Out of the approximately 11,154 known bird species, 159 (1.4%) have become extinct, 226 (2%) are critically endangered, 461 (4.1%) are endangered, 800 (7.2%) are vulnerable and 1,018 (9.1%) are near threatened. There is a general consensus among scientists who study these trends that if human impact on the environment continues as it has, one-third of all bird species and an even greater proportion of bird populations will be gone by the end of this century.
Since 1500, 150 species of birds have become extinct. Historically, the majority of bird extinctions have occurred on islands, particularly those in the Pacific. These include countries such as New Zealand, Australia, Fiji, and Papua New Guinea.
Some species are not extinct and seem numerous, but exist in highly reduced numbers from previous years. For example, the wood thrush population in North America has declined 50% in the last 50 years. According to the American Bird Conservatory, in the Western Hemisphere 12% of bird species are declining at a rate such that they will be extinct within the next century.
Human activity is the greatest cause of bird extinction around the world. The top human causes of bird extinction involve: the increased human population, Climate change, destruction of habitat (through development for habitation, logging, animal and single-crop agriculture, and invasive plants), bird trafficking, egg collecting, pollution (in fertilizers impacting native plants and diversity, pesticides, herbicides directly impacting them as well as the plant and animal food birds eat, including the food for their food source further down along the food chain), and climate change and global warming. Due to the increasing human population, people seek additional space from what was once wild. This is a major contributor to extinction.
As climate change is caused by a variety of activities, the effect that climate change has on bird extinction is immense. Due to the rapid changes in temperature and climate the bio diverse earth can not progress with these factors.