SAZONAL / BIRDS IN SERIDÓ REGION OF CAATINGA – ON THE PERSISTENCE OF INDIVIDUALS, POPULATIONS AND COMMUNITY IN A SEASONAL TROPICAL ENVIRONMENT
survival, population estimates, seasonal environments, tropical birds, demography.
In seasonal and sometimes unpredictable environments, populations may experience periods of low availability of food resources, influencing individual survival and productivity. Bird populations inhabiting seasonal environments are usually characterized by high productivities that compensate mortality rates from food-shortage periods or seasons. This mechanism of persistence has been established based on bird populations in the northern hemisphere. Harsh seasonal environments are also found in low latitudes, but little is known about population dynamics of birds in tropical seasonal environments. We studied the demography of four insectivorous passerines in the Caatinga, obtaining population estimates and monthly survival probabilities. Additionally, we tested hypotheses about the effect of rainfall, seasonality and a severe drought period on survival rates. The demographic parameters were estimated from mark-recapture-resighting data collected for three years, using Robust Design and Barker’s models. Our results suggest that insectivorous passerines in Caatinga have high monthly survival rates (> 85%) and experience low seasonal variation in these values (< 5%). Fluctuation in population estimates were not related to seasons and the density was highest in shrubby compared to arboreal caatinga. Our estimates represent one of the first efforts to better understand seasonality and unpredictability effects of the Caatinga climate on resident bird populations.