Determining barriers to fine-scale dispersal in two endangered migratory songbirds

Dispersal is one of the most important life history characteristics of any species, especially for species in fragmented habitats, yet it is the least understood. Dispersal is extremely important as it determines whether new suitable habitats will be colonized, or whether species will successfully relocate following disturbances. I am studying two species of endangered migratory songbirds -The Golden-cheeked Warbler and the Black-capped Vireo -both species that breed in oak-juniper forests of central Texas. Initial data on range-wide gene flow in these two species based on microsatellite markers indicates that populations are undergoing genetic differentiation. This worrying trend raises questions about habitat connectivity, or social barriers to dispersal. Populations exhibit spatial structure due to social or demographic factors that impose limitations on individual movements. By analyzing pedigrees and relatedness of individuals in space, I am trying to obtain an understanding of whether individuals disperse non-randomly with respect to proximity of related individuals. Additionally, by reconstructing parentage, I am also testing whether the genetic mating system differs from the social mating system, i.e., whether there is evidence for extra-pair mating. Since dispersal is a result of breeding behaviors in most songbirds, teasing out the nexus of dispersal-breeding biology is of central importance in population studies and in management of habitat for endangered species. GIS information about habitat connectivity together with information of fine-scale dispersal can be very beneficial to habitat management and species conservation.