Abstract

A flock of 100–150 Carduelis flammea (Common Redpolls) made at least 252 cavities and short tunnels in fluffy snow over 5 consecutive days in western Maine at temperatures from -26 °C to -14 °C. They produced neither structure during 4 days when temperatures were above freezing and the snow was wet, nor during a month of other variable weather. In the same area during two winters, Carduelis tristis (American Goldfinches), Carpodacus purpureus (Purple Finches), Pinicola enuncleator (Pine Grosbeaks), and Coccothraustes vespertinus (Evening Grosbeaks) exhibited no snow tunneling behavior at any time even though, excluding the Pine Grosbeaks and Goldfinches, I observed them throughout the entirety of 2 winters. Common Redpolls did not use the observed snow cavities as shelters, nor did the structures appear to be related to foraging. Social stimulation and play are likely proximate stimuli for the behavioral release of the Common Redpolls' snow-manipulating behavior.