Monitoring of terrestrial avifauna in six habitats on St. Eustatius, Caribbean Netherlands, 2009–2017

Abstract. The Caribbean is a biodiversity hotspot due to its rich biodiversity and wholesale loss of primary vegetation. Yet, there is a paucity of studies on the status and trends of terrestrial avifauna populations in the region. We combined survey data from six habitats (Quill and Gilboa Hill, Town, Botanical Garden, Garden Road, and Venus Bay) on a small Lesser Antillean island over a seven-year period. Species abundance and richness varied among habitats, with Town having the highest species richness. Logistic regressions revealed significant differences among habitat and year (P = 0.008), but not foraging guild, season, rainfall or elevation (P > 0.05). The Quill (P = 0.0003) and Town (P = 0.001) differed significantly from the other habitats surveyed. Granivorous + frugivorous and omnivorous species were most commonly detected in the Quill, whereas nectarivores and granivores were most commonly detected in Town. The influence of total annual precipitation on bird detection rates was unsubstantial. However, site-specific climate data for the different habitats are not available. Though resident landbird populations on St. Eustatius were stable over the survey period, we recommend that annual monitoring continue in the same habitats, especially following extensive vegetation damage caused by hurricanes Irma and Maria in September 2017 and in light of predicted global climate change. The results of our monitoring proved useful in evaluating protected areas and Important Bird Areas compared with non-protected areas. We encourage island researchers and conservation stewards to initiate similar long-term monitoring in order to determine the status of their resident landbird populations.