JOURNAL OF AVIAN BIOLOGY 35: 469 /470, 2004
Additional observations of age-dependent migration behaviour in western honey buzzards Pernis apivorus Nicolantonio Agostini
Agostini, N. 2004. Additional observations of age /dependent migration behaviour in western honey buzzards Pernis apivorus. / J. Avian Biol. 35: 469 /470. N. Agostini, Via Carlo Alberto n84, 89046 Marina di Gioiosa Jonica (RC), Italy. E-mail: [email protected]
The western honey buzzard Pernis apivorus is a summer resident in Europe that winters in west-central Equatorial Africa (Cramp and Simmons 1980). Individuals of different ages migrate in different periods. Adults move about two to three weeks earlier than juveniles (Kjelle´n 1992, Agostini and Logozzo 1995). In a recent paper, Hake et al. (2003) reported data on the autumn migration of nine honey buzzards (six adults and three juveniles) from Sweden that were tracked by satellite. The results showed that whereas adults crossed the Mediterranean Sea at the Straits of Gibraltar, juveniles migrated on a broader front and undertook long powered flights ‘‘somewhere’’ over the open sea. Visual observations in the central Mediterranean region clearly showed the existence of different spatial migration patterns between adult and juvenile honey buzzards during post-reproductive movements (Agostini and Logozzo 1997, Agostini et al. 1999, 2000, 2002). Unfortunately, Hake et al. did not quote these sources causing a gap in their work. Here I review these papers in an effort to fill this gap. In the central Mediterranean, adult honey buzzards migrate mainly from late August through early September (Agostini and Logozzo 1995). Here they tend to follow the Italian peninsula and, upon reaching the Straits of Messina between the ‘‘toe’’ of southern Italy and Sicily turn west. Many of them will fly across Sicily, and then southwest across the Sicilian Channel heading towards the Cap Bon peninsula (Agostini and Logozzo 1997, Agostini et al. 2000, Fig. 1). The experienced adult birds probably use the reverse of the spring route (Agostini et al. 1994, Agostini and Logozzo 1998).
Thus Agostini and colleagues concluded that adult honey buzzards apply true navigational abilities, thus avoiding a longer flight across the central Mediterranean, probably to minimize risks and energetic costs (Agostini and Logozzo 1997, Agostini et al. 2000). Only a few juveniles migrate together with adults on this migration route (Agostini et al. 1999, 2000). Most of them arrive at least two weeks later at the coasts of the Mediterranean, typically in all juvenile flocks or alone. Unlike adults, juveniles passing through southern continental Italy after the second week of September take off in southern Sicily and then concentrate over Malta to reach probably Libya, moving along a NE-SW innate axis (Fig. 1, Agostini and Logozzo 1995, Agostini et al. 1999). During their first migration, inexperienced juvenile honey buzzards are not familiar with the shortest route to cross the central Mediterranean and presumably are moving along innate migratory directions. It is interesting to note that observations at the Circeo promontory (central Italy, Fig. 1) and over Malta suggest that at least part of the juveniles crossing the Tyrrhenian Sea change their innate direction of migration in response to the open water (Agostini et al. 2002, see also Agostini et al. 2004). In the case of juvenile honey buzzards Agostini and colleagues (2000, 2002) concluded that these spatial migration patterns may explain why they show a broader front in migration, and why concentrations of juveniles but only a few adults are reported at many islands of the Mediterranean, such as Cabrera, Corsica, Capri, Pianosa, Malta and Cyprus (Frost 1994, Rebassa 1995, Agostini et al.
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Fig. 1. Approximate migratory flyways used by adult (solid arrow) and juvenile (dashed arrow) honey buzzards during autumn migration across the central Mediterranean (CB/Cap Bon peninsula).
1999, Jonze´n and Pettersson 1999, Schmid 2000, Paesani and Politi 2002). Hake et al.’s (2003) work confirms these earlier observations. Acknowledgements / I am grateful to K. Bildstein and to two anonymous referees for their useful comments to an earlier draft of the manuscript.
Agostini, N. and Logozzo, D. 1997. Autumn migration of Accipitriformes through Italy en route to Africa. / Avocetta 21: 174 /179. Agostini, N. and Logozzo, D. 1998. Primi dati sulla migrazione primaverile dei rapaci Accipitriformi sull’isola di Marettimo (Egadi). / Riv. Ital. Orn. 68: 153 /157. Agostini, N., Logozzo, D. and Coleiro, C. 1999. The orientation/navigation hypothesis: an indirect evidence in migrating honey buzzards. / Riv. Ital. Orn. 69: 153 /159. Agostini, N., Logozzo, D. and Panuccio, M. 2000. The island of Marettimo (Italy), important bird area for the autumn migration of raptors. / Avocetta 24: 95 /99. Agostini, N., Malara, G., Neri, F., Mollicone, D. and Melotto, S. 1994. Flight strategies of honey buzzards during spring migration across the central Mediterranean. / Avocetta 18: 73 /76. Agostini, N., Coleiro, C., Corbi, F., Di Lieto, G., Pinos, F. and Panuccio, M. 2002. Water-crossing tendency of juvenile honey buzzards during migration. / Avocetta 26: 41 /43. Agostini, N, Coleiro, C. and Panuccio, M. 2004. Analysis of the autumn migration of juvenile honey buzzards (Pernis apivorus ) across the central Mediterranean. / J. Raptor Res. 38: 283 /286. Cramp, S. and Simmons, K. E. L. 1980. The birds of the western palearctic. Vol. II. / Oxford Univ. Press, Oxford, UK. Frost, R. 1994. Observations of autumn Raptor Migration at Akrotiri salt Lake, Cyprus 19 September-9 October 1992. / RAF Ornithol. Soc. J. 23: 65 /73. Hake, M., Kjelle´n, N. and Alerstam, T. 2003. Age dependent migration strategy in honey buzzards Pernis apivorus tracked by satellite. / Oikos 103: 385 /396. Jonze´n, N. and Pettersson, J. 1999. Autumn migration of raptors on Capri. / Avocetta 23: 65 /72. Kjelle´n, N. 1992. Differential timing of autumn migration between sex and age groups in raptors at Falsterbo, Sweden. / Ornis Scand. 23: 420 /434. Paesani, G. and Politi, P. M. 2002. Monitoraggio della migrazione autunnale deirapaci diurni nell’isola di Pianosa (LI). / Infomigrans 10: 6 /7. Rebassa, M. La migracio` postnupcial de rapinyaires a l’illa de Cabreara: trets generals. / Anuari ornitolo`gic de les Balears 1995. Schmid, H. 2000. Getrennte Wege: Der Herbstzug von juvenilen und adulten Wespenbussarden Pernis apivorus / eine Synthese. / Orn. Beob. 97: 191 /222.
References Agostini, N. and Logozzo, D. 1995. Autumn migration of honey buzzards in southern Italy. / J. Raptor Res. 29: 275 /277.
(Received 23 April 2004, revised 26 July 2004, accepted 29 July 2004.)
JOURNAL OF AVIAN BIOLOGY 35:6 (2004)