Roughie

Rough-legged hawk (Buteo lagopus), an Arctic buteo wintering on the high plains of eastern Colorado. 

 

My ever-observant Jessa asked, "Is it just me, or are the feet really small?" It's not just her; the roughie's wingspan averages longer than a redtail's, but the feet and talons are significantly smaller. The only other North American buteo with a comparable body plan—large body, disproportionately small feet—is the ferruginous hawk (B. regalis), which also happens to be the only other North American buteo with legs feathered down to the feet. 

I'll try to post something soon on Allen's Rule, but suffice it to say for now that both the rough-legged hawk's namesake feathered legs and its small feet are cold-climate adaptations. The small feet also correspond with the roughie's diet, which is about 90% comprised of lemmings, voles, and mice. Did the roughie's small-mammal specialisation drive the evolution of small feet in conjunction with Allen's Rule, or is it the result of having smaller feet pursuant to Allen's Rule? I suspect...both. Natural selection is full of feedback loops.

Photos © Jessa and Mark Farrell-Churchill.