The book is about alien birds that must dock and flap their wings to keep islands afloat on their home planet. All of a sudden aliens attack them and slaughter most of them. The birds have at least one space ship, and a few escape on that.
The birds find a water planet, and decide to explore it. They notice a large object under water; when they try to check it out, they crash. Only one bird survives the crash; he finds some sort of tentacle monster (?), and survives off it.
The bird eventually leaves the water planet, becomes part of a space ship, and battles other aliens. Both sides have powerful ships which end up destroying galaxies.
The birds in the beginning also play a VR game about being god. They try to help one race become more powerful. A more detailed bit of the game is they main protagonist, the bird, has these animals that cannot lookup so he clears the sky so that they can look up which leads to the enemy destroying them because the enemy can finally see a race to kill (all in the simulation VR game). The game is something the birds have on their homeworld; I think it's implanted in their heads. It's an activity for them to do while they're docked, keeping the islands afloat.
As far as I can recall, the birds were presented as looking much like actual birds here on Earth, with wings and talons (no hands, for example).
I read the book in 2017; I'm not sure how old it was then, and I don't remember anything about the cover.
Extra detail: There might have been crystals on the islands crystals that helped keep them floating.