Autumn migration of Marsh Harriers (Circus aeruginosus) across the Central Mediterranean in 2002

Abstract

Observations on the autumn migration of the Marsh Harrier were made at two sites of the central Mediterranean: the Circeo promontory (central Italy) and the island of Malta. The aim was to investigate the passage of birds belonging to different sex and age classes. At the Circeo promontory a total of 787 individuals was counted, 37.5% of which were juveniles. Over the island of Malta the passage of 1535 Marsh Harriers was recorded with an evident peak comprising 906 birds on 13 September. At both sites males outnumbered females, mostly within the first half of September. Because, at least among adults, an imbalance towards females has been reported in the population wintering in central Europe, our results suggest that adult males could have a stronger tendency to migrate over a long distance, crossing the central Mediterranean area in large numbers. Whereas females, being larger than males, are able to tolerate colder temperatures and fast longer. Finally, our counts confirm the increase of the European population of the Marsh Harrier, which has occurred for the last three decades.

Migration of the Western Marsh Harrier to the African wintering quarters along the Central Mediterranean flyway: a 5-year study

“…Our results are consistent with previous surveys carried out during a single season in central (Circeo promontory; Agostini et al 2003) and southern Italy (Marcellinara Fig. 1) and confirm that adult birds are observed in larger numbers than juveniles, and that adult males are more frequent than adult females.…”

“…1) and confirm that adult birds are observed in larger numbers than juveniles, and that adult males are more frequent than adult females. This is in accordance with the hypothesis that adult males migrate over a longer distance to the wintering quarters in Africa, while many adult females (Agostini et al 2003) and many juveniles may stay in relatively higher latitudes during the winter (Agostini and Logozzo 2000;Panuccio et al 2005). In particular, age and sex composition of birds recorded in our study was similar to that recorded in previous surveys made in 1996 at the Marcellinara Isthmus (approx.…”

“…The asterisk shows the watchsite individuals after this "correction", weighted by the total number of individuals in each of the seven periods. For example, if 20% of the identified Western Marsh Harriers (after "bias correction") in the last five-day period of September during the 5 years were juveniles, 20% of the unidentified (individuals not identified to a specific age and sex class and not labelled as fem/juv) Western Marsh Harriers in this period were also assumed to be juveniles (see also Agostini and Logozzo 2000;Agostini et al 2003).…”

“…During both spring and autumn, large numbers of Western Marsh Harriers move through the Central Mediterranean flyway where substantial concentrations have been reported at several watchsites, peaking in late March/early April and in September, respectively (Agostini and Panuccio 2010). Previous field surveys made at different watchsites and during specific autumn migrations in 1996 and 2002 have suggested that, among adult Western Marsh Harriers, larger numbers of males head to the wintering quarters in Africa Logozzo 1997, 2000;Agostini et al 2003;Panuccio et al 2005). The aim of this study was to verify these results by analyzing data collected over 5 years.…”

Differential wintering area selection in Eurasian Marsh Harrier (Circus aeruginosus): a ringing recoveries analysis

“…This fits with the results of visual observations carried out in the Mediterranean basin, both at migration bottlenecks and at wintering sites, that showed a stronger tendency for adult male Eurasian Marsh Harriers to migrate over longer distances than adult females, because an imbalance towards males has been observed during migration en route and from Africa, with the opposite trend at wintering sites in Italy (Agostini & Logozzo 2000, Agostini et al 2003, Panuccio et al 2005a, 2005b, 2012, Agostini & Panuccio 2010. It has been suggested that this latitudinal segregation of the sexes is promoted by sexual dimorphism, because females, being larger, are more adept than smaller males in taking larger prey items and coping with colder temperature, on the basis of the Bergman's rule (Cristol et al 1999, Panuccio et al 2005a.…”