Using decline in bird populations to identify needs for conservation action

A large decline in population size is sometimes considered sufficient indication that a species merits conservation interest. One organization categorizes as critically endangered any species whose populations decline by 80% over 10 years, whereas others assign importance to species declining 50% over 25 years. Using these and additional conservation-alert categories, I determined how many of over 200 bird species that breed in Canada qualified for each category, based on population trends from the North American Breeding Bird Survey. The majority of qualifying species were not candidates for immediate intervention to halt or reverse declines. Moreover, species assigned to alert categories based on 5- and 10-year trends for past time periods frequently had positive trends in the subsequent decade. Results indicate that population decline should not be used to identify species at risk or as a basis for conservation action without detailed evaluation of the trend data and other characteristics of the species. However, assigning species to alert categories is a useful step in identifying species that may deserve conservation attention of some kind ( including better monitoring and research as well as direct intervention). Evaluation of trend quality and persistence is an important step in determining the most appropriate action. Deciding when to recommend intervention will be the most problematic for species that are still relatively common and widespread, and there is a need for development of species-specific population thresholds that would be appropriate for triggering such action.