Rats are natural students with human-like brain structure and problem-solving abilities. Pigeons can recognize all 26 English letters and show complex self-awareness. Crows are tool-using non-primates with largest avian brains. Pigs are highly trainable with 20 different communication sounds. Octopuses use high-order planning and can disguise themselves as rocks
Birds must have good proportions and smooth feathers. No birds with unusual beaks, wattles, or oversized features. No large bare patches or notable crops on head or neck
Common ostrich is largest by mass, reaching 2.8m height and 156.8kg weight. Wandering albatross has largest wingspan at 3.65m. Elephant bird likely largest ever, weighing 275-1,000kg and standing 3m tall. Pelagornis sandersi likely largest bird to fly with 5.2m wingspan
Swifts are highly aerial birds, resembling swallows but not closely related to passerines. Family name "Apodidae" means "footless" due to small, weak legs. Around 100 species grouped into two subfamilies and four tribes. Can reach speeds up to 169 km/h, covering 200,000 km annually
Two living species: common ostrich in Africa and Somali ostrich in Horn of Africa. Heaviest and largest living birds, weighing 63.5-145 kilograms. Can run at 70 km/h, fastest birds on land. Used for leather, feathers, eggs, meat, and oil production
Hummingbirds are small, flight-capable birds native to Americas. Family Trochilidae contains approximately 366 species. World's smallest bird is bee hummingbird at 5 cm length. Males have widest plumage color diversity among birds