Interestingly, I work with a raptor bander who has a colleague out west, and all of the birds he has caught have been in healthy body condition save for a couple of Snowy Owls at the start of the season (caught in Alberta), which is not unusual. Most of the Snowies in his study sites (in southern Ontario) are so well-fed they don't bother coming in to the traps. We only had one underweight bird this fall/winter - a Boreal. The rehab centre around here has had issues with emaciated Red-tails, but most of the owls have been admitted due to head trauma (cars, windows etc.) rather than emaciation.
Even so, it's the inevitable result of such a boom of young birds... raptor mortality for the first year is always incredibly high, it just seems higher in certain places this winter because a) they had more young and b) the rodent population is low this winter. If they all survived, the prey base would not support them long and the population would crash regardless.
