Acute but not chronic effects of predator presence on song sparrow (Melospiza melodia) singing behaviour

The North American Breeding Bird Survey (BBS) indicates long term declines for many songbird species. As surveys are based partially on auditory cues, a change in the song rate could affect survey numbers. Here I test the hypothesis that the danger posed by raptor presence affects songbird singing behaviour. I measured the singing behaviour of song sparrows (Melospiza melodia) in relation to both chronic (active Cooper’s hawk Accipiter cooperii nest nearby) and acute (playback of hawk calls) predator exposure. I found no evidence for a chronic effect, but song sparrows reduced their singing rate by 37.5% in the minutes after acute exposure. There was no reduction in response to control playbacks. My results suggest that the BBS census declines of songbirds could potentially be partially accounted for by a reduction in song as raptor populations recovered after the 1973 ban on DDT.