LAS VEGAS, N.M. (AP) — Dr. Douglas Thal has always been fascinated by golden eagles. He grew up on his family's ranch in Golondrinas, where for hours he would watch the majestic birds of prey that resided in large nests built on the ledges of sandstone cliffs.

"They've been there as long as any human beings can remember," Thal said. "I spent a lot of time watching those birds when I was tiny. I grew up with them, and they've always been something I dearly love."

But in recent years, Thal hasn't seen many golden eagles on the ranch, and the nests seem to have been vacated.

Last November, while...