Tom Stehn Reports from Aransas: April 9, 2003
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Tom Stehn and Survey Plane |
Oops! I actually found more whooping cranes at Aransas this week (a total of 121) than I had last week (116). How could that be? Had the cranes gotten tired of cold feet after encountering snow and ice in Nebraska and retreated back to the warmth of Texas? Although ducks will sometimes make a short reverse migration when encountering frozen conditions, I've never heard of this happening with whooping cranes. They can tolerate the cold very well.
I have a better explanation for why I found more cranes this week. On the April 9th census flight, we had perfect visibility with clear blue skies. Last week, the skies had been overcast, making it more difficult to find all the cranes. Apparently I had overlooked 10 cranes last week. I also found out that 5 cranes had started the migration between April 2-9, whereas 44 cranes had migrated the week before that. The cranes are currently spread out between the Texas coast and the Canadian border. With an improvement of weather up north, the cranes will soon be in Canada, anxious to build nests and lay eggs.
How are the cranes still at Aransas going to catch up with those already in North Dakota and get to the nesting grounds in time to lay eggs and raise young? It seems like the cranes that leave Aransas on the late side run into fewer cold weather storms as winter draws to a close. Thus, they can complete the migration more quickly, sometimes covering 2,400 miles in just 2-3 weeks. Sometimes it pays off to stay on the Texas Coast a little longer eating blue crabs, rather than finding little food in the north still frozen. How do cranes survive the long migration with most of their time spent flying? And how do cranes survive sitting on eggs for 30 days with the crane on the nest unable to feed?
While you're thinking of an answer, most of the cranes still at Aransas are just about to head north. Normally most pairs are gone by April 15, and all pairs by April 20. The cold front that hit the Texas coast April 8-9 prevented any cranes from migrating these last few days, but as soon as the winds turn back around to the south, forecast to occur April 11-12, I'm expecting many cranes to leave. It'll be fun to see if I'm right.
Tom Stehn, Whooping Crane Coordinator
U.S. Fish and Wildlife Service
Aransas NWR
P.O. Box 100
Austwell, TX 77950
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