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MARCH 2011 SHORT COMMUNICATION 89
Table 1. European Honey-buzzards and Circus spp.
observed migrating singly and with other individuals,
over the Strait of Messina, Italy, in spring 2004.
European Honey-buzzards SOLITARY IN FLOCKS
Circus spp. n (%) n (%)
266 (3%) 7403 (97%)
416 (33%) 844 (67%)
Figure 1. Observation point for monitoring spring rap- RESULTS
tor migration at the Strait of Messina in southern Italy.
Numbers on map denote locations mentioned in the text: Observers counted a total of 9439 raptors of 16 species.
(1) Strait of Messina (the white dot indicates the location Most were European Honey-buzzards (81.2%), Western
of observations), (2) island of Panarea, (3) island of Us- Marsh Harriers (10.6%) and Black Kites (4.5%). Other
tica, (4) island of Malta, (5) island of Pantelleria, (6) Cap species observed were: Montagu’s Harrier (187 individu-
Bon Promontory, (7) island of Marettimo. als), Pallid Harrier (26), Circus pygargus/macrourus (38),
Northern Harrier (7), Eurasian Buzzard (28), Steppe Buz-
riers (Circus cyaneus), analyzed together due to their simi- zard (Buteo buteo vulpinus; 6), Long-legged Buzzard (Buteo
lar wing morphology and behavior (Kerlinger 1989, Spaar rufinus; 2), Booted Eagle (Hieraaetus pennatus; 12), Short-
and Bruderer 1997, Meyer et al. 2000). The migration of toed Snake-Eagle (Circaetus gallicus; 3), Golden Eagle (Aq-
European Honey-buzzards, the most abundant species ob- uila chrysaetos; 1), Egyptian Vulture (Neophron percnopterus;
served, was also analyzed in relation to wind speed. The 1), Griffon Vulture (Gyps fulvus; 1), Eurasian Sparrowhawk
analysis period was limited to 25 April to 31 May for Euro- (Accipiter nisus; 4), Red Kite (Milvus milvus; 2), Osprey
pean Honey-buzzards, and from 27 March to 22 May for (Pandion haliaetus; 4). In 19 cases it was not possible to
Circus spp., to limit bias due to observations made outside identify the species.
of the migration period.
Flocking Behavior. European Honey-buzzards (n 5
Other researchers have considered the flock as the sam- 7669) migrated mainly in flocks, averaging 13.1 6 0.93
ple unit when counting birds crossing water (Agostini et al. (SE) individuals. Only four flocks were observed that con-
2005, 2007, Panuccio and Agostini 2010). However, in this tained more than one hundred individuals; one flock, on
study, individuals were considered to be the sample unit 11 May, consisted of 506 raptors. In addition, 266 Europe-
(see also Agostini 1992). In fact, the behavior of birds an Honey-buzzards (3.5%) migrated alone.
funnelling through the straits differs from that of raptors
approaching a long water-crossing, because Accipitri- Harriers migrated in smaller flocks, and a higher per-
formes show a stronger tendency to remain together in centage migrated alone (contingency table: x2 5 1585.4, P
front of the water barrier (Kerlinger 1989, Agostini and , 0.001, Table 1). In particular, marsh harriers migrated
Duchi 1994, Agostini et al. 2005, Panuccio and Agostini in small groups averaging 3.5 6 0.2 birds, with the largest
2010). For this reason, the observed flocking behavior flock containing 34 individuals (observed 2 April). A total
was reported below. I used t-tests to compare the mean hour- of 298 individuals (29.7%) migrated alone.
ly passage of raptors under the following conditions: head-
winds and tailwinds, and weak (,25 km/hr) and strong Of the other Circus spp., Montagu’s Harriers migrated
winds (.25 km/hr). Headwinds and tailwinds categories mostly alone (34.5%) or in small flocks of 2–3 individuals
were defined according to previous researches done in the (28.5%). Only two larger flocks were observed: groups of 42
study area (Agostini 1992, Agostini et al. 2007). and 28 individuals seen on 17 and 20 April, respectively. All
Pallid Harriers were observed migrating alone or in pairs.
Finally, Black Kites primarily migrated in small flocks
averaging 3.7 6 0.2 individuals. One hundred four kites
(23.4%) migrated alone.
Movement of raptors at the strait was not homogeneous
throughout the day: all three of the most commonly ob-
served species were less frequent during the first two hours
of the day (European Honey-buzzard (x2 5 1151.2, P ,
0.001), Western Marsh Harrier (x2 5 161.5, P , 0.001)
and Black Kite (x2 5 52.7, P , 0.01).
Migration and Wind Conditions. During the observation
period (excluding rain hours), the prevailing winds were
most frequently from N-NNE (headwind; 325 hr, 56%),
and from WSW-SW-SSW (tailwind; 162 hr, 28%). Wind
from other directions occurred during only 15% of the
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