habitat et que le nombre de lacs convenant à la reproduction risque d’être limité. Les territoires qui étaient occupés avaient de fortes probabilités de rester occupés par les deux espèces de huarts

Dissecting the Shared Genetic Architecture of Suicide Attempt, Psychiatric Disorders, and Known Risk Factors

Background Suicide is a leading cause of death worldwide, and nonfatal suicide attempts, which occur far more frequently, are a major source of disability and social and economic burden. Both have substantial genetic etiology, which is partially shared and partially distinct from that of related psychiatric disorders. Methods We conducted a genome-wide association study (GWAS) of 29,782 suicide attempt (SA) cases and 519,961 controls in the International Suicide Genetics Consortium (ISGC). The GWAS of SA was conditioned on psychiatric disorders using GWAS summary statistics via multitrait-based conditional and joint analysis, to remove genetic effects on SA mediated by psychiatric disorders. We investigated the shared and divergent genetic architectures of SA, psychiatric disorders, and other known risk factors. Results Two loci reached genome-wide significance for SA: the major histocompatibility complex and an intergenic locus on chromosome 7, the latter of which remained associated with SA after conditioning on psychiatric disorders and replicated in an independent cohort from the Million Veteran Program. This locus has been implicated in risk-taking behavior, smoking, and insomnia. SA showed strong genetic correlation with psychiatric disorders, particularly major depression, and also with smoking, pain, risk-taking behavior, sleep disturbances, lower educational attainment, reproductive traits, lower socioeconomic status, and poorer general health. After conditioning on psychiatric disorders, the genetic correlations between SA and psychiatric disorders decreased, whereas those with nonpsychiatric traits remained largely unchanged. Conclusions Our results identify a risk locus that contributes more strongly to SA than other phenotypes and suggest a shared underlying biology between SA and known risk factors that is not mediated by psychiatric disorders.Peer reviewe

International migration patterns of Red-throated Loons (<i>Gavia stellata</i>) from four breeding populations in Alaska

<div><p>Identifying post-breeding migration and wintering distributions of migratory birds is important for understanding factors that may drive population dynamics. Red-throated Loons (<i>Gavia stellata</i>) are widely distributed across Alaska and currently have varying population trends, including some populations with recent periods of decline. To investigate population differentiation and the location of migration pathways and wintering areas, which may inform population trend patterns, we used satellite transmitters (n = 32) to describe migration patterns of four geographically separate breeding populations of Red-throated Loons in Alaska. On average (± SD) Red-throated Loons underwent long (6,288 ± 1,825 km) fall and spring migrations predominantly along coastlines. The most northern population (Arctic Coastal Plain) migrated westward to East Asia and traveled approximately 2,000 km farther to wintering sites than the three more southerly populations (Seward Peninsula, Yukon-Kuskokwim Delta, and Copper River Delta) which migrated south along the Pacific coast of North America. These migration paths are consistent with the hypothesis that Red-throated Loons from the Arctic Coastal Plain are exposed to contaminants in East Asia. The three more southerly breeding populations demonstrated a chain migration pattern in which the more northerly breeding populations generally wintered in more northerly latitudes. Collectively, the migration paths observed in this study demonstrate that some geographically distinct breeding populations overlap in wintering distribution while others use highly different wintering areas. Red-throated Loon population trends in Alaska may therefore be driven by a wide range of effects throughout the annual cycle.</p></div

Data from: Changes in behavior are unable to disrupt a trophic cascade involving a specialist herbivore and its food plant

Changes in ecological conditions can induce changes in behavior and demography of wild organisms, which in turn may influence population dynamics. Black brant (Branta bernicla nigricans) nesting in colonies on the Yukon–Kuskokwim Delta (YKD) in western Alaska have declined substantially (~50%) since the turn of the century. Black brant are herbivores that rely heavily on Carex subspathacea (Hoppner's sedge) during growth and development. The availability of C. subspathacea affects gosling growth rates, which subsequently affect pre‐ and postfledging survival, as well as size and breeding probability as an adult. We predicted that long‐term declines in C. subspathacea have affected gosling growth rates, despite the potential of behavior to buffer changes in food availability during brood rearing. We used Bayesian hierarchical mixed‐effects models to examine long‐term (1987–2015) shifts in brant behavior during brood rearing, forage availability, and gosling growth rates at the Tutakoke River colony. We showed that locomotion behaviors have increased (β = 0.05, 95% CRI: 0.032–0.068) while resting behaviors have decreased (β = −0.024, 95% CRI: −0.041 to −0.007), potentially in response to long‐term shifts in forage availability and brood density. Concurrently, gosling growth rates have decreased substantially (β = −0.100, 95% CRI: −0.191 to −0.016) despite shifts in behavior, mirroring long‐term declines in the abundance of C. subspathacea (β = −0.191, 95% CRI: −0.355 to −0.032). These results have important implications for individual fitness and population viability, where shifts in gosling behavior putatively fail to mitigate long‐term declines in forage availability

Average temporal migration patterns by Red-throated Loon breeding population.

<p>Line length represents date ranges from earliest arrival to latest departure. Average date of arrival denoted by diamond (◊), and average date of departure denoted by asterisk (*). Multiple lines represent different spatially distinct stopover or wintering areas used by loons from a breeding population. Breeding areas represent Alaska’s Arctic Coastal Plain (ACP), Seward Peninsula (SP), Yukon-Kuskokwim Delta (YKD), and Copper River Delta (CRD).</p

The number of satellite transmitters (PTTs) deployed for each Red-throated Loon breeding population by year.

<p>The number of satellite transmitters (PTTs) deployed for each Red-throated Loon breeding population by year.</p

Migration patterns, stopover sites and wintering areas for Red-throated Loons breeding on the Arctic Coastal Plain (ACP) in northern Alaska.

<p>A) East Asian migration of Red-throated Loons. B) Pacific migration of a single Red-throated Loon from the Arctic Coastal Plain breeding area. Red dots represent breeding area locations, yellow dots are fall stopover sites, blue dots are wintering area locations, and green dots are spring stopover sites.</p

Migration patterns, stopover sites, and wintering areas of Red-throated Loons from 3 breeding populations.

<p>Red-throated Loon breeding areas in Alaska include the A) Seward Peninsula (SP), B) Yukon-Kuskokwim Delta (YKD), or C) Copper River Delta (CRD). Red dots represent breeding area locations, yellow dots are fall stopover sites, blue dots are wintering area locations, and green dots are spring stopover sites.</p

Average distance (km, ± SD) of migrations to fall stopover sites and wintering areas by Red-throated Loons.

<p>Red-throated Loon breeding populations represent Alaska’s Arctic Coastal Plain (ACP), Seward Peninsula (SP), Yukon-Kuskokwim Delta (YKD), and Copper River Delta (CRD).</p