Feathers are made darker by melanin, which is known to bind heavy metals. In this study, researchers test the idea that darker birds might be protected from things like lead by the ability to store that crap in their feathers.
Chatelain, M., J. Gasparini, and A. Frantz. 2016. Do trace metals select for darker birds in urban areas? An experimental exposure to lead and zinc. Global Change Biology. DOI: 10.1111/gcb.13170
This week’s decent puzzle is called “Two Trees.”