Tom Stehn's Report: Questions and Answers
April 11, 2008

As you read Tom's report this week . . .

  1. Where are the 266 cranes of the Western flock now?
  2. Why does Tom call this an early migration?
  3. What might explain why the cranes left earlier?
  4. What difficulty might lie ahead for the cranes?
  5. Do you think you'd like to do what Tom did today?

Dear Journey North,

On April 10 I finally flew over the refuge to count cranes. I found a total of 34 whooping cranes during the 3-hour flight. The rest of the flock has started migration! More about the count results >>

Off to Canada!
I estimate that 87% of the whooping crane flock of 266 has started migration. Seventeen groups of whooping cranes have been reported so far — all the way from central Texas to South Dakota. Most sightings have come from Kansas and Nebraska. Amazingly, the cranes currently as far north as Nebraska will be held up by a snow storm and unfavorable winds in that state over the next few days!

An Early Migration: Why?
At Aransas, all 34 cranes still present may be subadults We saw only one duo that could have been an adult breeding pair. Thus, the breeding pairs have started the migration earlier this year than in years past, since some adult cranes often wait until mid-April to take off. What might explain an earlier departure?

I think this earlier migration may be tied to the good food resources that were available to the cranes throughout most of the winter, leaving them in good condition to start the migration. The pre-migration body condition of the cranes at Aransas is very important since the 3-4 week migration to Canada will not include much feeding. Also, conditions may be still very cold, with only limited food available when they first reach the nesting grounds. Migration is generally a hard time for wildlife species. Their long-distance movements allow little time to find food to eat.

A Hot Job
The whooping crane survey was conducted in a Cessna 210 piloted by Gary Ritchey of Air Logistic Solutions of San Antonio, Texas with me and USFWS observer Darrin Welchert as passengers. It was incredibly hot in the airplane during today's flight, with full sunshine coming through the windows and of course no air conditioning. Outside temperature was 86 degrees and probably above 90 in the plane with us dressed in fire proof full-length clothing and helmets. We occasionally opened a window, but not for long because the wind noise interfered so much with our radio communications through our headsets. (Sometimes being a wildlife biologist is not fun and games, but I still think it beats most alternatives.)

Next Flight April 22
The next census flight is scheduled for April 22. How many cranes do you think I'll find then?

Tom Stehn
Aransas National Wildlife Refuge