Water reservoirs dynamics do not affect the abundance and productivity of the bearded tit (Panurus biarmicus) in “El Hondo Natural Park” (SE Iberia)

Abstract

Long-term fluctuations of the abundance and productivity of marshland passerines are affected by multiple factors. Water levels fluctuations in man-made wetlands can affect severely the breeding and wintering attempts of highly dependent reed passerines and decrease their abundances simply by dispersal towards better sites. In this work I study if water outputs and inputs in a western Mediterranean coastal semi-arid reservoir “El Hondo Natural Park” do not affect, apparently, the long-term abundances and productivity of the small Spanish endangered population of Bearded Tit Panurusbiarmicus ubicated in it. The watershed parameters analyzed during sixteen years (1992-2007) by a Principal Components Analysis (PCA) show that only two main axes, water inputs (PC1) and outputs (PC2) explained most total variance and were the drivers of the water in the reservoirs. None of the bird’s dynamics indexes were significantly correlated with the axes, so that water dynamics seem have not taken in to account for the fluctuations of this species, but the flooding of thereservoir with output capacity “Embalse de Poniente” could likely influence the annual productivity of this species, due to the negative but unsignificant correlation with PC2. The maintenance of ponds of enough water quantity and quality (e.g. “La Raja”, “Charca Sur”) in the “El Hondo Natural Park” during the nesting periods is fundamental for the preservation of this endangered population. The results indicate that further evaluations of the key biotic and abiotic factors who drive this threatened Bearded Tit’s population in this isolated and endangered man-made wetland are needed.