Plumecreed Mentor

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

Bellowing Crier

When Bellowing Crier enters, draw a card, then discard a card.

Kastral, the Windcrested

Flying
Whenever one or more Birds you control deal combat damage to a player, choose one —
• You may put a Bird creature card from your hand or graveyard onto the battlefield with a finality counter on it.
• Put a +1/+1 counter on each Bird you control.
• Draw a card.

Mockingbird

Flying
You may have Mockingbird 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 Mockingbird, except it's a Bird in addition to its other types and it has flying.

Driftgloom Coyote

When Driftgloom Coyote enters, exile target creature an opponent controls until Driftgloom Coyote leaves the battlefield. If that creature had power 2 or less, put a +1/+1 counter on Driftgloom Coyote.

Dire Downdraft

This spell costs {1} less to cast if it targets an attacking or tapped creature.
Target creature's owner puts it on their choice of the top or bottom of their library.

Jackdaw Savior

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

Ishai, Ojutai Dragonspeaker

Flying
Whenever an opponent casts a spell, put a +1/+1 counter on Ishai, Ojutai Dragonspeaker.
Partner (You can have two commanders if both have partner.)

Sugar Coat

Flash
Enchant creature or Food
Enchanted permanent is a colorless Food artifact with "{2}, {T}, Sacrifice this artifact: You gain 3 life" and loses all other card types and abilities.

Lifecreed Duo

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

Dazzling Denial

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

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.

Salvation Swan

Flash
Flying
Whenever Salvation Swan 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.

Sejiri Refuge

Sejiri Refuge enters tapped.
When Sejiri Refuge enters, you gain 1 life.
{T}: Add {W} or {U}.

Plains

Thistledown Players

Whenever Thistledown Players attacks, untap target nonland permanent.

Island

Waterspout Warden

Whenever Waterspout Warden attacks, if another creature entered the battlefield under your control this turn, Waterspout Warden gains flying until end of turn.

Brightblade Stoat

Intrepid Rabbit

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