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The 2014-2016 Pacific marine heatwave caused unprecedented die-offs and multi-year reproductive failures for Common Murres Uria aalge along the west coast of North America. Lingering impacts, such as declines in colony attendance and productivity, have persisted at some colonies following the heatwave and are attributed largely to changes in prey availability and quality. Here, we present evidence of an additional, top-down mechanism contributing to Common Murre breeding failures on Gull Island (Alaska): disturbance of nesting birds by aerial predators and associated egg depredation. We collected time-lapse images over five murre breeding seasons (2016-2020) on Gull Island to document the frequency, duration, and intensity of disturbances caused by aerial predators, as well as to quantify disturbance-associated egg depredation. To identify seasonal and inter-annual variability of disturbances, we calculated a daily disturbance index and compared years using generalized additive models. In all years, Bald Eagles Haliaeetus leucocephalus were the primary cause of disturbance, which led to periods of prolonged colony abandonment by murres and facilitated high levels of murre egg depredation by Glaucous-winged Gulls Larus glaucescens and Herring Gulls L. argentatus. We found that the seasonality of disturbance was an important factor in determining egg depredation rates. In years when disturbance levels were high and persisted later in the season, the colony experienced complete breeding failures due to disturbance-associated egg depredation. Our study revealed that the response of nesting murres to a strong environmental perturbation, such as the Pacific marine heatwave, can be complex and involve multiple stressors from both bottom-up and top-down factors. [ABSTRACT FROM AUTHOR]

Global fisheries kill millions of seabirds annually through bycatch, but little is known about population‐level impacts, particularly in species that form metapopulations. U.S. North Pacific groundfish fisheries catch thousands of Northern Fulmars (Fulmarus glacialis rodgersii) each year, making fulmars the most frequently caught seabird in federally managed U.S. fisheries. Here, we used genetic stock identification to assign 1,536 fulmars sampled as bycatch to one of four Alaska breeding colonies and quantified the similarity of bycatch locations at sea among colonies. We found disproportionately high bycatch from the Pribilof Islands (6% of metapopulation, 23% of bycatch), and disproportionately low bycatch from Chagulak Island (34% of metapopulation, 14% of bycatch). Overlap between fisheries and colony‐specific foraging areas diverge more during the summer breeding season, leading to greater differences in bycatch susceptibility. Contemporary and historical gene flow likely contributes to low genetic differentiation among colonies (FST = 0.003–0.01), yet these values may not represent present connectivity. Our findings illustrate how genetic stock identification can link at‐sea threats to colonies and inform management to reduce bycatch from impacted colonies. [ABSTRACT FROM AUTHOR]

In accord with melanism being uncommon in birds, we could find only six published records of completely melanistic Common Murres Uria aalge, one of the most widely and intensively studied of all seabirds. We added to the record by observing a Common Murre in completely dark, melanistic alternate plumage every summer from 2017 to 2021 at Gull Island in Kachemak Bay, Alaska, USA. In 2017, the bird frequented the colony periphery, indicating that it could have been a subadult. Subsequently, it occupied the same narrow rock ledge within the colony every summer from 2018 to 2021, an indication that it may have been attempting to breed. Because we have been conducting long-term monitoring on Gull Island, we are in the unique position to be able to monitor the attendance and reproductive performance of this distinctively marked murre into the future. [ABSTRACT FROM AUTHOR]

Aleutian Tern Onychoprion aleuticus numbers in Alaska appear to be in decline; however, colonies are difficult to count for the purposes of monitoring due to their co-occurrence with Arctic Terns Sterna paradisaea, low nesting densities, high variability in attendance, sensitivity to human disturbance, and remote terrain. We paired visual observations with unmanned aerial systems (UASs) to test the feasibility of using this technology to survey a small colony of nesting Arctic and Aleutian terns in southcentral Alaska. We used counts of terns in the air and nest attendance to test for disturbance from UAS flights. We conducted 11 UAS flights over seven days at altitudes ranging from 15-30 m and located 23 nests in the 4.1 ha (0.041 km²) colony site (5.6 nests ha-1) by systematically searching the orthomosaics. We were most likely to distinguish tern species in the 18-m and 15-m altitude photos; the white forehead was most visible in side angle rather than top-down. Nest attendance and the number of aerial birds were not influenced by the UAS in this colony, which experiences high Larus gull activity. Aleutian Terns arrived on 19 May and were attending nests by 02 June; nest attendance declined throughout June. We believe the best approximation of total nesting pairs will be achieved by counting nests 7-10 d after first initiation. In mixed species colonies, we recommend that UASs fly in a 'lawn mower' pattern with overlap to maximize side angle images and aim for an image resolution of < 4 mm (which was achieved by 15-m altitude flights with our camera setup). In single species colonies, 30 m is sufficient and can be achieved more efficiently. [ABSTRACT FROM AUTHOR]

• An Arctic Tern mortality event co-occurred with a harmful algal bloom (HAB) in Alaska in 2019 • Saxitoxin and other paralytic shellfish toxins (PSTs) were detected in bird carcasses, forage fish, and mussels • Our results implicate saxitoxicosis as a likely cause of death among adult and nestling Arctic Terns • High energetic demands of Arctic Terns and other seabirds can lead to harmful PST exposure through the food web • HABs present a hazard to northern seabirds and should be considered in future assessments of population health Harmful algal blooms produce biotoxins that can injure or kill fish, wildlife, and humans. These blooms occur naturally but have intensified in many locations globally due to recent climatic changes, including ocean warming. Such changes are especially pronounced in northern regions, where the effects of paralytic shellfish toxins (PSTs) on marine wildlife are of growing concern. In Alaska, seabird mortality events have increased in frequency, magnitude, and duration since 2015 alongside anomalously high ocean temperatures. Although starvation has been implicated as the apparent cause of death in many of these die-offs, saxitoxin (STX) and other PSTs have been identified as possible contributing factors. Here, we describe a mortality event at a nesting colony of Arctic Terns (Sterna paradisaea) near Juneau, Alaska in 2019 and report elevated concentrations of PSTs in bird, forage fish, and mussel samples. Concentrations of STX and other PSTs in tern tissues (2.5–51.2 µg 100g−1 STX-equivalents [STX-eq]) were of similar magnitude to those reported from other PST-induced bird die-offs. We documented high PST concentrations in blue mussels (>11,000 µg 100g−1 STX-eq; Mytilus edulis spp.) collected from nearby beaches, as well as in forage fish (up to 494 µg 100g−1 STX-eq) retrieved from Arctic Tern nests, thereby providing direct evidence of PST exposure via the terns' prey. At maximum concentrations measured in this study, a single 5 g Pacific Sand Lance (Ammodytes personatus) could exceed the median lethal STX dose (LD 50) currently estimated for birds, offering strong support for PSTs as a likely source of tern mortality. In addition to describing this localized bird mortality event, we used existing energetics data from adult and nestling Arctic Terns to calculate estimated cumulative daily PST exposure based on ecologically relevant concentrations in forage fish. Our estimates revealed potentially lethal levels of PST exposure even at relatively low (≤30 ug 100g−1 STX-eq) toxin concentrations in prey. These findings suggest that PSTs present a significant hazard to Arctic Terns and other northern seabirds and should be included in future investigations of avian mortality events as well as assessments of population health. [ABSTRACT FROM AUTHOR]

Abstract: Selection for chemical signals in birds could be influenced by parasitism as has been previously suggested for visual and acoustic displays. Crested auklets (Aethia cristatella), colonial seabirds from Alaska and Siberia, offer an example of how this might occur. Crested auklets secrete lipids in plumage, possibly as an indicator of status and attractiveness. Prominent among these secretions are aldehydes, which are noticeable as a pungent citrus-like odour. Octanal and hexanal, the most abundant aldehydes in the plumage of crested auklets, are potent invertebrate repellents, reported from the chemical defenses of heteropteran insects. These aldehydes occur at high concentrations within specialized secretory structures. Experiments presented here show that these compounds can paralyse lice. Lice obtained from auklets were paralysed or killed within seconds after exposure to volatiles from nicks in the integument of a crested auklet. Chemical analysis demonstrated the presence of aldehydes in the area of integument used for this experiment. Lice exposed to control tissues in the same manner were not affected. A synthetic blend of crested auklet odourant constituents caused a sequence of impaired behaviours in auklet lice comparable to the effects of neuroactive insecticides. The time until onset of effects was dependent on dose, suggesting that the rate of molecular diffusion into louse spiracles was the explanatory factor. Impairment was evident even at very low concentrations that can occur in crested auklet plumage during winter. The same aqueous emulsions were present in both experimental and control treatments but lice in controls experiments were not affected. Crested auklets inhabit crowded social neighbourhoods with larger social groups, closer interindividual spacing and higher rates of contact than sympatric least auklets (Aethia pusilla). This could help to explain why crested auklets can have higher louse abundances. Lice are spread through direct contact between hosts and louse-infected mates could transmit lice to offspring. Large differences in the louse loads on crested auklet fledglings suggest differences in the parental transmission of lice to offspring. [Copyright &y& Elsevier]

The Black-legged Kittiwake Rissa tridactyla is the most abundant gull species in the world, but some populations have declined in recent years, apparently due to food shortage. Kittiwakes are surface feeders and thus can compensate for low food availability only by increasing their foraging range and/or devoting more time to foraging. The species is widely studied in many respects, but long-distance foraging and the limitations of conventional radio telemetry have kept its foraging behavior largely out of view. The development of Global Positioning System (GPS) loggers is advancing rapidly. With devices as small as 8 g now available, it is possible to use this technology for tracking relatively small species of oceanic birds like kittiwakes. Here we present the first results of GPS telemetry applied to Black-legged Kittiwakes in 2007 in the North Pacific. All but one individual foraged in the neritic zone north of the island. Three birds performed foraging trips only close to the colony (within 13 km), while six birds had foraging ranges averaging about 40 km. The maximum foraging range was 59 km, and the maximum distance traveled was 165 km. Maximum trip duration was 17 h (mean 8 h). An apparently bimodal distribution of foraging ranges affords new insight on the variable foraging behaviour of Black-legged Kittiwakes. Our successful deployment of GPS loggers on kittiwakes holds much promise for telemetry studies on many other bird species of similar size and provides an incentive for applying this new approach in future studies. [ABSTRACT FROM AUTHOR]