Though human activities have allowed the expansion of a few species, such as the barn swallow and European starling, they have caused population decreases or extinction in many other species. Over a hundred bird species have gone extinct in historical times, although the most dramatic human-caused avian extinctions, eradicating an estimated 750–1800 species, occurred during the human colonisation of Melanesian, Polynesian, and Micronesian islands. Many bird populations are declining worldwide, with <answer>1,227</answer> species listed as threatened by BirdLife International and the IUCN in 2009.
How many species are listed as threatened by BirdLife International and the IUCN?
1,227