Influence of habitat quality, catastrophes, and population size on extinction risk of the Florida scrub-jay

Within the range of the Florida scrub-jay (Aphelocoma coerulescens), the on ly bird species endemic to Florida, there was a need for a population risk assessment that considered the impacts of declining habitat availability an d declining fire frequency associated with rapid human population expansion . We developed a population risk model to examine influence of population s ize, catastrophes (epidemics and hurricanes), and habitat management scenar ios on Florida scrub-jay populations. Extinction risk declined rapidly when initial population sizes increased from 20 to 100 breeding pairs. Hurrican es increased extinction risk for coastal populations by 10-30% compared to inland populations. Our results suggested that habitat in poor condition wa s unlikely to support a population for more than a few decades. Poor habita t quality conditions were common throughout the species' range because of f ire suppression or inadequate fire management. Habitat management was more effective than habitat restoration because population recovery occurred slo wly after restoration and only if habitat was restored to optimal condition s. Sensitivity analyses showed that fecundity and survival of experienced b reeders without helpers (adult nonbreeders) were the most important model p arameters. Slow recovery rates occurred because helpers were the only rapid source of colonists in restored habitat and because an absence of helpers reduced breeder survival and fecundity. Small population sizes and habitat degradation make the Florida scrub-jay vulnerable to rangewide decline and extinction unless habitat is protected, restored, and managed to maintain o ptimal conditions.