Today's Report Includes:
Bald Eagle Migration News
Look Who's in Labrador!
"Well, well, guess who finally decided to move!" exclaimed Peter Nye back on April 5th. Eagle E50 waited
until April to take off, but look at him now--he's in Labrador!
He flew 656 miles (1,056 km) in the 7 days between 4/16 and 4/22. Nye's rule of thumb seems to hold true: An
eagle that migrates late in spring tends to head to the far, far north. Eagle E63 crossed the border into Labrador
last week, too. (See this week's migration map.)
"I think Eagle E47 has arrived at her nest site...by 4/14, maybe?" pondered Nye when he wrote this morning.
Take a close look at today's migration map. Do you think all of the eagle have reached their nests yet? In next
week's update, we'll help you to summarize this spring's migration.
Golden Eagle Migration News
"Golden Eagle #004 is still cruising north," reported Peter Nye when he sent the latest data. Just think:
Nobody has a clue where this eagle is going!
And because Golden Eagle is a juvenile bird we asked you to consider...
Discussion of Challenge Question #19
"Why might the migration of a juvenile eagle be different from the migration of an adult eagle?"
Immature Eagles: Oh, Grow Up!
This time of year, we're so busy tracking eagles as they migrate back to their nests, that we often forget about
the many birds who are too young to nest but aren't babies anymore. After all, it takes Bald Eagles somewhere
between three and a half and five years to grow in the white head and tail feathers that mark them as adults, and
some of them don't actually start breeding until they are seven years old. So what are all these immature birds
doing when the adults are hard at work raising new eagles?
Young eagles spend much of their time traveling. Scientists can't accurately predict where a given nestling will
wander. They can disperse in any direction, and learn their own patterns for when and where to migrate. They
do seem to remember where they've been, and in the first couple of years many of them find the places where they
will spend most of their winters, and the place where they'll build their permanent nest.
Nye once tracked a juvenile eagle. You can look at the wandering travels of Eagle N99 back in spring, 1997 on Journey
North's GIS Map Server:
In the same way that children build pretend houses with blocks, some young Bald Eagles build pretend nests. Scientists
in Saskatchewan watched some eagles in immature plumage as they constructed stick nests. These nests were apparently
just practice ones, because they were never actually used for laying eggs or raising babies.
Practice Makes Perfect
Bald Eagles are not good at catching fish when they first leave the nest. They pick up dead fish along shorelines
first, and then progress to picking up dead fish floating in rivers and lakes. It may take months for an eagle
to start catching its own live fish, and much longer for it to become reliable at fishing. So young birds must
spend more time fishing to catch the same number of fish as adults.
All in all, the first years of a Bald Eagle's life are a time of enormous learning and exploring the world around
them. Why do you suppose young eagles take so long to grow up compared to hummingbirds and robins? Before reading
further, think up as many reasons as you can.
Possible reasons include:
1) Robins and hummingbirds are much smaller, with a much shorter life-span, than eagles. Smaller birds start
nesting when they are one or at most two years old, so many more of their behaviors must be "innate"-that
is, instinctive. That means they don't have to spend as much time learning new things as eagles do.
2) Hummingbirds take nectar from flowers. Robins search for worms on the ground and berries in trees and shrubs.
Their techniques for slurping up nectar, pulling out worms or plucking berries are fairly simple and straightforward.
Hunting for live and wary creatures is much trickier--a trout can wiggle away a lot easier than a berry can! So
hunting birds must be very adaptable and intelligent, and they need time to develop their skills.
The Next Bald Eagle Migration Update Will Be Posted on
May 1, 2001.
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