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.
