Northern Parula Parula americana
Flight call description A high, clear, descending "tsew".
Fig.1. New Jersey October 1, 1996 (MO).
Bird in flight.
Similar species Pine Warbler is typically weaker, higher, and less descending. Yellow-throated Warbler is lower and more downward-arched. See Cape May Warbler, Bachman's Sparrow, and descending seeps.
Behavior Primarily a nocturnal migrant but engages in redetermined migration. Gives flight call regularly while perched and in flight during the day, and during nocturnal migration.
Spectrographic description Measured calls (N=10) were 41.5-56.4 (47.7) mS in duration and in the 5.3-9.2 (6-8.5) kHz frequency range. The frequency track was single-banded, fairly steeply descending, and often with a slight downward hook at the beginning. There was often a fine modulation throughout the call with a spacing of 3.6-4.7 (4) mS between humps.