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Many migratory shorebird species using the East Asian–Australasian Flyway are declining rapidly. While the loss of staging habitats in East Asia is considered the primary cause, stressors to fitness often occur throughout the geographic range of declining species, and threats in the non-breeding grounds have been comparatively poorly studied. Three species of migratory shorebird, Curlew Sandpiper (Calidris ferruginea), Sharp-tailed Sandpiper (C. acuminata) and Red-necked Stint (C. ruficollis), use Australia's dynamic temporary wetland systems opportunistically, yet these large wetland systems have become increasingly degraded, with reduced frequency and extent of flooding. Here, we test whether variables related to wetland availability in Australia's interior can explain annual variation in apparent survival, abundance or immature to adult ratios at three well-monitored coastal shorebird areas in southern Australia (total area > 1315 km2). We show that coastal annual bird abundance and ratios of immatures at the coast were higher when inland Australia was relatively hot and dry. Also, a small but significant amount of variation in annual apparent survival can be explained by annual variation in inland conditions, with higher survival rates in years when inland conditions were relatively wet and cool. For the endangered Curlew Sandpiper, the impacts of Australian environmental conditions may be exacerbating the impacts of conditions experienced in other parts of its range on fitness and survival. While the effects we document here are relatively weak, they do suggest that management of inland wetlands for these shorebirds may positively affect survival rates of these sharply declining species. [ABSTRACT FROM AUTHOR]

Decreases in shorebird populations are increasingly evident worldwide, especially in the East Asian–Australasian Flyway (EAAF). To arrest these declines, it is important to understand the scale of both the problem and the solutions. We analysed an expansive Australian citizen-science dataset, spanning the period 1973 to 2014, to explore factors related to differences in trends among shorebird populations in wetlands throughout Australia. Of seven resident Australian shorebird species, the four inland species exhibited continental decreases, whereas the three coastal species did not. Decreases in inland resident shorebirds were related to changes in availability of water at non-tidal wetlands, suggesting that degradation of wetlands in Australia’s interior is playing a role in these declines. For migratory shorebirds, the analyses revealed continental decreases in abundance in 12 of 19 species, and decreases in 17 of 19 in the southern half of Australia over the past 15 years. Many trends were strongly associated with continental gradients in latitude or longitude, suggesting some large-scale patterns in the decreases, with steeper declines often evident in southern Australia. After accounting for this effect, local variables did not explain variation in migratory shorebird trends between sites. Our results are consistent with other studies indicating that decreases in migratory shorebird populations in the EAAF are most likely being driven primarily by factors outside Australia. This reinforces the need for urgent overseas conservation actions. However, substantially heterogeneous trends within Australia, combined with declines of inland resident shorebirds indicate effective management of Australian shorebird habitat remains important. [ABSTRACT FROM AUTHOR]

In differential migrants the members of different age-classes or sex travel to geographically separate non-breeding areas. Here, we test five competing hypotheses explaining differential migration using more than 40 000 records of 22 species of shorebirds (Charadriiformes) occurring at two non-breeding areas at different distance from the breeding grounds and that also differ in climate. We showed that across species, the larger sex was more abundant in south-eastern than in north-western Australia. Size, as indicated by wing-length, was greater in the south-east than in the north-west for both males and females, whereas bill-length showed the opposite pattern. Based on these trends we conclude that the interaction between ambient temperature, body-size and bill-length determines the geographical distribution of shorebirds wintering in Australia. Our findings are not consistent with the resource partitioning, dominance and arrival time hypotheses. This is the first study that disassociates overlapping predictions of competing hypotheses on differential migration, thus contributing to our understanding of the evolution of differential migration in birds. [ABSTRACT FROM AUTHOR]