Seasonal changes in bird communities of beech forests in the Cantabrian mountains

Full article

Published:

Volume 40(1), June 1993. Pages 1-11.

Language:

Spanish

Original title:

Evolución estacional de la avifauna en hayedos de la montaña cantábrica

Keywords:

annual community, beech forests, censuses, community structure.

Abstract:

By counting birds along line transects, two to seven monthly censuses were conducted in four beech forests located in central Cantabrian Mountains (North of Spain). Changes in species composition, density and biomass of birds present, as well as trends in structural diversity of the community were analysed. The avian community consisted of 41 species, among which 19 stayed in beech forests nine or more months (residents) and 22 were present for periods of one to eight months. The highest species richness and demographic stability were found in June, while winter brought both the lowest number of species and the lowest density. These two parameters, however, exhibited at that time great local variability mainly because of unequal spread of the three wintering species and the restrictive effect of snow ground cover. Early spring and fall were intermediate periods, when some long distance migrant birds arrived to the forest. Among resident species, there were several considered rare or with limited distribution in Spain (Capercaillie, Goshawk, Black Woodpecker, Marsh Tit, and Treecreeper). Average density of birds and biomass varied from 22 to 61.3 individuals per 10 ha (February and October) and from 0.47 to 3.43 Kg per 10 ha (February-March and October). Changes in these two parameters were parallel and independent of meteorological conditions, but the community's diversity was positively correlated with mild weather. The most abundant birds at any time were residents, and those weighting less than 25 g, with yearly mean densities of 86% and 90%, respectively. Some structural features of beech forests and other Iberian woodland bird communities were examined, raising the conclusion that although quantitative dominance of resident species is a common characteristic to all of them, it was specially intense in the beech forests, where changes in monthly density were, moreover, comparatively small. This fact might indicate a relatively rigid and compact structure of the bird community living in beech forests.