US Fish & Wildlife Service



Date of this Version



U.S. Fish and Wildlife (January 2002).


Are Birds in Danger?

Of the 836 species of birds protected under the Migratory Bird Treaty Act, about a quarter are known to be in trouble. There are78 bird species listed as Endangered and 14 species listed as Threatened in the U.S. An additional 144 species are on the National list of Birds of Conservation Concern 2001 (some whose populations are declining precipitously). It cannot be assumed that the remainder of U.S. birds are safe, as population data on essentially a third of these species are lacking, making status determination very difficult if not impossible. The problems that birds face in the U.S. are symptomatic of the problems they face globally.

What are the Human-Caused Threats to Birds?

Birds face tremendous challenges to their survival each day. The majority of these challenges are related to human activities. Vast numbers of birds are killed due to collision with human structures and equipment, poisoning by pesticides and contaminants, and attacks by cats and other introduced predators.

Diseases such as botulism, avian cholera, salmonellosis, and emerging West Nile virus can also have significant population impacts. Human activities, such an overuse of pesticides (enhancing the survival of pesticide-resistant mosquitos), for example, can help spread certain diseases.

The greatest threat to birds, and all wildlife, continues to be loss and/or degradation of habitat due to human development and disturbance. For migratory birds and other species that require multiple areas for wintering, breeding, and stopover points, the effects of habitat loss can be complex and far-reaching.

Added to deaths from natural causes, such as adverse weather; predation, or starvation, human-related bird deaths may result in greater mortality than a population can withstand. In other words, it is the cumulative or combined impact of all mortality factors that concerns scientist most. Thus, anything done to reverse human-related bird deaths- and thus potential impacts to bird populations- are of considerable interest to the Service.