And it’s NOT related to the oil spill! – If we could talk to the birds, what would they tell us? They would say, “Help, we’re shrinking!” US songbirds are getting smaller, becoming lighter in weight with shorter wings. This has happened in the last 50 years, which leads scientists to conclude that it’s a result of climate change. Biologists call this “Bergman’s Rule,” which states that animals tend to be smaller in warmer climates. Even in the same area, animals living at higher elevations (such as on mountains) are smaller than the same animals living down below. In the case of birds, this doesn’t seem to be harmful to them.
In BBC News, Matt Walker quotes researcher Josh van Buskirk as saying, “The body sizes of many species of North American birds, mostly songbirds, are gradually becoming smaller.” His team thinks more data is needed to see if it is happening to animals other than birds, as well.
Meanwhile, birds may be shrinking, but their BONES are as heavy as ever. Bird bones are surprisingly heavy, especially since they’re HOLLOW. We would think that the bones of creatures that fly would be lightweight, but this isn’t the case. Bird skeletons do not actually weigh any less than the skeletons of similarly sized mammals: In other words, the skeleton of a two-ounce songbird weighs just as much as the skeleton of a two-ounce rodent.
Bat researcher Elizabeth Dumont wanted to find out how bird skeletons can look so delicate and still be heavy. Over time bird bones have evolved specializations that maximize stiffness and strength. Dumont discovered that bird bones are denser than mammal bones, which makes them heavy even though they are thin and sometimes even hollow. She says, “Maximizing stiffness and strength relative to weight are optimization strategies that are used in the design of strong and stiff but lightweight man-made airframes.”
As the birds we know migrate back and forth between wintering and breeding grounds, it’s good to know that even tiny patches of woods in urban areas seem to provide adequate food and protection for some species. This is important because, with the expansion of cities worldwide, migrating land birds increasingly must pass through vast urban areas which offer very little of the forest habitats on which many species rely.
Researcher Stephen Matthews says, “The good news is that the birds in our study seemed to be finding enough food in even the smaller urban habitats to refuel and continue their journey.”
We’re not shrinking–in fact we’re bigger than ever–but we may go the way of the dodo if we don’t get more support from our readers and listeners: Despite having no advertising on other media, we have 60% more readers and listeners than we did a year ago, through word-of-mouth alone. Now if only more of you would support us, there’s a chance we might still be here tomorrow!
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Art credit: Dreamstime.com
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