BACK FROM AFRICA: WHO'S RUNNING AHEAD? ASPECTS OF DIFFERENTIAL MIGRATION OF SEX AND AGE CLASSES IN PALEARCTIC-AFRICAN SPRING MIGRANTS

Summary

Spina F., Massi A., Montemaggiori A. 1994. Back from Africa: who's running ahead? Differential migration of sex and age classes in Palearctic-African spring migrants. Ostrich 65:139-150.

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: Euro Nightjar Caprimulgus europaeus, Barn Swallow Hirundo rustica, Yellow Wagtail Motacill 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 subsample of 13 1 adults are found to migrate earlier than yearlings in 18 or 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.