Eurasian Marsh 25.Circus aeruginosus

For the present generations of birders and ornithologists, it is hard to imagine what looked like to previous generations, even as recently as the 1950s. Many wetlands, still in prime condition, had yet to be consumed by relent- less demands for farmland or urban sprawl. It may therefore come as a surprise that the extensive reedbeds of these wetlands harboured very few Eurasian Marsh Harriers, doubtless largely due to the persecution associated with “rational” game preservation, as proposed by Henning Weis (1923) with reference to Denmark, but aptly applicable to much of Europe. Continuous human persecution gave the Marsh Harrier a reputation as a secretive breeding . However, legislation to protect the species during the 20th century did not end covert killing. In The Netherlands, for example, gamekeepers shot and poisoned at least 400 Marsh Harriers in the Noordoostpolder in 1951, where numbers had boomed following its reclamation from the IJsselmeer in 1942 (Bijlsma 1993). Wilful extermination was exacerbated by large-scale cultivation of wetlands, reducing the available nesting habitat, and by the widespread application of persistent pesticides on farmland in the 1950s and 1960s. Marsh Harrier numbers remained at a low ebb in Europe until recently. Our generation is the fi rst in over 100 years to see and hear sky-dancing Marsh Harriers, wherever suitable habitat is available. This higher abundance is likely to be refl ected by higher densities in wintering areas, including the Sahel.

3304 Livvinng onn thee edge Breeding range is precisely what the evidence of 95 recoveries south of the Sahara tells us. Western European winter mostly west of 5°W and The lowlands of Europe, from the polders below sea level in The easterly breeding birds mostly east of 0°E; intermediate breeding Netherlands, northern and western France, the North German Plain populations in winter are distributed mainly between these longi- and Poland eastwards into the Baltic States, Belarus and much of tudes, although overlapping (e.g. in the Inner Niger Delta) consider- Russia, are bespeckled with swamps, marshes and lakes, often ably with the western wintering population. For example, of 35 fringed with dense reedbeds and other herbaceous vegetation. This Marsh Harriers ringed in eastern Germany, 9 were recovered from lowland belt held about 80% of the European population of Eura- Mali and only 3 from Senegal, but of 19 Marsh Harriers ringed in sian Marsh Harrier in 1990-2000 (93 000-140 000 pairs). A country The Netherlands, the reverse was the case: 3 from Mali as opposed like Ukraine, with its large deltas, is equally favoured as breeding to 9 from Senegal. The fact that these populations breed only some ground (13 800-23 600 pairs). North and south of this belt, densities 400-500 km apart, yet are largely separated in their African winter- decrease, except in southern Sweden, which has a sizeable popula- ing grounds, indicates that European breeding birds make seg- tion (1400-1500 pairs) (BirdLife International 2004a). Breeding in mented use of sub-Saharan wetlands. is restricted to Morocco (widespread and common; Thévenot Spring departure from the West African wintering grounds, as et al. 2003), Algeria (several dozen pairs; Isenmann & Moali 2000) shown by satellite tracked Swedish birds, occurred between 11 Feb- and Tunisia (50-70 pairs; Isenmann et al. 2005), which all hold resi- ruary and 17 April for adults (Strandberg et al.2008a). This study dent populations. showed that trans-Saharan migrants crossed the Mediterranean Sea between 18 March and 29 April. The average speed of spring migra- tion was 219 km in males and 233 km in females, only marginally Migration faster than during autumn migration (204 and 221 km respectively). Travel distances of juveniles in autumn were much smaller than of The migratory tendency of Marsh Harriers decreases from north to adults, i.e. on average 146 km (as was their total distance travelled, south, and from east to west across Europe. Breeding birds from Fennoscandia and eastern Europe abandon their breeding haunts completely in early autumn, mostly to winter in sub-Saharan Africa. Wintering is still rare in Germany, but in the (Ol- iver 2005) and The Netherlands (Zijlstra 1987, Clarke et al. 1993) this tendency is quite pronounced. The large population in western France is considered resident (Bavoux et al. 1992) and the same may apply to the small populations in Spain, Portugal (except birds breeding in the north; Rosa et al. 2001) and Italy. The frequency of wintering in western Europe seems to be on the increase in recent years (Oliver 2005), particularly of juveniles (probably mostly fe- males; Clarke et al. 1993). Long-term censuses in The Netherlands show local and temporal variations in wintering numbers, respec- tively peaking in the early 20th century (Zuiderzee; ten Kate 1936), 1977-1982 (Flevoland; Zijlstra 1987), northern Delta (early 1960s, late 1980s and early 1990s; Ouweneel (2008), and southern Delta (in- creasing since 1990s; Castelijns & Castelijns 2008). Harriers, including Marsh Harriers, cross the Mediterranean Sea in a broad front, as implied by the small numbers seen at migratory bottlenecks on either side of the Mediterranean (Bijlsma 1987). Di- rect observations in Italy (Agostini et al. 2003, and references there- in), radar studies on the southern coast of Spain (Meyer et al. 2003) and satellite tracking (Strandberg et al. 2008a) have indeed shown that Marsh Harriers readily crosses the sea, even during twilight and at night, preferably with following winds and under stable weather conditions. With a predominantly southwesterly course from breed- ing grounds towards sub-Saharan Africa (as indicated by ringing re- Fig. 175 European ringing locations of 102 Marsh Harriers recovered in coveries; Fig. 175), some segregation between eastern and western West Africa between 4° and 20°N. From: euring database, except one populations should be detectable in the wintering quarters, which recent recovery from Mali (Wetlands International).

EEuraasian Marsshh Haarrrier CCirrcus aerruginosus 305