the Tommy Thompson Park Bird Research Station in Toronto presents stellar comparisons of both the mainland and Greenland subspecies of Common Redpoll as well as Common to Hoary Redpoll. Fascinating stuff. If you’re in a Carduelis state of mind, Nick Sly has a slew of redpoll resources.
Mike is a leading authority in the field of standardized test preparation, but he's also a traveler who fully expects to see every bird in the world. Besides founding 10,000 Birds in 2003, Mike has also created a number of other entertaining but now extirpated nature blog resources, particularly the Nature Blog Network and I and the Bird.
Hey, thanks for the link! That Toronto site is fantastic.