The “falconry gloves” random glove appearance has some side benefit involving training pet falcons (or possibly all birds) to attack your foes.

Magpies, a bird that has a stealing attack; unlike monkeys, the stealing attack is limited to shiny objects (possibly based on their material) that are under a certain weight. Under that rule, rings, gems, and amulets are common targets of theirs. They probably have a rather fast speed, too. They should likely generate in small groups.

Magpies would have an alignment of 0 and lack the M2_HOSTILE flag, and thus may be peaceful to neutrals, but angering one makes all other magpies angry as well.

Bird pets are better at combat than mammals, but can carry much less due to weighing less.

Phoenixes: birds with fire resistance and who may automatically resurrect on death, or else revive from their corpse/ashes similar to trolls.

Thunderbirds: birds with lightning breath.

Rocs: large, rideable, fast and powerful birds.