The U.S. Geological Survey National Wildlife Health Center has analyzed representative samples of the migratory songbirds collected, cataloged and sent for analyses by New Mexico Department of Game and Fish biologists, in early September. The lab report indicates that the single abnormality shared by nearly all birds was body condition ranging from poor to severely emaciated.
Kerry Mower, the Department’s wildlife disease specialist, said, “The laboratory results are very informative but did not identify a single definitive cause of mortality. However, they did find that nearly all birds were severally emaciated.”
The single abnormality shared by nearly all birds was body condition ranging from poor to severely emaciated. These observations are evidence of physical exertion without nourishment to support recovery, including:
- the large breast muscles controlling birds’ wings were severely shrunken;
- kidney failure was apparent in many of the birds;
- stomachs and intestines were empty of foodstuffs;
- many intestines contained small amounts of blood, which is one of the effects of starvation;
- fat deposits, the stored energy for migration, were depleted; and
- lung tissues were irritated.
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.
“The Department would like to thank many partners and the public who reported mortalities across New Mexico,” said Erin Duvuvuei, the Department’s avian biologist. “Hundreds of reports were received through email, phone calls and the iNaturalist app.” Reports declined by late September.
The Department would also like to thank all of the partner organizations who were essential to this process. Partners include the: United States Fish and Wildlife Service, White Sands Missile Range, United States Forest Service, Bureau of Land Management, New Mexico Avian Conservation Partners, New Mexico State University, University of New Mexico, Audubon Southwest, Los Alamos National Laboratories and the New Mexico Wildlife Center.