Hawks in a hybrid rehabilitation shelter because his former owner got bored with him.
Got himself a new toy, leaving Hawks locked in a much too small cage, barely able to move or preen or even spread his wings.

So by the time he's rescued and put in a shelter he's a half feral matted mess.
Hates and attackes every member of staff the shelter has until they send Dabi in one day and Hawks basically imprints immediatly. That is HIS handler now, thank you very much.

And now hawks wants to put in effort again, preen, look pretty...he has to entice Dabi into becoming his mate after all.
Once he finds out that letting a handler touch him without the use of a tranquilizer gun includes a physical check up that always includes his wings...

Instant happy birdie. He hasn't let anyone touch his wings willingly in quite a while, nearly forgotten how good it feels. It satisfies some deep seated need to have someone else do such an intimate thing for him... to him. He can't help the little shudders, feathers ruffling and

Fluffing without his control because of the tiny burst of pleasure and satisfaction it sends through him to have Dabi's calloused but careful fingers comb through his feathers and realign the barbs.

He is still very much a bratty handful with everyone else but a mostly well behaved docile birdie for dabi.
...unless it's heat time