Wednesday, January 30, 2008

Birds and the Deep Freeze

This morning we looked out our kitchen window and saw a group of birds huddled together in the bushes, looking very puffy. During last week's deep freeze, I started thinking about our Minnesota wildlife and wondering how critters make it through these times of bitter cold. I did a little research and found some great information through the Wolf Ridge Environmental Learning Center about the adaptability of our feathered friends!

The first fascinating tidbit I learned is that of the roughly 650 species of birds that live in North America, about 75% of them participate in some sort of migratory behavior. Some of these migrate within the continental United States, and some head all the way down to South America. Some species that overwinter in Minnesota have migrated here from parts further north.

For the birds that call our neck of the woods home during the winter, their focus is naturally on finding food and staying warm. How much and what kind of food birds eat during the day determines how well they will be able to maintain a sufficiently warm body temperature during the night. Some birds hide or cache food during times of plenty, which gives them a little break when times are lean, assuming no other critters found it first!

Now about those puffy birds outside my kitchen window. They were apparently fluffing themselves up to create air pockets between their feathers and skin to help retain heat. To see what I mean about the fluffing up, compare the 2 pictures on the right of the robin. They can also shiver (like people do) to help them stay warm, will snuggle up with each other, and some birds also add extra feathers before winter.

The coolest adaptation I've read about is torpor, where the bird goes into a short-term hibernation-like state to conserve energy. Their metabolic rate dramatically drops, resulting in a drop in most of their body functions, including body temperature, heart rate, and respiration rate, and making them appear to be in sort of a trance. I wasn't able to find which species of birds in Minnesota have this adaptation, so if anyone knows, leave it in the comments section!

Photos by Bryce Mullet
Robin unpuffed:
Robin puffed:

1 comment:

Anonymous said...

Dad has read an article that Black-Capped Chickadees which stay here year round are able to lower their heart rate when they're resting usually out of the wind in a hole in a tree of somewhere similar.

On a related subject he read that owls (he thinks it's the barred owl or the great horned owl) has been observed with a rabbit or squirrel kill in a tree. After feeding on it, it covers it up and sits on it to keep it from freezing so it has food for the next few days.