I chose chickens and as possibly the most populous vertebrate on the planet, they truly intrigue me.
I like macaws. but just as a bird, not one people should own.
I volunteered and worked with them in Costa Rica. We rescued, housed, bred and reintroduced them to the wild. We had over 400 Scarlet and Great Green Macaws at the facility.
Next would be megapodes, the most precocial species of bird on the planet. They bury their eggs in mounds of decaying organic matter just like crocodilians. Chicks hatch under the mound, dig their way out, are fully feathered and able to fend for themselves from the beginning. Truly a miracle of evolution.