Bident of Thassa

Whenever a creature you control deals combat damage to a player, you may draw a card.
{1}{U}, {T}: Creatures your opponents control attack this turn if able.

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.

Favorable Winds

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

Counsel of the Soratami

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.

Cloudchaser Kestrel

Flying
When this creature enters, destroy target enchantment.
{W}: Target permanent becomes white until end of turn.

Clinquant Skymage

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

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.)

Strix Serenade

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

Urza's Incubator

As this artifact enters, choose a creature type.
Creature spells of the chosen type cost {2} less to cast.

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.

Thieving Magpie

Flying (This creature can't be blocked except by creatures with flying or reach.)
Whenever this creature deals damage to an opponent, draw a card.

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.

Propaganda

Creatures can't attack you unless their controller pays {2} for each creature they control that's attacking you.

Empyrean Eagle

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

Watcher of the Spheres

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

Island

Stormscape Familiar

Flying
White spells and black spells you cast cost {1} less to cast.

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.

Winged Words

This spell costs {1} less to cast if you control a creature with flying.
Draw two cards.

Quick Study

Plains

Steel-Plume Marshal

Flying
Whenever this creature attacks, other attacking creatures you control with flying get +2/+2 until end of turn.

Aven Mindcensor

Flash
Flying
If an opponent would search a library, that player searches the top four cards of that library instead.

Keeper of the Nine Gales

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

Sol Ring

Tempest Hawk

Flying
Whenever this creature deals combat damage to a player, you may search your library for a card named Tempest Hawk, reveal it, put it into your hand, then shuffle.
A deck can have any number of cards named Tempest Hawk.

Ishai, Ojutai Dragonspeaker

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

Sapphire Medallion

Blue spells you cast cost {1} less to cast.

Esior, Wardwing Familiar

Flying
Spells your opponents cast that target one or more commanders you control cost {3} more to cast.
Partner (You can have two commanders if both have partner.)

Healer's Hawk

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

Perch Protection

Gift an extra turn (You may promise an opponent a gift as you cast this spell. If you do, they take an extra turn after this one.)
Create four 2/2 blue Bird creature tokens with flying. If the gift was promised, all permanents you control phase out, and until your next turn, your life total can't change and you gain protection from everything.
Exile Perch Protection.

Warden of Evos Isle

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

Pearl Medallion

White spells you cast cost {1} less to cast.

Arcane Signet

{T}: Add one mana of any color in your commander's color identity.

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.)

Swan Song

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

Priest of the Crossing

Flying
At the beginning of each end step, put X +1/+1 counters on each creature you control, where X is the number of creatures that died under your control this turn.

Plumecreed Escort

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

Aerial Extortionist

Flying
Whenever this creature enters or deals combat damage to a player, exile up to one target nonland permanent. For as long as that card remains exiled, its owner may cast it.
Whenever another player casts a spell from anywhere other than their hand, draw a card.

Windbrisk Raptor

Flying
Attacking creatures you control have lifelink.

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.

Strix Lookout

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

Counterspell

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.

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.

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.

Kindred Discovery

As this enchantment enters, choose a creature type.
Whenever a creature you control of the chosen type enters or attacks, draw a card.

Lightning Greaves

Equipped creature has haste and shroud. (It can't be the target of spells or abilities.)
Equip {0}

Unbreakable Formation

Creatures you control gain indestructible until end of turn.
Addendum — If you cast this spell during your main phase, put a +1/+1 counter on each of those creatures and they gain vigilance until end of turn.

Land Tax

At the beginning of your upkeep, if an opponent controls more lands than you, you may search your library for up to three basic land cards, reveal them, put them into your hand, then shuffle.

Lieutenant Kirtar

Flying
{1}{W}, Sacrifice Lieutenant Kirtar: Exile target attacking creature.

Swiftfoot Boots

Equipped creature has hexproof and haste. (It can't be the target of spells or abilities your opponents control. It can attack and {T} no matter when it came under your control.)
Equip {1} ({1}: Attach to target creature you control. Equip only as a sorcery.)

Cartographer's Hawk

Flying
When this creature deals combat damage to a player who controls more lands than you, return it to its owner's hand. If you do, you may search your library for a Plains card, put it onto the battlefield tapped, then shuffle.

Kangee, Sky Warden

Flying, vigilance
Whenever Kangee attacks, attacking creatures with flying get +2/+0 until end of turn.
Whenever Kangee blocks, blocking creatures with flying get +0/+2 until end of turn.

Gravitational Shift

Creatures with flying get +2/+0.
Creatures without flying get -2/-0.

Scouting Hawk

Flying
Keen Sight — When this creature enters, if an opponent controls more lands than you, search your library for a basic Plains card, put it onto the battlefield tapped, then shuffle.