Use of seeded exotic grasslands by wintering birds

Abstract

Despite widespread population declines of North American grassland birds, effects of anthropogenic disturbance on wintering habitat of this guild remain poorly understood. We compared avian abundance and habitat structure in fields planted to the exotic grass Old World bluestem ( Bothriochloa ischaemum ; OWB) to that in native mixed-grass prairie. During winters of 2007–2008 and 2008–2009, we conducted bird and vegetation surveys in six native grass and six OWB fields in Garfield, Grant, and Alfalfa counties, Oklahoma. We recorded 24 species of wintering birds in native fields and 14 species in OWB monocultures. While vegetation structure was similar between field types, abundance of short-eared owls ( Asio flammeus ), northern harriers ( Circus cyaneus ) and Smith’s longspurs ( Calcarius pictus ) was higher in OWB fields during at least one year. The use of OWB fields by multiple species occupying different trophic positions suggested that vegetation structure of OWB can meet habitat requirements of some wintering birds, but there is insufficient evidence to determine if it provides superior conditions to native grasses.