Ghost Birds in the Sky

Nick Vinciguerra collecting dead
Violet-green swallows in Velarde, NM.
(American Birding Assn.)

The unusually strong storm that swept through the southern Rockies and Plains the second week of September pushed " a spectacular array of fall migrants to Albuquerque," as one biologist noted. 

Smoke from West Coast forest fires may also have forced some southbound birds further east as well.

The sad part is that many died — not so much from the smoke as from hunger, one New Mexico researcher, doctoral student Jenna McCullough writes for the American Birding Association website.

Sudden and dramatic unavailability of food caused by a historic and drastic cold snap is, I believe, a more parsimonious explanation than a widespread, smoke induced, mass mortality event. While we do not have data on how fast smoke inhalation would kill birds hundreds of miles away from the fires themselves, what we do have are data from the 258 Violet-green Swallows that Nick and I collected in Velarde this week. . . . .

If a lack of food contributed to the mortality event, birds would have less fat and no protection against hypothermia. Indeed, of the hundreds of birds we assessed, none had fat stores on their bodies. Furthermore, Though we have yet to perform any toxicology analyses or inspect their lungs for signs of smoke inhalation, I think it is safe to say that these birds were starved and succumbed to hypothermia. When USFWS autopsies of other birds are reported in the coming weeks or months, we suspect they will reveal a similar cause of death.

Cold and snow mean no flying insects, which is bad news for swallows and other insectivores.

Here in southern Colorado, I found one Lesser Goldfinch dead in the driveway, uneaten, during that brief cold weather. Considering it was only five seconds' flight from a sunflower seed feeder, it should not have been hungry. But M. and I both were briefly sick that week, which I blamed on the sudden shift from about 94° F to °27 F (34°C to -3° C). Maybe something hit the little goldfinch too.