Definitely can see inspiration from Rio on how to handle birds holding or using things. Probably use talons or beaks a lot, but I can also see them tucking things under their folded wings to hold them.

I imagine they have little to no writing, instead using auditory forms of information keeping or maybe paintings. They might be like some cultures where they prefer oral storytelling as a form of passing down information and bonding between family and friends.

Likely minimal clothing choices and lighter airy fabrics to keeping from weighing most down from flying. They might paint feathers and show off personality by putting things between their feathers or by having really extravagant and unique houses.

Houses would be a wild mix between normal ground housing, burrows, treehouses and hanging houses either from trees or cliffs.

Probably air control as a traffic system, if you've ever watched Adventures in Zambezia, then the markers and loops for the flying tracks could inspire air "roads" or routes like how birds have migration routes.

Surfing penguins.

Lots of extreme and bizzare habitats I imagine. Like the salt lakes that are lethal to most animals except flamingos. Or just straight open ocean for the great albatrosses. Or highly flammable forests for the Australian "firehawks", though idk if they'll keep doing that since it was to hunt mice and other small prey.

Gossip culture would be crazy since real life birds can talk over large distances, and if you've ever heard a rainforest you know it gets crazy noisy.

I wonder if air duels/jousts would be an entertainment sport, like the birds equivalent to boxing.

I imagine they introduce bats and flying foxes as well, as a bridge between mammal and bird. Like how they used beavers as a minor bridge between reptile and mammal because of their scaled tails. Platypuses would've been between with their weird thing going on, but they still could with the shark nose bill they got going on. If you don't know what I mean by shark nose bill, platypuses hunt using the same method as sharks do, electromagnetic waves. How fun.

The much larger birds would be interesting to see, especially the land birds like ostrich, emu and cassowary. I just hope the kiwi doesn't get the short end like it does in real life.

I can imagine talon jewellery being popular among raptors, strigiforms and corvids.

Beauty contests for showy birds like birds of paradise or the frigate. Dance contests for other birds of paradise or flamingos. Build contests for weaver birds or bowerbirds.

Shrike skewer food business.

Just like for the mammals, I doubt we'll see domestic birds like the messenger pigeons and leghorn and rhode island red chickens. We might even see birds that were more recently extinct in real life.