It is that time of year when people gather on a hill in Duluth to count every hawk, owl, eagle and vulture that soars over the bluffs near Lake Superior. From mid-August to December, raptors fly through Minnesota on journeys that begin as far north as the Arctic.
The researchers and volunteers of Hawk Ridge in Duluth count an average of 60 thousand birds per year. From Duluth, the raptors follow the Mississippi River, sometimes flying all the way to Central and South America.
MPR News host Cathy Wurzer talked with Lori Arent, Assistant Director of the University of Minnesota Raptor Center, to get to know two birds on the move in Minnesota this month.
Use the audio player above to listen to the full conversation.
We attempt to make transcripts for Minnesota Now available the next business day after a broadcast. When ready they will appear here.
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From mid-August to December, raptors fly through Minnesota on journeys that begin as far north as the Arctic. The researchers and volunteers of Hawk Ridge in Duluth count an average of 60,000 birds per year.
From Duluth, the raptors follow the Mississippi River, sometimes flying all the way to Central and South America. Joining us to introduce two of the birds that are on the move right now in Minnesota is Laurie Arent, assistant director of the University of Minnesota's Raptor Center. Hey, Laurie.
LORI ARENT: Hi.
INTERVIEWER: Oh, I'm so excited about this because I love Hawk Ridge. Let's talk about the ospreys that are coming through right now. For folks who have not seen them, describe them.
LORI ARENT: So osprey are kind of large raptors that usually inhabit areas where there's a body of water. They are primarily fish eaters, so that makes total sense that they'd be near water. And they are one of the earliest birds to get out of Minnesota and head to warmer climates.
INTERVIEWER: Really? OK, so they can sense something happening.
LORI ARENT: Yes. A lot of raptors are pre-programmed to move south. And Osprey do it probably more than likely because their food source gets harder to get. And of course, fish- once the temperatures start to decrease in the water, what do the fish do? They go deeper.
And so for the osprey, which are built to catch fish that are in shallow water, it's harder for them to go down. They can't really dive super deep in order to catch the fish. So they basically have to go to temperatures where the fish are going to be more accessible to them.
INTERVIEWER: Smart birds. What do we know about where they go?
LORI ARENT: Well, the Raptor Center in the mid '90s, we did a collaborative study where we actually put satellite transmitters on osprey-- both those that were in the Midwest and then some that are on the East Coast-- and we followed them south. And they actually go all the way to Mexico, Central, and South America. So thousands of miles. And they do this all within about a month or so.
INTERVIEWER: Oh, my gosh. By the way, do they glide? Are they power flappers? I mean, how do they-- poor things. I mean, how do they get to where they need to go?
LORI ARENT: That's a really good question, right? It takes a lot of energy. And like many raptors, they use a combination of soaring and powered-flapping flight.
INTERVIEWER: OK. So let's talk about another raptor that's coming through broad-winged hawks.
LORI ARENT: Yes. So broad-wing hawks are the smallest soaring hawk that we have in Minnesota. And like the osprey, they migrate through pretty early on-- so September-- and they do it within like a week or two.
Now, unlike the osprey, though, there's plenty of food for broad wings, so that's not the reason why they hightail it out here. What their issue is that since they're so small-- and they also travel all the way to South America-- that takes a lot of energy, right?
And so what they do is they use thermals, those rising pockets of warm air. And that is kind of a free ride. So if they can do that, they don't have to flap very much, and it can be less energy that they need, and they can fly faster. And those thermals decrease in intensity as the fall goes on. So they try to catch them when they're super strong.
INTERVIEWER: Oh, OK. So how many miles can they make in a day if you catch a good thermal? Do we know?
LORI ARENT: Well, I mean there's some studies anywhere from 70 to 100 miles per day.
INTERVIEWER: Oh, my gosh. Wow.
LORI ARENT: Yeah, so for them, it takes about two months for them to get all the way down to South America. They're a little bit slower than the osprey. The osprey can fly with their powered flapping flight. They can go almost 150 miles a day.
INTERVIEWER: Oh, my gosh. And of course, they're not using Google Maps. And I've always-- I think the instincts, bird instincts are amazing. How do migrating birds-- in these two species in particular, how do they know where to go?
LORI ARENT: Well, raptors are just so cool. They have a whole arsenal of tools that they can use to help navigate down south. First, there's a little bit of a genetic component. They're going to be genetically pre-programmed to head south.
But then, since raptors have such amazing eyesight, a lot of times, they'll migrate super high in the sky, like a couple thousand feet. And they can actually look at topographical cues. So things like ridges and cities and shorelines to help keep them heading south.
But in those areas where there aren't a lot of those cues, then they actually can use things like the position of the sun, which I find really cool because I'm not a very good navigator myself. I can't tell direction very well. So I'm always impressed when someone can tell me, oh, you're going South because this is where the sun is setting in the sky. I think that's so cool.
But in addition to that on cloudy days, there's yet another tool that these birds can use. And that is that they can sense the Earth's magnetic forces. So they can tell which way is south from that.
INTERVIEWER: Wow, I'm with you. I am directionally challenged.
LORI ARENT: [CHUCKLES] That's a good way to put it.
INTERVIEWER: I'm going to then assume that some of this might be-- some of these birds might get caught off guard or caught off course with flying over cities. I mean, you've got buildings to contend with. I would suppose maybe some power lines, maybe some strange weather patterns.
LORI ARENT: Exactly.
LORI ARENT: Yeah, there's a lot of obstacles. And you're right. Also you could get an unusual storm. Most of the time these birds are migrating when you have northwest winds coming through. They're flying with a tailwind because, again, it takes less energy for them to fly.
So if all of a sudden you get a weird, I don't know, weather system coming in from the, let's say, the east or something where the winds are not in the correct direction, they can definitely get off course. And then they can use one of these tools that I mentioned-- and most often it's the magnetic force of the Earth-- to kind of recalibrate their direction and head south.
INTERVIEWER: Are there things that humans can do to make these migrations a little easier on these poor species?
LORI ARENT: Well, sure. I mean, first of all, we have to realize that there's going to be a lot more raptors in our cities and our spaces. So just being aware of that and then doing some practices, which are good anyway.
Don't throw apple cores or banana peels out the window. Those just attract rodents to the side of the road. And what are the rodents do? They attract the raptors, and then more raptors get hit by cars. So that's something that we all can do to help.
If you do find an injured raptor, please contact the Raptor Center or a local rehabilitator close to you as soon as possible because certainly, the sooner we can get these birds into our care, the much better chance they're going to have of making it back out again.
INTERVIEWER: So are you telling us that you get pretty busy this time of the year?
LORI ARENT: Yes. Yes, we do. 10 or 12 new patients every single day is not uncommon.
INTERVIEWER: Wow. I understand you're releasing some of your patients back into the wild this weekend.
LORI ARENT: Yes. It is the one time every year where we invite the public to join us in the celebration of releasing a few raptors. It is our public bird release. And we conduct it with our friends at Carpenter Nature Center, which for those of you who have been there, it's actually absolutely beautiful habitat along the river there.
And yeah, we'll release several birds. We don't know exactly how many or which ones yet. People always ask us that, and we usually know like the day before who's ready to go. But at this time of year, it's always pretty much guaranteed that there'll be at least one migratory species that will be heading out.
INTERVIEWER: So get them up and--
LORI ARENT: And event is from 11:00 to 2:00.
INTERVIEWER: 11:00 to 2:00.
LORI ARENT: So it's a free event.
INTERVIEWER: OK, so get them up and get them out.
LORI ARENT: Yes.
INTERVIEWER: It's got to feel really good, not only for you, but for the staff to see a raptor that was injured that you've nursed him or her back to health, and they're free. That's got to be an amazing feeling.
LORI ARENT: Oh, there's no better feeling than that-- all the work that we put into it and even just the birds and their individual stories. Most of the time, they're injured because of something that humans have done or put in their space where they collide with them.
And so just knowing that, although we as humans have probably caused their injury in some way, we also have helped them to overcome their challenges and be released and get a second chance. There's no feeling quite like that.
INTERVIEWER: Well, good work. Laurie, thanks for joining us.
LORI ARENT: You're so welcome. It was my pleasure.
INTERVIEWER: Laurie Arent is the assistant director of the University of Minnesota's Raptor Center. If you want to know more about their work-- super interesting place-- just Google U of M Raptor Center and you'll get a lot of good information there.
It was fun. It was a big-- gosh-- packed show, for goodness sakes. We appreciate you joining us. If you missed something early on, we have a podcast. Get it wherever you get your podcasts. Thanks for listening to Minnesota Now here on MPR News.
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