Cconsequences of habitat fragmentation on the abundance of Greater Rhea, Rhea americana, in central Argentina.

BELLIS, L.M., M.B.MARTELLA, J.L.NAVARRO, C. DELLAFIORE AND M. DEMARÍA.

Birsbane, Australia.

Congreso; 2nd Southern Hemisphere Ornithological Congress; 2000

Habitat studies should be focused on all scale levels as a requisite for the conservation of threatened species, because the spatial distribution of their populations has considerable influence on their dynamics. The objective of this work was to study how different degrees of fragmentation affect the abundance of populations of Greater Rhea (Rhea americana). We conducted six aerial censuses, from October 1998 to May 1999 in three areas of the Pampas region: a native grassland area in San Luis province and in two agroecosystems of the SE and SW of Córdoba province with different degrees of fragmentation. The SE agroecosystem is characterized by remnant vegetation patches surrounded by a matrix of agricultural land and the other area is highly disturbed with xerophitic wood patches. We flew in a Cessna 182 airplane, at 90 m of altitude and 100 km/h of speed. Rheas were counted in strip transects and the positions of each group of individuals were recorded in a GPS. The estimated density was 1.08 rheas/km2 in the grassland, 0.23 rheas/km2 and 0.04 rheas/km2 in the SW and SE agroecosystems, respectively. These differences were significant (Chi2 = 3202.4, P  < 0.0001). The results show that progressive substitution of native grasslands by crops and cattle raising areas have adversely affected wild populations of rheas, stressing the importance of preserving natural habitats suitable for grassland species.