Laura Erickson's For the Birds

An irruptive species, this exceptionally hardy little finch appears in backyards in huge numbers some years, and is virtually non-existent in the same places in other winters. In the wild, it eats birch, willow, alder, spruce, and pine seeds, and (when not snow-covered), seeds of grasses, sedges, and wildflowers, and occasional berries. In our backyards, it takes nyjer and sunflower, on the ground as well as in feeders. Keeping feeding stations raked when warmish weather arrives is important to prevent redpolls and siskins from getting salmonella, botulism, and other diseases from decomposing seed.

Although they do not have an entry in Guinness World Records, one study found that Common Redpolls survived down to -65º F and Hoary Redpolls down to an astonishing -88º F in a laboratory (colder than the record for the Emperor Penguin’s “Lowest temperature endured by a bird”), but I don’t know if that says more about the extreme warm-bloodedness of redpolls or the astonishing cold-bloodedness of some researchers.

I wrote a LOT about redpolls in this blogpost: Redpolls!