Efecte dels murs de pedra seca en la recolonització d'una àrea cremada pels ocells

Abstract

The scarcity of refuges in a recently burned area can make it difficult for some species of birds to recolonize the territory after the fire, especially for birds with a preference for closed habitats, such as scrubs or forests. In this sense, a structure such as dry stone walls, so typical of Mediterranean landscapes and linked to ancient vineyards, may be important for birds due to their ecological functions and because they may be an alternative refuge for some species. This study analyzes the effect of dry stone walls on the recolonization of the area burned by the Llançà fire of July 2021 by birds. The pre-existing habitat before the fire was scrub, a habitat that retains very little structure after a severe fire like this, unlike a forest. Therefore, the shortage of shelters is likely to be greater. There are no previous studies focused on the ecological functions of dry stone walls in relation to birds, however they do exist with other faunal groups, although they are scarce. Giving value dry stone is important for its conservation in the face of the progressive deterioration it has been suffered for years. To carry out the study, bird censuses have been carried out at different sampling stations distributed throughout the burned area and densities of stone walls have been obtained. Other environmental variables have also been measured, such as the slope and orientation of the land, the severity of the fire and the presence of patches of unburned vegetation. The results obtained do not seem to show a clear relationship between the stone walls and the birds and a high percentage of unexplained variability has been obtained. New variables should be included in the study, such as the characterization of the habitat associated with the stone wall, as well as expanding the temporal and spatial scale to include a greater number of bird species in different postfire scenarios. Although rupicolous species could be considered good candidates for using stone walls to nest or take refuge because of their similarity to the preferred natural habitat of these birds, only two of these species (the blue rock thrush Monticola solitarius and the black redstart Phoenicurus ochruros) have appeared in the study area and, in addition, the results do not indicate that this hypothesis is fulfilled. On the other hand, the community of registered birds is quite heterogeneous with regard to the habitat preference of the species. The area burned less than a year ago offers patches of unburned vegetation, regrown trees, and a high density of herbaceous plants that seem to cover the needs of species in open spaces, thickets, and semi-forest spaces with scattered trees and shrub cover