A new bird study shows that the male Eurasian blue tits with white cheeks are healthier and more likely to mate with higher quality partners than their counterparts with duller cheek feathers.
Health and Attractiveness Linked to White Cheek Feathers
Male blue tits with white cheeks are healthier and more likely to mate with higher quality partners than their counterparts with duller cheek feathers.
Having purer white cheeks also indicates that a blue tit was better able to overcome infection with parasites during the previous year.
These findings are according to Elisa Pérez Badás of the Museo Nacional de Ciencias Naturales in Spain. Badás is the lead author of a study published in Springer’s journal The Science of Nature.
Diet and Health Impact Color of Feathers
Previous research has shown that the food consumed by a bird, as well as its general well-being, can influence the color of its feathers. Scientists also know that hardships suffered by birds in one season can be carried over into the next.
In the study, Badás and her research team wanted to test whether difficulties encountered by the blue tit (Cyanistes caeruleus) during the breeding season might influence the precise intensity of the new blue, white and yellow feathers growing once these birds have molted.
In the life cycle of this small bird, which is widespread in forests in Europe and Western Asia, molting happens once the breeding season is completed. Therefore, the birds show off their new plumage until the end of the next breeding season.
To prove their assumptions, the research team monitored a population of blue tits living in a forest in central Spain over the course of two breeding seasons.
In the first season, the researchers caught the birds and took blood samples to detect whether the blue tits suffered from parasitic infections. The team also used a spectrophotometer to gauge the spectrum of color of the birds’ feathers.
The results were compared with the hues, levels of saturation and luminance that blue tits are known to see.
In the following season, the researchers noted the birds’ mating patterns, and how these were influenced by changes that might have occurred in particular birds’ feather colors.
Blue Tits with Brighter White Cheeks are Healthier
Overall, the researchers found that males in a better physical condition (males that weighed more) during the highly demanding nestling provisioning stage sported brighter, whiter cheeks.
Birds not infected by the malaria parasite Plasmodium while breeding also showed purer white cheek feathers in winter.
According to Pérez Badás, this indicates that their feathers were of better quality and that acute parasitic infections can have an effect on a bird’s life cycle.
Brighter White Cheek Mates
“In the following season, those males with brighter cheeks paired with females that had noticeably brighter cheek patches compared to the male’s previous mate,” adds Badás.
The results suggest that the conditions that male blue tits experienced during reproduction are likely to affect molt and thus feather coloration, at least in their white facial feathers.
This enables the stronger males to find brighter females than the partners they paired with in the previous spring.
“Members of the same species were quite able to pick up such color differences,” notes Badás.
Read the full abstract, ‘Colour change in a structural ornament is related to individual quality, parasites and mating patterns in the blue tit’ published in The Science of Nature, 2018 here.