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Migration of Pallid Harrier across the central Mediterranean

                                                                                        Nicolantonio Agostini

                       141. Male Pallid Harrier Circus macrourus, Ustica, off northern Sicily, date unknown.

            perhaps be expected, surprisingly few have been  is relatively high (52.2% overall, 1997-2001),
            recorded, with just sporadic, single-figure  much higher than that at Eilat, where most of
            records (Beaman 1973; Beaman & Jacobsen  the birds are adults and few immatures are
            1974; M. Ozen pers. comm.).            recorded (Shirihai & Christie 1992; Yosef 1996).
               Apart from the spring counts at Eilat,  This may reflect differences on the wintering
            records of Pallid Harriers passing through the  grounds. For example, there seem to be clear
            Middle East in spring are not common, and the  differences in the age ratio of wintering Pallid
            bulk of the records are in autumn – the reverse  Harriers from East to West Africa. Thus, in Tan-
            of the situation in the central Mediterranean.  zania, c. 80% of the birds are adult males
                                                   (Stronach 1991), while observations in Senegal,
            Discussion                             Mauritania and Niger suggest that in these areas
            The Strait of Messina is the most important  there is a high percentage of juveniles (although
            European spring migration flyway for Pallid  fewer individuals in general than in East Africa;
            Harrier, and among the most important in the  K. Meyer pers. comm.). Most birds passing
            entire Western Palearctic. At this site, the  through the central Mediterranean in autumn
            numbers counted in spring have increased in  are juveniles and very few are adults, whereas in
            recent years, and the proportion of adults in the  the Middle East there are many more adults,
            migrant population counted has also increased.  perhaps even a majority (Shirihai et al. 2000).
            Generally speaking, the proportion of young  Like adult Montagu’s Harriers C. pygargus
            birds is an indicator of breeding success and the  (Arroyo & King 1996), most adult Pallid Har-
            general health of a population. A similar decline  riers are actively moulting during autumn
            in the proportion of migrant juvenile Steppe  migration (Forsman 1999; pers. obs.) so they
            Eagles, a species with a comparable breeding  would be expected to avoid long sea-crossings
            range, has been registered in Israel (Shirihai et  such as the Sicilian Channel where possible;
            al. 2000) and perhaps similar factors may be  perhaps most of them prefer to fly across the
            affecting these two species. Nonetheless, in  Middle East en route to the wintering grounds
            2000-02, record numbers were recorded in  in East Africa, and from there some eventually
            several European countries, with a high propor-  move westwards (to wintering grounds from
            tion of juveniles (see table 1), suggesting that  which they head north again in spring, crossing
            the West Palearctic population as a whole is  the central Mediterranean). The moult-related
            currently vibrant.                     hypothesis, that birds prefer to avoid crossing
               There appears to be a clear difference in the  long stretches of water in autumn, would also
            age profile of birds migrating through the  account for the large numbers of Pallid Harriers
            central Mediterranean in spring compared with  recorded in Israel and elsewhere in the Middle
            those moving through the Middle East. The  East in autumn.
            proportion of 2CY birds at the Strait of Messina  The timing of spring passage in the Middle

            British Birds 97 • May 2004 • 238-246                                   245
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