Birds don't seem to have the best of social skills when interacting with other pets. I have observed pets like dogs and cats approaching chicken and other similar birds and the latter start gawking in protest as if to notify the intruder that its approaching marked territory. I have even seen apes of birds attacking other pets almost to the stage of killing them. This happens irrespective of the period of time the animals have been together. I think birds are a bit territorial and respond by fight or flight mechanism whenever their territory is encroached. They also seen to have a sophisticated communication system and they all take flight simultaneously. But doves are in a category of their own and don't seem to have problems with other pets. However, some birds easily acclimatise to the herbivorous category of domestic animals.
What a coincidence. This morning as I was driving in our village, I noticed a big crow. Although there are a variety of birds in our village since there are lots of trees and vegetation in vacant lots, it is highly unusual to see a crow that big. Maybe it escaped a cage but certainly it is feeling its way because it moves slow and flies hesitantly.
I stopped the car, planning to take a video, when the crow flew up a lower branch of the tree. And there was that familiar noise of the mischievous birds - that's what we call those small black birds with a white streak on their tail - they are ferocious. Now, they attacked that poor big crow who seemed defenseless. And after being pecked for several times, the crow had no choice but to move to another distant tree.
I think you guys are biased.
You guys are comparing chickens and crows to pets.
Come on, many even pets do not get along with other pets of even the same species. Countless times I have seen dogs bark or even attack each other while their owners were walking them. The most popular pets of all, dogs and cats both can be territorial and mean to each other. They are also killers of smaller species. Pet birds, as one of the smaller species, of course they would be nervous when facing a giant dog or cat. It is their natural instinct to react such way. The smaller and weaker the species, the more defensive it will react around other animals of larger size.
I also remember a long time ago the local news said the cat of the fire department was killed by a dog... It happens a lot when you are not careful with different pets.
More often than not, the pet birds who played nice with dogs and cats ended up dead. All it takes is just one incident. Being unfriendly is how they protect themselves against possible hostile.