Habitat loss and alteration from land use change, species invasion, and more recently, climate change have reduced biodiversity and ecosystem function worldwide. Habitat decisions have important implications to individual fitness as well as population dynamics and community structure. Resource limitation, predation, competition, and unfavorable abiotic conditions all have the potential to influence survival and future reproductive potential. Understanding how changes to ecosystem structure and function impact species and populations of conservation concern is essential for conservation delivery to be effective. Similar to many migratory species, shorebird populations are declining worldwide and declines may be related to the loss of important stopover habitat in the form of mid-continental wetlands.
During 2010-2011, I examined how long-distance migratory shorebirds have responded to extensive, agriculturally-driven alterations to wetland habitats. I focused on a suite of ecological conditions that are expected to influence migrant fitness, including habitat preference, resource availability, and behavior. Additionally, because land use change is expected to act in conjunction with climate change to alter wetland habitats, I examined a number of phenologic variables and made predictions on how migrants might be affected in the future.
Results showed that migrant shorebirds were more likely to use highly-altered, agricultural wetlands than wetlands embedded in native grasslands and did so in greater numbers. Preference for altered habitat was unexpected because these habitats had lower food availability, but preference may be explained by the role of mud flat as an influential cue, which would increase the attractiveness of agricultural wetlands. Such a scenario can be indicative of an ecological trap, where individuals prefer lower quality habitat. However, behavioral analysis indicates that migrants have adapted to using novel habitats through increased foraging efficiency. Despite their apparent adaptability to changing conditions, migrant shorebirds may be susceptible to further population decline as a result of changes in phenology brought about by climate change. Results showed that peak migration is correlated with the availability of food resources. Given that shorebirds already prefer habitat with lower resource availability, any changes to invertebrate or migration phenology that is not congruent in magnitude and direction to the other could affect migrant populations.
