For: Minecraft 1.21.1, NeoForge 21.1.x. Requires: GeckoLib 4.8+. Optional: Jade, Butchery, Incubation, Naturalist, Autumnity.
Seven kinds of realistic-but-Minecraft-like birds, each with several breeds and a separate look for males, females and chicks:
Real behaviour: roosters crow at dawn, toms and peacocks fan their tails, ganders guard goslings, guinea fowl sound the alarm. Breed them: the hen lays a clutch in a straw nest, goes broody and hatches chicks that inherit their parents' breeds, with the odd mutation. Hoppers can empty nests. Peacock feathers craft faster, farther-flying arrows. Eggs and cooked meats for every bird.
Soft support (never required) for Jade (tooltips), Butchery, Incubation, Naturalist and Autumnity.