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Independent tests, radar help explain bird deaths

Date01/26/2011
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BEEBE - Three laboratories' test results on red-winged blackbirds that died in Beebe's Windwood neighborhood Dec. 31 show the cause of death was blunt-force trauma.

Results from the Southeastern Cooperative Wildlife Disease Study, released Wednesday, are the same as earlier results from the Arkansas Livestock and Poultry Commission and the U.S. Geological Survey's National Wildlife Health Center in Madison, Wis. The SCWDS lab is part of the University of Georgia's College of Veterinary Medicine.

The tests ruled out bacteria, viruses, heavy metals, pesticides and avicides (chemicals used to kill birds) as causes of death. The SCWDS lab tested 13 red-winged blackbirds and one common grackle, submitted by Karen Rowe, the Arkansas Game and Fish Commission's bird conservation program coordinator.

Tests revealed hemorrhaging "consistent with blunt trauma." The SCWDS report concluded, "In most instances, such traumatic injuries in wild birds are due to flying into stationary objects such as trees, houses, windows, power lines, towers, etc."

A recent count estimated the size of the roost flock near the neighborhood at 1.6 million birds.

Weather radar also reinforces the width and breadth of the event. Sidney Gauthreaux, Centennial Professor Emeritus of Clemson University's department of biological sciences says the cloud of birds rising from the roost is documented.

"There is no question that the exodus of birds from the roost is visible in the radar display images," said Gauthreaux, a zoology professor who created Clemson's radar ornithology laboratory in 1990. "The first exodus occurred about 10:20 (p.m.) and contained approximately 6,000-7,000 birds per cubic kilometer. . . . At 11:21 p.m., another pulse of birds with a slightly smaller density left the roost."

Windwood residents first observed the birds flying at roof top level and flying into structures and objects around 10:30 p.m.  Beginning at about 11:30 p.m., AGFC wildlife officers received reports of blackbirds falling from the sky in and around the Windwood neighborhood. It's estimated that 4,000-5,000 birds fell before midnight. It appears unusually loud noises, reported shortly before the birds began to fall, caused the birds to flush from the large roost. Additional New Year's Eve fireworks in the area may have forced the birds to fly at a lower altitude than normal. Blackbirds have poor night vision and typically do not fly at night.

Gauthreaux's report says no severe weather was "over or near the roost" at the time. Since 1992, Gauthreaux has used NEXRAD - Next Generation Weather Radar - to archive bird movements to track migration routes and stopover areas.

The AGFC flew over the area in a helicopter to gauge the scope of the event. No dead birds were found outside the initial area of fallen birds.