Use of two song categories by Golden-cheeked Warblers

I tape-recorded and counted the songs of color-banded Golden-cheeked Warblers (Dendroica chrysoparia) on Fort Hood, Texas in 1993 and 1994 to determine whether males use a two-category song system common to many wood-warbler species. More than 97% of all songs I documented belonged to two categories: A and B. A songs were higher in frequency, shorter, less complex, and were delivered at lower rates than B songs. Males used A songs primarily early in the nesting season, when near females, and from the interior of territories. In contrast, B songs were more common later in the nesting season, at dawn, and when males sang near territory boundaries. Songs delivered near territory edges were usually sung from one or two preferred perches on each male's territory that often coincided with the edge of a cliff or a break in the forest canopy. Based on these data, and in contrast to the implications of an early account of Golden-cheeked Warbler song use, this species shares the song system used by many wood-warbler species. Furthermore, the patterns of song use that I observed suggest that males do not sing randomly with respect to time or location on territory, and monitoring efforts that assume random singing across time and space may result in inaccurate or biased estimates of population sizes and habitat preferences.