English Other General / Conversation / Greetings / Letters English grammar

I'm translating a text about wild nature, and I have a question - is it OK to use "he" or "she" when talking about male and female birds, or should I just use "it" everywhere? Which way is more common or more naturel? I'm no native English speaker, so I'm not 100% sure - please advise!

Here is an extract:

Now it is more often that they trumpet and sing in pairs. The male starts HIS part – HE raises HIS body, stretches HIS neck and beats HIS wings, trying HIS voice. The female joins HIM, and now they trumpet together, head to head, fluttering their wings and bowing to each other. This is a kind of confirmation of their mutual affection, which is especially important before the nesting season. And God forbid that some nearby whooper make a careless movement and enters the pair’s private space – the offender will be immediately attacked. At the best case, the male starts slapping the water with HIS feet as if running in place, making a lot of noise – this is simply a display of strength and good physical fitness. Or there can be a direct attack when the opponents try to peck each other on the wing or at its root. An interesting fact is that the pen usually joins the attack, too, although HER aggression is directed toward another female should SHE be not too eager to give ground. A short pursuit – and both partners come back together again, vying to tell each other in loud voices about the beaten opponent.