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Tom Stehn Reports from Aransas: April 24, 2002
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Tom Stehn and Survey Plane |
I did a thorough search of the whooping crane area from a small airplane on April 23 and found only 2 cranes still here. An estimated 116 cranes have migrated since the last flight on April 10. Most of these departures were believed to have occurred prior to April 18th since ground searches that day failed to find any cranes. The two remaining cranes have a very dingy and slightly gray appearance indicating they are molting body feathers. They presumably will still migrate in the coming 7-10 days since they probably are not molting their all-important flight feathers. They are probably young cranes that won't be nesting in Canada this summer, so they are in no rush to head north.
When I think about bird migration and the two non-breeding cranes still
here, I ask myself: "Why do young birds still not old enough to breed make the trip all the way north and face the hazards of migration twice a year? Wouldn't it make sense for young cranes to stay in Texas until they reach 3+ years of age and are ready to nest?." I'm not sure there is an answer to this other than the migration urge is so strong and so rigidly fixed that it occurs annually and not just in years when birds are going to nest.
On my flight, I did extra searching for the whooping crane with the injured wing on San Jose Island that I have been watching all winter, but could not find it. I think this bird could fly and presumably started the migration. I'll make one more flight May 2 to see if the final two cranes have departed, and to look again for the bird with the injured wing just in case I missed it.
"A necropsy of the adult female whooping crane killed in Texas April 13th indicated trauma with internal bleeding as the cause of death, consistent with striking a power line near where the bird was found. I'm going to think long and hard about this power line issue since it is the number one cause of death of migrating whooping cranes. The line this bird hit was very low and next to an isolated field and NOT the type of line that usually gets marked to make them more visible. The power line situation is a real hazard that whooping cranes and many other types of birds face as the natural world which they need in order to survive gets developed."
Tom Stehn
Whooping Crane Coordinator
U.S. Fish and Wildlife Service
Copyright 2002 Journey North. All Rights Reserved.
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