Pennsylvania's Spectacular Golden Eagle Migration

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- Hi, Sanford Smith here with Penn State Extension.

Today I'm joined by Ornithologist Nick Bolgiano, and we are up on Tussey Ridge, outside of State College.

We're observing the migration of golden eagles coming from the south and heading to the north, it's March.

Nick, this type of migration that goes on at this time of year is something that we didn't always look at very much in the past.

- No, we really only became aware of it when Dave Brandes, a Penn State graduate student, started watching here in the mid-90s.

And, as we've watched over the years, we've learned that the western regions of the Appalachians are the core migration corridor for golden eagles, both in the fall and the spring.

- [Sanford] Okay.

People often think about the fall as the main migration time, but they all come back, don't they, in the spring?

- [Nick] Yes. Yeah, we think roughly a thousand golden eagles come north and south in these ridges that we can see from the south to the north.

- [Sanford] Do they come at a specific time?

You know, is it, like, over a one-week period or is it stretched out?

- [Nick] In the spring, it's primarily the first three weeks of March.

In the fall, it's much more leisurely, it's mainly late October through mid-December.

- [Sanford] And why do they follow ridges?

- [Nick] They do follow ridges because they get wind updrafts, and so they can surf the top of those updrafts and get motion north for free.

- [Sanford] Are they flying all night long?

- [Nick] Well, they usually, it's usually during the peak of the sun because they're also getting energy from the thermals.

So they get up in the morning, they start flying maybe nine or 10 o'clock, and they usually quit by four or five.

- [Sanford] Oh, okay, so those thermals, by that you mean the heat that's coming kind of radiating back up from the hills and keeping the air more buoyant, so to speak?

- [Nick] That's exactly right.

So they might be 500 or 1,000 feet up above us using the wind updrafts and the thermals.

Well, the golden eagle eagles, at the farther south they go is the Southern Appalachians, like in Northern Alabama.

- [Sanford] These are not what you'd call Neotropical migrants?

- [Nick] No, no, they're North American migrants.

So, and mostly might fly a couple hundred miles a day.

- [Sanford] Wow, that's a lot of distance.

And then, what's their destination?

- [Nick] So, the eastern golden eagles breed up in Northern Canada, and Labrador and Northern Quebec, and Ontario.

So way up in the Arctic.

They nest on cliffs or in large pine trees.

- [Sanford] Wow. Huh.

I understand also that there are some ways they can track those birds with small radio transmitters or cell transmitters.

- Yes. So, transmitters have been put on them, and that's how we know what routes they follow.

We first learned there were golden eagles in the east in the 1930s when Hawk Mountain watchers started recording them.

And at the time, they would record about 30-40 every year.

But, over time, we've seen the golden eagles population increase, especially after DDT was banned in the 1970s.

And so, it's a much higher population now but is thought to be generally stable.

- Nick just noticed a golden eagle flying up here, going around in circles way, way out there.

And what amazes me is, it's so far away, and yet he can tell a lot about it.

What can you tell by just looking at that little golden eagle over there?

- [Nick] Well, it's, actually, it has seven-foot wing span, and it's circling relatively slowly compared to a red tail or a broad-winged hawk.

So, I just know, and it's all dark.

By the dark shape, dark color and shape, I know it's a golden eagle.

- [Sanford] You know if it's a male or a female?

- That's really hard to tell.

So females are about 10% bigger.

I can't tell at this distance.

- Okay, interesting.

So, Nick, what do the birds eat as they migrate north?

- [Nick] Yeah, the golden eagles primarily eat off of deer carcasses that they find in the forest.

- [Sanford] Okay.

The ones that didn't make it through the winter, I suppose.

- [Nick] Primarily.

Or hit by cars.

- [Sanford] Right.

You know, another thing I'm curious about is why do you do this?

- [Nick] Golden eagles are like the wildest creatures and it's a spectacular migration through here.

One of the most spectacular migrations we could witness.

- These have been a few thoughts about bird migration in the spring.

Thank you very much for listening, and thank you, Nick.

- Oh, you're welcome, Sandy.