Original Title: Estudio comparado de los principales parÁmetros reproductivos de Passer hispaniolensis y Passer domesticus en España centro-occidental
Summary:
This study presents a comparative analysis of some basic reproductive parameters of the Spanish sparrow and the Rouse sparrow in Iberia. The dates for the initiation of the first clutches are nearly identical in both species. For both the interval between the laying of the first egg in two consecutive successful clutches is longer, the mean number of clutches per nest-season higher, but the synchronization is lower in the House sparrow. Therefore, the breeding season lasts longer for the House sparrow. The mean clucth size is 4.997 eggs in the Spanish sparrow and 4.87 eggs in the House sparrow, but the seasonal variation patterns of this parameter are very similar in both species. Losses of eggs are 31 .4 % in the Spanish sparrow and 25 % in the House sparrow, and nestling mortalities 47.8 % and 35.9 % respectively, the difference owing to the higher percentage of nest destruction and desertion in the former species as a consequence of their higher vulnerability. However, losses of eggs in successful clutches are higher to the House sparrow. The mean number of fledged young per successful nesting is 3.1 in both species, but the productivity is higher in the House sparrow (4.71 young fledged per nest-season) than in the Spanish sparrow (2.36). In addition, several aspects of the biology of the Spanish sparrow that may reduce the mortality rate in adults and juveniles are mentioned, and the relationships between the reproductive strategies of both species and the different environmental stabilities of their nesting babitats are discussed.
