Vol. 44, No. 4
David M. Larson
Increasing numbers of studies have shown that global climate change alters phenology of plant and animal communities and is implicated in changes in bird populations and behavior. One potential problem involves reductions in habitat availability, especially for species dependent upon restricted habitats, e.g., loss of salt marshes for Saltmarsh Sparrow. Another set of problems that has been well documented is mismatches between migratory bird movement times and prey availability peaks. Birds have evolved migratory strategies that rely on abundant prey at migratory stopover points and during crucial feeding periods for nestlings. When food resource availability peaks earlier due to altered climatic conditions but bird migration does not or cannot adjust as rapidly, the result can be reduced adult fitness and migration delays. Mismatches between breeding and peak resources on the breeding grounds can lead to increased mortality of hatchlings. But climate-induced effects need not be so obviously direct.