Hornbills are a diverse group of tropical birds found across Africa, Asia, and Melanesia, known for their distinctive long, curved bills that are often vividly colored and feature a casque on the upper mandible. Their neck vertebrates are uniquely fused for stability under the weight of their bills, which serve multiple purposes such as fighting and foraging. Omnivorous in diet, these birds feed on both fruit and small creatures and are considered monogamous nesters, using tree cavities or cliffs for nesting. Some species face extinction threats, particularly certain island dwellers in Southeast Asia. Size among hornbills varies greatly, with the smallest being the black dwarf hornbill and the largest being the southern ground hornbill, which is also the most massive. Their vivid plumage is often black, white, grey, or brown, set off by bright colors on their bills or skin patches. Hornbills have binocular vision, even though their large bills partially obstruct their visual field. They are distributed over various habitats, with arboreal species living in forests and the terrestrial ground hornbills found in the open savanna. They are generally diurnal and may form flocks, with some species exhibiting territorial behavior, particularly those dependent on fruit. Breeding involves the female sealing herself inside a nest cavity to lay eggs, while the male brings food. Hornbills have symbiotic relationships with other species like mongooses and also play a vital ecological role as seed dispersers. Taxonomically, they have been classified in various ways, with some studies suggesting the separation of the ground hornbills into their own lineage. Cultural significance, especially in Asia, has led to hornbills being hunted for their casque, most notably in the helmeted hornbill. The conservation status varies, but many Asian hornbill species are at risk, while African species are generally less threatened. Hornbills have featured in popular culture, such as the Disney franchise "The Lion King," where the character Zazu, a hornbill, makes appearances.