Habitat associations of landbirds in southern Texas during migration

Abstract

It is estimated that about 80% of North American avian migrants travel along the southern coast of Texas. Quality of stopover habitat for landbirds in southern Texas is a concern, however, due to agricultural and wind energy development and increasing urbanization. Since little regional research has been conducted on stopover habitat use, we investigated habitat associations of migratory birds to identify important factors driving density along the southern Texas coast. We did this using data from landbird surveys, which took place during spring and autumn migrations from 1991 to 1993 and 2006 to 2008, within 6 land-cover types common in southern Texas. We found that oak motte had the highest density among most bird guilds. A total of 125 species of birds were detected over the course of our study and species richness was highest in oak motte and lowest in grassland. In general, land-cover types with more woody vegetation cover tended to have higher species richness and diversity than those with minimal to no woody vegetation. Although grassland ranked lowest in other metrics of bird use, it ranked highest in habitat conservation value, which accounts for species of concern. At the time of this study, Golden-winged Warbler (Vermivora chrysoptera) was the only species on Partners in Flight's Red Watch List (highly vulnerable and in need of special attention) that we observed, with recorded observations occurring in oak motte and woodland exclusively. Oak mottes are likely a prime location for species to land after flying over the Gulf of Mexico during their journey north to their breeding grounds, thus land managers that wish to provide high-quality stopover sites for migratory landbirds should preserve them.