Hi Tweeters,
I would agree with Doug regarding Snowy Owls. I don't know anyone working with this species that can say why they come down in certain years.
I was talking with Denver Holt of the Owl Institute in Montana about the irruption this year. He has studied breeding Snowys at Pt. Barrow, AK, over the last 14 years. This year, they only had 4 breeding pairs there. He did say that after the hatching period, they had the highest numbers of lemmings they have ever seen in their study area. But the late "lemming bloom" does not impact the number of eggs produced. So this is unlikely to be the cause. I have talked to other Alaskan raptor people that also think weather is the most likely factor but, as far as I can tell, no one really knows for certain.
Also I would agree with Mike Patterson's comments about sexing and ageing them. It is definitely not as easy as you might think. I hope Mike puts together another excellent distribution map as he did during the last irruption.
In addition, some people will tell you that all of the Snowys that come down here will die down here. Certainly, some do. However, among the 10 that we caught and wing-tagged here in western WA in 1997, two definitely returned. One bird came back the following year (98) and another returned the next year(99). At those times they were far more "mobile" and showed up all over the Skagit Flats. In contrast, during their first year here, they regularly roosted together in the same fields and were quite predictable. One large Snowy actually learned to roost inside a large barn like a Barn Owl.
We have also had late influxes of Snowys in Skagit County. One winter, a group of 6 showed up overnight in a single field in mid-February on the Samish Flats.
Finally, I notice that alot of people have commented on the number on Short-eared Owls around this year. Well, unfortunately Snowy Owls will catch and eat Short-ears. There have been several observations of this in WA. So you can likely expect Short-ear numbers to be noticeably lower next year.
One of the things that I like most about Snowy Owls is that they remind us that we still don't know it all when it comes to birds.

Bud Anderson
Falcon Research Group
Box 248
Bow, WA 98232
(360) 757-1911
bud at frg.org