Scientists Crack Cuckoo Mystery

How a cuckoo chick is able to hatch in advance of a host's eggs has always been a mystery. Now scientists from University of Sheffield have cracked the mystery. The team was headed by Professor Tim Birkhead, from the University's Department of Animal and Plant Sciences.

The researchers discovered that cuckoo eggs are internally incubated by the female bird for up to 24 hours before birth. This internal incubation gives the cuckoo a 24 hour head start over its host's eggs.

When eggs are incubated by the adult birds in the nest, their eggs are at about 36oC. Inside the female, the egg is at a body temperature of 40oC. This difference in temperature gives the cuckoo egg a 31 hour head start to be precise.

The results of the study appear in the latest issue of  the journal Proceedings of the Royal Society of London, Series B