Avian Diversity in the Rio Platano Biosphere Reserve, Honduras: The Influence of Indigenous Agricultural Practices

Publication Date


Type of Culminating Activity


Degree Title

Master of Science in Raptor Biology



Major Advisor

Marc J. Bechard


This thesis consists of two chapters describing my investigation into the avifauna of the Río Plátano Biosphere Reserve (RPBR) in northeastern Honduras. The purpose of my field research was to (1) determine what effects, if any, Pech and Miskito Indian agricultural practices were having on the diurnal raptor assemblage of the RPBR, (2) examine the relationship between human-induced landscape heterogeneity and diurnal raptor density, species diversity, and species richness, (3) characterize the avifauna of the RPBR, and (4) test the efficacy of above-canopy surveys for birds. Information contained in this thesis should be particularly valuable in the management of tropical forest reserves containing native human populations, and to biologists conducting bird surveys in lowland tropical rain forests.

Tropical Forest Conservation and Native Human Populations

We live at a time when the alarming rate of tropical deforestation is causing a rate of species extinction unprecedented in the history of the Earth. By different estimates, the present extinction rate may be as high as 10,000 to 17,500 species lost each year due to deforestation of tropical forests (Meyers 1988, Wilson 1988). If, on the other hand, the current periodical literature is any indication, the increasing rate of tropical deforestation is manifested in a second relationship: more biologists are conducting research in tropical forests than ever before. However, despite our best efforts, certain truths are clear: a minute percentage of tropical organisms have been described by science, and the rate of deforestation continues unabated (Raven 1988, Whitmore 1997).

Although the creation of biological reserves - e.g., national parks, wildlife refuges, biosphere reserves - is one solution to the loss of tropical biodiversity, our efforts to protect extant ecosystems are hindered by our limited understanding of tropical forest ecology. Furthermore, because native peoples frequently inhabit newly created biological reserves in the tropics, information on the effects of native societies on forest systems is needed if we are to protect or conserve intact forest ecosystems in which these peoples live. In the past, native peoples have been portrayed as "successful managers of the forest" whose traditions preserve, or exist harmoniously with, the forest ecosystem (Taylor 1988). However, scientific studies increasingly cast doubt on this perceived role of forest conservators (Hames 1990, Alvard 1995). Furthermore, as native societies increasingly enter the cash economy, and as their population densities continue to grow, we cannot expect native peoples to affect the environment in the same ways that they have in the past (Neitschmann 1972, Redford and Stearman 1993). For these reasons I designed my study to better understand human-forest ecology relationships, and to contribute to the continued conservation of one particular ecosystem: the lowland rain forest of the Río Plátano Biosphere Reserve, Honduras.

Overview of Chapters One and Two

In Chapter One I present the findings of a study on the effects of native farming practices on diurnal raptors. I chose diurnal raptors as indicators of both biological diversity and integrity because they possess characteristics of species prone to extinction (Karr 1977), because many species are vulnerable to forest fragmentation (Terborgh 1974), and because they may be keystone species in the rain forest ecosystem (Terborgh 1992). I counted raptors from above-canopy viewpoints in intact primary forests, forests with low amounts of clearing for agriculture, and forests with moderate amounts of clearing for agriculture. After mapping the size and distribution of five natural and anthropogenic habitats, I was able to assess the importance of each habitat, and of landscape heterogeneity, on diurnal raptor species density, diversity, and richness.

Diurnal raptor species density, diversity, and richness all increased directly as a result of increasing landscape heterogeneity. Although two of five habitats significantly influenced raptor diversity, changes in landscape heterogeneity best explained differences in raptor diversity. In addition, four of 18 species detected differed significantly in abundance between the three levels of landscape heterogeneity. Therefore, in this particular forest, native peoples appear to have a significant impact on the composition of the diurnal raptor assemblage.

In Chapter Two I characterize the avifauna of the RPBR and compare it to two well-known sites in Central America: La Selva, Costa Rica, and Barro Colorado Island, Panama. I also discuss the usefulness of canopy-based surveys in census programs for rain forest birds. I observed 248 breeding species and regularly occurring migrants, including 190 core forest species, over two field seasons using a combination of canopy-based surveys and incidental observations. Based on published ranges and habitat affiliations, I conservatively estimate the total avifauna of the RPBR at 351 species, including 251 upland forest species. The lower number of species in the RPBR compared to La Selva and Barro Colorado results from a greater distance from South America, and by having fewer species adapted to human-modified habitats. Canopy-based surveys proved vital in detecting birds in the top layers of the forest and the air, and could be a valuable addition to traditional ground-based survey techniques.

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