Gwaihir, Greatest of the Eagles

Flying
Whenever Gwaihir attacks, target attacking creature gains flying until end of turn.
At the beginning of each end step, if you gained 3 or more life this turn, create a 3/3 white Bird creature token with flying and "Whenever this token attacks, target attacking creature gains flying until end of turn."

Seaside Haven

{T}: Add {C}.
{W}{U}, {T}, Sacrifice a Bird: Draw a card.

Black Chocobo

When this permanent transforms into Black Chocobo, search your library for a land card, put it onto the battlefield tapped, then shuffle.
Landfall — Whenever a land you control enters, Birds you control get +1/+0 until end of turn.

Sidequest: Raise a Chocobo

When this enchantment enters, create a 2/2 green Bird creature token with "Whenever a land you control enters, this token gets +1/+0 until end of turn."
At the beginning of your first main phase, if you control four or more Birds, transform this enchantment.

Sidequest: Raise a Chocobo // Black Chocobo

Choco, Seeker of Paradise

Whenever one or more Birds you control attack, look at that many cards from the top of your library. You may put one of them into your hand. Then put any number of land cards from among them onto the battlefield tapped and the rest into your graveyard.
Landfall — Whenever a land you control enters, Choco gets +1/+0 until end of turn.

Scour the Desert

Exile target creature card from your graveyard. Create X 1/1 white Bird creature tokens with flying, where X is the exiled card's toughness.

Dazzling Denial

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

Animal Sanctuary

{T}: Add {C}.
{2}, {T}: Put a +1/+1 counter on target Bird, Cat, Dog, Goat, Ox, or Snake.

Kangee, Aerie Keeper

Kicker {X}{2} (You may pay an additional {X}{2} as you cast this spell.)
Flying
When Kangee enters, if it was kicked, put X feather counters on it.
Other Bird creatures get +1/+1 for each feather counter on Kangee.

Hermes, Overseer of Elpis

Whenever you cast a noncreature spell, create a 1/1 blue Bird creature token with flying and vigilance.
Whenever you attack with one or more Birds, scry 2.

Rise of Eagles

Create two 2/2 blue Bird enchantment creature tokens with flying. Scry 1. (Look at the top card of your library. You may put that card on the bottom.)

Chocobo Racetrack

Landfall — Whenever a land you control enters, create a 2/2 green Bird creature token with "Whenever a land you control enters, this token gets +1/+0 until end of turn."

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.

Gwaihir the Windlord

This spell costs {2} less to cast as long as you've drawn two or more cards this turn.
Flying, vigilance
Other Birds you control have vigilance.

Roc Egg

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

Knightfisher

Flying
Whenever another nontoken Bird you control enters, create a 1/1 blue Fish creature token.

Gysahl Greens

Create a 2/2 green Bird creature token with "Whenever a land you control enters, this token gets +1/+0 until end of turn."
Flashback {6}{G} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

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.

Aven Fogbringer

Flying
When this creature enters, return target land to its owner's hand.

Emeria Angel

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

Celestial Gatekeeper

Flying
When this creature dies, exile it, then return up to two target Bird and/or Cleric permanent cards from your graveyard to the battlefield.

Summon: Fat Chocobo

(As this Saga enters and after your draw step, add a lore counter. Sacrifice after IV.)
I — Wark — Create a 2/2 green Bird creature token with "Whenever a land you control enters, this token gets +1/+0 until end of turn."
II, III, IV — Kerplunk — Creatures you control gain trample until end of turn.

Strix Serenade

Counter target artifact, creature, or planeswalker spell. Its controller creates a 2/2 blue Bird creature token with flying.

Flurry of Wings

Create X 1/1 white Bird Soldier creature tokens with flying, where X is the number of attacking creatures.

Sazh Katzroy

When Sazh Katzroy enters, you may search your library for a Bird or basic land card, reveal it, put it into your hand, then shuffle.
Whenever Sazh Katzroy attacks, put a +1/+1 counter on target creature, then double the number of +1/+1 counters on that creature.

Ordered Migration

Domain — Create a 1/1 blue Bird creature token with flying for each basic land type among lands you control.

Keeper of the Nine Gales

Flying
{T}, Tap two untapped Birds you control: Return target permanent to its owner's hand.

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.

Airborne Aid

Draw a card for each Bird on the battlefield.

Aven Brigadier

Flying
Other Bird creatures get +1/+1.
Other Soldier creatures get +1/+1.

Bartz and Boko

Affinity for Birds (This spell costs {1} less to cast for each Bird you control.)
When Bartz and Boko enters, each other Bird you control deals damage equal to its power to target creature an opponent controls.

Azorius Keyrune

{T}: Add {W} or {U}.
{W}{U}: This artifact becomes a 2/2 white and blue Bird artifact creature with flying until end of turn.

Swan Song

Counter target enchantment, instant, or sorcery spell. Its controller creates a 2/2 blue Bird creature token with flying.

Wingmate Roc

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

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.)

Migratory Route

Create four 1/1 white Bird creature tokens with flying.
Basic landcycling {2} ({2}, Discard this card: Search your library for a basic land card, reveal it, put it into your hand, then shuffle.)

Call

Create four 1/1 white Bird creature tokens with flying.
Fuse (You may cast one or both halves of this card from your hand.)

Beck

Whenever a creature enters this turn, you may draw a card.
Fuse (You may cast one or both halves of this card from your hand.)

Beck // Call

Murmuration

Birds you control get +1/+1 and have vigilance.
At the beginning of your end step, for each spell you've cast this turn, create a 1/2 blue Bird creature token with flying named Storm Crow.

Traveling Chocobo

You may look at the top card of your library any time.
You may play lands and cast Bird spells from the top of your library.
If a land or Bird you control entering the battlefield causes a triggered ability of a permanent you control to trigger, that ability triggers an additional time.

Soulcatchers' Aerie

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