It actually surprises me that the only bird mob in the game are chickens and parrots, while we have multipple mammals, fishes, and even arthropods. So, I wanted to suggest a new bird mob, that being the Crow.
Crows are Neutral mobs that can be found in every Overworld biome, are about the size of a Cave Spider, and spawn in groups of 4-8 members. They can, and often will, pick up items using their beak, and they have various behaviour patterns that depends on what players do or don't do. They are also afraid and avoid carved pumpkins.
Normal Behaviour
When no players are nearby, Crows would simply perch on trees, peck on leaves, make crow noises, and/or fly around the area.
Once a Crow detects a nearby player, it and the other Crows of its group becomes aware of them. Once they are aware of a player, Crows will watch their everymove. If the player does not interact with the aware Crows, they will eventually become bored and continue their regular routine, though they will occasionally stare over at the player for a few seconds.
Befriending A Crow
Players can get close to Crows and they wouldn't fly away from them. If a player has a food or a mineral on their hand, Crows will slowly follow them. Feeding a crow with any food will increase their "Friend" meter. Giving a mineral to a Crow by right clicking a crow with a mineral in you hand will also increase the Friend meter. Once a Crow's Friend meter is full, they will become Befriended by the player that filled that meter.
Befriended Crows are like pets, except they can't be commanded by the player to sit still or to move. However, Befriended Crows will always follow the player unless they physically can't, in which case they will just sit idly until they are able to follow their friend again.
When a player is in combat, their Befriended Crows will fly in the air, circling them. Every 3-5 seconds, a Befriended Crow will make a choice on whether or not they will do nothing or they will perform a swoop attack, where they will charge at the hostile mob nearest to the player, dealing moderate damage, and then quickly flying away and will circle the air again, repeating the cycle.
When a Befriended Crow performs a swoop attack on a hostile mob, the mob they attacked will focus their attention, and thus their attacks, on the Crow for a short while. This distraction, while short, can be lengthened by the swoop attacks of other Befriended Crows. A Befriended Crow has an equal chance to do nothing or to perform a swoop attack.
Befriended Crows can be given either a helmet or a sword by the player. Helmets increases the health of a Befriended Crow, while swords increases their attack damage.
Finally, if a player has any Befriended Crows and they went to sleep, when they wake up, they will find that a number of items based on the number of their Befriended Crows have appeared at the foot of their bed. These items range from fairly common to very rare, and are randomly selected by the game.
Hurting A Crow
If a player attacks a crow or feeds it poisonous food like pufferfish or spider eye, but does not kill it, the Crow and nearby Crow will become Wary. Wary Crows will avoid players they are wary about, and will not follow them even if they have something that Crows like in their hands. Additionally, whenever a Wary Crow meets a non-Wary Crow that has not been Befriended, the non-Wary Crow becomes Wary as well. If a Wary Crow does bot despawn, it will lose its Warryness over time.
Killing a Crow
If a player kills a Crow, every nearby Crow will become hostile, and will try to attack the player. Hostile Crows fight similarly to Befriended Crows, circling around their target in the air, and deciding if they will do nothing or if they will perform a swoop attack. These swoop attacks can not "distract" players like it distract mobs, but it can apply a new effect called Feathered, which puts a bunch of black feathers on their screen, messing up their vision. The Feathered effect lasts for 8 seconds, but fortunately, once a player loses the Feathered effect, there is a 26 second cooldown before they can become Feathered from swoop attacks again.
Killing a Crow will make them drop a Black Feather, an item that can be used as a replacement for feathers in recipes. Additionally, killing a Crow has the chance to give a Bad Omen to the player that killed the Crow.
Crows and Wolves
Sometimes, a group of Crows will spawn alongside a group of Wolves. The birds and mammals are Friends with one another, and they will hunt together. The way they hunt is actually very unique (and is mostly different from how their real life versions hunt together).
First, the Crows will find the nearest "prey" mob. Once they do, they will make a caw that signals their Wolf friends to come to their current position. Once their Wolf friends are close to them, the Crows will perform a swoop attack on the chosen prey. These swoop attacks forces the prey mob to focus on the Crows, which can be long enough for the Wolves to jump in for the kill. Once the Wolves have killed the chosen Prey mob, they and the Crows will gather on the sight of the death of their prey, simulating the Wolves and Crows feeding together.
If a Wolf that is friends with a Crow becomes hostile to a player, their Crow friends will become hostile to that player as well, and vice versa. If a player tames a Wolf that is friends with a Crow, one of the Crows will become Befriended to the player that tamed the Wolf, and vice versa.
And that's all for my suggestion for Crows. What do you guys think?