Link to nice Barn Swallow illustration
I saw this article in last Wednesday's San Francisco Chronicle about a study some biologist did with barn swallows.
They caught some male barn swallows in mist nets and used a marker to darken the breast feathers of lighter colored birds to match the naturally darker colored birds. Female barn swallows find the darker ones more attractive, trust me on this one...
They measured the birds' hormone levels and weight before releasing them in their new more colorful duds, er...feathers.
After one week sporting their colorful plumage, the biologists trapped these guys again and re-measured. The birds' testosterone was up 36 percent after only one week! They also gained weight (which is a good thing in birds.) The birds that didn't get the marker makeover experienced a drop of 50% in their testosterone levels.
The theory is that the makeover birds felt better about themselves because they were getting more attention from the female barn swallows, which caused their hormone levels to go up.
Interesting. What will these scientists dream up next?