Ecology and conservation of a diurnal raptor community within a protected area in northwestern Peru

Piana, Renzo Pierluigi (2013) Ecology and conservation of a diurnal raptor community within a protected area in northwestern Peru. Doctoral thesis (PhD), Manchester Metropolitan University.

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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. iii 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.