Warm weather has drawn Minnesota's state bird, the loon, back to the state's lakes earlier than usual.
Carrol Henderson, supervisor of the Minnesota Department of Natural Resources nongame wildlife program, spoke about the temperate weather's impact on the state bird population with Tom Crann, host of All Things Considered.
An edited transcript of that discussion is below.
Tom Crann: How do migratory birds like waterfowl and songbirds who go south... how do they know it's warmer back here in Minnesota and it's time to come back?
Carrol Henderson: They use some basic instincts, a lot of our water birds — ducks, geese, swans and loons, among others — will move north with the spring thaw. As waters become open, they push their way northwards.
What happened with the loons is that often they might come north in the spring and stop over in the southern end of Lake Michigan or in some of the lakes of southeastern Wisconsin and hang out there for a week or two weeks. And finally move westwards over into Minnesota as the waters open up.
This year, when they moved northward, everything was already open, so they just moved right on into Minnesota. We had birds showing up as early as the last couple days of March, which was quite surprising.
It was nice because we have this wonderful new window on nature with the satellite transmitters on the loons so we can track them continually throughout all of their travels, in their migrations south to the Gulf of Mexico and then back north again in the spring.
Crann: This is the first year that Minnesota's loon chicks who were born in the Gulf of Mexico after the BP oil spill are going to be migrating back. We talked about this and you said it was too early to tell the effect. Do we have a better idea of the effect of that oil spill now on these chicks?
Henderson: We do have this major study underway that was funded with the environment and natural resources trust fund last year, in which we're looking at both white pelicans and loons. And it's a multi-year study. We're gathering information...about the migrations and the numbers and what reasons loons have for dying. But it's going to take the next couple years to tease out either [that] there's no change or whether there might have been changes in their numbers due to the oil spill.
Crann: We had the warm weather, then a cold snap, especially up north. Does that have any effect on the birds that came back early, are they going to be OK?
Henderson: If any birds came back that will have trouble, it will be the insect eaters. I just saw the first few Tree Swallows arriving back late last week. They can have trouble if we have a cold spell more into early May. A lot of the other insect-eating birds like warblers, wrens, they don't normally show up until the first week of May. At that point you have much better chances for those birds to find emerging insects. If they came back too early, they might have trouble surviving.
Crann: What effect has the mild winter and early spring, especially the warm March, had on the bird population in general in Minnesota?
Henderson: For many of the birds, this mild winter and early spring has been a benefit to the birds because it didn't put late winter stress on them from any late blizzards or cold conditions. Birds that would have wintered here, like pheasants, they would have done very well.
The stresses of really bad winter weather or freezing rain often can be a late winter disaster for many species and we just did not have that this year. Even though we've had a little bit of a cool setback for a few days, I think we're going to have some good conditions in the upcoming weeks to enjoy the remainder of the spring migration as a lot of our other songbirds come back from the southern United States and central and southern South America.
Interview transcribed and edited by Jon Collins, MPR reporter.