Responses of Bird Populations in a Puerto Rican Forest to Hurricane Hugo: The First 18 Months

Abstract

Bird populations in a subtropical wet forest were monitored every two to three weeks with mist nets and point counts beginning two weeks after the passage of Hurricane Hugo in September 1989. The results were compared with those of a pre-hurricane study in the same locations in which birds were sampled in forest understory and openings. Capture rates were initially higher than in the previous study, due to displaced canopy dwellers foraging in the understory. The shift ofcanopy dwellers may have obscured expected declines in nectarivores and fruit/seedeaters and contributed to increased detections of omnivores and insectivores. Bird captures and fruit production peaked 93-156 days after the storm in pre-existing gaps, where higher capture rates and a distinct assemblage of birds occurred in contrast to sites without fruit (forest understory and a powerline opening). Captures in pre-existing gaps decreased as fruit production ceased, and overall captures declined to baseline levels after 198 days. After one year of recovery, new gaps and forest understory became distinguishable on the basis of their unique foliage profiles. Although different bird assemblages had been found in forest understory and in gaps prior to the hurricane, these assemblages lost their distinctiveness after the storm. It may take many years after a hurricane for forest understory and gaps to become sufficiently distinct in structure and resources before birds differentiate between the two habitats.