Zebra finch parents can tell their young while they’re still developing in the egg that it’s hot outside. This is vital information for a growing chick. In hot climates, birds need to be able to lose heat, which is easier with a smaller body. When zebra finch parents are breeding in a hot climate, and the nest hits a temperature above 80 degrees Fahrenheit, they’ll chirp the news to their unborn chicks in the last third of the incubation period—the moment when the embryos are developing their temperature-regulation system. In response to these “hot calls,” the chicks will actually curtail
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