Patterns in habitat selection between breeding and wintering grounds of Neotropical migrant passerines

Abstract

Migratory animals must select suitable habitat in different locations to take advantage of abundances of resources and escape harsh climates during seasonal changes. Niche tracking occurs when migratory animals fill the same niche space on the breeding and wintering grounds. Overlap of niche space is expected to occur because of physiological or behavioral needs, even though resources available on native and migratory ranges may differ. Neotropical birds migrate to breed where there is an abundance of potential mates and nesting sites and to winter where environmental conditions are less harsh. My objective was to assess whether Neotrocal migrants tracked niche space between the breeding and wintering grounds. I measured microclimate and vegetation structure in the Ouachita National Forest (breeding) in southeastern Oklahoma and La Milpa Field Station in Orange Walk, Belize (wintering). I predicted that microclimate would be tracked by more species than vegetation structure. I did not find strong evidence that niche tracking occurred in Neotropical migrants for microclimatic conditions or vegetation structure, even though some patterns were apparent between microclimate and vegetation structure selection on the breeding and wintering grounds. Investigations of niche tracking at finer scales will help further our understanding of which physiological constraints and necessary resources contribute most to habitat selection in breeding and wintering grounds of migratory bird species, and how to predict future distributions in the face of major environmental changes.