Aerial scratching, leeches, and nasal saddles in green-winged teal

Black Scoters Melanitta americana were marked with satellite transmitters on Atlantic and Pacific coasts of North America to examine continental-scale population delineation. Scoters marked on the different coasts did not overlap at any stage of the annual cycle, suggesting that birds in the two regions could be monitored and managed as separate populations: 1) an Atlantic population, which winters along the Atlantic coast and Great Lakes and breeds from northeast continental Canada westward to the Northwest Territories, and 2) a Pacific population, which winters along the Pacific coasts of Alaska, British Columbia and the Pacific northwest states, and breeds in western Alaska. Range maps for Black Scoter could reflect these distributions revealed by satellite telemetry. Our data provide new information on the distribution of Black Scoters in North America, which can be used to improve the design of future surveys.

Alaska↗

USGS2020

Survival of Laysan Teal Anas laysanensis differs among island populations: Role of chronic avian botulism

Monitoring demographic response over time is valuable for understanding population dynamics of endangered species. We quantified the variation in survival patterns for three small isolated island populations of endangered waterfowl in the Hawaiian Archipelago. Laysan Teal Anas laysanensis were individually marked and the fate of 1,150 individuals were followed from different cohorts among the two reintroduced (Kure and Midway Atolls) and the single relict (Laysan Island) populations for time series of 4, 10 and 15 years respectively. We applied a non-parametric Kaplan-Meier estimator to describe variation between the populations in survival for different cohorts. For Laysan Island and Midway Atoll, we used log-rank tests to determine the effects of cohort, island and sex on survival. Birds in the Laysan Island population had significantly higher survival than those in the Midway population, and males had higher survival than females in both populations. The proportion of females surviving at Midway Atoll was 40% lower than for females on Laysan Island at year 5. The oldest bird observed from Laysan Island was at least 15.5 years old and had been ringed as an adult. The Kure Atoll founder cohort ( n = 28) had 100% survival 18 months post-release, but this dropped by 39% during the first avian botulism type C outbreak. Ten of twenty-eight founders and a population of 60–70 birds persisted on Kure Atoll in 2020. We summarised mortality records to generate hypotheses to explain the cause-specific mechanisms driving the observed survival differences. Mortality data showed that the survival differences between islands in Laysan Teal survival was driven by chronic epizootics of avian botulism type C at Midway and Kure Atoll.

Wildfowl↗

USGS2020

Migration routes and population status of the Brent Goose Branta bernicla nigricans wintering in East Asia

Of the world’s Brent Goose Branta bernicla populations, the migration routes and winter distribution of the East Asian population of Brent Geese B. b. nigricans are the least well known. We therefore marked Brent Geese at their primary pre-migratory staging area in Notsuke Bay, Hokkaido, Japan to describe their migration between breeding and wintering areas in East Asia. Additionally, count data were compiled from the literature to identify important wintering and staging sites for the species, following Ramsar Convention criteria, and to assess trends in numbers of Brent Geese recorded in Japan and South Korea. The tracking data provided the first direct evidence of migratory connectivity between staging sites in northern Japan and the Korean Peninsula. A total of 26 internationally important sites were identified in the Russian Far East (7), northern Japan (16), northeast China (2) and the Korean Peninsula (1). Autumn surveys made at staging sites in Japan indicate that the East Asian population is increasing, although more extensive surveys for Brent Geese in China and on the Korean Peninsula are needed to confirm overall population trends and to identify critical habitats and wintering sites. We encourage the continuation of tracking studies, to describe more precisely the main migration routes, staging areas and, importantly, the breeding grounds for this vulnerable Brent Geese population.

Wildfowl↗