Correlates of population recovery goals in endangered birds

Endangered species recovery plans commonly set goals for population size th at are used to define the success of recovery efforts. We examined variatio n in these population recovery goals for bird species listed under the U. S . Endangered Species Act to determine whether there were simple predictors of recovery population size. The median population sizes that must be met f or a species to be removed from the list or downlisted to the threatened ca tegory are 4000 and 1500 respectively, but the thresholds varied considerab ly. Most variation in population recovery goals (greater than or equal to 7 5%) was explained by the population size when the recovery plan was written . Species listed when their population's size was relatively large have hig her population recovery goals, whereas those listed when populations were s mall have lower population goals. Population sizes set for recovery also in creased over time and were higher for species listed throughout the United States rather than for part of the country. In combination, these three var iables explained 86% of the variance in population goals for delisting and 94% of the variance in goals for downlisting. Body mass, annual fecundity, maximum lifespan, whether the population was listed as threatened or endang ered, and whether a formal population viability analysis was conducted were variables not significantly associated with population recovery goals. Thu s, we found that variables relating to the circumstances under which the po pulations were listed could explain almost all of the variance in recovery population goals, and that biological traits of the endangered birds explai ned little of the variance.