Distribution, Abundance and Issues Affecting the Status of Selected Vertebrates in Barbados By J.A. Horrocks, Ph.D. Dept. Biological and Chemical Sciences University of the West Indies Cave Hill, St. Michael Barbados November,1997 1. Introduction There are a number of biogeographical features of Barbados that would have restricted the number of wildlife species originally colonising the island, thereby ensuring that Barbados’ indigenous fauna was probably never very diverse. The most important of these features are the small size of the island and its low-lying coralline topography, which result in a restricted number of available habitat types, and its easternmost and relatively isolated position, both from the other W est Indian islands and from North and South America. The terrestrial habitats with the greatest species diversity in the tropics are forests and wetlands. Prior to European colonisation, forest covered much of Barbados, with at least three distinct forest types evident (Gooding 1977). The higher, wetter, central areas of the island were covered with primarily evergreen tropical mesophytic forest, extending towards the west in the shelter of the higher coral cliffs. Turner’s Hall woods and some of the less accessible gullies still remain as relics of this type of forest. In the lower, drier areas surrounding this central forest would have been a less well-developed forest type, still partly or predominantly evergreen. Much of the undercliff regions of the Scotland District would have been covered with this type of forest. The drier northern, eastern and southern coastal areas would have been typified by the third forest type, a deciduous woodland grading into xerophytic woodland/scrub closer to the water’s edge. Wetland habitat in Barbados was much more extensive prior to European colonisation than it is today. The entire west and south coasts from Maycocks to Palm beach was almost certainly characterised by wetland habitats, with large mangrove swamps at Heywoods, Holetown, Paynes Bay, Batts Rock, the Spring Garden highway and the Bridgetown area. Along the south coast, mangroves and/or marshy grassland were present from Accra to Graeme Hall swamp, as well as at Oistins, Silver Sands and Chancery Lane. The wetland areas along the drier east coast would have been largely tidal marshy estuaries, such as currently exist at Long Pond and Green Pond. Most of the forest cover was cleared by 1665 (Watts 1987), and wetland habitats were drained to make way for settlements. Relatively undisturbed woodland areas now remain only on steep slopes e.g. Turners Hall woods and parts of Hackleton’s cliff, and in less accessible gullies or parts of gullies. The remaining significant wetland areas are Graeme Hall Swamp and Chancery Lane Swamp on the south coast, and Long Pond and Green Pond on the east coast. All of the remaining woodland and wetland areas can be considered as critical habitats in Barbados, particularly for indigenous birds and reptiles. 2 The indigenous vertebrate species that are still present and breeding in Barbados are shown in Table 1. The number of non-indigenous vertebrates that are present and breeding in the island are shown in Table 2, and the indigenous species for which there is historical or prehistorical evidence that they once bred in Barbados are shown in Table 3. The data summarised in these Tables clearly suggest that the destruction of forests and wetlands led to the loss of indigenous species. This effect was almost certainly compounded by over- exploitation of some and by the introduction of exotic competitors and predators. At the beginning of this century, Barbados had only 18 resident species of birds remaining (Table 1). Of these, only the Lesser Antillean bullfinch, Loxigilla noctis, is endemic, and the Barbadian race of the Florida gallinule, Gallinula chloropus, is suspected to be endemic (K. Watson, UWI, pers.comm). Information derived from fossilised remains and historical accounts suggests that at one time more than forty native bird species bred in the island (compare Tables 1 and 3). It should be noted that overall bird species diversity has increased in recent decades, due to geographical range expansion of some species bringing them into contact with Barbados, due to the escape/release of exotics into the wild, and perhaps due to the increase in woodland cover over the last thirty years (Table 2; D. Watts, University of Hull, pers.comm. for woodland cover increase). There are currently eight or perhaps nine indigenous species of reptiles and amphibians in Barbados (Corke, 1992; but see Schwartz, 1967; Table 1), several of which are endemic. At least two species (a giant Geochelone tortoise and an iguana) have gone extinct. Overall mammalian faunal diversity increased greatly following European colonisation, since many species were accidentally or deliberately introduced. The house mouse, black and Norway rats, green monkeys, hares and raccoons were all presumably human-assisted range expansions and introductions (Table 2). Although the former three species were accidentally transported by humans, monkeys and hares were deliberately brought to the island, the former as pets or gifts for planters, and the latter presumably for food. Both hares and monkeys may then have been accidentally introduced into the wild. The history of raccoon introduction is unknown and the species is now presumed extinct (Section 2.2.1). The mongoose was deliberately introduced as a biological control agent against rats. This increased mammalian diversity resulted in declines and extinctions of indigenous species. For example, competition from other rodents and predation by the mongoose are likely the blame for the demise of an indigenous rice rat, Oryzomys sp. (Table 2), and the mongoose is probably largely responsible for causing the decline of Barbados’ only known endemic snake, Liophis perfuscus (Section 2.3.1.1). 3 Table 1. Indigenous terrestrial vertebrate fauna present and breeding in Barbados (E = endemic; E* endemic sub-species; I? Possibly introduced). (Compiled from Corke 1992; Jones and Phillips 1970; Lazell 1972; Ray 1964; Watson 1993,1996). Common name Scientific name Status Habitat Audubon’s shearwater Puffinus lherminieri Rare Sea coast, islet off northeast St. Lucy coast Yellow warbler Dendroica petechia Rare Inlets on coast, mangroves, Graeme Hall Lesser Antillean grackle Quiscalis lugubris Very common Gardens, pasture land Lesser Antillean bullfinch E Loxigilla noctis Very common Gardens, enters houses Blackfaced grassquit Tiaris bicolor Very common Large gardens, grassland Zenaida dove Zenaida aurita Very common All over Ground dove Columbigallina passerina Common All over Antillean bananaquit Coereba flaveola Common Gardens Grey kingbird Tyrannus dominicensis Common Town and country, perched on telephone lines Caribbean elaenia Elaenia martinica Common All over, east coast scrub Caribbean martin Progne dominicensis Common Town, sea cliffs Black-whiskered vireo Vireo altiloquus Common All over, in tree tops Scaly-breasted thrasher Margarops fuscus Rare Forested areas on east coast, Hackleton’s cliff Antillean crested hummingbird Orthorhyncus cristatus Common All over Green throated carib Sericotes holosericeus Common All over Eastern green heron Butorides virescens Fairly common All over Florida gallinule E* Gallinula chloropus Fairly common Graeme Hall swamp; ponds in countryside Pearly-eyed thrasher Margarops fuscatus Rare Undefined Green lizard E Anolis extremus Very common All over Ground lizard Kentropyx borkiana Rare Central parishes Leaf-toed gecko E Phyllodactylus pulcher No information No information Burrowing ground lizard Gymnopthalmus underwoodi No information No information Skink Mabuya mabouya No information No information Six inch snake; two-lined snake Leptotyphlops bilineata No information In leaf litter; central parishes Snake I? Mastigodryas sp. Rare Border of St. Joseph/St. John Snake E Liophis perfuscus Probably extinct Border of St. Joseph/St. John Hawksbill turtle Eretmochelys imbricata Rare Nests on leeward beaches; coral reefs Leatherback turtle Dermochelys coriacea Rare Nests on windward beaches Green turtle Chelonia mydas Rare Seagrass/algal beds Bat Monophyllus plethodon No information No information plethodon Fruit bat Brachyphylla cavernarum No information No information Fruit bat Artibeus jamaicensis No information No information jamaicensis Fish-eating bat Noctilio leporinus leporinus No information No information House bat Molossus molossus molossus Common House eaves; caves 4 Table 2. Non-indigenous terrestrial vertebrate fauna present and breeding in Barbados. Presence due to expanded geographic range (ER) or deliberate introduction (I). Species present due to expanded range may have had non-deliberate human assistance (Compiled from Censky 1988; Feilden 1890; Marsh 1981; W atson 1993, 1996). Common name Scientific name Status Places seen Arrival date if known Cattle egret RE Bubulcus ibis Very common Four breeding 1957 colonies; all over Ramier RE/I? Columba squamosa Very common All over Violet-eared dove RE Zenaida auriculata Uncommon Grassland, scrub in St.Philip, Ch.Ch Glossy cowbird RE Molothrus bonariensis Common All over 1923 Cayenne nighthawk RE Caprimulgus cayennensis Rare Eastern parishes Yellow-crowned night heron RE Nyctanassa violacea Uncommon Graeme Hall swamp Snowy egret RE Egretta thula Uncommon Graeme Hall swamp Little egret RE Uncommon Graeme Hall swamp Orange-winged parrot I Amazona amazonica Few, but readily seen Bridgetown