Treesearch

Population viability analyses for a number of endangered species have incorporated a metapopulation approach. The risk assessments of these viability analyses have indicated that some extant populations should be subdivided into numerous subgroups with exchange of individuals among them in order to reduce the chance of catastrophic loss of the species. However, routine application of a policy of extensive subdivision may have detrimental consequences for certain endangered species. We examine the Puerto Rican Parrot as a case history in which this policy is ill-advised. In 1989, a populatio...

Pueden utilizarse diferentes métodos para estudiar la distribución de una especie de ave terrestre o para llevar cuenta de los cambios en sus poblaciones. El método apropiado dependerá de si el objetivo es sencillamente documentar la presencia de una especie, o cuantificar su abundancia relativa, densidad poblacional, tendencias poblacionales a largo plazo, uso de hábitat, presunción de supervivencia, o las condiciones físicas de individuos de la especie. Una vez definido el objetivo es necesario considerar la selección del lugar de estudio, el total de unidades muestras, la hora del día,...

Fifteen juvenile Puerto Rican Parrots (Amazona vittata) from wild nests in 1985, 1986 and 1987 were radio monitored an average of 110 +_ 15.9 (SE) d (range 4-209 d) post-fiedging.. Minimum survival was 67% (n = 3) in 1985, 100%( n = 4) in 1986 and 43% (n = 7) in 1987. Most mortality (three of five deaths) occurred during the first 35 d following fledging. A major cause of mortality was predation by raptors. This research shows that additional studies are needed to define mortality causes to juvenile and adult free-flying Puerto Rican Parrots and to develop management guidelines to increase...

Different census methods can be used to survey the distribution of a terrestrial bird species or to monitor population changes. The appropriate method depends on whether the objective is simply to document the presence of a species or to quantify its relative abundance, population density, population trends over time, habitat use, survivorship, or the physical condition of individuals. Once the objective is defined, consideration should be given to selecting a study site, the number of sampling units, the time of day, the time of year, and the experience of field personnel. The various...

Signs of deterioration of the global environment and threatened destruction of the vast Amazon forest have stirred a call for action.Conservationists have always been concerned about the tropical forests; now funds are being made available for increased work on problems in the region. Brazilian scientists struggle to communicate with colleagues in the rest of the world while scientists from other areas are discovering that to work effectively in Brazil, one must speak Portuguese. One must also be able to read Portuguese to benefit from the local tech-nical literature.

Changes in wood density, nutrient content, and invertebrate populations throughout the decay of Cyrilla racemiflora (Cyrillaceaea) were compared with those observed in temperate woody tree species. Wood density tended ro remain constant as decay advanced except in the late stages. Nutrients (N, P, Ca, Mg) were in highest concentrations in intact bark, surface wood, and wood in advanced decay. Concentrations of N and P were highly correlated, as were concentrations of Ca and Mg. The C/N ratio was determined mainly by changes in N because C tended to remain constant as decay proceeded. The...

Wintering nearctic migrants constitute a high proportion of the birds present in many terrestrial habitats in the Bahamas and greater Antilles, But their proportions decline southward through the Lesser Antilles. many migrants winter on densely populate islands which have been extensively deforested.

Beginning in the 17th century, the forest lands of Antigua and Barbuda were cleared for agriculture, burned, cut over, and grazed severely. A survey by personnel of the USDA Forest Service, International Institute of Tropical Forestry and previous surveys were used to assemble lists of native and exotic woody plants. A large majority of the original woody flora still grows on both islands.