Biology Reference
In-Depth Information
A
Blue-footedBoobies,fish-eatingrelativesofpelicans,breedintropicalandsubtropical
islands in the Pacific Ocean, most notably the Galápagos. They have large webbed feet
ranging in color from pale turquoise to a deep aquamarine. Males flaunt these feet in
courtshipdances,holdingthemupandstampingthemontheground.Maleswiththemost
brilliant feet are the most attractive to females. Booby foot color is brightest when birds
are well fed on nutritious fish — in captivity when deprived of a good diet, the foot color
grows noticeably duller within 48 hours. So this is an excellent cue for females to use to
determine a male's ability to find food, a direct signal about how well he will provide for
young. Interestingly, if a scientist dulls the color of a male booby's feet with paint after
his mate has laid her first egg, her second egg will be small, perhaps to reduce the food
resources necessary to raise that chick.
AlthoughthemaleBlue-footedBoobydances,showingoffhisbluefeetconspicuously
in a courtship ritual, the blue foot color is present on both males and females throughout
the year, not just during the breeding season. Both sexes use their feet to incubate their
eggs and to keep the chicks warm, but the color doesn't enhance those functions.
AMAZING COURTSHIP DISPLAYS
Western Grebes, grassland grouse, Calliope Hummingbirds, manakins, tropical wrens —
the vast array of spectacular courtship displays fills humans with wonder even as they set
bird libidos on fire.
Many people have seen film footage of a pair of Western Grebes (elegant, long-
necked, black-and-white diving birds from the American West) dancing in synchrony on
the surface of a lake. In these spectacular dances, called the “rushing display,” two birds
turn to one side and lunge forward with their bodies completely out of the water and run
rapidly across the surface side by side. Occasionally one or more other birds join them.
After “rushing” back and forth for 5 to 20 minutes, the birds lower their wings and dive
