"That cat is eating a bird!"

Translation: Ta kočka žere ptáka!

[Bog999]

is ptak male? is it in accusative?

[endless_sleeper]

Yep, masculine animate accusative (singular).

[Bog999]

I forgot that animate masculine declines in accusative, so it took me a while to understand my mistake

[AntonBaidzionak]

Tell me please, why it was jedí several questions ago (also with cat and birds but in present simple) and now it is žere? I thought that žere is for an animals and jist for a man, am I wrong?

[VladaFu]

You can use jíst for animals as well. Most often for pets eating the food served to them.