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Tom Stehn Reports from Aransas: April 30, 2004




Tom Stehn and Survey Plane at Aransas NWR

Dear Journey North,

On the April 28th census flight, the pilot and I both anticipated that all the whooping cranes would be gone from Aransas. But during our survey, it was hard to deny the sight of three 5-foot tall white birds standing together around the same pond. Thus, three "stragglers" are still here, while 190 whooping cranes (98% of the flock) have migrated. I've had non-breeding cranes (and once a widowed adult) stay at Aransas into the first week of May before departing, so I'm not concerned yet. But I am ready for them to be gone and for me to get a break from monitoring cranes.

A Chick Left Behind?
One of the three cranes yesterday was the chick from the one-parent family group. The chick had some rusty brown feathers remaining on its head and back, but mostly was all white. Was one of the two cranes with the chick its parent, or had the parent started migration and left the chick behind? I had no way to know. (I talked about what might happen in my April 16 report.)

Migration: the Most Perilous Time for Cranes
Most deaths of adult whooping cranes happen during the migration. What are
the main hazards the cranes face? When whooping cranes migrate, they fly
during the daytime and stop every night, often in unfamiliar territory. This is because they fly on a slightly different migration pathway every year as they get blown off course slightly to the east or west, depending on the winds. The main hazard the cranes face and the number one cause of death of fledged whooping cranes is collisions with power lines. The cranes sometimes simply don't see the lines when flying, especially in low light conditions or bad weather. Collisions are usually fatal, although not always. This spring, one of the eastern whooping cranes was observed
bouncing off a power line and continuing on in flight with the group, apparently shook up but not injured to any great extent. With the human population growing in North America and more and more power lines being built, the migration becomes more hazardous for whooping cranes every year. Whooping cranes can also fly into fences that they don't see, especially when a fence crosses a wetland that the cranes may be attracted to. Some wetlands harbor diseases, such as fowl cholera or botulism in the water and expose the whooping cranes to these diseases. Cranes have to avoid
predators such as bobcats and coyotes whenever they stop for the night.They do this by standing all night long in shallow water. This allows them to hear predators coming during the night. Cranes also can be attacked in flight by eagles, especially golden eagles that are more common in the western U.S. Hunters may occasionally shoot a whooping crane by mistake. We have also documented one instance when an airplane struck and killed a whooping crane.

A Question for You
Every year, after the cranes migrate 2,400 miles to Canada and then return in the fall, I expect that about 10 of the cranes will have been killed. With a population not quite at 200 cranes in the last natural migratory flock, the loss of 10 is significant. We need to do everything we can to enure the cranes can migrate safely. Do
you have any suggestions about how to do this?

Tom Stehn, Whooping Crane Coordinator
U.S. Fish and Wildlife Service
Aransas NWR
Austwell, Texas


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