St. John is the smallest of the U.S. Virgin Islands with 28 square miles, 53% (7,000 acres) of which is the Virgin Islands National Park. Most of the landscape is second growth with relatively few introduced plant and bird species. Diverse habitats include rocky and sandy coastlines, semi-arid thorn-cactus communities, a comprehensive assortment of tropical dry forest formations from coastal hedge to shrublands and canopied upland forests, moist forests, mangrove wetlands, freshwater and saltwater ponds, small agricultural/pasture lands, and small towns. The island receives an average of 44 inches of rainfall annually, but is highly seasonal, with the heaviest precipitation occurring from August to November, augmented by a late-spring wet period. The winter-spring dry season normally lasts 3 months or more.
A total of 120 bird species have been confirmed on St. John. Key waterbird species are itemized in Table 1. Widespread terrestrial species include Red-tailed Hawk, American Kestrel, Scaly-naped Pigeon, White-crowned Pigeon, Zenaida Dove, Bridled Quail Dove, Common Ground Dove, Mangrove Cuckoo, Smooth-billed Ani, Green-throated Carib, Antillean Crested Hummingbird, Belted Kingfisher, Caribbean Eleania, Gray Kingbird, Puerto Rican Flycatcher, Black-whiskered Vireo, Caribbean Martin, Barn Swallow, Northern Mockingbird, Pearly-eyed Thrasher, Northern Parula, Yellow Warbler, Prairie Warbler, Blackpoll Warbler, Black and White Warbler, American Redstart, Northern Waterthrush, Bananaquit, Black-faced Grassquit, and Lesser Antillean Bullfinch. Among the wood warblers, only the Yellow Warbler (Dendroica petechia) is a nesting resident in the Virgin Islands. The White-crowned Pigeon (Columba leucocephala), listed by Birdlife International as “near threatened” nests in coastal mangroves and forests.
Non-bird biodiversity: Green Turtles (Chelonia mydas) and Hawksbill Turtles (Eretmochelys imbricata) have been seen on St. John beaches and may nest. The Virgin Islands tree boa (Epicrates monensis granti) is listed as endangered by the VI Dept. of Fish & Wildlife. A number of endangered plant species have been identified on St. John including Eugenia earhartii (Earhart's eugenia), Solanum conocarpum (Marron baccora), Agave eggersiana (Eggers' agave), Erythrina eggersii (Eggers' cockspur), Machaonia woodburyana (Woodbury's machaonia), Calyptranthes thomasiana (St. Thomas lidflower), Zanthoxylum thomasianum (St. Thomas Prickly ash).
BirdLife International (2019) Important Bird Areas factsheet: St John. Downloaded from http://www.birdlife.org on 15/09/2019.