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科学美国人60秒:奇鸟迁徙两次繁殖后代

日期: 来源:比比西英语网

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This is Scientific American's 60-second Science, I'm Susanne Bard.
Most migratory birds spend their winters in one habitat and then fly to a new area in the springtime to breed. They'll raise one or more broods of young there. Then, come fall, they begin the trip back to their wintering grounds.
But a new study suggests the phainopepla, a jet-black bird with a body type like a small cardinal, may have a different strategy.
"They might be itinerant breeders.So they breed once in one area, then they migrate—they go somewhere else, and they breed a second time in that new area."
State University of New York, Oswego, evolutionary biologist Daniel Baldassarre.
For the phainopepla, that means nesting in the desert Southwest during the springtime before flying to the oak woodlands of the California coast for the summer.
Baldassarre says bird-watchers have long suspected that phainopeplas are itinerant breeders. One hint that the same birds might be breeding in two different habitats was their vocal behavior. The pointy-headed songbirds are talented mimics, often copying the vocalizations of other bird species.

(CLIP: Female vocal mimic)
"If you look at desert birds, they actually can mimic some species that you don't find in the desert—bird species that you would only find out in these woodland habitats."
And the reverse is also true: phainopeplas in woodland habitats will mimic species that are only found in the desert.
But to confirm that individual phainopeplas really do spend the breeding season in two different places, Baldassarre and his team outfitted the birds with tiny GPS transmitters and tracked their movements.
"They all left those desert breeding habitats, migrated out to these coastal woodland habitats and stayed in a small kind of territory for basically the duration of summer, when we know that phainopeplas are breeding in these woodland areas."
The researchers also found that both populations were very similar genetically, suggesting that they're all members of the same gene pool.
The study appears in the journal the Auk.
Baldassarre says itinerant breeding has only been documented in two other bird species to date and is most likely an adaptation to unpredictable sources of food.
"That food supply disappears, and so the birds literally have to physically move to follow the food."
Such behavioral flexibility seems to be unusual, Baldassarre notes. Phainopeplas could thus be especially resilient in the face of climate change—a challenge other species may not be able to meet.
Thanks for listening for Scientific American's 60-second Science. I'm Susanne Bard.

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