Photo by Karine Aigner kaigner / Last year on a hike along the Rio Grande in New Mexico, I came across a dead violet-green swallow. I thought nothing of it at the time, just that it was unfortunate the bird had met its demise. Further up the dirt path lay a yellow warbler. All told, I found seven dead birds that day, and feather remnants of many more. It turns out the birds were part of a mass death event during the summer of 2020 that spanned five southwestern states as well as Mexico. Subsequent studies have determined that fires in the West at the time, along with a severe cold snap, left birds emaciated as they began their migration. Once again birds are dying, along the East Coast from Connecticut to Florida. Since May birds have been showing up with crusty eyes, blindness, and apparent neurological issues—and then dying. Experts are desperately searching for answers. Tests have ruled out avian viruses, but human-linked toxins and infectious disease still remain in question. Mo...