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Sent to a friend[25242] Madagascar's Paradise Flycatchers
Adult male Madagascar paradise flycatchers come in two distinct color types, or morphs, a rare phenomenon among birds. (Males of only one other known bird species, a Eurasian sandpiper called the ruff, have such color variations.) One flycatcher morph, the rufous type, is a reddish brown; the white morph is mostly white and black. Once these plumages emerge---after about three years or so--they're permanent. But why the two different hues?In nature, color evolves in part to attract mates. If one male flycatcher had a mating advantage, the other should have gone extinct. It hasn't so each color must provide some sort of benefit--and that's where things get complicated.
It's possible, says Mulder that female flycatchers choose to mate with whichever morph type is less common at the time, a form of sexual selection known as the rare-male effect.
Geographic location may also play a role. One morph color may stand out beter---and thus attract more females--in bright, open spaces, while the other may be more visible in dense shade. But he who gets the most dates may also die young, because the morph color that females prefer may also be more visible to forest predators.
Mulder thinks the white morph is more susceptible to predation. "Our color measurements show that white morphs are more conspicuous than rufous males," he says. "We've set up trials using stuffed mounts of both male types. The white ones are always attacked first. The predators are sparrow hawks, and we've seen them kill white males."
So, do females prefer their mates in white? "Since white males suffer more predation, you might expect them to have a mating benefit to compensate for this cost," says Mulder. But the data suggests that females are highly unfaithful to both types."
In breeding season, a female lays up to three eggs on consecutive days. Though she pairs with one male that helps tend the nest, she may also copulate with males in nearby territories and can store their sperm, so each egg could be fertilized by a different father.
Using DNA analysis, Mulder and his team have determined the paternity of some 700 nestlings. Half the nests held chicks fathered by different males of one or both colors. "Females apparently do not have fixed preferences for particular males or morph types," says Mulder. In future studies he hopes to detect paternity that may shed more light on the mystery of flycatcher color.
National Geographic
April 2005
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