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Population declines of Leach's Storm Petrels Hydrobates leucorhous in the western Atlantic have both led to the species' recent assessment as Threatened in Canada and contributed to a Vulnerable designation by the IUCN. Limited information suggests low adult survival rates are an important contributing factor. Off eastern Nova Scotia, Canada, Country Island is managed for avian predators and mustelids to protect nesting endangered Roseate Terns Sterna dougallii. The island also hosts a colony of Leach's Storm Petrels. In 2016, a capture-markrecapture program was initiated for storm petrels, from which we estimated apparent survival and recapture probabilities for 571 breeding birds using data collected from 2016 to 2021. Models with a time-since-marking effect were consistently ranked higher than those without; annual apparent survival estimates in the first year after capture were lower than in subsequent years, presumably due to some captured birds not returning to the study area. Apparent survival in the years subsequent to first capture was lowest in forested areas with no understorey vegetation, slightly higher in forested areas with fern understorey, and highest in open areas with dense fern cover. While the mechanism driving habitat differences in adult survival is unknown, predation pressure may be strongest in forested areas with open understorey where it is easier for predators to find burrow entrances. Although apparent adult survival rates were higher than reported previously for nearby Bon Portage Island where predation is significant, Country Island may represent a best-case scenario for Leach's Storm Petrel in Atlantic Canada, since predators are managed and adult mortality from avian predators is relatively low at this site. Even so, survival rates at Country Island are lower than those reported previously at two Pacific colonies and provide evidence that adult survival rates of Leach's Storm Petrels in eastern Canada are depressed. [ABSTRACT FROM AUTHOR]

During late summer and early autumn, the Bay of Fundy, Canada, is an important foraging area for many species of post-breeding and migratory seabirds, yet there has been limited effort to quantify the number of birds using these waters. Furthermore, the numbers of phalaropes Phalaropus spp. using this region as a stopover during autumn migration is much lower than in previous decades, but an explanation of their disappearance remains elusive. We examined the species composition, abundance and distribution of seabirds using the lower Bay of Fundy during September, 2015. Aerial surveys were conducted in three regions known to encompass good habitat for seabirds: Brier Island Ledges (hereafter Brier: 622 km2), shoals southeast of Grand Manan Island (hereafter Grand Manan: 531 km2), and Lurcher Shoals/German Bank (hereafter Lurcher: 7 433 km2). Using distance sampling, detection probabilities, densities and abundance estimates were calculated for phalaropes, shearwaters (Procellariidae), Northern Gannets Morus bassanus, gulls (Laridae), storm-petrels (Hydrobatidae), and alcids (Alcidae). All species were found in higher densities in Brier and Grand Manan than in the larger area of Lurcher, with phalaropes, shearwaters, and Northern Gannets being the most numerous. Among the three regions, we estimated >100 000 phalaropes during each of two survey periods, and upwards of 30 000 shearwaters, 3 500 Northern Gannets, 2 800 gulls, 2 000 alcids, and 2 000 stormpetrels during one of the two periods. Our abundance estimates for phalaropes were similar to recent surveys, and the low numbers seen in Lurcher suggests this area is not an alternative stopover. Areas of tidal upwelling around Brier and Grand Manan islands provide important foraging habitat for a diverse community of resident and migratory seabirds, but these areas do not account for the disappearance of very large numbers of Red-necked Phalaropes P. lobatus from the nearby Passamaquoddy Bay since the 1980s. [ABSTRACT FROM AUTHOR]

Diet during the non-breeding period influences condition and subsequent reproduction. Physiological mechanisms underlying such carry-over effects are poorly understood but could be clarified by studying physiological responses to variation in diet during non-breeding. The hormone corticosterone provides a functional link between diet and survival and reproduction, but methodological limitations have prevented previous studies from testing the hypothesis that, on an individual level, avian corticosterone levels during the non-breeding period reflect broader patterns in feeding ecology during that time. Using museum specimens (1859-2002) and live birds (2012), we found that corticosterone from feathers ( CORTf) is negatively related to trophic position ( TP) inferred from feather stable-nitrogen isotope values ( δ15N) in Leach's Storm-petrels Oceanodroma leucorhoa. CORTf was not related to stable-carbon isotope values ( δ13C). We detected no temporal trends in CORTf or δ15N, and neither was related to a large-scale index of winter climate, suggesting a general ecological phenomenon rather than a reflection of historical environmental changes. However, we detected a temporal trend in feather δ13C, and δ13C was related to δ15N. Our findings suggest a physiological benefit of feeding at higher TPs, either through increased nutritional value or reduced foraging costs associated with higher TP prey, and future research should aim to distinguish between these two explanations. Nevertheless, ours is the first evidence of a correlation between individual endocrine levels and foraging ecology, and demonstrates non-lethal variation in a physiological mediator in turn related to variation in resource use. [ABSTRACT FROM AUTHOR]

Knowledge of foraging movements during the breeding season is key to understanding energetic stresses faced by seabirds. Using archival light loggers (geolocators), a Bayesian state-space model, and stable isotope analysis, we compared foraging movements of Leach's storm-petrels Oceanodroma leucorhoa during their incubation periods in 2012 and 2013. Data were collected from two colonies, Bon Portage Island and Country Island, which are 380 km apart along the coast of Nova Scotia, Canada. Based on allometry for procellariiform mass, predicted foraging ranges for Leach's storm-petrels are 200 km; however, observed maximum distances from the colony were 3 to 5 times that. Storm-petrels from Country Island travelled 1015 ± 238 km southeast to the Laurentian fan and south of the Grand Banks whereas storm-petrels from Bon Portage Island travelled 613 ± 167 km southeast, beyond the continental slope, east of Georges Bank. The average distance travelled in a return trip was 2287 ± 603 km and 1303 ± 351 km for Country Island and Bon Portage Island, respectively. There were no differences between years in cumulative distances travelled within islands, but foraging trips did not last as long in 2013 (4.7 ± 1.5 d) as they did in 2012 (6.2 ± 2.1 d). Stable isotope analyses indicated that, during the incubation period, prey items from Country Island were from higher trophic levels and possibly had higher energy content than those from Bon Portage Island, perhaps explaining the more distant and longer foraging trips for Country Island birds. [ABSTRACT FROM AUTHOR]

The article presents a study on the variability and dietary partitioning between herring (Larus argentatus) and great black-backed gulls (Larus marinus) during incubation and early chick rearing on Kent Island, New Brunswick. The study employed pellet analyses and stable-isotope analysis of prey items and tissues of chicks and adults such as blood and feathers. Results showed that both species relied on fish and crabs and they fed at higher trophic levels on breeding.

Background: Among the most widespread seabirds in the world, shearwaters of the genus Puffinus are also some of the deepest diving members of the Procellariiformes. Maximum diving depths are known for several Puffinus species, but dive depths or diving behaviour have never been recorded for great shearwaters (P. gravis), the largest member of this genus. This study reports the first high sampling rate (2 s) of depth and diving behaviour for Puffinus shearwaters. Methodology/Principal Findings: Time-depth recorders (TDRs) were deployed on two female great shearwaters nesting on Inaccessible Island in the South Atlantic Ocean, recording 10 consecutive days of diving activity. Remote sensing imagery and movement patterns of 8 males tracked by satellite telemetry over the same period were used to identify probable foraging areas used by TDR-equipped females. The deepest and longest dive was to 18.9 m and lasted 40 s, but most (>50%) dives were <2 m deep. Diving was most frequent near dawn and dusk, with <0.5% of dives occurring at night. The two individuals foraged in contrasting oceanographic conditions, one in cold (8 to 10°C) water of the Sub-Antarctic Front, likely 1000 km south of the breeding colony, and the other in warmer (10 to 16°C) water of the Sub-tropical Frontal Zone, at the same latitude as the colony, possibly on the Patagonian Shelf, 4000 km away. The cold water bird spent fewer days commuting, conducted four times as many dives as the warm water bird, dived deeper on average, and had a greater proportion of bottom time during dives. Conclusions/Significance: General patterns of diving activity were consistent with those of other shearwaters foraging in cold and warm water habitats. Great shearwaters are likely adapted to forage in a wide range of oceanographic conditions, foraging mostly with shallow dives but capable of deep diving. [ABSTRACT FROM AUTHOR]

Shearwaters are among the most abundant seabirds globally and breeding birds often travel thousands of kilometres during foraging trips to productive marine areas. Great Shearwaters Ardenna gravis are endemic breeders of the Tristan da Cunha Archipelago with a population of 5-6 million breeding pairs making them key top predators within the South Atlantic Ocean. We deployed satellite transmitters on 42 breeding and non-breeding shearwaters at two nesting islands and one foraging site in the northern hemisphere to quantify their movements and space use with respect to age, sex, colonies and breeding phases. During the pre-laying period, birds from Gough Island made trips of 2400 km to the Benguela upwelling region off South Africa, or > 4000 km to the Patagonian Shelf; patterns which overlapped with immature birds from the Bay of Fundy, Canada. During the incubation period, males and females from Inaccessible Island showed differences in trip durations, but no difference in foraging ranges: both sexes made trips of 1500-2000 km to the Sub-Antarctic Front or 4000 km to the Patagonian Shelf, among the furthest foraging trips of breeding seabirds observed to date. Although the colonies are separated by only 400 km, during the incubation period, the at-sea distribution of non-breeding birds from Gough Island was spatially segregated from breeding and failed birds from Inaccessible Island, whereas immature birds from Fundy overlapped with birds from both colonies. During the post-breeding period, all tagged populations overlapped on the Patagonian Shelf. Argentina’s Exclusive Economic Zone was used extensively during pre-laying, incubation, and post-breeding periods, highlighting the global importance of the Patagonian Shelf for this species. [ABSTRACT FROM AUTHOR]