One female Hooded Warbler (Wilsonia citrina) was discovered singing in July 1993, and another in May 1996 among a color-banded breeding population under investigation. The first female's song structurally resembled the typical male Hooded Warbler mixed-mode song in duration, frequency range, and number of syllables, although it had an atypical raspy quality. Males responded similarly to playbacks of the female song and a male song from the same population. We suggest that age and high breeding density may be explanatory factors for this rare behavior.
Evans Ogden, Lesley J.; Neudorf, Diane L.H.; Pitcher, Trevo E.; and Stutchbury, Bridget J.M., "Female song in the hooded warbler" (2003). Northeastern Naturalist, 10, 4, 457-464.