Thrummingbird

Flying
Whenever this creature 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.)

Salvation Swan

Flash
Flying
Whenever this creature or another Bird you control enters, exile up to one target creature you control without flying. Return it to the battlefield under its owner's control with a flying counter on it at the beginning of the next end step.

Finch Formation

Offspring {3} (You may pay an additional {3} as you cast this spell. If you do, when this creature enters, create a 1/1 token copy of it.)
Flying
When this creature enters, target creature you control gains flying until end of turn.

Ledger Shredder

Flying
Whenever a player casts their second spell each turn, this creature connives. (Draw a card, then discard a card. If you discarded a nonland card, put a +1/+1 counter on this creature.)

Three Tree Mascot

Changeling (This card is every creature type.)
{1}: Add one mana of any color. Activate only once each turn.

Mockingbird

Flying
You may have this creature enter as a copy of any creature on the battlefield with mana value less than or equal to the amount of mana spent to cast this creature, except it's a Bird in addition to its other types and it has flying.

Frost Trickster

Flying
When this creature enters, tap target creature an opponent controls. That creature doesn't untap during its controller's next untap step.

Skyskipper Duo

Flying
When this creature enters, exile up to one other target creature you control. Return it to the battlefield under its owner's control at the beginning of the next end step.

Seedpod Squire

Flying
Whenever this creature attacks, target creature you control without flying gets +1/+1 until end of turn.

Plumecreed Escort

Flash
Flying
When this creature enters, target creature you control gains hexproof until end of turn.

Empyrean Eagle

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

Healer's Hawk

Flying
Lifelink (Damage dealt by this creature also causes you to gain that much life.)

Strix Lookout

Flying, vigilance (Attacking doesn't cause this creature to tap.)
{1}{U}, {T}: Draw a card, then discard a card.

Barkform Harvester

Changeling (This card is every creature type.)
Reach
{2}: Put target card from your graveyard on the bottom of your library.

Swiftwing Assailant

Flying
Start your engines! (If you have no speed, it starts at 1. It increases once on each of your turns when an opponent loses life. Max speed is 4.)
Max speed — This creature gets +0/+1 and has vigilance.

Clinquant Skymage

Flying
Whenever you draw a card, put a +1/+1 counter on this creature.

Aerie Auxiliary

Flying
When this creature enters, support 2. (Put a +1/+1 counter on each of up to two other target creatures.)

Lotusguard Disciple

Flying
When this creature enters, target creature or Vehicle gains lifelink and indestructible until end of turn.

Jackdaw Savior

Flying
Whenever this creature or another creature you control with flying dies, return another target creature card with lesser mana value from your graveyard to the battlefield.

Dazzling Denial

Counter target spell unless its controller pays {2}. If you control a Bird, counter that spell unless its controller pays {4} instead.

Plumecreed Mentor

Flying
Whenever this creature or another creature you control with flying enters, put a +1/+1 counter on target creature you control without flying.

Lifecreed Duo

Flying
Whenever another creature you control enters, you gain 1 life.

Healer's Flock

Pileated Provisioner

Flying
When this creature enters, put a +1/+1 counter on target creature you control without flying.