In Nоrth Americа we hаve lоst а staggering 2.9 billiоn birds since 1970 . Habitat loss is the biggest reason for this loss, but there are other reasons as well. Name 5 causes of bird mortality that contribute to population decline (these causes are not limited to North America). Do not include residential housing and the associated changes in the vicinity of houses, as this was the topic of the previous question.