Landscape supplementation in adjacent savannas and its implications for the design of corridors for forest birds in the central Cerrado, Brazil

We examined landscape supplementation (sensu [Oikos 65 (1992) 169]) by forest birds along forest/savanna boundaries in central Brazil to: (1) verify the role of savanna vegetation in providing resources to forest bird communities; (2) suggest minimum amounts of savannas to be conserved within corridors, to provide adequate foraging habitat for forest birds outside reserves. Transect counts parallel (n=64) and perpendicular (n=64) to forests were conducted in eight savannas (cerrado sensu stricto) between February 2000 and January 2001. Patterns of species richness and abundance of birds in relation to distances from forests were examined using Generalised Linear Mixed Models. Omnivores were the most abundant birds foraging in savannas, followed by insectivores and frugivores. Landscape supplementation in savannas was proportional to the density of savanna vegetation. Also, it was higher in the breeding season than in the non-breeding period. These two patterns suggest that surrounding savannas play a major role in providing additional foraging areas for forest bird species. We suggest that the environmental policy currently protecting 20 m of gallery forests along each side of rivers be modified to include at least 60 m of savanna along these forests through central Brazil. The study suggests that appropriate conservation efforts should also encompass the surrounding matrix to which the home ranges of target species are expanded, and not only their major habitat.