Songbirds in the US are getting smaller, and climate change is suspected as the cause.
A study of almost half a million birds, belonging to over 100 species, shows that many are gradually becoming lighter and growing shorter wings. This shrinkage has occurred within just half a century in response to warmer temperatures, and at this rate, many may disappear by 2035.
In biology, there is a general rule of thumb that animals tend to become smaller in warmer climates: an idea known as Bergman’s Rule. Usually this trend can be seen among animal species that live over a range of latitude or altitude, with individuals living at more northern latitudes or higher up cooler mountains being slightly larger than those below. But global warming has thrown this process into overdrive, and many of the birds in North America will soon become so small, they will literally wink out of existence.

A black-capped chickadee is half as large as it cousins of thirty years ago
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The WWF funded study examined the weight and size of 48 individual birds that had been caught and measured at the ringing station from 1961 to 2007. What the scientists found was striking. The birds in North America are getting small. Lead Ornithologist Steve Martin was laughed at when he first proposed his thesis, but his critics are laughing no more.
The differences in size are stunning.
“On average, the decline in mass of spring migrants over the 46 year study was 50%. That’s shocking as a young boy changing shoe sizes in reverse” says Doc Martin. The rose-breasted grosbeak has declined in mass by about 40%, while the Kentucky warbler has dropped 30.3% in weight and the scarlet tanager 20.3%.

Kentucky warblers are now 30% lighter
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The trend is particularly noticeable among those birds that have bright colors.
“In one obvious sense, the consequences are positive,” says Dr Rajendra Pachauri, head of the IPCC. “Now people will have to take global warming and the IPCC more serious, or else we will lose the ability to buy downy blankets or goose feather pillows”.

Rose-breasted gosbeaks are now 40% lighter
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“Luckily, India has few birds, and this problem is not seen in the bird populations in my country, so we in India will not have to cut our greenhouse gas emissions” he added.
Dr. Martin laments “When we take pictures, we ask you to ‘watch the birdie’. Future generations will have no idea what that means and will think you’re cuckcoo. It’s really tragic”.
Original Story Here.