I just received this response to Jane Stein's question about dispersal and
lemming abundance from a Snowy Owl researcher:
"Post-breeding dispersal movements are poorly known in snowy owls. The main
reason for this is that they breed in remote locations, far from a fair
density of avid birders...
Using satellite transmitters, we were able to track the movements of adult
male and females over the years, but it is not known what happen at the
family level as to who is chasing off who and how right on the breeding
The thing is, lemmings can be abundant and readily available during summer,
a season that we call the "snow-free period". When snow comes back however
(this could happen anytime between August and November), lemming become
more difficult to get to. So the super-abundance of the snow-free period
can become just plain regular abundance or even low abundance, depending on
how thick and hard is the snow cover up there.
So, more research is need on this critical period that is straight after
breeding (post-breeding movement and behaviors)...
Dr. JF Therrien
Senior Research Biologist
Hawk Mountain Sanctuary