Text Margus Ots, coordinator of Great Tit Year
Looking at an incubating great tit in the webcam the question might come up – how can it incubate the eggs through the fluffy plumage? Feathers have a very poor heat transmission capacity after all. To make the body heat reach to the eggs the feathers of the female great tit on the abdomen drop off, and a skin area without plumage is created – the brood patch. So during the brooding period the eggs come into contact with the skin of the abdomen that is rich in blood vessels and the heat needed for the development of the chicks reaches the eggs.
The formation of the brood patch does not mean that female great tits fly around with a bare belly during the nesting period. Since the covering feathers on the sides of the body still cover the area without plumage, the brood patch is not at all visible on a bird moving outside the nest. When the female goes to the nest for brooding she first adjusts and shakes herself – in order to get the eggs in between the covering feathers, and against the brood patch. This can be seen several times a day in the webcam.