There is the famous peppered moth of the U.K., which flipped from light-colored to dark-colored as a result of the discoloration of its habitat by coal soot in the 19th century and then back again towards the end of the 20th century as those conditions cleared up. Nevertheless, the Finnish tawny owl may join a relatively short list of animals that have been shown to have evolved in response to human-induced changes to the environment. In fact, browner and grayer owls have roughly the same level of survival through winter these days (an improvement for the browns and stasis for the grays). In fact, since at least 1961, the proportion of brown tawny owls caught by ornithologists throughout Finland has increased, adding more circumstantial evidence in support of the finding.Īt the same time, there is no direct evidence yet to support any of those possible explanations for why brown owls would do any better than gray owls, even in milder winters, as the researchers admit. Or it may be that the brown coloration is also tied to the owl's physiology, like the strength of its immune system or how much food it needs to eat. Less snow means less chance of brown owls standing out against a white landscape as they stalk their prey-or falling prey to the dread Bubo bubo (the eagle owl). The reason? Unknown for sure, but Finnish winters have become milder in recent decades thanks to climate change-with much less snow. More specifically, more brown owls survived Finnish winters. Over the course of the study led by bird ecologist Patrik Karell of the University of Helsinki-from 1981 to 2008-the brown owls started to increase in numbers. Since the owls do not seem to show a sexual preference for either darker or lighter feathers, the main driving force for any change in plumage would be natural selection, in this case, most likely, whether a dark or a light coat helped in catching more voles, the raptor's primary food. ( Scientific American is part of the Nature Publishing Group.) Finnish researchers scored tawny owls ( Strix aluco)-a raptor common to all of Europe-on the color of their plumage, specifically how brown (dark) or gray (pale) their feathers were. For want of snow, the tawny owl of Finland has become more brown in the past half-century, according to new research published February 22 in Nature Communications.
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