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.

Background In-flight conditions are hypothesized to influence the timing and success of long-distance migration. Wind assistance and thermal uplift are thought to reduce the energetic costs of flight, humidity, air pressure and temperature may affect the migrants’ water balance, and clouds may impede navigation. Recent advances in animal-borne long-distance tracking enable evaluating the importance of these factors in determining animals’ flight altitude. Methods Here we determine the effects of wind, humidity, temperature, cloud cover, and altitude (as proxy for climbing costs and air pressure) on flight altitude selection of two long-distance migratory shorebirds, far eastern curlew (Numenius madagascariensis) and whimbrel (Numenius phaeopus). To reveal the predominant drivers of flight altitude selection during migration we compared the atmospheric conditions at the altitude the birds were found flying with conditions elsewhere in the air column using conditional logistic mixed effect models. Results Our results demonstrate that despite occasional high-altitude migrations (up to 5550 m above ground level), our study species typically forego flying at high altitudes, limiting climbing costs and potentially alleviating water loss and facilitating navigation. While mainly preferring migrating at low altitude, notably in combination with low air temperature, the birds also preferred flying with wind support to likely reduce flight costs. They avoided clouds, perhaps to help navigation or to reduce the risks from adverse weather. Conclusions We conclude that the primary determinant of avian migrant’s flight altitude selection is a preference for low altitude, with wind support as an important secondary factor. Our approach and findings can assist in predicting climate change effects on migration and in mitigating bird strikes with air traffic, wind farms, power lines, and other human-made structures.

Following publication of the original article [1], errors were identified in the presentation of some of the reference citations in the Background section (page 2 of the PDF) and the Conclusion section (page 10 of the PDF) due to a typesetting mistake.

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The global aquaculture industry has expanded rapidly and is increasingly important for maintaining food security and providing habitat for many waterbirds. Clarifying how waterbirds use aquafarms and how aquafarm use affects waterbird population maintenance can help improve management of the aquafarm landscape such that it can provide habitat for waterbirds. We investigated aquafarm use by waterbirds in China, the world's largest producer of aquaculture products. We used data from the literature on and expert knowledge (questionnaire survey) of waterbird use of aquafarms in China and Bayesian phylogenetic generalized linear mixed models to analyze the relationship between the degree of aquafarm use and population trends of waterbirds. Sixty‐nine percent of waterbird species in China have been recorded at aquafarms. Approximately one quarter of all waterbird species and about the same proportion of threatened species were found to forage at aquafarms, consuming either cultured aquatic products or other food stuffs. In general, species with a high degree of aquafarm use were unlikely to exhibit a population decline over the past 2 decades, when rapid loss of natural habitat occurred in China. This relationship was not detected in threatened species, despite there being no significant difference in the degree of aquafarm use between threatened and nonthreatened species. Our results suggest that the large and expanding aquaculture industry is important for maintaining waterbird populations in China. However, aquafarms are not a replacement for natural habitats because threatened species benefited less from aquafarm use. Given that aquafarms often negatively affect natural wetlands, the degree to which aquafarms compensate for natural habitat loss probably depends on the quality of aquafarm habitat and the habitat requirements of waterbirds. We recommend an integrated ecological and economic analysis to formulate management policies that help conserve wildlife within the constraints and opportunities associated with maintaining human livelihoods.