Scientists theorized that birds look blue for the same reason the sky looks ... set of fine blue feathers signifies a healthy, well-fed male, advertising his good genes to potential mates.

Blue-footed boobies are aptly named, and males take great pride in their fabulous feet. During mating rituals, male birds show off their feet to prospective mates with a high-stepping strut.

The bill is thin and pale gray. Breeding male: blue-gray above, including most of head and back. Crown has a black line at the forecrown that extends along the sides of crown; white eye ring ...