ARI SHAPIRO, HOST:
This time of year, many birds nest and lay eggs. In Portland, Oregon, one unusual couple of nesters has drawn the attention of local birders. Oregon Public Broadcasting's April Ehrlich has the story about two waterfowl finding love despite their differences.
(SOUNDBITE OF GEESE HONKING)
APRIL EHRLICH, BYLINE: There are lots of geese at this regional park along the Columbia River outside Portland, so rangers weren't surprised when they found a Canada goose nesting near some picnic benches. But there was something strange about the other goose guarding the nest. So they reached out to Katy Weil, the natural resource scientist for Metro, a government agency that manages this park.
KATY WEIL: So we have a Canada goose, female, on the nest, incubating eggs, and a male greater white-fronted goose helping in supporting that nest.
EHRLICH: These are two totally different species of goose. They've paired up and actually produced eggs. There are huge flocks of Canada geese around this park. But this male white-fronted goose is kind of a lone ranger. Weil isn't sure why he's decided to pair with a Canada goose.
WEIL: So it's possible that the only available mate happened to be a Canada goose, and she was receptive to the concept (laughter). That's probably what happened.
EHRLICH: It's also not clear why the white-fronted goose is even in this Oregon park. Rob Wilson studies zoology at the University of Nebraska-Lincoln and says they usually breed farther north. Wilson says this goose might not have been able to migrate because of an injury, or he might have been raised by Canada geese.
ROB WILSON: Canada geese and white-fronted geese are known to parasitize other nests. That just basically means that a female will dump one of its eggs in another species' nest.
EHRLICH: So if something happens to her own nest, she at least has a backup egg somewhere else, ensuring her genes are carried on. That goose could later seek mates that look similar to its foster parents. As for interspecies couples like the one near Portland, they're actually not unheard of. It's called hybridization.
WILSON: Geese do regularly hybridize.
EHRLICH: Whether or not two species can successfully procreate depends on their genes and other biological factors. Wilson says goose hybrids have been spotted elsewhere before, but what's unusual here is seeing the parents.
WILSON: Just to be able to witness the actual pair themselves, and if they can actually successfully reproduce. I mean, it's quite unique. I'm kind of jealous that you guys get to see it.
EHRLICH: Sometimes different species will intermingle because of human changes in the environment, according to Kathryn Grabenstein, a postdoctoral fellow at the Cornell Lab of Ornithology.
KATHRYN GRABENSTEIN: Humans can kind of change the physical landscape, either by planting trees or putting out feeders. And in doing that, they change the way that species interact.
EHRLICH: For example, two species of chickadee may encounter each other more often when people plant trees they like and be more likely to mate. Grabenstein says environmental factors like this could have brought the two Oregon geese together. Geese are basically grass-eating machines, so they're drawn to parks. The white-fronted goose could have stopped at this park because there was so much food and at least one lady interested in pairing up. They haven't had any viable eggs yet, but Katy Weil, the regional natural resource scientist, says there's still time left this spring.
WEIL: So many people who love the park are keeping an eye out for them, and they're rooting for them. We have park rangers doing the same.
EHRLICH: Geese typically mate for life. Weil says this unlikely couple will likely stay by each other's sides.
For NPR News, I'm April Ehrlich in Portland, Oregon.
(SOUNDBITE OF MUSIC) Transcript provided by NPR, Copyright NPR.
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