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Update from the Whooping Cranes' Winter Headquarters
Aransas National Wildlife Refuge
Austwell, Texas
March 14, 2000

Dear Students,

Finally, a breakthrough! For more than two months, two family groups of whooping cranes have not been at Aransas. If they had been here, I would have identified them by plastic colored leg bands on one adult in each family. On February 29th, one of the missing family groups was right back on their territory on Central Matagorda Island. Since I had documented 185 in the flock without this family, their presence brought the whooping crane population to a record 188. This is 5 more than last winter.

See if you can follow this math. Last spring we had 183 total whooping cranes in the population. They migrated to Canada, nested and raised young, and brought back 17 juveniles. If all of the 183 whoopers had survived the summer, the flock could have reached 200 in size. Thus, since I can only account for 188, that means 12 whooping cranes died between spring and fall, 1999.

Is the loss of 12 birds unusual? Let's look at percentages. The loss equals 12 out of the flock of 183. Twelve divided by 183 = 6.5%. This mortality is not unexpected or unusually high. Mortality can run as high as 10 or even 12% of the population in bad years. Whooping cranes probably live 20-30 years in the wild, so we have to expect population turnover.

So where was the missing family group between mid-December and February 29? I can only guess. Sometimes a few whooping cranes leaving the wintering area at Aransas and join flocks of sandhill cranes. They may travel up to 50 miles and spend 1-2 months with the sandhills. Then right before the spring migration, the whoopers return to Aransas, whereas the sandhills head north and congregate on the Platte River in Nebraska.

A recap of my census flight is provided below.

An aerial census of the Aransas NWR and surrounding areas made February 29, 2000 provided evidence that a record 188 whooping cranes are present.

Recap of cranes observed: (159)

Refuge Lamar San Jose Matagorda Welder Other Total
68+10 4 +1 22+1 23+2(inc) 26+2 43+16 =159

Remarks: Overcast skies, smoke from a prescribed burn on a portion of Matagorda Island, and haze that formed on the windshield throughout the day made viewing difficult. Some cranes were overlooked, and an incomplete census was done on Matagorda Island.

Crane movements on the refuge blocked attempts to get an accurate count. A total of 159 whooping cranes were located, including 16 chicks.

The highlight of the flight was the presence of the Central Matagorda family with female YbY-GwG back on their territory. They had not been found since December 14 and are believed to have left the census area for an extended period. With strong evidence of 185 cranes present last flight, the addition of the Central Matagorda family indicates a record 161 + 17 = 188 whooping cranes in the flock. Banded family GwG-YbY is still missing.

Whooping cranes are continuing to leave their Matagorda territories to utilize refuge prescribed burns, including the South Matagorda and North Cottonwood families. A total of 32 whoopers were seen on burns, including 15 cranes on Unit 41E and 8 on Unit 37. Five were on a recent burn at Welder Flats. Nineteen cranes were found in open water (bays or lakes). Nine cranes were at freshwater.


Tom Stehn
Whooping Crane Coordinator

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