Getting up later in the morning might gain you more sleep, but it could mean you end up fathering fewer offspring—at least if you are a songbird called the great tit. Ecologists from the United States and Germany have discovered that compared with early birds, late risers are more likely to be cuckolded, meaning that they unknowingly end up raising young in their nest that had been fathered by another male. It appears that in the early morning hours, they're still asleep rather than being awake and defending their mate.
The study, published in the British Ecological Society's journal Functional Ecology, sheds new light on the evolution of the body clock and its role in reproduction.
"Our results indicate that delaying activity early in the morning and rising late may influence a male songbird's fitness via an increased risk of being cuckolded, implicating a potential role for sexual selection, in addition to natural selection, to shape circadian traits in a wild vertebrate," said Dr. Timothy Greives, lead author of the study.
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Functional Ecology, DOI: 10.1111/1365-2435.12440