Vegetation and Population Survey of the Red-footed Booby (Sula sula L.) Colony in Mona Island

Andrew J. Blinn; Tomás A. Carlo

Vegetation and Population Survey of the Red-footed Booby (Sula sula L.) Colony in Mona Island

Andrew J. Blinn¹ and Tomás A. Carlo^1,*

¹Department of Biology, The Pennsylvania State University, University Park, PA 16802, USA.*Corresponding author.

Caribbean Naturalist, No. 70 (2019)

Abstract
The Sula sula (Red-footed Booby) colony located in the remote Cabo Norte region of Mona island is one of the 3 largest of the West Indies but has been known from only a single informal account from nearly 50 years ago by H. Raffaele. Here we report the first spatially explicit, fully georeferenced survey of birds and nests of this S. sula colony. Our goals were to map the location and extent of the colony, to estimate the number of birds and nests, and to assess the structure of the vegetation and how S. sula select plant species to build nests in relation to their availability in the environment. We registered 1351 perched birds and 652 nests of S. sula on 364 georeferenced trees extending over 19.6 ha. The area is larger than the entire nearby island of Monito, and the population appears to be half of what it was when Raffaele visited, although we only registered perched birds and avoided those flying over. More than 90% of the nests were constructed on Guapira discolor (Longleaf Blolly) and Ficus citrifolia (Shortleaf Fig). Guapira discolor is the most abundant tree in Cabo Norte but a species that is notably absent from the rest of the island, suggesting an important resource for S. Sula. Nests were never found on many common tree species such as Euphorbia petiolaris (Manchineel Berry) and Plumeria alba (West Indian Jasmine or White Frangipani). Results suggest that S. sula select nesting sites based on tree attributes such as height and foliage density given that G. discolor and F. citrifolia have tall dense canopies that provide good structural support to nest platforms, especially G. discolor. Our map can guide future surveys in using area-based estimates and robust distance-sampling methods to monitor the population of this important seabird colony.

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