Flying with Aquila by E.J. Darling

Being the fated mate of the infamous War Eagle was something she never saw coming.

On the run from something much bigger than she, Echo Broadwing seeks the help of the last remaining member of her clan. A clan destroyed long ago by the same hand threatening her now. But even he, a legend in his own right, is just one against an army.
Aquila spent the last two centuries running from the only thing that connected him to his old life— Echo. When she appeared out of nowhere, he was forced to come to terms with a past he could never truly run from. Then, she asked him for the biggest test of all—facing his demons.
But there is more going on in Bestian Creek as a new threat tries to take hold of the shifter world. Secrets become known, Alphas come into power, and hiding in the shadows may very well be a thing of the past.