Thrummingbird

Flying
Whenever Thrummingbird deals combat damage to a player, proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)

Squadron Hawk

Flying
When Squadron Hawk enters, you may search your library for up to three cards named Squadron Hawk, reveal them, put them into your hand, then shuffle.

Warden of Evos Isle

Flying
Creature spells with flying you cast cost {1} less to cast.

Airborne Aid

Draw a card for each Bird on the battlefield.

Favorable Winds

Creatures you control with flying get +1/+1.

Aven Gagglemaster

Flying
When Aven Gagglemaster enters, you gain 2 life for each creature you control with flying.

Empyrean Eagle

Flying
Other creatures you control with flying get +1/+1.

Augury Owl

Flying
When Augury Owl enters, scry 3. (Look at the top three cards of your library, then put any number of them on the bottom and the rest on top in any order.)

Windbrisk Raptor

Flying
Attacking creatures you control have lifelink.

Soulcatcher

Flying
Whenever a creature with flying dies, put a +1/+1 counter on Soulcatcher.

Plains

Judge's Familiar

Flying
Sacrifice Judge's Familiar: Counter target instant or sorcery spell unless its controller pays {1}.

Crookclaw Elder

Flying
Tap two untapped Birds you control: Draw a card.
Tap two untapped Wizards you control: Target creature gains flying until end of turn.

Island

Soulcatchers' Aerie

Whenever a Bird is put into your graveyard from the battlefield, put a feather counter on Soulcatchers' Aerie.
Bird creatures get +1/+1 for each feather counter on Soulcatchers' Aerie.

Battlefield Raptor

Embrose, Dean of Shadow

{T}: Put a +1/+1 counter on another target creature, then Embrose, Dean of Shadow deals 2 damage to that creature.
Whenever a creature you control with a +1/+1 counter on it dies, draw a card.

Shaile, Dean of Radiance

Flying, vigilance
{T}: Put a +1/+1 counter on each creature that entered the battlefield under your control this turn.

Shaile, Dean of Radiance // Embrose, Dean of Shadow

Wingmate Roc

Flying
Raid — When Wingmate Roc enters, if you attacked this turn, create a 3/4 white Bird creature token with flying.
Whenever Wingmate Roc attacks, you gain 1 life for each attacking creature.

Watcher of the Spheres

Flying
Creature spells with flying you cast cost {1} less to cast.
Whenever another creature you control with flying enters, Watcher of the Spheres gets +1/+1 until end of turn.

Emeria Angel

Flying
Landfall — Whenever a land you control enters, you may create a 1/1 white Bird creature token with flying.