THE MAGNITUDE AND TIMING OF MIGRATION BY SOARING RAPTORS, PELICANS AND STORKS OVER ISRAEL

The magnitude and timing of the autumn and spring migrations of 35 spe cies of medium- and large-sized raptors, White Pelicans Pelicanus onoc rotalus and White Storks Ciconia ciconia were studied in Israel. Obser vations were carried out from the ground by a line of observers coveri ng most of the width of Israel across the line of migration and by rad ar. There was a high correlation between the counts obtained by ground observers and by radar, On average, about half a million raptors (mai nly Lesser Spotted Eagles Aquila pomarina, Honey Buzzards Pernis apivo rus and Levant Sparrowhawks Accipiter brevipes), 250,000 White Storks and 70,000 White Pelicans passed during autumn, and about a million ra ptors (mainly Honey Buzzards, Steppe Buzzards Buteo vulpinus, Steppe E agles Aquila nipalensis and Black Kites Milvus migrans) and 450,000 Wh ite Storks passed during spring. Peak numbers were higher-over a milli on raptors and half a million White Storks. There was high interyear v ariation in the number of migrants recorded during the study, probably caused by weather and counting efforts. For some species, the whole w orld (Lesser Spotted Eagle and Levant Sparrowhawk) or Palaearctic (Whi te Pelican) population passes over Israel during migration, allowing a n estimate of the world populations of these species. Mean dates of ar rival of most raptors are highly predictable, with confidence limits r anging between 1.5 and 5.5 days. The migration periods of White Storks and White Pelicans are longer and their mean day of appearance is les s predictable (confidence limits range from 4.2 to 13.8 days), During autumn, 90% of the migrating populations of flocking species, such as Levant Sparrowhawk, Lesser Spotted Eagle, Honey Buzzard and Red-footed Falcon Falco vespertinus, pass within 13, 15, 16 and 18 days, respect ively, while nonflocking species, such as Egyptian Vulture Neophron pe rcnopterus, Marsh Harrier Circus aeruginosus and Short-toed Eagle Circ aetus gallicus, generally take twice as long to pass. Similar passage periods were recorded in spring. For most species, the autumn migratio n period was longer than the spring migration period, probably because in autumn adults move before the young birds. Three factors affected the timing and spread of the migration wave: age at first breeding, di et and size of the breeding area.