Journey North Whooping Crane Spring 2006

Meet Tom Stehn

March 9, 2006

Dear Journey North,

March is a critical time for the whooping cranes at Aransas. Food supplies for them were limited in January and February when tides were extremely low, draining the marshes. Their favorite food, the blue crabs, had moved out into the bays to deeper water. That meant the crabs were not available to the cranes. Tides are now higher. I hope crabs have moved back into the crane “refrigerators” (meaning the salt marshes where cranes spend the winter). The whooping cranes need a steady diet of crabs to build up fat reserves as they gain weight just before the spring migration. These fat reserves are used during the migration and also help them get through the nesting season. Fat reserves help then because the males and females take turns sitting on the eggs and don't have as much time to find food.

Bad News and a Discouraging Year
I found more bad news on my last census flight (March 1st). Another juvenile has died. This juvenile's father had died earlier this winter at the age of 28 years. For a crane, this is approaching old age. (I wish I were still 28! I'm double that age.)

The juvenile had stayed with its mother after its father died. But for several weeks we sometimes saw it alone, a sign that perhaps it wasn't feeling well. I can only speculate that perhaps the juvenile had gotten a fatal disease, such as avian tuberculosis.

The loss of this bird leaves 215 whooping cranes in the flock, the exact same number that were present last spring. It has definitely been a "break even" year for whooping cranes—a very disappointing turn of events considering the excellent nesting season they had last summer with 30 juveniles making it to Aransas last fall. Twenty-six of the older birds died last year. This is way too many. A total of 5 whooping cranes (1 adult and 4 juveniles) have died this winter. This has been a discouraging year.

All Cranes Still Present
My March 8 census flight had to be cancelled due to winds gusting up to 45 miles per hour (tropical force strength and very unsafe for flying). Although there have been two reports of whooping crane groups in migration, my best guess is that all the whooping cranes are still at Aransas. Every year, people get anxious and think the whooping cranes are going to leave "early," and often we get false sighting reports. But the whooping cranes "know" that it is still too early to head for Canada and they would encounter snow and frozen conditions if they left now.

The Rewards of Good Timing: A Question for You
The correct timing for most of the breeding whooping cranes to leave Aransas starts the last week in March and continues through April 20. I mislead you when I said the whooping cranes "know" not to leave too soon. How is it determined when they should leave? Think about what bad things could happen if they leave too early, or what would happen to them on the nesting grounds if they got there too late. Nature has a system of "rewarding" the birds that leave at just the right time, and in that way the timing of the migration has evolved. Your Question: What reward do the whooping cranes get?

Tom Stehn
Whooping Crane Coordinator
USFWS