Some of these pictures and descriptions may give away plot details that you might not want to know before watching the film.
This movie bombed in theaters despite a good cast that includes two huge stars - Jennifer Lawrence and Bradley Cooper, who play Serena and her husband Pemberton. It's slow, dark, somber, and violent and the protagonists, Serena and Pemberton, are unlikable people. Both are willing to commit murder to protect their interests, and to make things worse, they're trying to cut down all the trees on their land in the Smoky Mountains before the trees are saved when the land is designated a National Park. Pemberton convinces the locals to side with him because only the rich will enjoy the park while the working people need jobs cutting trees. And if that's not bad enough, Pemberton's main goal is to hunt and kill one of the last remaining "panthers" (mountain lions) left in the mountains. These are not a couple that cares about the environment at all. The best one can say is that the movie takes place in 1929 before consciences had been raised enough to want to save what was left of our natural resources.
After they meet and get married while Pemberton is at home on business in Boston, Serena and Pemberton return to his logging camp in the Smokie Mountains. When they arrive, they see a man with a bloody ankle from a rattlesnake bite. Pemberton's partner tells him they've lost 6 men in the two months that he was away in Boston. Serena tells them that at her father's logging camp in Colorado they had a trained eagle flying over the logging site to catch rattlesnakes. Nobody takes her seriously and she's told they don't have eagles in the Smokies. She tells them they need to import one, and so she does.
After Serena trains her imported eagle, we see her at a logging site with the bird flying overhead. She explains that the prey tries to hide, but the bird can see any movement below. Then we see it swoop down on a snake and grab it. She points to where the bird should take it and the bird brings the snake to Serena who holds it up in triumph while the loggers cheer.
I don't really know if rattlesnake bites were ever much of a problem at logging sites in the Appalachian mountains or anywhere else, but it's impossible that using one trained eagle would help to solve the problem if it even existed. Native hawks and eagles would stay away from the humans while a trained raptor might tolerate their presence and continue hunting, so that part's not too far-fetched. But I just don't accept this as a realistic solution to a problem I doubt existed. It was a far-fetched idea inserted to give Serena a chance to prove how capable she is, and it worked. I'd be interested in knowing if the eagle and snakes were in the book the movie is based on, but it's not worth it to me to read the book.
The movie was filmed in the Czech Republic where there are probably aren't any rattlesnakes available to rent, and it would be dangerous to use one anyway, so the "snake" we see appears to be a fairly realistic fake snake prop, except that the markings don't make it look much like a Timber Rattlesnake and they didn't bother to put a rattle on the tail. Of course, when we see it crawling, we hear all the usual unrealistic hissing sounds we always hear in movies.