BACK FROM AFRICA - WHOS RUNNING AHEAD - DIFFERENTIAL MIGRATION OF SEX AND AGE CLASSES IN PALEARCTIC-AFRICAN SPRING MIGRANTS

The differential migration of sex and age classes in 16 species of Palearctic-African migrants during their northward spring journey through the Central Mediterranean has been investigated from a large data set collected on 4 Italian islands during the ''Progetto Piccole Isole''. Species investigated were: European Nightjar Caprimulgus europaeus, Barn Swallow Hirundo rustica, Yellow Wagtail Motacilla flava, Common Redstart Phoenicurus phoenicurus, Whinchat Saxicola rubetra, Northern Wheatear Oenanthe oenanthe, Black-eared Wheatear O. hispanica, Subalpine Warbler Sylvia cantillans, Whitethroat S. communis, Blackcap S. atricapilla, Collared Flycatcher Ficedula albicollis, Pied Flycatcher F. hypoleuca, Golden Oriole Oriolus oriolus, Red-backed Shrike Lanius collurio, Woodchat Shrike L. senator, Ortolan Bunting Emberiza hortulana. The seasonal trapping patterns of males and females have been analysed both from the total samples and on a yearly basis. Males have been found passing earlier than females in 14 out of 16 cases, with differences reaching the level of significance in 13 out of 16 species. In the selected species, although the general trapping patterns may vary significantly among years, a temporal gap between males and females remains a fairly constant feature. In a sub-sample of 13 species, adults are found to migrate earlier than yearlings in 18 of 26 cases (significant differences found in 12 cases), with a slightly higher incidence of earlier movements of adult birds in females than males. This strategy seems to be another feature of spring migration, as confirmed by more detailed analyses referred to samples collected on single years and/or sites.