Comments on the Ecology and Status of the Hispaniolan Crossbill (Loxia Ieucoptera megaplaga), with Recommendations for its Conservation

– The rare and unique Hispaniolan White-winged Crossbill (Loxia Ieucoptera megaplaga) is endemic to the mountains of Hispaniola. It is specialized for harvesting seeds from the cones of Pin us occidentals, and is dependent on the perpetual production of cone crops. Because large cone crops are produced only once every three or so years in any single area, crossbills require large areas to sustain their population. Pine forests throughout the mountains of Hispaniola need protection from cutting to ensure that sufficient pine seed is available every year. Such protection is necessary to reduce the risk of extinction to a crossbill that I argue should be recognized as a distinct species, and whose population size may number less than a thousand. A pressing demand of biology is to provide the ecological information necessary for ensuring the survival of endangered populations and communities. Nowhere is this information more critical than in the tropics, especially in the West Indies. For example, 44 of the 139 resident bird species on Hispaniola have been classified as threatened or endangered (Hartshorn et al., 1981). One threatened species is the Hispaniolan White-winged Crossbill (Loxia leucoptera megaplaga). The Hispaniolan Crossbill is confined to pine forests on three mountain ranges in Hispaniola (Cordillera Central, Sierra de Baoruco, and Massif de la Selle; Wetmore and Swales, 1931; Kepler et al., 1974; Dod, 1987). The crossbill is found in pine forests because (1) it is specialized for foraging on seeds in the cones of Pinus occidentals (Benkman, 1989) (which is found almost entirely on Hispaniola [Mirov, 1967]), and (2) presumably like other crossbills, this species is unable to compete with other species for other types of foods (Benkman, 1988). Consequently, the future of the Hispaniolan Crossbill is contingent on the perpetual availability of P. occidentals seeds. Below I discuss both the crossbill and its food resource, and use this information to guide recommendations for the crossbill’s conservation. Pinus occidentals Seed Availability and the Annual Cycle of the Hispaniolan Crossbill Pine seed availability fluctuates within and among years. The cones and seeds of most conifers, including those of P. occidentals, develop during the summer and mature by September. Pinus occidentals seeds remain in the cones until they begin opening between January and March (pers. ohs.). This pine undoubtedly holds at least some seeds in its cones into summer; other fire-adapted conifers with non-serotinous cones hold seeds in partly open cones during extended periods (Burns and Honkala, 1990). Hispaniolan Crossbills probably forage on a given cone crop from July or August, when the seeds and cones are still developing, until the following July when most of the seeds have been shed; such behavior has been found for the Red Crossbill (L. curvirostra) foraging on ponderosa pine (P. ponderosa) in the Rocky Mountains (Benkman, 1987a, 1993a). Because few seeds likely remain in the cones more than a year, crossbills need to find a new cone crop each year. Locally, P. occidentals produces a large cone crop about every three years (G. Basilisi and E. Marcano, pers. comm.). Large