Bridled Quail-dove Geotrygon mystacea population assessment after hurricanes Irma and Maria, St. Eustatius, Caribbean Netherlands

Structural vegetation damage and food limitation are important effects of major hurricanes, particularly for fruit/seed-eating, forest-dependent Caribbean birds with restricted distributions and small populations, such as the Bridled Quail-dove Geotrygon mystacea. Motivated by the lack of abundance estimates, corrected for detection probability, we conducted distance-sampling surveys inside and outside the Quill National Park each May in 2016-2019. Detection mode was the most important covariate, with others receiving no support from the data. Detectability of available single individuals and clusters of individuals within 60 m of transect centrelines averaged 0.957 +/- 0.114 standard error for audio detections, 0.434 +/- 0.052 for visual detections, and 0.693 +/- 0.064 for detection modes combined. Availability averaged 0.475 +/- 0.138 and the product of detectability and availability averaged 0.329 +/- 0.098. Density averaged 1.459 +/- 0.277 individuals ha(-1) and population size averaged 642 +/- 122 individuals in 440 ha. Density did not differ along and away from forest trails, but was higher inside than outside the park and at elevations within 201-400 m than 100-200 m and 401-600 m. Density declined by 76% after hurricanes Irma and Maria in 2017. We suggest that major hurricanes together with free-ranging livestock overgrazing degraded foraging habitats, limited food supply, and caused a population bottleneck. Our methodology can be implemented across the distribution range to assess population status and trends and evaluate the result of management actions at key conservation sites. Bridled Quail-dove populations probably were declining on most islands before the 2017 hurricanes and population status warrants revision.

Automated summary

The study conducted distance-sampling surveys of the Bridled Quail-dove in the Caribbean from 2016 to 2019, finding that detection mode was the most important covariate while other covariates had no effect on the data; hurricanes and overgrazing leading to habitat degradation and food scarcity may have impacted the population.