Heavy Metals Dull Bird Feathers Making Males Less Attractive To Females

Animal courtships routinely involve vocalizations, distinctive scents and colorations. This is especially true of birds where females are attracted to colorful males, but at least one species is dealing with an environmental handicap: metal contamination known to alter the color of their feathers, and, in some case,s make them less attractive. Metals including mercury, copper and chrome tht are natural to the environment are increasing in concentration, becoming toxic to surrounding wildlife, according to a news release.

This is what researchers from the Spanish Foundation for Science and Technology are saying after taking a closer look at how toxic metals affect the physiology and reproductive success of male great tits (Parus major).

Great tits can commonly be seen throughout Europe and are characterized by their distinctive feathers, or plumage. The birds have a black head and neck, bright white cheeks and olive-to-yellow colored bellies.

In total, researchers studied the relationship between plumage changes and eight different heavy metals and found that mercury, in particular, could significantly reduce the brightness of a bird's yellow feathers. This is because mercury reacts negatively with carotenoids, which are certain pigments that are responsible for yellow coloration. Ultimately, this reduces a male's attractiveness in the eyes of a female great tit.

"The yellow coloring of the male is an indication to the female of its state of health and ability to find food. Therefore, a paler yellow great tit, as a result of exposure to mercury, will be less attractive to females," Joan Carles Senar, one of the study researchers from the Museum of Natural Sciences in Barcelona, explained.

Chrome has a similar effect when reacting with melanin pigments, causing the bird's black neck to appear dull. "The 'black tie' is a sign of dominance and aggression in defense against predators, as well as being linked to aspects relating to the bird's personality," Senar added.

Comparatively, copper has a positive effect; when it reacts with melanin pigments it actually increases the size of the bird's black "neck tie."

In the future researchers plan to test how birds are more specifically affected in urban environments where there may be more pollutants and therefore an increased amount of toxic metal exposure. In this case, great tits may have adapted to unavoidable physical changes and females may be more accepting of males with smaller neck ties.

Their study was recently published in the journal Science of the Total Environment.