Delineating pattern and process in tropical lowlands: Mealy parrot migration dynamics as a guide for regional conservation planning.

摘要

Most reserves fail to capture the habitat heterogeneity necessary to maintain viable populations of wide-ranging species. Methods to determine defensible dimensions of reserves and reserve networks are needed. The primary goal of this study was to develop such methods for lowland tropical forests by examining habitat- and spatial-use patterns of the Mealy Parrot ( Amazona farinosa) in northern Guatemala. Regional connectivity has been demonstrated by altitudinal migration of birds that track seasonal fruit availability; it is now recognized that a suite of habitats along the elevational gradient must be protected to conserve biodiversity of tropical montane ecosystems. However, in tropical lowlands, little is known about spatiotemporal patterns of resources and animals that rely on them. I considered the large-bodied, frugivorous Mealy Parrot a useful focal species because its movements and habitat use should be coupled with the ecological factors determining fruit distribution. Individual- and population-based methods were developed in this study. In each of 4 years, radio telemetry revealed that adult Mealy Parrots breeding in northeastern Guatemala engaged in predictable seasonal migrations within mature lowland forest. Although the area covered by these parrots was considerable (10,000 km2), more significant was the consistency of their movements and specific locations utilized. Canopy-based population surveys were used to estimate densities of all 6 locally occurring parrot species as a function of landscape type and season over a two-year period; the data suggest that migration is common in this parrot community. Mealy Parrots rely on mature lowland forest arrayed along regional environmental gradients. Over distances of a few hundred kilometers and a range in elevation of ∼200 m, variation in fruiting phenology, forest composition, and rainfall shape this species' movement patterns. Basing reserve design on size alone is insufficient. Large protected areas, such as the 600 km2 Tikal National Park and even the 21,000 km2 Maya Biosphere Reserve, will not maintain this population of Mealy Parrots without inclusion of areas that encompass the range of spatiotemporal variability governing migration patterns. The Mealy Parrot occurs from Mexico through Amazonia and may serve as a valuable focal species for conservation planning in other parts of its range.