Wilson's Warbler Wilsonia pusilla
Flight call description An abrupt, liquid "spiv".
Fig.1. New Jersey September 16, 2001 (MO).
Perched bird.
Similar species Sounds similar to Canada Warbler but softer and less buzzy. Similar to Black-throated Blue Warbler but softer and more complex.
Behavior Primarily a nocturnal migrant but engages in redetermined migration. Seems to give flight call primarily while in active migration flight (either at night or in active migration flight).
Spectrographic description Measured calls (N=5) were 15.9-37.5 (27.5) mS in duration and in the 4.4-8.8 (5.4-7.9) kHz frequency range. The frequency track was single-banded or with a partial second band and had an initial steeply rising section followed by an equally steep descending section creating an inverted "V". In some cases there was an additional variable rising section. Presumed Wilson's nocturnal calls were typically longer and more often showed a rising section at the end of the call.