Seattle (and PNW) has a type of crow called Northwest crow, don't know exactly how it differs from other crows but they do. Anyway here at UW they have lots of studies of these crows and their behaviors so when you see these crows sometimes both legs are covered with different colored bands - one for each of the studies that they're in. A friend told me that there was one study that found that the crows with bands on their legs were finding easier (by far) times of finding mates, for some reason the crows seem to be attracted to the jewelry.
Now people are upset because most of these "banded" studies are long term so it would disrupt them to remove the bands, but naturalists are saying that this amounts to human intervention, giving the banded crows a far greater advantage over non banded crows. I find the debate quite humorous, especially since crows are omnivorous, so they are major garbage pickers! Which seems to me like human intervention
