Eat to stay warm

On these intensely cold days, the birds hit the feeders before sunrise to replenish their energy for the day.  I found this cardinal digging around at the base of one of the feeders and realized it must be mostly empty.

A bunch of sunflower seeds had piled up underneath the feeder, and I assume the cardinal dug through the snow to find them.

A bunch of sunflower seeds had piled up underneath the feeder, and I assume the cardinal dug through the snow to find them.  Smart bird!

Sub-zero temperatures make the suet cakes concrete-hard so that the woodpeckers have to drill them to get a bite.

This stuff is as hard as tree bark at -12F.

“This stuff is as harder than tree bark at -12F.”  Red-bellied Woodpecker

Peanut butter suet seems more attractive to the Downy Woodpecker and easier to extract.

Peanut butter suet seems more attractive to the Downy Woodpecker and easier to extract.

Animals convert their daily food intake to fat stores, which are then metabolized overnight at a prodigious rate.  Black-capped Chickadees, for example, can turn-over 25% of their body weight overnight on a very cold night.

But energy costs (metabolic rate on the Y-axis below) go up as the temperatures go down (on the X-axis below), and the smaller the animal, the higher that rate of fuel consumption and energy burn, as shown in the graph below.

Avian Energy Balance and Thermoregulation (http://people.eku.edu/ritchisong/birdmetabolism.html)

Avian Energy Balance and Thermoregulation (http://people.eku.edu/ritchisong/birdmetabolism.html)

At some point, there is a limit to how much heat a small animal like a Downy Woodpecker can produce in order to stay warm, and still make it through the night revving its furnace to that high level.  A friend of mine found that 80% of the Downy Woodpeckers they tested in the winter in South Dakota became hypothermic (3-5 degrees below normal) after 30 min exposure to 5F, which leads me to wonder how these birds are faring at our current below 0F temperatures.

18 thoughts on “Eat to stay warm

  1. We have a pretty nice collection of birds that clean up after our hens. I think some of them recognize faces as they come near when my man or I exit the house but take off if anyone comes to visit.

    • Interesting. I didn’t realize birds paid attention to human differences, but why not?! You’d think they would do threat assessment to survive.

      • Crows sure do–the U of Washington did some really cool experiments on that–they recognize human faces (the crows, that is, though presumably the researchers do too 😉 and that makes me wonder if other birds do too?

      • I think some of them might recognize me. While cardinals and sparrows will always dive into a shrub when I go out to the yard, some of them look up from the feeder, see me, and just keep eating. The downies and doves just ignore me.

  2. Oh, dear. Now I am really going to worry more about these poor birds at night around here! I really do not see how they make it thru the night, if 30 minutes at 5F starts to do them in!

    • Me either, but remember those data were from a lab experiment with birds in a tin can, not their normal wooden roosting hole. So hopefully, micro environments help somewhat.

  3. I worry about the little birds too. We haven’t had temps this cold in the Chicago area for several years so this is probably a new experience for many of the year-round residents. I’m the local “bird buffet” serving four types of seed, suet, peanuts and water, and I’ve had a lot of visitors the past few days.

    I noticed the woodpeckers really pounding on the suet too. I usually switch to a homemade peanut butter variety for the coldest months – have to make a batch of that soon.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s