MICHELE NORRIS, host:
Spring has been coming earlier as the world warms up. A new study suggests that some songbirds may be evolving to adapt to the changing world. NPR's Richard Harris reports.
RICHARD HARRIS reporting:
One worry about rapid climate change is that plants and animals may not all adapt quickly and keep in sync with the changes. Birds, for example, do best when they reach their breeding grounds early in spring, when insects and other food is most abundant. Nils Christian Stenseth at the University of Oslo heads a group that's studying the timing of bird migration.
Mr. NILS CHRISTIAN STENSETH (University of Oslo): We are trying to understand to what degree climate (unintelligible) have affected the arrival time of birds.
HARRIS: Conventional wisdom has it that birds that winter in southern Europe would notice that spring has come early in Europe and would fly north to their breeding grounds in Scandinavia sooner. But scientists assume that birds that start that journey from Africa would not leave their wintering grounds early. They'd have no way of knowing that spring is starting early in the far north.
Now Stenseth has found that the birds from Africa are showing up early.
Mr. STENSETH: They are advancing their arrival time even more than the short distance migrants.
HARRIS: Stenseth says the birds that fly north from Africa if anything are doing better at anticipating the arrival of spring. This study in Science Magazine finds African migrants are showing up ever earlier on Italy's Isle of Capri on their way north. He says they are adapting very rapidly to climate change.
Mr. STENSETH: I'm a bit surprised myself when I saw the result. And really the only explanation we could come up with is that some sort of evolution has been going on.
HARRIS: So climate change is driving evolution?
Mr. STESETH: Yeah.
HARRIS: Here's what Stenseth thinks is happening. Birds that just happen to leave Africa earlier are more likely to thrive in their breeding grounds and to leave more offspring than birds that show up later. And the early birds' offspring presumably carry the genes that told their parents to start that migration early.
Mr. STENSETH: Those birds that come at the right time, they will pass on the genes at the higher rate than those that come at the wrong time.
HARRIS: Stenseth has no idea what genes might regulate migration or even if such genes exist. But it's reasonable to think that they do.
Mr. STENSETH: We do know there is a genetic base for a lot of behavioral traits. So why not for the time that they go from Africa?
HARRIS: And this finding suggests that these birds can evolve with extraordinary speed, fast enough, it seems, even to keep up with the unprecedented pace of global warming.
David Winkler from Cornell University says it's a very provocative finding, but he's cautious.
Dr. DAVID WINKLER (Cornell University): I don't think the authors have really made the case that there are actual genetic changes that have occurred, but that's certainly something that needs to be explored.
HARRIS: Winkler says the researchers haven't ruled out the possibility that the birds in Africa get some subtle environmental clue that tells them when spring is starting in Europe.
Dr. WINKLER: I think that's at least as likely an interpretation and that really needs some more research. In this case, in the case of this present paper in Africa, but in general we don't much about how long distance migrants are timing their return migration in the spring.
HARRIS: The finding raises a lot more questions for Winkler than it answers.
Dr. WINKLER: The really interesting question is, well, what's happening with the short distance migrants? Why haven't they responded as quickly?
HARRIS: And he says what about the birds that live year round on their breeding grounds? Some of those species seem not to be breeding sooner, even though they must notice that springtime is coming sooner.
Dr. WINKLER: So, there's some very interesting paradoxes here and we're just scraping the surface and coming up with interesting results now, but we really don't understand the whole system.
HARRIS: And he says birds are just one element of an entire ecosystem that's being pushed by a rapidly changing climate.
Richard Harris, NPR News.