Counts In Israel

Israel lies near the east end of the Mediterranean Sea, at the junction of the Eurasian and African land masses. In consequence, most of the species that breed in Eurasia and winter in Africa pass through Israel, some in very large numbers (Figure 7.5, Table 7.3). The Rift Valley runs roughly north-south through the length of Israel and Jordan, creating optimal conditions for rising updrafts and thermals. It is narrow in this region, and the fault escarpment reaches altitudes of hundreds of metres. This combination of steep cliffs cut by narrow gorges creating updrafts, and high average temperatures creating thermals in the valley, provide an ideal route. In addition, Israel's central mountain ridge stretches almost parallel to the Mediterranean coast, and fairly close to it, providing further good conditions for migrating raptors.

Three main migration tracks for soaring birds run through Israel (Figure 7.5). Two extend mainly along the western and eastern sides of the central mountain chain (the latter along the Jordan Rift Valley) and the third cuts across the southern end of the country in a northeast-southwest direction between Jordan and Sinai through Eilat (Leshem & Yom-Tov 1998). The birds using these routes cross to and from Africa via the Gulf of Suez, mostly at its northern or southern ends. Further east, as mentioned earlier, another flyway runs across the Arabian peninsula, crossing to Africa at the narrow Bab el Mandeb Straits at the southern end of the Red Sea (the so-called Caspian-Arabian route, Alon et al. 2004). By these various routes, the birds use the shortest water crossings and avoid the wider parts of the Red Sea. The actual positions of the migration streams shift east or west to some extent during the course of each day, as well as from one day to the next,

Spring

Spring

Autumn

Figure 7.5 Main migration routes for soaring birds through the Middle East, autumn and spring (left), and through Israel alone (right); the western route -over the western slopes of Israel's central mountain spine; the eastern route - mainly along the Jordan (Rift) Valley, continuing south during most of the day, but crossing to join the western route during part of the day; the Eilat mountain route - crosses southern Israel in the region of the Eilat Mountains, running northeast-southwest through Jordan and Sinai. From Leshem & Bahat (1999).

Figure 7.5 Main migration routes for soaring birds through the Middle East, autumn and spring (left), and through Israel alone (right); the western route -over the western slopes of Israel's central mountain spine; the eastern route - mainly along the Jordan (Rift) Valley, continuing south during most of the day, but crossing to join the western route during part of the day; the Eilat mountain route - crosses southern Israel in the region of the Eilat Mountains, running northeast-southwest through Jordan and Sinai. From Leshem & Bahat (1999).

and from the early to the later part of each season, as wind and other conditions change. In autumn, birds enter northern Israel on a single narrow route, with 87% of all soaring birds encountered within a 20-km-wide strip, some 11-31 km in from the Mediterranean coast. For reasons not fully understood, some species fly along routes to the east or west of others. Surveillance radar photographs show long lines of thousands of soaring migrants progressing south-southwest parallel to the coast, moving inland with the sea breeze during the course of the day (Leshem & Yom-Tov 1998).

Over several years from the early 1980s, attempts were made to count the numbers of soaring birds passing through Israel on each day of the migration season in autumn (August-November) and spring (March-May) (Leshem & Yom-Tov 1996a, Shirihai et al. 2000, Alon et al. 2004). Because many birds take somewhat different routes at the two seasons, different sites were used for counting in autumn and spring, by groups of observers spaced 2-3 km apart across the migration route. Although not every passing raptor is likely to have been counted, the volume of the migration, as assessed each day by these ground observers, was correlated with the volume of migration as assessed on the same days by radar (in autumn, r2 = 0.66, P < 0.001). This correlation indicated the general reliability of ground counts for large soaring birds that in this region move mainly within visual range.

The resulting counts were some of the most thorough and complete ever made of soaring bird migration, involving 35 species (Table 7.3). On average, about half a million raptors (mainly Lesser Spotted Eagles Aquila pomarina, Western Honey Buzzards Pernis apivorus and Levant Sparrowhawks Accipiter brevipes) passed through northern Israel each autumn, as did 250 000 White Storks Ciconia ciconia and 70 000 Great White Pelicans Pelecanus onocrotalus. In the spring in southern Israel, about a million raptors (mainly Western Honey Buzzards Pernis apivorus, Steppe Buzzards Buteo b. vulpinus, Steppe Eagles Aquila nipalensis and Black Kites Milvus migrans) passed northeast, plus about 450 000 White Storks. Only Steppe Eagles, which use breeding areas further to the east than the other species, used the southern (Eilat) route in large numbers in both autumn and spring. The whole Eurasian populations of Lesser Spotted Eagles, Levant Sparrowhawks and Great White Pelicans are thought to pass through Israel each year. For the two raptors, this represents the entire global population.

The totals of each species seen in autumn or spring varied greatly from year to year, depending partly on wind conditions (which sometimes pushed birds off their normal route), altitude of flight (which sometimes put birds beyond the visual range of ground-based observers), and probably also on the numbers and experience of observers (Table 7.3). Overall, however, the counts indicated that around half as many soaring raptors pass through Israel each autumn as in spring. The seasonal difference arose largely because the majority of Black Kites, Steppe Buzzards and Steppe Eagles missed Israel in autumn and took more easterly routes, as shown by counts elsewhere (Table 7.4). The counts for Western Honey Buzzards alone in spring 1985 exceeded 851 000 individuals, with up to 145 000 seen on a single day (at Eilat on 6 May 1985).

The timing and duration of passage varied between species (Table 7.6), but within each species both autumn and spring peak dates were remarkably consistent from year to year. The confidence intervals of the mean dates of appearance for raptors in different autumns ranged between 1.5 and 5.5 days, depending on species, whereas for White Stork Ciconia ciconia and Great White Pelican Pelecanus onocrotalus they were 4.2 and 13.8 days respectively, reflecting the fewer years of data and the longer and more variable migration periods of these species. The equivalent confidence intervals for spring migration were 2.1-5.5 days for raptors and 6.1 days for White Storks.

Table 7.6 Timing of passage of migrants through Israel, spring and autumn. Only species with the largest totals at each season are shown

Species

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