Two weeks ago, it rained on us for a solid 22 hours. (Which, I discovered, is exactly the time it takes for puddles to start forming inside my tent.) So when it got grey and thundery at the beginning of last week, I jumped: “We’ve got to process this junco quickly! Take down the nets! We have to get back to camp to cover the firewood!”
Of course, it didn’t rain. The next time it got grey and thundery, I jumped less: “Let’s take down one net and keep this one. Tell me if you see lightning.” It didn’t rain.
The third time it got grey and thundery, I didn’t jump at all. Then it actually started raining—but I really wanted another junco. So we caught a male in (very light) rain and banded him under a tree, naming him KKRA, which sounds a bit like the thunder that was rolling in the distance.
KKRA, who has one white feather on his cheek
Happy New Year! In honor of brand-shiny-new 2013, I have… a continuation of the last post. I left a few things out of that post, since it was starting to get quite long; and then in the course of researching to answer some comments, I found some more things; so here are a few more ways that birds keep warm.
I’m currently visiting Chicago, relishing the finger-stiffening, face-numbing cold and wind that make up a proper midwest winter. Whenever I look out from the warmth of my big puffy coat and see a bird, I feel a little bad for enjoying the weather so much. I can go home and make myself hot tea; they can’t.
Very cold Tree Swallows (up in the Yukon, not Chicago!). Photo by Keith Williams
Like mammals, birds are endothermic (“warm-blooded”), meaning that they maintain their body temperature independent of the outside environment. This almost always means keeping themselves warmer than the outside air. Birds have quite high natural body temperatures, even higher than ours, so any given outside temperature seems even colder to them than it does to us.
Birds are also smaller than we are (well, omitting the ostrich), which means that they have a higher surface-area-to-volume ratio than we do. This is a problem because the volume (inside) of an animal is where heat is produced and stored, while the surface (skin) of the animal is where heat is lost to the environment. Imagine holding your hand in a bitter wind: how would you keep it warm? By making a fist. Making a fist reduces the surface-area-to-volume ratio of your hand, and lets it keep warm longer. In contrast, if you hold your hand out flat with all the fingers spread, your surface-area-to-volume ratio is larger, and your hand will get cold very quickly. Because birds have higher surface-area-to-volume ratios than we do, keeping warm is harder for them. How do they do it?
Climate change will affect every corner of the globe in some way, from rising average temperatures to ocean acidification to increasingly extreme and unpredictable weather. It may eventually lead to coastal habitat becoming submerged and the desertification of once-green areas. Currently, however, one of the areas in which climate change exhibits its most dramatic effects is on mountains.
Sierra Nevada mountains
On mountains, the variation in elevation causes habitats to change over relatively small areas. Species may be adapted to just a small strip of habitat within a certain elevational range. With changing climatic conditions, those strips of habitat may move on the mountain, and species then have to follow that strip – track their climatic niche – or stay put and adapt rapidly to the new conditions there.