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Publication
InfluĂȘncia do pastoreio nas aves do montado
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Advisor(s)
Abstract(s)
O montado Ă© um sistema agro-silvo-pastoril que cobre cerca de 4 milhĂ”es de hectares na PenĂnsula IbĂ©rica e Ă© o tipo de uso do solo mais importante no sul de Portugal. O coberto arbĂłreo Ă© dominado por azinheiras (Quercus rotundifolia) e/ou sobreiros (Quercus suber) e a sua gestĂŁo tradicional baseia-se na agricultura extensiva e pecuĂĄria. Contudo, as prĂĄticas de gestĂŁo estĂŁo a mudar e, por isso, Ă© crucial perceber como Ă© que estas influenciam o montado e a sua avifauna, particularmente as espĂ©cies que se alimentam no solo. Os objectivos deste estudo sĂŁo: (i) identificar as caracterĂsticas do microhabitat que determinam a utilização por aves de locais de alimentação no solo; (ii) determinar o papel do pastoreio na definição dessas caracterĂsticas; (iii) avaliar a influĂȘncia do pastoreio na abundĂąncia de aves em alimentação no solo, e (iv) propor medidas de gestĂŁo do pastoreio no montado, de forma a preservar a diversidade de aves. AnalisĂĄmos qual o efeito de trĂȘs nĂveis de pastoreio por ovelhas â ausĂȘncia, baixa e alta intensidade â nas aves que se alimentam no solo em 12 talhĂ”es. EfectuĂĄmos transectos de contagem de aves em alimentação no solo e utilizĂĄmos modelos lineares generalizados mistos para comparar as suas abundĂąncias nos vĂĄrios talhĂ”es. LocalizĂĄmos com precisĂŁo os locais de alimentação das aves e caracterizĂĄmo-los (altura da vegetação, nĂșmero de invertebrados, excrementos e bolotas, e percentagens de solo nu, solo revolvido e folhas mortas). UtilizĂĄmos modelos logĂsticos condicionais para determinar quais as caracterĂsticas seleccionadas pelas aves. Os resultados mostram que o pastoreio influencia o habitat ao nĂvel do solo e os locais onde as aves se alimentam. Todas as espĂ©cies de aves alimentaram-se em locais em que a altura de vegetação era menor que a mĂ©dia e a maioria preferiu locais com maior abundĂąncia de invertebrados. Contudo, diferentes espĂ©cies tendem a alimentar-se em intensidades de pastoreio distintas e, por isso, Ă© necessĂĄrio manter um mosaico de regimes de pastoreio, para garantir a diversidade de aves e a sua integração com as actividades humanas do montado.
Montado is an agro-silvo-pastoral system that covers about 4 million hectares of the Iberian Peninsula and is the most important land cover in southern Portugal. The tree cover is dominated by holm oaks (Quercus rotundifolia) and/or cork oaks (Quercus suber), and its traditional management involves low intensity agriculture and livestock grazing. Management practices are changing, so it is crucial to understand how they affect montado and its rich bird community, and in particular ground-foraging species. The objectives of our study were to (i) identify the characteristics of the sites chosen by ground-foraging birds; (ii) determine how grazing influences those characteristics; (iii) evaluate the effect of grazing on the abundance of ground-feeding birds, and (iv) propose grazing management strategies to preserve bird diversity in montado. We evaluated the effect of three levels of sheep grazing â no grazing, light and intensive grazing â on birds foraging activity in 12 fenced plots. We did transects to count foraging birds in those plots, and used generalized linear mixed models to compare abundances in the three grazing levels. In addition, we located with precision the sites where birds were observed feeding on the ground and characterized them (vegetation height, abundance of invertebrates, dung and acorns, percentage of bare ground, revolved soil and dead leaves). We used conditional logit models to determine which characteristics are preferred by feeding birds. The results demonstrated that grazing influences the characteristics of the ground level habitat and influences where birds forage. All ground-foraging bird species fed mostly where grassy vegetation height was lower than average and most preferred sites with higher invertebrate abundance. However, different species tend to choose different grazing intensities to forage. Therefore, it is important to maintain a mosaic of grazing regimes, to assure bird diversity and its integration with human activities in montado.
Montado is an agro-silvo-pastoral system that covers about 4 million hectares of the Iberian Peninsula and is the most important land cover in southern Portugal. The tree cover is dominated by holm oaks (Quercus rotundifolia) and/or cork oaks (Quercus suber), and its traditional management involves low intensity agriculture and livestock grazing. Management practices are changing, so it is crucial to understand how they affect montado and its rich bird community, and in particular ground-foraging species. The objectives of our study were to (i) identify the characteristics of the sites chosen by ground-foraging birds; (ii) determine how grazing influences those characteristics; (iii) evaluate the effect of grazing on the abundance of ground-feeding birds, and (iv) propose grazing management strategies to preserve bird diversity in montado. We evaluated the effect of three levels of sheep grazing â no grazing, light and intensive grazing â on birds foraging activity in 12 fenced plots. We did transects to count foraging birds in those plots, and used generalized linear mixed models to compare abundances in the three grazing levels. In addition, we located with precision the sites where birds were observed feeding on the ground and characterized them (vegetation height, abundance of invertebrates, dung and acorns, percentage of bare ground, revolved soil and dead leaves). We used conditional logit models to determine which characteristics are preferred by feeding birds. The results demonstrated that grazing influences the characteristics of the ground level habitat and influences where birds forage. All ground-foraging bird species fed mostly where grassy vegetation height was lower than average and most preferred sites with higher invertebrate abundance. However, different species tend to choose different grazing intensities to forage. Therefore, it is important to maintain a mosaic of grazing regimes, to assure bird diversity and its integration with human activities in montado.
Description
Tese de mestrado. Biologia (Biologia da Conservação). Universidade de Lisboa, Faculdade de CiĂȘncias, 2012
Keywords
PastorĂcia Aves Montado de sobro Conservação da natureza Teses de mestrado - 2012