Stopover ecology of shorebirds on the Northern Gulf of Mexico: How different migration strategies affect habitat use

Background/Question/Methods

Twenty-eight species of migratory shorebirds rely on the coastlines of the northern Gulf of Mexico (NGOM) to fuel long-distance migrations to near-arctic breeding grounds. As the processes of global change accelerate, habitats on the NGOM are expected to experience dramatic land loss. Shorebird species vary in their migration ecology: some species are believed to use a “jump” strategy; migrating long distances in the spring from coastal habitats on the Gulf without stopping while other species, use “skip” and “hop” strategies; stopping to refuel at shorter intervals along their migratory journey. Migration theory suggests that such differences in migration strategy will result in variation in the requirements of migration physiology, and, therefore, predicts that the importance of a stopover site to a species can vary according the migration strategy. We compared refueling rates (plasma metabolite concentrations), body condition (fat scores and size-adjusted mass), and stopover duration in three species of Calidrid sandpipers (Calidris pusilla, C. mauri, C. alpina) predicted to vary in their migration strategies. We hypothesized that C. alpina, a “jump” migrant, in an effort to reach higher fuel loads, would have higher refueling rates and/or stopover for longer periods on the NGOM than the shorter migrant species.

Results/Conclusions

Results from over 350 shorebirds sampled from 2011-2012 across 4 sites on the NGOM during spring migration indicate C. alpina is reaching higher fuel stores before departing on migration than C. pusilla and C. mauri. However, refueling rates did not differ significantly between species, suggesting it was the stopover duration that varied. Results from color banding studies during Spring 2013 indicate C. alpina is indeed spending longer (3-5 days on average) on the NGOM than the shorter migrant species. The results of this study indicate that the threatened NGOM habitats may be particularly important for migration success in C. alpina. This knowledge will enable us to evaluate the potential population level consequences of global change for NGOM shorebird populations and allow for the development of conservation plans that mitigate these impacts.