Japan team discovers why crows are black

The study by the team led by Okayama University professor Sakae Takeuchi shows that the "switch that produces black color" is always on in the species.

About 30 years ago, Takeuchi discovered that MC1R, a receptor found in pigment cells of birds and mammals, controls feather color.

He also found that the receptor is activated by hormone stimulation and encourages the synthesis of black melanin pigment. Still, the detailed workings of this mechanism in wild birds were not well understood.

The research team created the large-billed crow MC1R in cultured cells and conducted a detailed analysis.

The results showed that MC1R in crows is always active, even without hormone stimulation, promoting the synthesis of black melanin pigment.

In other birds, a mutation in only one specific part of the MC1R gene sequence was found to cause black coloration.

But in crows, multiple mutations exist, leading to the constant activation of MC1R, the team said.

"As I think my mission is to fully explain the obvious fact that crows are black from a scientific perspective, I'm glad we've elucidated this," Takeuchi said.

The team's paper was published in April in an international journal of endocrinology.