Female marsh harrier

This afternoon Chris and I braved the uncertain weather to go and watch the marsh harriers at King's Dyke nature reserve, a mosaic of wetland and grassland habitats in a disused brick pit at Whittlesey. All seemed fairly quiet when we arrived, but after a moderate trek along slippery clay tracks, we reached the path overlooking the reed-bed where they nest.

It wasn't long before we spotted the first female, who obliged us by flying almost overhead. And then we spotted another...and another! In total there were three pairs in a relatively small area, and we saw and heard plenty of interaction, though a lot of it was too distant to get good photographs (at least with the lenses available to us!) Marsh harriers have the most amazing aerobatic courtship displays, and although we only saw a few brief plunges and pirouetes, it was still breath-taking to watch.The females have brownish plumage with a pale head - this one also had quite a few pale feathers on her back, suggesting that she is a mature bird. The males are a little smaller and have tri-coloured plumage of grey, brown and black.

Like the red kite, the marsh harrier is a conservation success story. Before the 19th century harrier species were not separated in the field, but marsh harriers probably bred in many English and Welsh counties and throughout Ireland. Drainage of its reedbed habitat reduced its numbers considerably. By the 1870s habitat loss and persecution had restricted this species to Northumberland and Norfolk. At this time it was extinct in Northern Ireland, though still present in small numbers in Eire. By the end of the century it had entirely disappeared from the UK.

Odd nests were recorded between 1911 and the mid-1920s and by the 1930s it was breeding every year in Norfolk and Suffolk; by the '40s there were five pairs and by the '60s 15 pairs. Its expansion was slowed by persistent pesticides, but continued once they were withdrawn. Certainly it was considered a very rare breeding bird when I first became involved in nature conservation in the mid-1980's. I went on a study trip to the Netherlands and was amazed to see marsh harriers everywhere! These continental birds re-colonised eastern England, and the provision of more suitable habitat and a reduction in persecution has allowed numbers to grow, so that there are now probably in excess of 400 breeding pairs.

The main population is in East Anglia and Lincolnshire, but it is now also established on the north Kent coast, the Somerset Levels and in Lancashire. They usually nest on the ground in reedbeds and increasingly in maize crops. Diet is varied depending on prey availability. Small mammals, birds and their nestlings are most common, while amphibians, reptiles, insects and carrion are also taken. When hunting they fly low and depend on surprising their prey. King's Dyke nature reserve is situated next to the Nene Washes, a Special Protection Area for rare breeding waders. There is an interesting quandary here: the harriers predate the chicks of some of these waders, including those of the very rare black-tailed godwit, and Natural England have requested that no further reed bed habitat is created within the Whittlesey brick-pits to control harrier numbers locally!