Bird diversity and density through a site quality range and canopy gaps in a Nothofagus pumilio forest (Argentine).

LENCINAS MV; MARTINEZ PASTUR G; GALLO E; BUSSO C

Bathurst (Australia), 4-7 December

Conferencia; Australian Ornithological Conference; 2001

Charles Sturt University

Few forest ecosystem studies describe site quality influences over their biotic components. Our objective was to evaluate bird diversity and density in virgin timber forests of Nothofagus pumilio along a site quality range in Tierra del Fuego, and to analyze canopy gaps presence. Sampling was taken in homogeneous stands with complete density in two site qualities (I=27m; V=15m) and within natural gaps. Ninety plots were done, based on a 10-min period (2-min accustoming; 8-min counting), measuring distance and feeding locations (crown, stem, understory). Density was calculated from bird counting observed on the half of maximum measured distance. Thirteen species of five orders were observed, being Passeriforms (83%) and Psittaciforms (14%) the most abundant. Diversity did not vary with site quality (8 species), and there was a little difference with gaps (9 species). Density was similar in high and low sites (10.1 and 9.5 ind/ha), although it was higher in closed forests than in gaps (5 ind/ha). Density used an average distance of 22m. The most visited environments were crowns (82% to 91%), and there was an increased understory use in better quality site. Preference in gaps was similar, except in stem use (16%) over the edge. The sampled species use wide environmental ranges, but some of them prefer humid places (Cinclodes patagonicus or Scytalopus magellanicus) or higher tree canopies (Milvago chimango). Timber forests along a site quality range have the same bird conservation values, but it is necessary to consider the maintenance of gap environments during any forest management planning.