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Charms of small males may collapse a Darwin’s finch species

Mating rules may be changing for one of the storied Galápagos birds

TELL DARWIN Crossing species lines and mating with the small tree finch (yearling shown) may be the undoing of a second species of Darwin’s finches in the Galápagos Islands.

The lure of little guys of the wrong species — plus an invasion of flies — may drive one of Darwin’s finch species toward extinction.

Diverse finches that Darwin saw scattered across the Galápagos Islands have become favorite subjects for studying how species diverge or blur together in time frames a person can observe.

Now, on the island of Floreana, females of the medium tree finch (Camarhynchus pauper) are blurring species lines by crossbreeding with males of a smaller finch species (C. parvulus), says Sonia Kleindorfer of Flinders University in Adelaide, Australia. Just why isn’t clear yet. But recent invasion by flies with blood-sucking larvae and the relative rarity of medium finches may play roles, Kleindorfer and her colleagues report in the March American Naturalist.

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