Final Report, Florida Scrub-jay Disease Analysis

Woolfenden, Glen; Garvin, Mary

INTRODUCTION: The Florida Scrub-Jay (Aphelocoma coerulescens) is declining in numbers and distribution because of loss of its native scrub habitat. Small fragments of scrub now support the remaining populations of this bird, which in 1987 was listed by the USFWS as Threatened. Careful management of the remaining populations and habitat fragments, based on detailed information on reproduction and survival (Soule 1987), is necessary to protect the species. The Florida Scrub-Jay population at Archbold Biological Station has been the focus of an intensive demographic study for over 25 years (Woolfenden and Fitzpatrick 1984, 1990, 1996). This population occasionally experiences sudden catastrophic declines. Although existing survivorship models take into account these catastrophes (Fitzpatrick et al. 1991), they do so only crudely, in part because the causative agents are unknown. Little is known about the frequency and impact of diseases in wild populations of almost all species. Although small populations may be especially vulnerable to disease (Jackson 1977), infectious agents are rarely considered in ecological studies of natural populations. The lack of knowledge is primarily attributable to two factors: (1) monitoring sick individuals within a natural population is difficult because usually they are quickly taken by predators or scavengers, which often precludes identification of the pathogen (Wobeser and Wobeser 1992), and (2) the impact of pathogens on populations is difficult to measure (Toft 1991), in part because normal variation of demographic parameters prior to an epidemic usually is unknown. The objective of this study-was to determine the relative prevalence and intensity of pathogens present in a Florida Scrub-Jay population at Archbold Biological Station. The results provide baseline data for identification of causative agents of future epidemics and for future long-term studies of pathogens in this population.