Seasonal and population differences in migration of Whimbrels in the East Asian–Australasian Flyway

Abstract

Background: Conserving migratory birds is challenging due to their reliance on multiple distant sites at different stages of their annual life cycle. The concept of "flyway", which refers to all areas covered by the breeding, nonbreeding, and migrating of birds, provides a framework for international cooperation for conservation. In the same flyway, however, the migratory activities of the same species can differ substantially between seasons and populations. Clarifying the seasonal and population differences in migration is helpful for understanding migration ecology and for identifying conservation gaps. Methods: Using satellite-tracking we tracked the migration of Whimbrels (Numenius phaeopus variegatus) from nonbreeding sites at Moreton Bay (MB) and Roebuck Bay (RB) in Australia in the East Asian-Australasian Flyway. Mantel tests were used to analyze the strength of migration connectivity between the nonbreeding and breeding sites of MB and RB populations. Welch's t test was used to compare the migration activities between the two populations and between northward and southward migration. Results: During northward migration, migration distance and duration were longer for the MB population than for the RB population. The distance and duration of the first leg flight during northward migration were longer for the MB population than for the RB population, suggesting that MB individuals deposited more fuel before departing from nonbreeding sites to support their longer nonstop flight. The RB population exhibited weaker migration connectivity (breeding sites dispersing over a range of 60 longitudes) than the MB population (breeding sites concentrating in a range of 5 longitudes in Far Eastern Russia). Compared with MB population, RB population was more dependent on the stopover sites in the Yellow Sea and the coastal regions in China, where tidal habitat has suffered dramatic loss. However, RB population increased while MB population decreased over the past decades, suggesting that loss of tidal habitat at stopover sites had less impact on the Whimbrel populations, which can use diverse habitat types. Different trends between the populations might be due to the different degrees of hunting pressure in their breeding grounds. Conclusions: This study highlights that conservation measures can be improved by understanding the full annual life cycle of movements of multiple populations of Whimbrels and probably other migratory birds.

Diverse patterns of migratory timing, site use, and site fidelity by Alaska‐breeding Whimbrels

“…Travel durations of the migrations were also 2–4 times shorter for Whimbrels in these two Atlantic populations than those in our study. Whimbrels using the East Asian–Australasian Flyway (Kuang et al 2020), however, have migratory patterns more similar to those in our study. Whimbrels migrating between two non‐breeding locations in Australia and breeding sites across high‐latitude areas of Asia moved over periods of similar durations to those conducted by Alaska‐breeding Whimbrels, but migrations entailed fewer stops (four and three stops during southbound and northbound migration, respectively; Kuang et al 2020) than migrations by Alaska‐breeding Whimbrels in our study.…”

“…Whimbrels at southerly non‐breeding sites also began northbound migration earlier than those at more northerly locations. In contrast, Kuang et al (2020) found little variation in the timing or duration of migratory movements of Whimbrels in the East Asian–Australasian Flyway, possibly due to the relatively restricted ranges of breeding (~ 10°) and non‐breeding (~ 5°) latitudes of birds in their study. Similarly, Johnson et al (2016) and Carneiro et al (2019a,b, 2020) monitored Whimbrels in the Atlantic Flyway from one breeding site each across non‐breeding latitudes that were relatively restricted (~ 10° in both studies) compared to those in our study.…”

“…Thus, Whimbrels breeding at Churchill, Canada (Johnson et al 2016), and Iceland (Carneiro et al 2019a) appear to prepare for migration at or near breeding sites, whereas Alaska‐breeding Whimbrels leave breeding sites and begin pre‐migratory fattening at sites in western and northwestern Alaska. During northbound migrations, however, Whimbrels from all populations studied to date typically conduct long initial flights from non‐breeding locations (Johnson et al 2016, Allport et al 2018, Carneiro et al 2019b, Kuang et al 2020, our study). Such movements require high fat loads, indicating that Whimbrels initiate pre‐migratory fattening at non‐breeding sites prior to northbound migration.…”

“…We deployed satellite transmitters (both battery‐powered implant units and externally mounted solar‐powered units) on Whimbrels breeding in Alaska to describe their migratory movements. More broadly, we compare our results to those reported for other Whimbrel populations (e.g., Allport et al 2018, Carneiro et al 2019a,b, Kuang et al 2020) for insights into factors that influence population‐specific migratory traits.…”

Shorebirds wintering in Southeast Asia demonstrate trans-Himalayan flights

“…1 , Supplementary Table S1 ). Most Whimbrels that we tracked from Singapore took a similar route to birds from Australia that migrated through coastal east China to breed in the Russian Far East 24 , 39 . The Whimbrel that crossed the Himalayas probably represents a different breeding population than those migrating along the EAAF, whereas for Common Redshanks, those crossing the Himalayas tended to be the more westerly breeders within one population.…”