Ecology and Conservation of a Diurnal Raptor Community Within A
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Ecology and conservation of a diurnal raptor community within a protected area in northwestern Peru Renzo Pierluigi Piana A thesis submitted in partial fulfilment of the requirements of the Manchester Metropolitan University for the degree of Doctor of Philosophy School of Science and the Environment Manchester Metropolitan University January 2013 Abstract ______________________________________________________ Birds of prey are difficult to study and the status and distribution of many species is poorly known. As top predators usually occurring at low densities, raptors may be particularly sensitive to habitat degradation. Conservation of raptors might be vital to prevent further loss of species and ecosystems. Between April and December in 2008 and 2009, raptors and associated habitat data were surveyed using a distance sampling transect method in 70 randomly selected one square kilometre plots in the Cerros de Amotape National Park, the Tumbes National Reserve and buffer areas within the North West Biosphere Reserve in Peru. A total of 1261 detections of 19 diurnal raptor species were recorded. I examined community structure, diversity across land uses and relationships between abundance and niche attributes within species. Abundance and richness were highest outside protected areas and lowest in the national park. A Canonical Correspondence Analysis (CCA) of raptor species and habitat variables ordinated them according to latitude, elevation, percentages of vegetation cover, and, in some cases, individual tree species. I used logistic regressions (GLMs) to obtain habitat distribution models for eleven raptor species. Twenty eight habitat models were obtained and twelve habitat variables were included. Best models included measured percentage of vegetation cover at different strata, elevation and latitude. My findings suggest that vertical structure of forested areas is of particular importance for raptors in extreme northwest Peru. ii Density and population size estimates were calculated for 15 species using distance sampling line transect counts. Densities were stratified by time of detection (morning or afternoon) and by habitat type. Flying birds were included in the analysis. For all but two species, density estimates were higher in the morning than in the afternoon. Absolute density was higher than 1 individual km- 2 for three species and for seven species it lay between 0.34 and 0.86 individuals km-2. Some species showed a marked preference for particular habitat types. I used generalized additive models (GAMs) to examine the relationship between the occurrence of six diurnal raptors and species diversity and abundance to vegetation structure, elevation and cattle „density‟ in 39 km² plots within my study area. Percentage of vegetation cover 5-15 m above the ground was the most important feature influencing the distribution of most species, including the rarer ones. Raptors responded differently to cattle density: Presence of species that foraged in open habitats increased with cattle density, while presence of range restricted or declining species decreased. Conservation efforts of raptors in extreme northwest Peru should also be conducted in areas outside the North West Biosphere Reserve by protecting remaining forests. Moderate cattle densities can benefit some species and help maintain a high raptor diversity in the study area. However, this activity should be strictly monitored so further fragmentation of forests and damage to vegetation structure is significantly reduced particularly inside the Tumbes National Reserve. iii Acknowledgements ______________________________________________________ I would like to express my profound gratitude to Dr. Rick T. Watson and Dr. Hernán Vargas from The Peregrine Fund. Dr. Watson offered me the opportunity to do this PhD and Dr. Vargas provided follow up and support during field work and writing up. The Peregrine Fund provided me with most of the funds required during the whole PhD process. Lloyd Kiff and Travis Rosemberry from The Peregrine Fund Library provided all the articles I requested and this proved vital for getting very specific literature on raptor conservation. I would also like to acknowledge Dr. Stuart Marsden who showed infinite patient during the whole PhD process. Stuart was not only and excellent advisors but a good friend. At MMU, Dr. Alan Fielding, and my colleagues from the Research Office gave assistance, support and company while in Manchester. In Peru, Mr. Virgilio Rueda and Wilson Rueda, guides from the town of Pampas de Hospital, in Tumbes provided guiding and company during long field seasons. Data collection would not have been possible without their help and support. In the field Sebastian Oré and Juan Jose Novoa showed great skills as field assistants. Aldo Durand (from Biosfera Tours), and Jose Antonio Otero (from El Huayco Breeding Centre) also provided help in logistics while conducting field research. Pedro Vásquez, and Fernando Regal from the Centro de Datos para la Conservación Universidad Nacional Agraria-La Molina granted access to excellent literature and insights on dry forest ecology in Peru. iv The Servicio Nacional de Áreas Naturales Protegidas and Aldo Aguirre, chief of the Cerros de Amotape National Park and Tumbes National Reserve issued research permits necessary for field work. Several park rangers in the park and reserve provided company and lodging while in the field. Valeria Biffi was excellent company and help while in the field and in Manchester. Many thanks indeed to all of you. Funds and equipment necessary for the completion of my studies where provided by The Peregrine Fund, Idea Wild, Cleveland Zoological Society, Cleveland Metropark Zoo, Rufford Small Grants, and the Association of Field Ornithologists. Finally I dedicate this thesis to my two little birds: Falco and Laerke Piana Rasmussen. All my love to you. v Contents _______________________________________________________ Abstract…………………………………………………………………………………....i Acknowledgements…………………………………………………………………….iv Contents…………………………………………………………………………………vi List of Tables…………………………………………………………………………….x List of Figures…………………………………………………………………………..xii List of Appendices…………………………………………………………………….xiii Chapter 1: An introduction to tropical raptors: Ecology, status and study .......... 1 1.1 Raptor diversity and distribution ........................................................................................ 1 1.2 Morphology ......................................................................................................................... 2 1.3 Reversed sexual dimorphism .............................................................................................. 3 1.4 Raptor studies ..................................................................................................................... 5 1.5 Habitat ................................................................................................................................. 5 1.6 Migrations ........................................................................................................................... 6 1.7 Hunting ................................................................................................................................ 7 1.8 Diet ...................................................................................................................................... 9 1.9 Breeding ............................................................................................................................ 10 1.10 Communities ................................................................................................................... 11 1.11 Demography .................................................................................................................... 13 1.12 Raptor conservation and threats .................................................................................... 14 1.13 Raptors in Peru ................................................................................................................ 17 1.14 Aims of the PhD and overview and aims of chapters ..................................................... 19 Chapter 2: Tropical dry forests, study area and field methods ......................... 26 2.1 Tropical dry forests ............................................................................................................ 26 2.2 The Tumbesian Centre of Endemism in Peru .................................................................... 26 2.3 Protected areas in extreme northwest Peru ..................................................................... 27 2.4 Study area ......................................................................................................................... 31 2.5 Field methods .................................................................................................................... 35 vi 2.5.1 Raptor surveys and habitat recordings ...................................................................... 35 2.5.2 Habitat evaluations .................................................................................................... 37 Chapter 3: Diversity, community structure and niche characteristics within a diurnal raptor assemblage of northwest Peru ................................................... 41 3.1 Abstract ............................................................................................................................. 41 3.2 Introduction......................................................................................................................