Feather changes with food

A new analysis of songbirds shows that what they eat during the hair loss process can affect their color. The change in color due to diet also helps create momentum for the development of new species.

Ryan Norris and colleagues at Guelph University in Ontario, Canada, marked and followed more than 200 American red-tailed red birds ( Setophaga ruticilla ) in the Caribbean.

Setophaga ruticilla - Setophaga ruticilla
(Photo: Peregrineprints)

These migratory birds spend the summer in regions between British Columbia in Canada and Louisiana in South America. After breeding in the north, they grow new feathers within 3 weeks before moving south.

Researchers can determine where each bird has gone on vacation by analyzing the ratio of heavy and light hydrogen isotopes in the coat. Norris explained that there will be more heavy isotopes in the feathers of summer birds in low latitudes. Hydrogen isotopes in water follow the food chain entering the bird.

Birds with dark colored feathers often take summer vacation in southern America. Yellow-feathered birds have three times more heavy isotope content than those with dark orange feathers.

The color of the feathers depends on the amount of caratinoid pigments in the hairs - the darker the feathers, the more substances they have. Norris believes that birds in different shedding areas will have different coat colors because at latitudes, they eat different caratinoid-like insects or fruits.

Rich diets that alter the color of feathers can affect the choice of partners and thus lead to differentiation of species, Norris added.

MT