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Migration of Pallid Harrier across the central Mediterranean

             Fig. 3. The age distribution of Pallid Harriers Circus  Fig. 4. The proportion of males and females
             macrourus recorded in spring (April and May), Strait  among adult (third-calendar-year or older)
             of Messina, southern Italy, 1997-2000 (n=203). Note  Pallid Harriers Circus macrourus recorded in spring
              that % 3CY refers to males only as 3CY females  (April and May), Strait of Messina, southern Italy,
             could not be safely distinguished from older females  1997-2001 (n=160).
               and so have been included in the % adult total.

            were identified positively, but also to the more  extreme difficulty of identification, the separa-
            thorough and systematic survey protocol in  tion of 3CY females from older females was not
            later years. Indeed, an increase in numbers has  attempted. In terms of the sex ratio, 37.5% of
            also been shown by other migrating raptors  the adults were males and 62.5% were females.
            (Corso 2001). Nonetheless, looking simply at  Juveniles were sometimes sexed using iris
            the period 1996-2001, when survey effort and  colour (exceptionally!) or by plumage charac-
            identification expertise would have been fairly  teristics/wing shape, but this is not considered
            constant, a clear increase in numbers is still  further here. A detailed breakdown of the
            evident (fig. 2), suggesting that our data reflect  age/sex composition in each year is given in
            a genuine rise in numbers.             table 1.
               Detailed records of the age and sex composi-  The timing of migration of different age/sex
            tion of migrating Pallid Harriers were made  classes in 1997-2000 is shown in fig. 5. This
            during 1997-2001 (figs. 3 & 4; table 1). In this  shows clearly that, in spring, males migrate
            period, we observed 335 birds, of which 60  earlier than females, while adults tend to
            (17.9%) were adult males, 100 (29.9%) were  migrate earlier than 2CY birds. Similar findings
            adult females and 175 (52.2%) were second-cal-  have been reported for other harriers (Gustin &
            endar-year (2CY) birds. Of the 60 adult males,  Pizzari 1998) and raptors (e.g. Shirihai &
            only seven (11.7%) were identified as being in  Christie 1992, Yosef 1996). There is also some
            their third-calendar-year (3CY). Because of the  variation in timing between years. For example,

              Table 1. Migrant Pallid Harriers Circus macrourus recorded in spring (April and May), Strait of Messina, southern
                     Italy: percentage of males, females and second-calendar-year birds in each year, 1997-2001.
                             Male         Female         2CY            n
             1997            52             20            28            25
             1998             7             31            62            58
             1999            13             41            46            37
             2000            35             34            31            83
             2001             7             26            67           132

            British Birds 97 • May 2004 • 238-246                                   241
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