Determinants of bird species richness: role of climate and vegetation structure at a regional scale

V. R. CUETO; J. LOPEZ DE CASENAVE

JOURNAL OF BIOGEOGRAPHY

Blackwell

Año: 1999 vol. 26 p. 487 - 492

0305-0270

We examined the respective roles of climate and vegetation structure on geographic variation in bird species richness. The Province of Buenos Aires (central-eastern Argentina) was divided into 146 squares of 50 km on a side. For each square we evaluated the number of bird species, the value of 13 climatic variables, and the number of vegetation strata. The climatic matrix was analyzed by Principal Component Analysis (PCA), and the first factors resulting from PCA were considered as multifactorial climatic gradients. Simple and partial correlation analysis among bird species richness, vegetation strata, and the first two factors derived from PCA (65% of total variation) indicated that bird richness distribution was determined by the availability of vegetation strata, associated with different vegetation types that, at the same time, were influenced by the climatic conditions summarized in the first climatic factor (a gradient of precipitation, relative humidity, annual termical amplitude, and frost occurrence). This relationships reflect the complexity of factors that can act directly as well as indirectly on the geographic patterns in species richness. Also, we evaluated the importance of study scale comparing our results with previous studies at macrogeographic and local scales, and we found out that the vegetation structure was the principal determinant of bird species richness at these three geographic scales.