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, with the birds thought to be evolving into a smaller size in response to warmer temperatures. However, there is little evidence that the change is harmful to the birds. Details of the discovery are published in the journal Oikos. In biology, there is a general rule of thumb that animals tend to...