>> below the horizon -- >> reporter: biologist doug bell, sean smallwood, and joe diganado study golden eagles. >> it's got white in its tail which means it's a younger bird. characteristic of a golden eagle is that the birds have what it at the base of the tail and wings in their earlier years, year 1 to year 3 or 4. >> reporter: many young golden eagles live in the alta mont says biologist doug bell. >> the alta mont pass wind resource area is adjacent to one of the densest nesting populations of golden eagles in the world. >> reporter: golden eagles are protected under federal law. it's illegal to kill a single eagle without a permit. according to county estimates, 35 golden eagles were killed by the alta mont turbines in 2013. scientists call the alta mont a population sink. >> their population's going down the drain. the alta mont is killing more eagles than the local population can reproduce. so it's taking out more youngsters than they can produce and replace themselves with. >> reporter: that appears to be what happened to this young eagle. >> the primary injury on this bird is