Subject: Fw: [Tweeters] phenomenon's to consider (re: Snowy Irruptions)
Date: Dec 18 21:49:24 2005
From: Jeff Kozma - jkozma at charter.net




I believe that raptors do not move south and congregate in areas of high rodent populations because they "know" there are high populations of rodents there. It seems perfectly plausible to me that the birds are simply moving through on migration and find these areas of elevated prey populations and stay because of the food. Also, these areas can support the high raptor populations because of the high prey. I have seen this when I worked on the Yakima Training Center in regards to Rough-legged Hawks and Short-eared Owls, both being extremely abundant in winters when it is hard to walk through the sagebrush without stepping on a vole (exaggeration of course). In these situations, the Short-eared Owls were also present in high numbers during the following breeding season, presumably staying to breed in above average numbers to take advantage of the abundant vole population. In addition, it was not uncommon to encounter a lone Rough-legged Hawk or two into the following May. This is similar to the congregation of crossbills and other seedeaters as mentioned earlier.

Jeff Kozma
Yakima