When Call wakes up and sees the three vultures on Gus's corpse, the vultures are all turkey vultures. The close-up shows a much larger and more aggressive black-headed vulture pecking at the corpse. When Call screams and runs at the birds, all three are turkey vultures again.
Miles City is shown to have large mountains surrounding it, with a landscape similar to western Montana. In reality, Miles City is nowhere near any mountains but is in fact in the middle of the great plains in the valley along the Yellowstone river in eastern Montana.
The location of the ranch they build in Montana is surrounded by mountains and looks like it is in mountainous western Montana. However, according to everything they say in the film, along with the map provided in the DVD extras, the ranch is supposedly located in eastern Montana, a land of vast flat grasslands and no large mountains at all.
The long-distance shot of the ranch shows tracts of clear-cut logging in the background. Also, you can see that the snow is composited in, as the snow caps of the distant mountains do not shift between winter and spring.