Occurrence and Habitat Associations of Diurnal Raptors Along the Bio-Bio River, Chile

Publication Date

12-1994

Type of Culminating Activity

Thesis

Degree Title

Master of Science in Raptor Biology

Department Filter

Biology

Department

Biology

Supervisory Committee Chair

Tom J. Cade

Abstract

The biodiversity of the Bio-Bio River ecosystem is under imminent threat from a plan to build a series of six hydroelectric dams over the next decade. The purpose of this project was to survey pre-dam diurnal raptor species presence and habitat use along the Bio-Bio River corridor. My objectives were to: 1) establish areas of local species occurrence; 2) compare species abundance, richness and diversity in selected habitats; and 3) examine patterns of habitat association; and 4) provide baseline data for future ecological monitoring. The survey comprised an opportunistic, downriver, boat-based survey, and a terrestrial, limited distance point-circle count at selected study sites in the 165-km transect along the Bio-Bio River. Observations during the ten survey trips (1992-1993) produced an overall count of 12 diurnal raptor species and 419 individuals, with 255 individuals observed during the downriver survey, and 164 individuals observed during the terrestrial point-count survey. The highest species abundance occurred during the downriver survey (255), while the highest species richness index was recorded during the terrestrial point-circle count (12) survey. Species diversity varied between the two methods with mean values of (H’=1.90, H’=2.05) for the downriver and terrestrial circle-point count, respectively. Along an environmental gradient, the most productive habitats for species abundance are located between river km 100-140. The most productive habitat for species richness, abundance, and diversity in the downriver survey was located in disturbed areas, whereas Nothofagus woodland supported the highest indices in the terrestrial circle-point count survey. Andean Condor, Peregrine Falcon, and Bicolored Hawk may function as individual indicator species or as a guild of habitat specialists that could be used to monitor environmental change along the Bio-Bio River corridor.

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