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WESTERN Bald Eagle Migration Update: April 20, 1998

Todays Report Includes:

News from Biologist Jim Watson
Announcing the winner:

Photo: USFWS

It appears Eagle #05 is the first bird back to her nest! According to Jim, "Eagle #05 is back on her territory as of last week. She reached her nest site on the Smith River in British Columbia as Tuesday (4/14/98). (Both locations shown in today's data are 'A class', so I suspect the second one, 04/19/98, is a little off target.)"

Latest Travels of Western Eagles
Click to see full map.

Meanwhile, still back at the start we're waiting for Eagle #12. She has finally crossed into Canada: "Eagle #12 has moved slightly to the Sumas River in southern B.C.," says Watson. And as to the other 2 eagles:

"Eagle #16 is still on the McKenzie River. Since he is probably not a breeder, his locations will not really stabilize from here on out. Last year he moved up and down the McKenzie River throughout the summer. Eagle #13 is on the Finlay River and--if I had to guess--is headed to interior Alaska...we'll see by this Thursday."

Good luck,

Jim Watson
Washington Department of Fish and Wildlife
Latest Satellite Migration Data

Note: Next Monday, April 27th we'll post the latest migration data, so you'll have the most current news.

Discussion Questions
  • How far did Eagle #13 move between 04/08/98 and 04/13/98? On average, how many miles/day did this eagle travel during that 5 day period?
  • How many miles from the wintering region has #16 traveled? Why do you suppose eagles bother to go so many miles north if not to breed? What do you think non-breeding eagles do in the north during the nesting season?

Weather and Eagle #16's Journey North
Eagle #16 traveled a long way north between March 29 and April 8--10 degrees latitude, in fact. Meterologist Glen Schuster took a look at the weather during that time for clues as to when he made his move.

One in a Thousand (or Two!)
A Perspective on Tracking Migration by Satellite

Photo: USFWS

As you track individual eagles by satellite this spring, don't forget: These individuals are not traveling alone. They actually represent of a wave of migratory movement. We asked Jim Watson's help in putting this into perspective. Here's what he had to say:

"Now that you have been following the western eagles for a few weeks, it might be interesting to reflect on the significance of these movements to the entire eagle population. After all, a biologist's job is to sample a population (in this case 4 birds, plus another 19 that we are also monitoring) to learn more about the entire populations from which they come.

Photo: USFWS

"The 4 eagles you are tracking this spring are among an estimated 6,000 - 10,000 eagles that winter in Washington, Oregon, and southern British Columbia and travel to the far north to nest. Based on our telemetry locations, we see that their tendency is to move a few hundred kilometers for 1 or 2 days, and then stay at a location for a couple of days before moving again.

"Imagine for a moment that you are standing on the Fraser River at Lillooet, or at Powell River on the coast of British Columbia, on a clear but breezy morning in late March or early April. You look up down the river (or coast), and about 200 m above the ridge line you see 2 eagles flying headlong, with a rapid wingbeat, and they pass out of sight to the north. About 2 minutes later you see another eagle, 100 m higher, but on the same course as the other birds. Pretty soon, several more eagles have passed, and by noon you have counted 70 eagles from that one location, all moving northward to nesting areas!

"While exact numbers are is certain, if we make a conservative estimate of 3,000 eagles flying past Lillooet between 15 March and 15 April, that's about 100 birds/day moving through the area! Of course, some days you would see just a few birds, depending on weather conditions and whether it was early or late in the season. On other days you would see more eagles.

"Thus, when you plot the locations of our 'sample' population of telemetered eagles on a large map it looks like these birds are traveling alone, while in reality there are several hundred birds moving along with them back to nesting areas in Alaska, the Yukon, Northwest Territories, and British Columbia."

The Next Bald Eagle Migration Update will Be Posted on May 4, 1998.
(However, the latest Migration Data will be posted on April 27, 1998.)

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