"Once we realized we could get at some parentage data, that was clearly the priority," Ryan said.
She took blood samples from both the nestlings and the male parent.
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Using microsatellite DNA fingerprintinga method used to determine paternity in animalsresearchers determined that the samples suggested the female had been visiting neighboring males for sneaky copulations.
This behavior was supported by samples later taken from other black rosy-finch nests, with around 25 percent of chicks sired by males other than the female's nesting mate. For the first time this bracketed female rosy-finches with a range of other birds, from flamingoes to sparrows, that also "play" away from home.
"Let me point you to thousands of scientific papers on the subject," McDonald joked, before offering some possible reasons for this behavior: avoiding harassment, provisioning for nestlings, increasing genetic diversity in offspring, boosting the chances of successful egg fertilization.
The team's findings raise the possibility that in the two other species of rosy-finch females mate with multiple males.
Through their DNA studies, the researchers also hope to resolve the question of whether or not the three birds really are separate species.
Some scientists have suggested they all belong to one species, while McDonald says at least five forms are easily distinguishable in the field.
If three species are confirmed, McDonald says this could have significant implications for the futures of at least two of them, particularly in light of the looming threat from global warming.
"The black and brown-capped have fairly small global ranges," he said. "The brown-capped, in particular, is essentially restricted to the Colorado Rockies. Because it is the most southerly form, global warming could push it up to the point that its total habitat would be greatly diminished.
"Add other insults such as intense UV [ultraviolet light] and you might have a recipe for endangerment." (Increased UV due to a thinning ozone layer, caused by human-made chlorofluorocarbons in the atmosphere, has been implicated in declines and malformations in amphibians.)
With summer soon to mellow into fall, further mountain forays by McDonald and his team will have to wait until next year.
Meantime, the latest generation of rosy-finches, many with dubious paternity, will be descending from their snowcapped nurseries before winter sweeps in once again.
The University of Wyoming's rosy-finch research is supported by funding from the National Geographic Society and the National Science Foundation.
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