With at least four rare whooping cranes, including one last seen in North Dakota, still en route to their wintering grounds in Texas, North America's only wild flock should hit a record 266 birds.

That's the latest estimate from the U.S. Fish and Wildlife Service's national whooping crane coordinator Tom Stehn, who's based at Aransas National Wildlife Refuge on the central Texas Gulf Coast.

Biologists in North Dakota tasked with monitoring the stopovers in the state during the endangered whooping cranes' semi-annual migrations between Texas and northern Alberta, Canada, could not be reached for comment on the laggardly crane, which Stehn identified as a subadult. The biologists are off for the holidays.

Stehn conducted a pre-Christmas aerial census and located 253 of the white-plumed cranes, which are the tallest birds in North America, on the 115,000-acre Aransas refuge complex and surrounding areas.

Stehn estimates that eight cranes previously counted this fall at the wintering grounds were missed on the flight, which was conducted Dec. 20.

Of the other three whooping cranes still migrating, a juvenile was last reported in West Texas in late November, and two whooping cranes were reported Dec. 19 near the Texas coast north of Aransas NWR.

"One additional whooping crane is presumably with sandhills using agricultural lands just north of the wintering area," Stehn wrote in an e-mail.

The Aransas-Wood Buffalo flock numbered 237 whooping cranes when spring migration started, but one adult died near Almont in April during the migration.

Stehn attributed the estimate of 266 whooping cranes to "an excellent production of 40 juveniles sighted on the nesting grounds at Wood Buffalo Park in August."

Thirty-eight juveniles have been counted at Aransas and one in West Texas, meaning survival of the juveniles since August has been excellent, Stehn added. The carcass of one juvenile was found this fall in Saskatchewan, but researchers could not determine the cause of death.

Mortality of adult cranes between spring and fall, 2007 is believed to be nine birds at most, Stehn continued.

The number is down compared to the past two years, Stehn said.

"Mortality between spring and fall has been above average and totaled over 20 birds each year," he wrote.

(Reach outdoor writer Richard Hinton at 250-8256 or richard.hinton@bismarcktribune.com.)