Washington Evening Journal
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Fairfield Ledger   Mt. Pleasant News
Neighbors Growing Together | Sep 24, 2017

Birds preparing for annual migration

Sep 08, 2017

Within the last few weeks, our birds have changed their behavior. At some point this last month, the birds stopped focusing their energies on raising young and began preparing for fall. It’s a subtle difference, but if you pay attention, you can feel it.

Every so often now, at our hummingbird feeder, a male stops and visits. Usually, we have only females, which can be told by the lack of their namesake ruby throat. I assume it means we have good nesting habitat. While male hummingbirds defend good feeding territories (to attract females), the females prefer areas that provide safe homes for their young.

At the close of summer, we begin to see male visitors. I initially thought these were young of the year fledgling. Considering ruby-throated hummingbirds are one of the first migratory birds to leave, I now believe these birds are passing through on the way to Mexico.

Our hummingbirds exemplify the marvels of migration. While most birds will avoid traveling across large bodies of water as much as possible, our tiniest bird will fly nearly 700 miles across the Gulf of Mexico in one non-stop flight. In order to do this, they must stop over in the Gulf States and almost double their weight in order to have the necessary energy for the trip.

Hummingbirds make the trip solo though they are occasionally found with other migrants. Many other birds, on the other hand, form flocks for the trip. Traveling together means more eyes on the lookout for predators and help finding food and rest stops. Birds exhibit flocking behavior long before they begin the journey south. This change in mood, from defending individual territories to cooperation, is another notable end-of-season behavior.

Changes in day length usually trigger such behavioral as well as physiological changes. As the days become shorter, birds may begin storing up high energy fat reserves. To do this, some switch from eating primarily insects to a diet high in fruit and berries. Their flight muscles become even more efficient and stronger. They also begin exhibiting a certain type of restlessness called zugunruhe.

Centuries ago, people observed a seasonal disturbance in their caged birds’ behavior. Every spring and fall, confined migratory birds would become agitated and flutter in the direction of their wild relatives’ migration paths. German scientists eventually called this zugunruhe, a migration-related anxiety.

When the weather turns favorable for a flight south or freezes available resources, birds are already well-prepared to leave. Some birds begin the flight as soon as possible, while others wait till the last possible moment. Already, we can observe birds traveling through Iowa on their way to their wintering grounds. As the season progresses, more birds will pass through.

Migratory season is an excellent time to watch birds. In addition to our local migrants, we can also see northern birds heading south and those that think Iowa is far enough south. Because of the high cost of traveling, care must be taken not to interrupt these birds’ activities. Necessary energy reserves may be used up when unintentionally flushed or disturbed.

So the next time you are out and about, turn an ear to your local bird life and pick up on this buzz of energy now happening.

Pamela Holz, is the Washington County Conservation Board Naturalist.

 

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