Bird diversity in the forests of central and southern Chile: a macroecological approach
The need to quantify the patterns of diversity and to improve our knowledge of the processes that underlie their generation and maintenance, has become a fundamental issue within ecology. In this thesis, the patterns of the diversity of non-raptor land birds that inhabit the forested environments of...
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| Format: | doctoral thesis |
| Status: | Published version |
| Publication Date: | 2004 |
| Country: | Chile |
| OAI Identifier: | oai:repositorio.anid.cl:10533/246641 |
| Online Access: | https://hdl.handle.net/10533/246641 |
| Access Level: | Open access |
| Keyword: | Ciencias Naturales Otras Ciencias Naturales |
| Summary: | The need to quantify the patterns of diversity and to improve our knowledge of the processes that underlie their generation and maintenance, has become a fundamental issue within ecology. In this thesis, the patterns of the diversity of non-raptor land birds that inhabit the forested environments of the Mediterranean and Temperate zones of Chile were analyzed. The main objective was to analyze the spatial patterns of the richness and abundance of forest birds, and to evaluate what historical and environmental factors, and what qualities of the species determine the changes in the diversity of the assemblages. Specifically, the validity of the productivity hypothesis as the main explanatory factor of bird diversity was thoroughly studied, and two of the mechanisms proposed to explain the positive relationship between energy and number of species were evaluated. After analyzing 26 local assemblages, it was found that there is a non-linear pattern of richness in a latitudinal gradient between 30º and 55º South. A similar pattern was observed for both the degree of endemism and the degree of rarity. The variation in these three properties of the assemblages can be satisfactorily explained by the glacial history of the biota and by the productivity of the system. When studying which life history characteristics explain the distribution and abundance patterns of the species, it was found that those with more restricted ranges tend to be forest specialists, residents and of medium or large body size, while species with low abundances have insectivorous or omnivorous diets and also a body size> 50 grams. In a subsequent analysis carried out in 14 coastal forest sites located in the Mediterranean zone (between 31 and 38º South), the study showed that more productive places maintain an assemblage of species with higher body weights and lower abundances. On the other hand, when separating the assemblage into two groups of species - habitat specialists and generalists - it was shown that productivity was the best predictor of richness and abundance of forest specialist species, but not of generalist species. Some characteristics of the habitat related to the amount and variety of available resources, such as the number of snags, the height of the canopy and the biomass of walking insects, were significantly related to the presence and abundance of specialist birds and not to the richness and abundance of generalist birds, which supports the mechanism of "greater specialization" as the best explanation of the positive relationship between wealth and energy. The main conclusion of the thesis is that the patterns of diversity of birds that inhabit the forests of central and southern Chile are the result of three factors: the glacial history of the biota, the amount and variety of environmental resources and the degree of habitat specialization and dispersal capacity of species. |
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