Non-coincident altitudinal distribution of bird and bat species richness in a Mediterranean mountain range: patterns and prospects
Elena Tena and José Luis Tellería (under review)
We analysed the distribution of bird and bat species richness in a Mediterranean mountain range (Sierra de Guadarrama, Spain) by counting the number of species detected in sampling points (species density). We observed that bird richness had the highest scores at mid elevations while bat richness increased monotonically with altitude. Bird and bat richness were positively related to net primary productivity but decreased and increased, respectively, with woodland cover. In addition, bird richness tracked habitat complexity and shrub richness, while bat richness did not track these fine-grained habitat traits. These patterns could be related to the different spatial scales of habitat use, since most birds move within small home ranges and many bats fly many km away from breeding sites in search of the most productive areas. These results are used to outlook the potential effect of climate and habitat change on species richness in the Sierra de Guadarrama and to discuss the difficulties of monitoring bird and bat assemblages.
Figura: Distribution of bird and bat species density along the elevation gradient of the Sierra de Guadarrama
Figure: Relationship between nodf scores (Nestedness metric based on Overlap and Decreasing Fill) and the mean distance to the Strait of Gibraltar of the species range.
Loss of forest bird richness in the south-western border of the Palaearctic
Roberto Carbonell. Ricardo Hernández-Lambraño, José Luis Tellería (in preparation)
We studied the distribution of species richness and abundance of forest birds in the south-western border of the Palaearctic (Morocco, Maghreb). To do this, we counted birds along transects in forests distributed north to south and tested the potential effect of location and habitat suitability (forest cover, productivity and habitat complexity) on species richness and abundance. Results showed that species richness and abundance reduced from north to south and were positively related to habitat suitability. Other variables, as distance to Atlas mountains (a tree covered area) or shrub species richness, reported less influence. In addition, we observed a nested pattern of species loss within this geographical setting, which was mainly related to the geographical location of sampled forests.