There are approximately 10,000 known bird species distributed among a vast range of habitats, from tropical rainforests to icy shores. Exhibiting amazing behavioural and morphological diversity, birds play an essential role in in the functioning of healthy ecosystems.
Many plants depend on birds to disperse their seeds and sometimes a seed has to be digested and deposited by a bird before it will germinate. Several bird species act as pollinators for wild plants and birds are also important to agricultural crops as they remove insect pests.
BirdLife International is the Red List Authority for birds, coordinating the process of evaluating all of the world's bird species against the Red List categories and criteria in order to assess their extinction risk. As of 2015, BirdLife has established that 1,375 bird species (13% of the total, or roughly one in eight) are threatened with extinction.
The Red List Index (RLI) provides a clearer view of real trends within different taxonomic groups, and for biodiversity as a whole. It shows that for birds, the overall trend is one of decline.