“…The earliest and most thoroughly studied bird song systems come from temperate zone species where females are largely songless (Catchpole & Slater 2008;Slater & Mann 2004). In contrast to their temperate zone counterparts, many tropical females are prolific singers, performing coordinated vocal duets with males that function to defend territorial resources, guard their mate against intruding females, solicit copulations from their mates, and/or cardinal, red-winged blackbirds), occasionally in some (black-capped chickadees, black-headed grosbeak, dunnock, European robin, song sparrow, tree swallow, white-crowned sparrow, whitestripe morph of the white-throated sparrow, yellow warbler) and rarely in several others (Baltimore orioles, chestnut-sided warbler, common yellowthroat, hooded warbler, indigo bunting, rufous-sided towhee, Wilson's warbler (see Langmore 1998 for partial review; additional species : Beletsky 1982;Byers & King 2000;Gilbert & Carroll 1999;Hahn, Krysler, & Sturdy 2013;Lowther & Falls 1968;Nolan 1958;Ogden et al 2003;Sharman, Robertson, & Ratcliffe 1994;Taff, Littrell, & Freedman-Gallant 2012). For most of these species, however, the function of song remains unknown.…”