Plains

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.

Aven Skirmisher

Apex Hawks

Multikicker {1}{W} (You may pay an additional {1}{W} any number of times as you cast this spell.)
Flying
Apex Hawks enters with a +1/+1 counter on it for each time it was kicked.

Mistveil Plains

({T}: Add {W}.)
Mistveil Plains enters tapped.
{W}, {T}: Put target card from your graveyard on the bottom of your library. Activate only if you control two or more white permanents.

Aven Sentry

Dovescape

({W/U} can be paid with either {W} or {U}.)
Whenever a player casts a noncreature spell, counter that spell. That player creates X 1/1 white and blue Bird creature tokens with flying, where X is the spell's mana value.

Cloudreach Cavalry

As long as you control a Bird, Cloudreach Cavalry gets +2/+2 and has flying.

Seller of Songbirds

When Seller of Songbirds enters, create a 1/1 white Bird creature token with flying.

Eyes in the Skies

Create a 1/1 white Bird creature token with flying, then populate. (Create a token that's a copy of a creature token you control.)

Rustwing Falcon

Roc Egg

Defender (This creature can't attack.)
When Roc Egg dies, create a 3/3 white Bird creature token with flying.

Healer's Hawk

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

Aven Warhawk

Amplify 1 (As this creature enters, put a +1/+1 counter on it for each Bird and/or Soldier card you reveal in your hand.)
Flying

Battle Screech

Create two 1/1 white Bird creature tokens with flying.
Flashback—Tap three untapped white creatures you control. (You may cast this card from your graveyard for its flashback cost. Then exile it.)