I often think of the many birds who brave winter temperatures in these parts down to -30°C/-22°F at night. Many species are small and therefore their surface area to volume ratio is a lot higher than a big animal. This creates a lot more potential for heat loss. However, they have many adaptations to survive including a fantastic plumage that traps warm air against the body (down) and protects against the wind and damp (outer contour feathers). Each feather can be raised or lowered to adjust the "loft" of the plumage to ambient conditions. That's why they often look like balls of fluff in really cold conditions. They seek sheltered locations during the night to reduce wind chill and often sun themselves to warm up. There's lots more but you get the idea.
Feeding ecology is also important in winter survival and most that stay eat nutritious, fat-rich seeds. This means they need the type of bill that is able to crack open or get at seeds, such as the finches and crossbills have. Insect/invertebrate eaters which usually have longer, thin bills usually migrate to places where their is food available.
OK, now to my main point of the post. I rarely see Brown Creepers in my back garden but they do spend the winter in the area. They are insect/invertebrate consumers but how do they scrape a living together in the dead of a Canadian winter? Well, I watched one today for about 30 minutes feeding up and down a Jack Pine tree in about -12°C/10°F temperatures. The bird was sticking its long, thin bill in crevices behind bits of bark on the trunk of the tree. It was not obvious to me what he/she might be finding until I reviewed the images I made of the little guy. The last one showed the bird with a spider in its bill (attached- not the best bird image I've ever made!). Upon closer study several of the other images showed some small animal in the bill but they were not easy to ID.
Anyway there you have it. There's insect food out there in the winter if you just know where to look for it, like a Brown Creeper!







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