Thanks Mike. Many of the Snowy Owls I've seen in the Calgary area have been
adults, and in the study by Kerlinger and Lein (1988), most of the specimens
in the sample of Snowies from Alberta were also adults. Therefore I'm not
particularly surprised by the study's findings, since it stands to reason
that adults make better hunters than immatures.

In addition to the potential sources of bias mentioned by the authors, there
is the fact that we are not told when the specimens were collected. If the
sample was biased toward specimens collected in early winter, the ratio of
adults to immatures might be such that starvation would seem to be a
significant cause of mortality.

I know that Snowy Owls have been turned in to wildife rehabilitation centers
in the Pacific Northwest and found to be emaciated. Perhaps the data
collected at these centers could shed some light on Snowy Owl irruptions in
this region.

Regards,
Jason Rogers
Banff, AB
hawkowl at hotmail.com