It turns out that, while lemmings are an important food resource
for Snowy Owls, Snowies have a fairly varied diet which includes
voles, deer mice, hares, ptarmigans and seabirds up in their usual tundra
haunts. During the irruption of 1996-97, snowies were seen chasing
Black-bellied Plovers and Sanderlings along the coast.

See:
PARMELEE, D.F. 1992. Snowy Owl. In The birds of North American
No. 10 (A. Poole, P. Stetttenheim, and F. Gill, eds.). The Acad.
of Nat. Sci., Philadelphia, and The Am. Ornithol. Union, Washington, DC.

and for a re-examination of the controversial lemming/Snowy Owl
connection see:

KERLINGER, P., M.R.LEIN, and B.J.SEVICK. 1985. Distribution and
population fluctuations of wintering Snowy Owls (Nyctea scandiaca) in
North America. Canadian J. Zoo. 63:1829-1834.

Kerlinger suggests that Snowy Owl irruptions are more probably
associated with weather events rather than lemming events.

--
Mike Patterson
Astoria, OR
celata at pacifier.com

Book Review: _Rare Bird_ by Maria Mudd Ruth
http://www.surfbirds.com/blogs/mbalame/archives/003190.html