(Julie Craves, 31 January 2017)
If liquid water is unavailable, a number of species will bathe using snow. When the snow penetrates ruffled feathers, it melts, dampening the feathers. Birds then preen as they would after a water bath, cleaning their feathers and using oils from the preen gland for waterproofing. Birds use the same types of maneuvers in snow that they use when bathing in water — lowering the head and flicking the wings.
I’ve read fascinating reports of Common Redpolls performing movements that seem to be derived from snow-bathing. The birds put their heads into fluffy snow and flutter their wings. Then, rather than lifting their heads, shaking the snow into their feathers, and preening, the redpolls simply move forward, creating tunnels. Biologist Bernd Heinrich, the well-known author and professor emeritus at the University of Vermont, published detailed observations of the behavior. He noted that it appeared to be stimulated by the related actions of flockmates: When one bird started tunneling, others joined in. Heinrich found no evidence that the tunneling served any obvious purpose and concluded the play-like behavior was potentially useful in conditions where it might be necessary to shelter in snow tunnels.