Distribution, diversity, abundance, and richness of Grenadian terrestrial birds, including endemic and restricted-range species
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Date
2020-03-05
Authors
Williams, Ramon
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Abstract
The conservation status of Grenadian terrestrial birds is not fully understood because there has been no comprehensive study surveying all land bird species across the extent of Grenada. Currently, Grenada is experiencing rapid anthropogenic development and habitat alteration that may be affecting the conservation status of endemic, restricted-range, and native land bird species. To examine the impacts of anthropogenic habitat alteration on terrestrial birds and to identify bird species and bird habitat of conservation concern in Grenada, I collected baseline data on the distribution, diversity, and abundance of Grenada's resident land birds by applying both single and dependent double-observer point count surveys across 54 field sites. At field sites, I conducted eight five-minute point-count surveys within a 25-meter radius with each point count plot separated by 100-meters. Percentage habitat type and land use were also recorded within each 25-meters point count plot. I used the program DOBSERV to calculate each species perceptibility, Shannon diversity index to evaluate species diversity, and General Linear Models (GLMs) to analyze the distribution and abundance of Grenada's resident land birds. Higher densities of most species were found in anthropogenic cultivated and secondary grasslands, while lower densities generally occurred in cloud and secondary forests. Nonetheless, even the natural cloud and secondary forests with lower species densities were selected for by some species of conservation concern, such as the regional endemic Lesser Antillean Tanager and all nectarivores. Additionally, all nectarivores and a granivore avoided urban habitats. My overall results emphasize the importance of maintaining a habitat mosaic of natural and anthropogenic habitat types within Grenada. This information can inform habitat management decisions and conservation strategies, which will aid in the conservation of the land birds of Grenada and other Caribbean islands that have similar species and habitat requirements.
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Keywords
Grenada, Land-use, Habitat types, Land birds, Anthropogenic, Conservation, Island