Influencia de la edad del nidal y de la presencia de otras especies sobre las fechas de puesta de la Carraca (Coracias garrulus, L.) en estepas de Extremadura (SO península ibérica)

Resum

Growth of nestling rollers (Coracias garrulus) in steppes of Extremadura (SW lberian peninsula): effect of rainfall
The dynamics of weight and the growth of second primary in nestling rollers was studied over two years in the Serena region. Logistic and Gompertz growth models fitted the mean daily values of the weight and the length of the second primary respectively. In 1990, ayear with standard climatic conditions in the area, the mean weight of the hatchlings was 15.00 ± 6.54 gr (n = 8). Chick weight oscillated around adult weight frorn day 14 onwards. Maximum weight was reached on day 18 (151.25 ± 1.57 gr; n = 8). when a clear weight recession began. The estimated asymptotic weight was higher than adult weight. The second primary appeared on day 3, but could only be rneasured accurately as of day 5 (1.55 ± 0.07 mm; n = 2). The mean length of second primary on the last nesting day was 70.25 ± 13.95 mm (n = 4). Comparing these results with those obtained in an exceptionally rainy year during the pre-laying period a faster increase of weight was detected in the rainy year. However, the length of feathers did not show annual differences in growth rate. We discuss the possible effect of unusual climatic conditions on the growing strategy of rollers.