Migration and food resources for shorebirds in a changing climate

In many areas of the world including the Great Plains of North America, climate change is causing precipitation to become more variable and extreme, which is affecting availability of wetlands for water-dependent wildlife such as shorebirds (e.g., plovers, sandpipers). Research is needed on the response of shorebirds to changing wetland availability and the implications of those responses to inform conservation plans. However, many shorebird species’ migrations remain unstudied. In Chapter 1, I used GPS trackers to evaluate migration paths and stopover locations use of the understudied Western Willet (Tringa semipalmata inornata) in the Great Plains. Western Willets migrated rapidly in the spring (6.6 ± 1.4 days; mean ± standard error; n = 9) and the fall (6.3 ± 2.0 days; n = 5) compared to other shorebird species’ migrations and relied on several stopovers during each migration (spring: 3.4 stopovers ± 0.6; n = 9; fall: 3.3 stopovers ± 1.6 ; n = 5). Of the 25 spring stopovers, the land cover type with the greatest coverage within a 5 km buffer was grasslands (50%), followed by crops (17%). Of 13 fall stopovers, the dominant land cover type was open water (46%), followed by emergent herbaceous wetlands (29%). In Chapter 2, I collected invertebrate samples from lakes and depressional wetlands in the southern Great Plains to compare abundance, biomass, and nutritional content of food resources at two types of stopovers that are used in different precipitation conditions. We found that during late spring, when many shorebird species are migrating through the study region, invertebrate abundance did not differ significantly between lakes and wetlands, and biomass was greater at wetlands than lakes. However, in midsummer when shorebirds begin southward migration, abundance was greater at lakes than wetlands and biomass did not differ between the two. A descriptive comparison of common diet items reveals no obvious difference in macronutrient content between lakes and wetlands. Collectively, these chapters highlight the importance of regional and population-specific information to understand and manage migratory bird populations and illustrate the importance of several types of waterbodies for provision of food resources for shorebirds in the Great Plains.