Whooping Crane Migration Update: April 1, 1999
Today's Report Includes:
The Journey North Begins!
The whooping crane migration is underway! Six adult pairs and one family group (2 adults with their chick) have headed north. I did an aerial census flight on March 25 and found only 164 out of the flock total of 183.
Saying Good bye to the Neighbors?
All kinds of vocalizations are going on as the cranes depart. I wish I knew what they were saying. We might think they are saying the equivalent of "See you later. I'm off to Canada to nest". But in reality, the loud whoops are presumably more related to their territorial and dominance behaviors.
When a territorial pair departs, this often influences their neighbors to leave shortly afterwards. Departures are never randomly spread across the wintering grounds. Instead they occur in a clumped pattern.
This year for example, all of the documented migrating pairs so far have departed from the Aransas National Wildlife Refuge--not the nearby wetlands. The Lobstick pair, (named after the creek where they build their nest up north), started the migration approximately March 21. They are usually one of the first pairs to arrive in Wood Buffalo National Park, 2,600 miles to the north in the Northwest Territories of Canada. The Pipeline Flats pair, the Middle Pond pair, and the Middle Sundown Bay family, have all departed from neighboring territories at Aransas. In contrast, no adult pairs or families have migrated from areas next to the Aransas Refuge, where whooping cranes also spend the winter. No birds have left from San Jose, Matagorda, or Welder Flats. This chart shows where birds were as of my March 25 flight:
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Keep Your Eyes on the Skies
Watch the weather conditions along the Texas Gulf Coast this week, because the whooping cranes should be leaving any day! After the migration begins, plan to keep a close eye on the skies of the Central Plains. During the month of April, whooping crane migration updates will be posted every Thursday, so you can follow their progress closely. You'll need these daily weather maps to analyze the weather:
A Good Day to Fly?
How Do They Know When it's Time to Go?
One of the most important abilities of any migratory animal is its ability to tell time. An animal's very survival depends on being at the right place at the right time. The hormonal changes Tom Stehn mentions are controlled by invisible "biological" clocks that work within the cranes' bodies.
Researchers have learned that people have over 100 "biological" clocks which control the rhythms of our lives. These clocks control sleep, hunger and energy cycles in interesting ways. In the lesson below, explore the concept of time--and learn about your own biological clocks. Then consider the importance of biological clocks to migratory species.
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The Next Whooping Crane Migration Update Will be Posted on April 8, 1999
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