Feb 15 2013

Bigger Is Better In Winter

Published by at 7:30 am under Songbirds,Tenth Page

Male House Sparrow (phot by David Lofink via Wikimedia Commons)

Much as we're unhappy with the results, the introduction of house sparrows from Europe began a grand experiment in avian adaptation.

House sparrows were introduced to both the U.S. and New Zealand in the 1850s where they immediately became isolated from their native populations.  More than 150 years later they differ based on where they live.

In addition to changes in plumage the birds are different sizes.  In locations where winters are harsh, the birds are large.  Where the climate is moderate, they are smaller.  This effect is called Bergmann's rule and is true of birds around the world.

In 1992 William A. Buttermer studied house sparrows at a winter roost in Ann Arbor, Michigan where he found that the largest males survived the best.

Not only were the large birds able to thermoregulate better than the small ones but they had two other advantages.  The larger birds claimed the most favored roosts and they were able to fast longer.

During winter storms birds must roost and wait for the weather to improve, so they are forced to fast.  The larger birds survived fasting better than small ones.

It's better to be bigger in winter.

(photo by David Lofink via Wikimedia Commons.  Click on the image to see the original.  Tenth Page is a "wild card" inspired by page 161 of Ornithology by Frank B. Gill.)

2 responses so far

2 Responses to “Bigger Is Better In Winter”

  1. kcon 15 Feb 2013 at 9:25 am

    Sort of an aside…but I am a small person. I spend a lot of time outside and I live in a freezing cold house. I swear to you that every fall my appetite is markedly greater. I always seem hungry. I don’t know that I gain weight, but my body seems to be wanting me to.

  2. Kate St. Johnon 15 Feb 2013 at 8:39 pm

    kc, I agree! When it’s cold I am always hungry. This is true of birds too. In a book by Berndt Heinrich called Winter World: The Ingenuity of Animal Survival, I read that chickadees can die of *starvation* on a cold winter night if they don’t eat enough during the day.

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