Nocturnal migration is a common strategy among North American passerines. Birds of the Fringillidae have typically been labeled as predominately diurnal migrants. We used pressure-zone microphones and automated sound detection software to record flight calls of nocturnally migrating birds from 2 to 16 October 2008 from 2000 to 0600 hrs EST at three locations near Gardiner, Maine. We detected and recorded 190 Pine Siskin (Spinus pinus) flight calls from throughout the night at three separate locations. This is the first published documentation of apparent nocturnal migration in this species. Nocturnal migration may be a facultative migration strategy in the Fringillidae that occurs only in years in which large irruptive movements occur as for Pine Siskins in fall 2008.