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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