sentences:  The common ostrich is extirpated in Oman and is not included in the species count.Twelve species are globally threatened.This list's taxonomic treatment (designation and sequence of orders, families and species) and nomenclature (common and scientific names) generally follow the conventions of "The Clements Checklist of Birds of the World", 6th edition with a few changes based on the list of the Ornithological Society of the Middle East.