To a female barn swallow (Hirundo rustica), darker colors on the males will be the preferred mate choice. Females judge males by their reddish colored breast and belly feathers. The reddish feathers indicate a males quality, health, their ability to raise young, and is linked to a signal of high testosterone. Kevin McGraw, Cornell Ph.D. an assistant professor at Arizona State University in Tempe. Conducted studies of barns wallows finding that "Factors like ultra violet radiation from the sun, soiling and even feather degrading bacteria are known to affect the color of bird feathers once they are grown, and perhaps the best males are those who spend more time preening and protecting their plumage." These males with darker
To a female barn swallow (Hirundo rustica), darker colors on the males will be the preferred mate choice. Females judge males by their reddish colored breast and belly feathers. The reddish feathers indicate a males quality, health, their ability to raise young, and is linked to a signal of high testosterone. Kevin McGraw, Cornell Ph.D. an assistant professor at Arizona State University in Tempe. Conducted studies of barns wallows finding that "Factors like ultra violet radiation from the sun, soiling and even feather degrading bacteria are known to affect the color of bird feathers once they are grown, and perhaps the best males are those who spend more time preening and protecting their plumage." These males with darker