IUCN Red List assessments for birds are carried out periodically by Birdlife International . During this process, all known species of birds have been repeatedly assessed, and a Red List Index for birds has been developed.
Birds play a vital part in the food web, both as predator and prey, and are important seed dispersers, pollinators, insect and rodent controls, and disposers of carrion, to name just a few. Birds are also used as an indicator species for environmental health, because the monitoring of bird species is often more economically viable and less labour-intensive than trying to sample other species within a system.
Birds are one of the best studied groups assessed for the IUCN Red List, with less than 1% of Data Deficient species. Overall, 13% of birds are currently estimated to be threatened with extinction. Some regions have specifically high levels of extinction risk for birds, such as the tropical Andes, the Atlantic forests of Brazil, the eastern Himalayas, and the archipelagoes of Southeast Asia. Like many other species, the spread and intensification of agriculture and logging are the principal causes behind bird declines, as well as invasive species. The Red List Index for birds shows that 8.8% of species have deteriorated significantly enough to be uplisted to a higher threat category.