Grenada Dove
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| Leptotila wellsi (Lawrence, 1884) |
The Grenada Dove (Leptotila wellsi) is a medium-sized New World tropical dove. It is endemic to the island of Grenada in the Lesser Antilles. Originally known as the Pea Dove (Lawrence 1884) or Well's Dove (Goodwin 1970), it is the National Bird of Grenada. It is considered to be one of the most critically endangered doves in the world (Bird Life International 2000).
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[edit] Description
The Grenada Dove is characterised by a white throat; face and forehead pale pink shading to dull brown on crown and nape; upperparts olive brown; underwing chestnut; neck and upper breast pink-buff fading to white on lower breast, belly and undertail coverts (Goodwin 1970).
[edit] Taxonomy
First described in 1884 by Lawrence as a member of the genus Engyptila, it was established as a distinct species using sonographic analysis by Blockstein and Hardy (1988). Now officially known as the Grenada Dove, it was designated as the national bird in 1991 and is one of the flagship species for conservation efforts in Grenada (Butler et al. 1992, Rosenberg and Korsmo 2001).
[edit] Distribution and habitat
The Grenada Dove is a little-known species endemic to the main island of Grenada, West Indies (Raffaele et al. 1998). Historically, it has been recorded from locations throughout Grenada, including offshore islands (Caribbean Conservation Association 1991), and the type specimen was collected from Fontenoy, on the west coast (Lawrence 1884). More recent investigations imply Grenada Doves are associated with dry forest communities in the west and southwest parts of the main island (Blockstein 1988, Blockstein and Hardy 1989, Blockstein 1991, Bird Life International 2000). True dry forest ecosystems are remnants of a type of xeric scrub habitat that dominated the West Indies at the end of the Pleistocene (Pregill and Olson 1981, Wunderle 1985), and most areas classified as dry forest in the Caribbean are mosaics of degraded habitat, and do not represent natural ecosystems (Murphy and Lugo 1986, Roth 1999, Vidal and Casado 2000). Beard noted the degraded nature of forested areas in Grenada in 1949.
More recently Rivera Lugo (2005) has suggested that past disturbance may have created new artificial vegetative cover types that are difficult to classify as natural forest communities. Recent classification of land cover types through satellite imagery found that Grenada’s dry forest might be more appropriately considered as ecological complexes, and that there may be correlations between human impacts and vegetative cover (Plume 2005). The Rivera Lugo investigations suggest that Grenada Doves are using a mixture of three seasonal forest formations: semi-evergreen forest, deciduous seasonal forest, and thorn woodlands. These categories are based on work by Beard (1949) and are applied widely throughout the Caribbean.
Beard considered the thorn woodland seasonal formation to be a highly degraded habitat created by heavy grazing and intensive agricultural practices. Additionally, preliminary surveys and recent census data (Clouse and Rusk 2004) indicate Grenada Doves occur in both highly fragmented semi-urban areas and more rural environments composed sometimes of highly contrasting levels of housing and economic development. Other members of the genus Leptotila are reported to use a variety of habitats, ranging from areas associated with human disturbance, deciduous woodlands, humid forests, thickets, and semi-arid areas (Skutch 1964, Goodwin 1993).
Grenada Doves have been documented in south-western Grenada within the Mount Hartman, Clark’s Court Bay, and Richmond Hill watersheds (Wunderle 1985, Blockstein 1988, Blockstein and Hardy 1989, Blockstein 1991, Clouse and Rusk 2004). The Mount Hartman watershed has received the greatest amount of scientific investigation and is considered by other researchers to be the representative habitat for the species (Blockstein 1988, Blockstein and Hardy 1989, Blockstein 1991). Part of this watershed has been designated as a national park and is the only official national park in Grenada. Grenada Doves also have been recorded from western Grenada (Wunderle 1985, Blockstein 1988, Blockstein and Hardy 1989, Blockstein 1991).
The most recent distribution census included individuals from the Beausejour, Perseverance, Woodford, and Black Bay watersheds (Clouse and Rusk 2004). Part of the Perseverance watershed, adjacent to the island’s new sanitary landfill and across the street from the old landfill, has been established as a Grenada Dove sanctuary. This area includes a designated travel corridor to link areas of habitat on the north and south sides of the new landfill (Rosenberg and Korsmo 2001). The old landfill is currently on fire and has been burning since February 2004. An emergency landfill, which has been established to accommodate the large volume of debris created by Hurricane Ivan in early September 2004, is encroaching on the Perseverance sanctuary.
[edit] Behaviour
[edit] Breeding
Grenada Doves are assumed to be territorial, and current population estimates are based on this assumption (Blockstein 1991, Clouse and Rusk 2004). Grenada Doves in the Mount Hartman area have been observed fighting (Blockstein 1988), and other Leptotila species show varying degrees of territorial behaviour (Skutch 1964, Goodwin 1983). Herbert Bright (1926) maintained captive Leptotila doves in England and documented a breeding pair killing other congeneric doves introduced to the aviary. Bright refers to these birds as Well’s Doves, although his physical descriptions of the birds indicate that they may have been L. verrauxi imported from Tobago.
Only one active Grenada Dove nest has been documented (Blockstein 1991). This nest was active during January and February and was found in a palm. Juveniles also have been found on the ground and photographed by Grenada’s Forestry and National Parks Department (FNDP) staff; no nest was documented for this encounter. Additionally, there is a record of a Dove flushing from a nest (Clouse and Rusk 2004). There may be peaks in breeding activity associated with increased calling by Grenada Doves from June until December. Other researchers suggest that there may be differences in calling cycles between Grenada Dove populations on the west coast, which appear to call year round, and calling activities of populations in the southwest, which may be more seasonal. Bright (1926) noted that Leptotila doves in captivity abandoned their nest when disturbed, but by using artificial nesting substrates, he successfully collected eggs and hand-reared young. Bright’s doves produced two buff-coloured eggs per clutch. This is consistent with literature reports from other members of the genus (Skutch 1964, Goodwin 1983).
The majority of information on the nesting ecology for the genus is associated with Leptotila verrauxi. Studies from Texas[verification needed] indicate that L. verrauxi primarily nests on edges and interiors of brushlands and forest dominated by Pithecellobium ebano and Celtis laevigata (Boydston and DeYoung 1987, Hayslette et al. 2000), and nests are located in a wide variety of nesting substrates (Skutch 1964, Hayslette 1996, Hogan 1999).
[edit] Diet
Observations have been made of Grenada Doves foraging on the ground (Blockstein 1998, Clouse and Rusk 2004). Leptotila in captivity have been documented consuming mealworms (Bright 1926). Other Leptotila species have been observed eating fruits, seeds, and agricultural grain. L. verrauxi is known to visit bird feeders (Skutch 1964, Goodwin 1983), and other members of the genus have been observed eating fruit from the forest floor (Estrada et al. 1984, Coates-Estrada and Estrada 1986), as well as directly from plants (Goodwin 1983).
[edit] Conservation
Very little is known about this species. Population estimates by various researchers indicate that there may be fewer than 100 individuals remaining in the wild (Blockstein 1988, 1991), and declines in numbers may have occurred between 1987 and 1991 (Blockstein 1991).
This dove is classified as critically endangered by BirdLife International. The current population is estimated at fewer than 200 individuals, and possibly fewer than 100. The Grenada Government - in cooperation with the World Bank - set up two reserve zones in 1996 to preserve the Dove: the Perseverance and adjacent Woodford Estates in the west of the island and a sanctuary of c.150 acres within the Mount Hartman Estate in the south. This sanctuary holds approximately 50% of the population of the Dove, with about 22% within the section now considered a national park. Any future development of the Mount Hartman Estate needs to respect the restricted zones therein which comprise about 25% of the entire estate.
[edit] Threats
The primary threat to the Grenada Dove is considered to be habitat fragmentation (Birdlife International 2000). As early as 1947, Bond indicated that one of the primary causes of rarity and extinction for avifauna in the West Indies was habitat destruction by human activities. Jackson and Associates (1998) noted many factors that could affect Grenada Dove populations, including land development, livestock grazing, and harvesting of firewood, the underlying cause being lack of land development regulation.
In addition to habitat destruction, predation may impact Grenada Dove populations. There may have been two separate introductions of exotic species on Grenada. Of these, the Common Opossum, Didelphis marsupialis, which was originally introduced to Grenada by Ameridians, is a potential predator of all life stages of the Grenada Dove, and other manicou species (Marmosa spp.) are potential nest predators. Exotic mammals introduced with European colonisation include Rattus species, Indian Mongooses (Hepestes aropunctatus), Mona Monkeys (Cercopithicus mona) and feral cats (Felis silvestris).
Hunting may have had an impact on the population in the past, and the Grenada Dove has previously been regulated as a game bird (Knight 1946). Currently, hunting is not considered a major threat.
[edit] Current issues
In late 2006, information was released stating that the Government intends to sell a portion of Mount Hartman Estate to a private promotor for the development as a tourist resort under the probable management of Four Seasons Hotels. The Grenada Government has issued statements stating categorically that any new project within the Mount Hartman Estate will have to respect the dove sanctuaries and that any project will have to meet the criteria of providing a "win-win" situation. Four Seasons Hotels have issued a statement asserting that they are not the developer of the project but only a potential operator, if the project should proceed. The Government of Grenada has not made any final decision about the development yet.
BirdLife International and other organisations have questioned whether a "win-win" situation can be achieved. BirdLife International, with other organisations (including the American Bird Conservancy) and private individuals (including authors Graeme Gibson and Margaret Atwood), have campaigned against the proposed development. They argue that, being restricted to dry, coastal scrub-woodland and seasonal forest, habitat loss remains the most significant thread to survival of the Grenada Dove. Other threats are hurricanes and predation of nestlings and eggs by the introduced mongooses, cats and rats.
Supporters of the proposed development have claimed that the Mount Hartman area is not critical to Grenada Dove survival. According to some studies, the Mount Hartman Sanctuary was never considered adequate for the dove’s survival (Jackson and Associates 1998) and other understudied populations are located along the western coast in the Beausejour and Black Bay watersheds (Clouse and Rusk 2004). Some of these populations have been recognised since the 1980s. Further populations may exist but there has never been a complete island-wide survey to verify this.
Moreover, the Grenada Dove is not restricted to dry coastal scrub areas, and many of the locations where the bird is found are composed primarily of degraded mosaics of evergreen forest (Rivera-Lugo 2005). The overall uniting factors in Grenada Dove habitat issues are the degraded nature of the habitat and close proximity to human habitation. This is readily apparent at the Mount Hartman sanctuary, which is an old government cattle farm with vegetation composed primarily of exotic species such as Leucaena leucocephala and Heamatoxylon. Populations of doves associated with the old golf course below Jean Anglaisare are under heavy pressure from development for private homes, and are well outside the boundaries of the Mount Hartman Sanctuary as are most Grenada Doves (Clouse and Rusk 2004, Jackson and Associates 1998). Mount Hartman could be considered prime cattle habitat and has been developed as such until recent times. Current population estimates for the species (Clouse and Rusk 2004) have not been published for peer review, as the last published population estimates were conducted by David Blockstein in 1991.
[edit] References
- American Bird Conservancy (2007) Four Season Resort Spells Doom for Grenada's National Bird Accessed 20/2/2007.
- Beard, J. S. (1949). The natural vegetation of the Windward and Leeward Islands. Oxford, Clarendon Press.
- BirdLife Species Factsheet
- Birdlife International (2006) Government of Grenada sells off National Park for Four Seasons resort Accessed 8/1/2007.
- Birdlife International (2007) Grenada Government defiant as dove sanctuary protest grows Accessed 20/2/2007.
- Blockstein, D. E. (1991). Population declines in the endangered endemic birds on Grenada, West Indies. Bird Conservation International 1: 83-91.
- Bond, J. (1960). Birds of the West Indies. London.
- Bright, H. (1926). Nesting of the Well's dove. Avicultural Magazine, page 221.
- Butler, P., A. Joseph, and B. A Lazarus. (1992). Promoting love for the Grenada dove: Grenada’s conservation education campaign. RARE Center for Tropical Conservation. St. Georges, Grenada
- Caribbean Conservation Association. (1991). Grenada: country environmental profile. Caribbean Conservation Association, St. Michael, Barbados.
- Clouse, L. J., and B. L. Rusk. (2004). Grenada dove census 2003/2004. Grenada Dry Forest Biodiversity Ecosystem Project, St. George’s, Grenada.
- Jackson and Associates. (1998). Plan for the Mount Hartman national park and Perseverance sanctuary. Unpublished report. Project Implementation Unit Government of Grenada, Grenada, W.I.
- Knight, E. G. (1946). The Grenada handbook and directory. The Advocate Company, Bridgetown, Barbados.
- Goodwin, Derek. (1970). Pigeons ad Doves of the World. British Museum (Natural History): London.
- Grenada Dove Campaign Accessed 19/2/2007.
- Grenada Government Press Release of 01/03/2007[1]
- Lawrence, G. N. (1884). Characters of a new species of Engyptila, from the island of Grenada, West Indies. Auk 1:180.
- Pregill, G. K., and S. L. Olson. (1981). Zoogeography of West Indian vertebrates in relation to Pleistocene climatic cycles. Annual Review of Ecology and Systematics 12: 75-98.
- Raffaele H., J. Wiley, O. Garrido, A. Keith., and J. Raffaele. (1998). A guide to the birds of the West Indies. Princeton University Press, Princeton, New Jersey, USA.
- Rivera Lugo, P. J. R. (2005). Composition and structure of Grenada's forest in relation to the Grenada Dove (Leptotila wellsi) habitat. Grenada, W.I., Grenada Dry forest Biodiversity Conservation Project: 1-109. Unpublished report.
- Rosenburg, J., and F.L. Korsmo. (2001). Local participation, international politics, and the environment: the World Bank and the Grenada dove. Journal of Environmental Management 62: 288-300.
- Roth, L. C. (1999). Anthropogenic change in subtropical dry forest during a century of settlement in Jaiqui Picado Santiago Province, Dominican Republic. Journal of Biogeography 26: 739-759.
- Skutch, A. F. (1964). Life histories of Central American pigeons. Wilson Bulletin 76: 211-247.
- Smith, G. (1824). Reference to the plan of the island of Grenada. Government of Grenada, St Georges, Grenada
- Wunderle, J. (1985). An ecological comparison of the avifaunas of Grenada and Tobago West Indies. Wilson Bulletin 97(3): 356-365.
