Tuesday, August 25, 2020

Puerto Rican Parrots

by J. Michael Meyers

National Biological Service

The Puerto Rican parrot (Amazona vittata) had shared its habitat with the peaceful Taino Indians for centuries before the arrival of European settlers in the Caribbean.

Status and Trends

Upon arrival of the Spanish in 1493, the Puerto Rican parrot lived in all major habitats of Puerto Rico and the adjacent smaller islands of Culebra, Mona, Vieques, and possibly the Virgin Islands (Snyder et al. 1987). Parrots occupied eight major climax or old-growth forest types (Little and Wadsworth 1964) that covered Puerto Rico and were interspersed only by small, scattered, sandy, or marshy areas near the coast (Snyder et al. 1987). Parrots nested in cavities of large trees that were plentiful throughout the forests. Fertile, moist lowland forests in the coastal plain as well as forested mountain valleys contained much of the fruits and seeds necessary to feed a thriving parrot population. The forests of Puerto Rico probably supported a parrot population of 100,000-1,000,000 at the end of the 15th century (Snyder et al. 1987; Wiley 1991).

Little habitat change occurred in Puerto Rico during the first 150 years of European settlement. By 1650 the Spanish population had increased to 880 (Snyder et al. 1987); parrots still occupied all major habitats and were plentiful. During the next two centuries the human population soared to almost 500,000, and clearing for agriculture, especially in the lowlands, eradicated forests in Puerto Rico (Wadsworth 1949). By 1836 reports by Moritz, a German naturalist, indicated that the Puerto Rican parrot population had begun to decline (Snyder et al. 1987).

By 1900 the human population had doubled to a million. About 76% of the land area of Puerto Rico had been converted from forest to agriculture (Snyder et al. 1987); less than 1% of the old-growth forest remained after more than 400 years of European civilization. At this time, the parrot population must have been low, but no data exist. By 1937 U.S. Forest Service (USFS) rangers estimated the Puerto Rican parrot population at about 2,000 birds (Wadsworth 1949).

A few years later, parrots were found only in the Luquillo Mountains, formerly a forest reserve of the Spanish Crown and now managed by the USFS. This area contained the last forest habitat suitable for Puerto Rican parrots.

Population surveys of the Puerto Rican parrot were not conducted until the 1950's. Early estimates of the parrot population in Puerto Rico are based on few written records and general observations (Snyder et al. 1987), knowledge of the parrot's biology, and extrapolation of population surveys conducted by Rodríguez-Vidal (1959). During the 1950's, Rodríguez-Vidal of the Puerto Rico Department of Agriculture and Commerce conducted the first extensive study of the Puerto Rican parrot. He reported a population of 200 Puerto Rican parrots by the mid-1950's. About 20 years later the population had dwindled to 14 individuals that inhabited an isolated rain forest of the Luquillo Mountains.

In 1968 Kepler, U.S. Fish and Wildlife Service (USFWS), organized parrot surveys by placing observers at strategic sites, including overlooks from prominent rocks, road-cuts, and building roofs. Snyder et al. (1987) improved the survey method in 1972 by constructing 10 treetop lookouts in areas of major parrot use. Parrot surveys are conducted from these platforms during the breeding season and pre- and postbreeding season (Snyder et al. 1987). Observers collect information on parrot numbers, directions, and their distance from the platform by the time of day. By 1993 this treetop lookout system was expanded to 38 platforms (Vilella and García 1994).

In 1968 implementation of the Puerto Rican Parrot Recovery Plan began; it is a cooperative effort of scientists and managers of the Puerto Rico Department of Environmental and Natural Resources, USFS (Caribbean National Forest and International Institute of Tropical Forestry), USFWS Puerto Rican Parrot Field Office, and the National Biological Service. After the recovery program began, the parrot population increased to 47 birds by 1989 (Wiley 1980; Lindsey et al. 1989; Meyers et al. 1993); however, about 50% of the population was destroyed by Hurricane Hugo that same year. A small population of 22- 24 individuals remained in late 1989. Since then, the population recovered to 38-39 by early 1994 (F.J. Vilella, USFWS, personal communication). After the hurricane, the number of successful nesting pairs increased from a maximum of 5 to 6 pairs from 1991 to 1993 (Meyers et al. 1993; Vilella and García 1994).

Research and Management

Puerto Rican parrots declined in relation to the increasing human population. Conversion of forests to agriculture and loss of forest habitat, on which the species depended for food and nest cavities, was the primary cause for decline. Shooting parrots for food or protection of crops and capture for pets were secondary causes for decline. The remnant parrot population in the Luquillo Mountains was further stressed when trails and roads were created and when human uses of the forest timber were encouraged in the early 1900's (Snyder et al. 1987).

Storms before the arrival of Europeans probably had little effect on the parrot population because the population was more widespread, and hurricanes tend to affect only a small geographic area. Severe hurricanes in 1898, 1928, 1932, and 1989 reduced small, now-isolated populations even further. The apparent ability of the population to rebound after these storms is suggested by increases in the parrot population and in nesting pairs after Hurricane Hugo hit the island in 1989 (Meyers et al. 1993).

Intense research and management strategies during the last 27 years have prevented the extinction of the Puerto Rican parrot. Much of the effort to rebuild the population has involved research and management of nesting sites (Wiley 1980; Snyder et al. 1987; Lindsey et al. 1989; Wiley 1991). Predators, such as black rats (Rattus rattus) and pearly-eyed thrashers (Margarops fuscatus), have been controlled (Snyder et al. 1987). Bot fly (Philornis spp.) infestations of nestlings are still a minor problem (Lindsey et al. 1989). Management of nests by fostering captive-reared young into wild nests, guarding nests, controlling honey bees (Apis mellifera), improving and maintaining existing nest cavities, and creating enhanced nesting cavities should increase the population of the Puerto Rican parrot (Wiley 1980; Lindsey et al. 1989; Wiley 1991; Lindsey 1992; Vilella and García 1994).

Hurricanes will continue to threaten the wild population of the Puerto Rican parrot. Researchers estimate that storms equal to the intensity of Hugo (sustained winds of 166 km/h or 104 mi/h) occur at least every 50 years in northeastern Puerto Rico (Scatena and Larsen 1991). The risk of extinction caused by hurricanes will be reduced by establishing a geographically separated wild population (USFWS 1987).

Introduced parrots and parakeets are common in Puerto Rico, including some of the genus Amazona. Monitored populations of these non-native birds have increased from 50% to 250% during 1990-93 (J.M. Meyers, National Biological Service, unpublished data). If they expand their ranges to include older forests, these populations may pose a threat to the Puerto Rican parrot by introducing diseases and by competing for resources. At present, none of the introduced Amazona populations are found near the Luquillo Mountains; however, orange-fronted parakeets (Aratinga canicularis) have foraged and nested in these mountains at lower elevations (J.M. Meyers, NBS, unpublished data).

As the Puerto Rican parrot population increases, it is possible that suitable nesting sites may limit population growth. Before this occurs, research and management should concentrate on increasing the wild population. The ability of the Puerto Rican parrot to expand its population in a manner similar to the exotic parrots in Puerto Rico, in a variety of natural and human-altered environments, should not be underestimated and may be the key to its recovery.

For further information:

J. Michael Meyers
National Biological Service
Patuxent Environmental
Science Center
PO Box N
Palmer, Puerto Rico 00721-0501 USA

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