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Tom Stehn's Whooping Crane Report: March 1, 1999

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Tom Stehn's Report: March 1, 1999
Dear Journey North,

Refuge Biologist
Tom Stehn

This year has been a struggle for the whooping cranes, and disappointing for us. However, the flock has managed to INCREASE their numbers by ONE to reach 183, a record number. Here is a brief chronology of their year:

Summer 1998, Wood Buffalo National Park
In Canada, 49 nesting pairs produced 48 chicks, including 12 pairs with twin young. However, none of the sets of twins young survived, and only 24 chicks were still alive in mid-August as they began flying lessons at about 10 weeks of age. Only 18 of these made it to Aransas by the end of the year. This compares with 30 chicks that reached Aransas last year.

Fall Migration, 1998: Canada to Texas
Several notable events occurred during the fall whooping crane migration, including bird(s) injured and/or blown off course.

Juvenile whooping cranes are tawny colored, in contrast to the full white of the adult.

One injured adult female was sighted at the Quivira NWR in Kansas on November 10. She apparently had a broken leg just below the knee and was basically using only one leg. She flew up to 8 miles daily to feed in grain fields, making capture difficult. We tried, but were unsuccessful. After the marshes at Quivira froze up and thousands of sandhills had all departed, the injured female apparently also migrated on December 29. She has not been seen since that date. Her mate and chick that had left the female behind at Quivira arrived at Aransas by November 23. The male subsequently found a new mate starting about one week after reaching Aransas.

Another hazardous event involved a party of American hunters in Saskatchewan on September 30 firing at a flock of sandhills containing one whooper. Fortunately, the whooper apparently was not hit.

An unusual weather condition November 10 brought record low pressure and strong west winds to the upper U.S. Thousands of sandhills were blown eastward into Iowa where sandhills are rarely seen. One probable report of a single whooper took place in central Iowa near Des Moines, and a confirmed single whooper was photographed in flight over Illinois Beach State Park north of Chicago. No one has ever this century seen a whooping crane in Illinois. Back in the 1700's, whoopers occurred in that area.

1998-1999 Winter: Aransas
Generally mild weather delayed the whooping crane migration, with the first arrival at Aransas documented October 28. This is about two weeks later than average.

Weekly aerial census flights documented the arrival of cranes, the presence of chicks and banded birds, and mapped the location of territories.

Date Number of Cranes
(Adults + Young)
October 22, 1998 0
October 29 7 + 0 = 7
November 5 16 + 0 = 16
November 13 30 + 2 = 32
November 19 66 + 3 = 69
November 25 128 + 12 = 140
December 3 156 + 16 = 172
December 17 160 + 18 = 178
December 30 161 + 18 = 179
January 8, 1999 164 + 18 = 182

More About Winter Sightings
A record 182 cranes arrived at Aransas, including 18 young birds. On January 4, 1999, an adult-plumaged whooping crane was confirmed wintering with sandhill cranes located west of San Antonio near Sabinal, Texas. This was a record 183rd bird in the flock. A whooping crane was observed with sandhills on January 24 near Brazos Bend State Park in Fort Bend County, Texas and was still present through February 7. It could be the crane observed near Sabinal (i.e. last seen January 21), an Aransas bird that moved north, or a new bird, possibly the juvenile during the 1997-98 that wintered with sandhills in Brazoria County and could have returned to the same general vicinity. Because of this uncertainty, the peak winter count remained at 183.

Population Size
Average mortality apparently kept flock size below the 190+ cranes hoped for. Sixteen adult/subadult cranes (9% of the population) failed to arrive at Aransas. Another indication of mortality during the fall migration was that of the 24 juveniles fledged in August in Wood Buffalo, only 18 made it to Aransas, indicating 25 % mortality of the young post-fledging, an above average figure. In some cases, family groups were reported in Saskatchewan but failed to arrive at Aransas with their juvenile.

With 18 young added to the population, if mortality had been les