Mass bird die-off apparently result of weather events

The mass die-off of birds across New Mexico this fall appears to have resulted from a perfect storm of weather events, according to pathology results from a national wildlife laboratory.

The U.S. Geological Survey National Wildlife Health Center in Wisconsin analyzed dead birds collected by the New Mexico Department of Game and Fish in September.

Game and Fish Director Michael Sloane said the bird analyses showed no evidence of bacterial or viral disease.

"The best we can say is that the timing of the record cold, the (wildfire) smoke, the high winds, combined with their timing of migration may have depleted their stores," Sloane told the Game Commission at Thursday's meeting. "They may have come in (to New Mexico) depleted because they left early from places to the north."

New Mexico had record-breaking heat on Labor Day. For the next several days, extreme winds were accompanied by record early freezes and snowfall. At the time, wildfires were raging across the West, which may have prompted an early migration for some birds.

After Labor Day, bird enthusiasts and residents across New Mexico and other Southwestern states began reporting large numbers of dead migratory birds.

"Consistently across the board, the birds were undernourished, had no or limited fat stores and generally had no foodstuffs in their stomachs or intestines," Sloane said.

The lab findings are consistent with a theory posed by Jenna McCullough, a Ph.D. student at the University of New Mexico and the Museum of Southwestern Biology, who helped collect 300 of the dead birds from Rio Arriba County in September. That region had experienced the lowest temperatures and the most snow from the unseasonably early storm.

"These migratory birds that stop to roost for the night, if they don't have enough fat stores, they might die of hypothermia right then and there," McCullough said.