June target bird: Marsh Harrier

The largest of Britain’s harriers, Marsh Harrier can be seen throughout the year, often quartering low over reedbeds or arable fields. In spring and autumn it is possible to encounter migrants well inland, often soaring high.

The species breeds as far north as Finland and as far south as North Africa, extending eastwards to Central Asia. There are two subspecies: aeruginosus breeding in Europe across to Central Asia and harterti found in north-west Africa. East Asian birds are now generally treated as a separate species, Eastern Marsh Harrier Circus spilonotus, with the western species more correctly referred to as Western Marsh Harrier.

Once nearly lost as a breeding bird in Britain, it was absent from much of England during the 19th century and a large part of the 20th, with only occasional breeding noted. Persecution and the effects of pesticides were two of the biggest factors in the species’ disappearance. In 1971 just one pair remained, at Minsmere in Suffolk. Then a recovery began, probably fuelled by successful breeding in The Netherlands. By the 1990s numbers had increased to more than 100 females and this had almost doubled by the year 2000.

In Britain, most breeding birds are found in eastern England, with East Anglia still an obvious stronghold. However, birds are increasingly being seen in the North-West and South-West. The population, measured largely as breeding females, rather than pairs, was between 387 and 423 in 2007, according to the Rare Breeding Birds Panel, and may now be at least 450 pairs.

Only a handful of pairs breed in Scotland, mainly in southern and eastern areas. Although the species was once found in large reedbeds in Ireland, it is now only a scarce visitor there, although a pair bred in Northern Ireland in 2009. It is a scarce passage migrant and winter visitor to Wales, and while none breed, there was a nesting attempt in 2000.

The northern and eastern European populations are migratory, wintering from the Mediterranean south to central and southern Africa. Western Asian birds migrate down to the Nile Valley and East Africa. British birds are partial migrants, with some overwintering; migrants probably depart in September and October, moving south through France and Spain, on to north-west Africa and perhaps as far south as the Equator.

Most of the migrants appear to be males, with many of the overwintering birds being the larger females. By March the majority of wintering birds have left West Africa, and they usually arrive at breeding sites around the beginning of April.

Marsh Harrier usually migrates singly, while during the breeding season it can nest in small concentrations. A male will sometimes have two or more mates and the display between a pair involves ‘sky dancing’ and spectacular aerial food passes. Outside the breeding season groups can be seen at roosts, with 36 at one East Anglian reedbed in September and gatherings as large as 300 birds in its winter range. Because of its localised breeding, Marsh Harrier is amber listed as a bird of conservation concern in Britain.

How to see
In summer, Marsh Harriers are found in their traditional breeding areas, many of which are on nature reserves with reedbeds and marshes, but it is increasingly found on arable farmland close to wetlands. As a Schedule One bird, Marsh Harrier is specially protected on its breeding grounds, so the best way to see one is to visit an official watchpoint; visit the RSPB website for details. It is best found in flight, but may be picked up perched on a tree or bush.

Where to watch
Most of the sites below are breeding locations on nature reserves, but migrant birds can be seen in south coastal counties in spring and autumn.

England
• Lancashire: Leighton Moss RSPB
(SD 478750)
• East Yorkshire: Blacktoft Sands RSPB (SE 843232)
• Lincolnshire: Frampton Marsh RSPB (TF 356392)
• Cambridgeshire: Nene Washes RSPB (TL 318991) and Wicken Fen NT
(TL 562705)
• Norfolk: Titchwell Marsh RSPB
(TF 750438) and Strumpshaw Fen RSPB (TG 341065)
• Suffolk: Minsmere RSPB (TM 473672)
• Essex: Old Hall Marshes RSPB
(TL 959122)
• Kent: Stodmarsh NNR (TR 220609) and Elmley RSPB (TQ 937678)
• Dorset: Arne RSPB (SY 971876)

Scotland
• Perth and Kinross: Tay reedbeds
(NO 253215)
• Angus: Loch of Kinnordy RSPB
(NO 361539)