How Human Constructions Influence the Spatial Distribution of Birds of Prey in Northwest Patagonia?

BARBAR, F.; WERENKRAUT V; MORALES J. M; LAMBERTUCCI, S.A.

Bariloche

Congreso; I Worldwide Raptor Conference; 2013

Human activities affect biological diversity and species distribution patterns in numerous ways. For instance, cities produce physical changes leading to landscape homogenization, and roads cause habitat fragmentation. Both sources of human disturbance modify the availability of resources and generate novel environments where generalist species are often abundant (considered ?winners?), and specialist species tend to be absent (?losers?). We studied the abundance, richness and composition of raptor species, including carrion eaters, generalist hunters and facultative species (families Cathartidae, Accipitridae and Falconidae) in relation to distance to roads and cities. We worked in Northwestern of Patagonia, a region with the highest population growth rate of Argentina, but still with large unpopulated areas. We conducted stationary point counts with a fixed observation radius and time, recording every raptor inside a grid of 22 km by 8 km (77 point counts). We then related the presence of raptors with different distances to sources of human disturbances such as cities, farms, roads, fences and power lines using zero-inflated Poisson regressions. Raptor richness and abundance were positively associated with human environments. Consistent with the ?winner/loser species? hypothesis, these results were driven mostly by a strong association of the medium-size generalist species to human environments. Our data did not suggest negative effects on those species presumably called ?losers?. A possible explanation for this may be the fact that large species (i.e. Andean Condor) need large home-ranges and they could be flying above suboptimal environments to reach areas where human pressure is reduced. Because roads and cities are increasing in Argentina, our results suggest that the structure of raptor communities will change in the immediate future, as species which take advantage of those novel environments increase.