Use and possible functions of large song repertoires by male Eastern Bluebirds

Abstract

Abstract Five male Eastern Bluebirds (Sialia sialis) were observed and songs recorded over entire breeding seasons in central Kentucky. Songs consisted of an average of 3.02 notes and the mean time between the beginning of successive songs within a bout was 7.26 s. Most songs (63.7%) given by male bluebirds were low volume, while 14.8% were moderate volume, and 21.5% were high volume. Individual male bluebirds possessed large (x = 59.4) repertoires of song types, and few were shared among two or more males. Singing rates varied among breeding stages, with high rates during the pre-pairing period suggesting that song plays a role in mate attraction. However, male bluebirds also sing during interactions with conspecific males, indicating an aggressive or territorial function, to facilitate the transfer of food to incubating or brooding females, nestlings, and fledglings, and to warn mates, nestlings, or fledglings about the presence of a potential predator. Thus, as reported in an increasing number of spec...