Bird responses to landscape heterogeneity in highland mountain forests of central Argentina

13. BELLIS, L. M. A. PIDGEON , C. ALCÁNTARA CONCEPCIÓN, L. HEIL AND V. RADELOFF.

Congreso; 25th International Ornithological Congress,; 2010

Polylepis forest is of particular international concern because its extraordinary biodiversity and high levels of endemic species. To date, the uneven and dwindling distribution as well as forest degradation is worrying and has particular importance on bird conservation. We took a landscape-scale approach to analyzed the relationships between avifauna and landscape features in Polylepis australis fragments of central Argentina with different degrees of degradation: forest and shrubland. Bird data were collected in woodlands (n = 105) and shrublands (n= 67) using 10-min point counts located 150 m apart. Vegetation characteristics were estimated from a Landsat 5 TM image. We calculated NDVI as a measure of plant productivity and volume and 4 texture measures (mean, contrast, homogeneity and uniformity) to characterize differences in vegetation distribution among patches. Also, we calculated 2 fragmentation measures (patch area and connectivity) and 3 variables indicatives of human disturbance: proportion of eroded land (as an indicator of long-term soil loss) and distances to roads and human settlements (as an indicator of long-term livestock impact). We tested bird-habitat relationship for overall bird species and for selected guilds using logistic regression. Bird richness was negatively related with elevation and erosion (Nagelkerke’s R2 = 55 %). Avian assemblages were dominated by disturbance-tolerant species, i.e. species that use edges and open lands. Occurrence of disturbance-sensitive species was determined by the forest presence and connectivity (Nagelkerke’s R2 = 48 %) while disturbance-tolerant species were only related to connectivity of Polylepis fragments (Nagelkerke’s R2 = 61%). We concluded that in P. australis forest of central Argentina the long-lasting human impact is contributing to a homogenization of regional avifauna toward species resilient to human disturbance.