THE list of species that are shrinking due to climate change keeps on growing. Birds now join sheep and trees in wasting away as the temperature rises.
To discover whether there had been any change in bird size over the past century, Janet Gardner of the Australian National University in Canberra and colleagues measured the wingspan of 517 birds held in museum collections. The birds, belonging to eight species native to Australia, had been collected between 1860 and 2001. They found that four species had shrunk by up to 4 per cent in 100 years (Proceedings of the Royal Society B, ).
Two factors could explain this. Environmental degradation could have made the birds’ diet poorer, or warmer temperatures could have given an edge to birds with smaller body sizes, as they are better able to cool off. Using feather length as a proxy for nutritional status in birds, the researchers were able to rule out the possibility that smaller birds were less well nourished than their ancestors. This left global warming as the most likely culprit.
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