Western Bald Eagle Migration Update: April 7, 1999

Field Notes from Biologist Jim Watson

Today's Satellite Data from WESTERN Eagles

Eagle #18 Heads for Home
Here's half of the news we've been waiting for: Bird #18 has left Washington! Notice how many miles he flew since he left the Columbia River in Washington on March 20th and arrived at his April 2nd location.

• On your study map, overlay a string connecting the 4 locations. Hold it up to a ruler to measure the distance he moved in miles.
• Convert his movement into a DAILY rate of travel (miles/day).
• Then estimate an HOURLY rate (miles/hour). Remember, Eagle #18 is not flying at night, so base your hourly right on daylight hours (12 hours), not total daylength (24 hours).

As you ride in a vehicle down the highway, think about how fast Eagle #18 migrated compared to how fast you are going. Remember, when you walk, you typically move 1-2 miles per hour, and maybe 4-5 miles per hour when running.

Challenge Question # 16
"How many miles/hour did Eagle #18 travel? Was this slower or faster than you expected? If you said slower, what would account for this 'slow' rate of travel? Finally, where is Eagle #18 now? Name the body of water you think he might be visiting."

Discussion of Challenge Question #11
Challenge Question #11 asked about the migration route Eagle #18 used as he began his migration. You can see the Columbia River was the "flight corridor" he used to move from the previous location. Rather than flying over barren land, he flew along a "logical" landscape--water. Why? For food and orientation (see discussion below). Where might you expect him to fly in the upcoming weeks based on this early movement? Answer: to the headwaters of the Columbia River. (We can't tell for certain, because the data only provides readings every few days, but it appears he may have traveled along the Columbia between March 20 and March 24.)
Plans Still a Secret for Eagle #12
Eagle #12 still hasn't shown the same type of movement at this point. Last week I asked Challenge Question #12, "Do you think Eagle #12 could be nesting in Washington? Why or Why not?"

I believe that this is unlikely, because eagles nesting in Washington are already on eggs. If Eagle #12 were nesting, satellite data would show her stationary at a location on a nesting territory. (See today's data to see how much she's moving.)

Challenge Question # 17
"Can you suggest any other reasons why eagle #12 has not left Washington, when others seem to have migrated by now?" (Note: Her transmitter has changed to a 10-day cycle, so I now receive a location every 10th day.)

Challenge Question #18: Guess the Nest
Jim Watson has placed his guess--what about you? There's still time to guess where you think our WESTERN eagles' nests are located. Be sure to give the exact latitude and longitude for each eagle's nest.

Challenge Question #18
"Where do you predict Eagle #12 and #18 will go to nest? Give the exact latitude and longitude of their final destination."

For help, take a look at Eagle #12's migration data from last year, and read today's interview with Jim below.

Migration Routes to the North
Interview Biologist With Jim Watson
We interviewed Jim Watson about the routes taken by the eagles he's studied over the years. Here's what he had to say:

How to Respond to Today's Challenge Questions

Please answer ONLY ONE question in EACH e-mail message.

1. Address an e-mail message to: jn-challenge-eagle@learner.org
2. In the Subject Line of your message write: Challenge Question #16
(or Challenge Question #17 or #18.)
3. In the body of EACH message, answer ONE of the questions above.

The Next Bald Eagle Migration Update Will be Posted on April 21, 1999.

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