To avoid harassment from males, some female white-necked jacobins have a disguise. "The Hummingbird Effect" premieres Wednesday, April 12 at 8/7c on PBS. [VID: White-necked jacobins are notorious bullies. Aggressive and territorial around any food source, they're always ready for a brawl. Their metallic blue tuxedos and flared white skirts distinguish them from females, who sport a less glitzy green. This vast difference in coloration makes females a target for constant harassment. It's almost i