Thanks for the information, Mike. Interesting to hear that they have a much
more varied diet!

On documentaries I have seen, bountiful lemming years lead to higher
clutches and increased chick survival in Snowies. In abundant lemming
years, literally stacks of dead lemmings can be found around the nests of
Snowy Owls that they cache for the young to consume when needed. These
years of high nest success and high fledging rates result in higher
populations of adult birds in subsequent years. Thus, in down populations
of lemming years, usually following a boom year, food becomes scarce and
many birds, particularly juveniles, move south in search of food. Thus,
although they may feed on more than just lemmings, lemming cycles seem to
dictate, at least to some degree, large numbers of snowies moving south.
So, I guess one could say, an abundant lemming year inadvertantly leads to
irruptions...:-)

Thanks for the article you mentioned from Kerlinger et. al. I will have to
find that and read up on it.

Good birding.

Jeff Kozma
Yakima