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Factors affecting the abundance of the little bustard Tetrax tetrax : implications for conservation

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Resumo:The little bustard is a grassland bird with more than half of its population concentrated in the Iberian Peninsula. It has declined dramatically over the last decades, mainly due to changes in agricultural practices and is now one of Europe’s most threatened species. Being so reliant on human active management, it is essential to understand the main factors that influence its abundance, from where sound agricultural practices can be identified and reverted into agro-environmental prescriptions. The main objective of this thesis is to analyze these factors along the yearly cycle and at different scales, within a population that still occurs in high densities. At a regional landscape scale it was demonstrated that the highest densities were found in less heterogeneous landscapes with greater availability of continuous grasslands, their preferred breeding habitat, rather than in heterogeneous landscapes with small agricultural fields, as stated in previous works. At the plot scale, female and male habitat preferences, were found to be similar, preferring to occur in larger grassland fields with short vegetation. Male density was found to vary only with grassland field size. Larger grassland fields presented higher levels of vegetation heterogeneity, which possibly favors the occurrence of both males and females, at a micro-habitat scale. During the post-breeding season important population shifts were recorded, due to the abandonment of their breeding grounds towards areas with more productive soils, with greater availability of green plants i.e. food availability. Particularly during the summer season the little bustard was found to avoid grasslands, showing that their habitat preferences vary seasonally. The agricultural system that better fits the little bustard’s habitat needs along the yearly cycle is the extensive cereal farming. Finally, the presence of overhead transmission power lines was identified as a new threat for the species, by creating an avoidance effect, negatively affecting its distribution and abundance.
Autores principais:Silva, João Paulo Campbell Alves da, 1968-
Assunto:Tetrax tetrax Selecção de habitat Reprodução animal Conservação das espécies Teses de doutoramento - 2011
Ano:2010
País:Portugal
Tipo de documento:tese de doutoramento
Tipo de acesso:acesso aberto
Instituição associada:Universidade de Lisboa
Idioma:inglês
Origem:Repositório da Universidade de Lisboa

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