As regular CFZ-watchers will know, for some time Corinna has been doing a column for Animals & Men and a regular segment on On The Track... particularly about out-of-place birds and rare vagrants. There seem to be more and more bird stories from all over the world hitting the news these days so, to make room for them all - and to give them all equal and worthy coverage - she has set up this new blog to cover all things feathery and Fortean.

Tuesday, 26 January 2016

Why some cuckoos have blue eggs

Cuckoo eggs come in a wide variety of colors and patterns, but why?

Date:January 21, 2016
Source:Norwegian University of Science and Technology

For roughly a century, researchers have been trying to figure out how different female cuckoos manage to lay such a variety of different egg colors to match different host birds. Now, a group of researchers at the Norwegian University of Science and Technology (NTNU) has come up with an answer to this puzzle, in cooperation with researchers from all over Europe and Asia.

The short answer is that "the female bird decides everything," says researcher Frode Fossøy.

Fossøy is part of the cuckoo research group at the Department of Biology at NTNU. The results of the group's work have just been published in Nature Communications.

"We've been able to show for the first time that the blue egg color is inherited via the female cuckoo only. The father has no effect on the color of his daughter's eggs," says Fossøy.

Researchers have investigated a wide variety of samples from Europe and Asia. They found a clear relation between blue eggs and genetic material that only comes from the mother (mitochondrial DNA), and no relation between egg color and genetic material that comes from both parents (nuclear DNA).

Cuckoos (Cuculus canorus) are parasitic. Female cuckoos lay their eggs in the nests of other bird species, as is well known.

The young cuckoo then usually throws the other chicks out of the nest, getting rid of any competition for the parents' attention.

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