Ecología Austral (Aug 2008)
Spatial structure and scale-dependent microhabitat use of endemic “tapaculos” (Rhinocryptidae) in a temperate forest of southern South America
Abstract
Endemic tapaculo birds (Rhinocryptidae) are biological indicators of habitat degradation in the temperate forest of southern South America, but little is known about the physiognomical features that determine the use of space in natural habitats. We studied the spatial structure and the microhabitat use at different spatial scales of species of tapaculos in a well-conserved forest of NW Patagonia (Argentina). We recorded the abundance of tapaculos and forest characteristics along a 1500 m transect divided in 75, 20 x 20 m contiguous plots. We evaluated the spatial patchiness in abundance of birds by Moran’s I correlograms. We disentangled the spatial variability of bird abundance at three different, progressively finer (broad, intermediate, fine), spatial scales by using Principal Coordinates of Neighbour Matrices analysis (PCNM). We assessed the microhabitat use of each bird species with stepwise regression analyses using habitat physiognomical features as independent variables and bird abundance predicted by PCNM at each spatial scale as dependent variables. The clumps of Scelorchilus rubecula were smaller and more regularly distributed than those of Pteroptochos tarnii. The PCNM analysis detected significant spatial variation at the different scales for both bird species. Microhabitat use was only evident at the broadest spatial scale, but differed between bird species. Scelorchilus rubecula used areas with higher tree cover and woody plant volume but lower abundance of fallen branches, whereas P. tarnii was found mostly in areas of higher abundance of branches but lower woody plant volume and plant species richness. The differences between bird species in the use of space can also be interpreted in terms of differences in body size, family system and feeding behaviour. The management of this temperate forest needs to consider the scale- and species-specific response of endemic tapaculos to habitat features in order to predict their response to the changes in heterogeneity that operate at different spatial scales and are driven by different degradation processes.
