The U.S. Geological Survey’s National Wildlife Health Center in Madison Wisconsin determined that the migratory bird mortality event that occurred in the Southwest in early September was caused by starvation that was exacerbated by the early winter storm. The New Mexico Department of Game and Fish (NMDGF) sent bird carcasses to the lab for analysis shortly after the mortality event. While the laboratory results were not definitive for one single cause of death, nearly all of the birds were severely emaciated. The necropsies found evidence of starvation including shrunken breast muscles, kidney failure, empty stomachs and intestines, blood in intestines, and depleted fat stores.

According to the press release from the NMDGF: “The USGS National Wildlife Health Center, located in Madison, Wis., is renowned for the thoroughness of the diagnostic tests for wildlife disease diagnosis and management. The center conducted numerous tests during analyses, ruling out contagious bacterial disease, contagious viral disease including avian influenza and Newcastle disease and parasites as cause of death, as well as finding no evidence of smoke poisoning or pesticide poisoning.

From the lab reports, Department biologists know that migrating birds entered New Mexico in poor body condition and some birds were already succumbing to starvation. The unusual winter storm exacerbated conditions, likely causing birds to become disoriented and fly into objects and buildings. Some were struck by vehicles and many landed on the ground where cold temperatures, ice, snow and predators killed them.”