THE MARSHLAND MIRACLE
Reduced to a single breeding pair in Britain 50 years ago, the marsh harrier is now thriving in its wetland strongholds. Pete Dommett visits Somerset’s Avalon Marshes in spring to witness the raptors’ spectacular airborne courtship display
Its silhouette nicks the sky like a razor; a sharp-cut chevron on a backdrop of blue. Simple, subtle and with just a suggestion of menace.
It is a spring morning on the Somerset Levels, one of the largest lowland wetlands in the UK, and I’m watching a marsh harrier surf the warm air. Its lazy flight – a few slow flaps followed by a long, wavering glide – allows the light to linger on its wings. Silver, black and rusty-red mark it out as a male. Through my binoculars, I can see something small held tight in his talons – a vole or frog perhaps. Then, below him, a female harrier surfaces from a rippling sea of reeds, her dark brown body noticeably bigger. This could get interesting. Half a century ago, an opportunity to glimpse the marsh harrier’s spring courtship would have been an exceptional privilege. In 1971, the marsh harrier was Britain’s rarest breeding bird of prey: just one pair nested at Minsmere in Suffolk that year. The species – along with other raptors, such as the peregrine falcon – had been all but wiped out by the widespread use of agricultural pesticides, including the nowinfamous DDT, which built up in the birds’ bodies. Coming after a century and a half of extensive habitat destruction and relentless persecution, this was very nearly the final nail in the coffin. To avoid extinction as a British breeding bird, the marsh harrier would have to bounce back from this perilous position.
Which, astonishingly, it did. A gradual withdrawal of insidious insecticides, stronger legal protection and the redevelopment of wetland habitats paved the way for a long-term revival. The UK’s breeding population of marsh harriers has almost tripled over the last 25 years and is still on the up; the most recent estimate (published in the journal British Birds in February 2020) puts the figure at between 590 and 695 pairs. The majority of these, at around 70%, are in the east and south-east of England – it’s still the species’ stronghold. However, this bird has recently expanded its range, spreading north to counties such as Cumbria, Northumberland and Aberdeenshire and west to Somerset.
Marsh harriers were West Country birds long ago. Go back thousands of years and these graceful raptors would have been here in the heart of the Levels, then a vast marshy sea. In fact, the UK’s only fossil records found for this species are from Iron Age lake settlements in the area. The marsh harriers later lost their marshland habitat as the land was drained, first for farming and, centuries later, by a rapidly expanding peat industry. The latter – which peaked in the 1960s as the demand for horticultural peat resulted in large-scale extraction – left huge, dark scars across the landscape; these are the Levels that I remember, growing up here in the ’70s and ’80s.
Since then, the abandoned peat workings have been restored to their former wetland glory. The Avalon Marshes – an almostcontiguous collection of national nature
“The harriers lost their habitat as the land was drained, first for farming then for peat extraction”
reserves not far from Glastonbury – is a 1,500hectare patchwork of open water, reed bed, wet meadow and ferny woodland. A diverse habitat such as this attracts a wealth of wildlife.
SPRING SPECTACLE
Visitors flock to RSPB Ham Wall Nature Reserve and nearby Shapwick Heath (managed by Natural England) in mid-winter to watch the starling murmurations. But in spring the reserves really come to life. In April the bitterns are booming, cuckoos are calling and all sorts of warblers, having just flown in from Africa, are making their voices heard. If you’re lucky – as I was a couple of years ago – you might even catch the song of a nightingale, as the smell of the soft black earth pervades the evening air.
Like many casual birders, I’m easily seduced by the elusive and exotic species. Though tricky to spot, bitterns are found here in greater numbers than anywhere else in the country. Great white egrets also breed in the reed beds and are easier to see. These are two of the Avalon Marshes’ ‘big three’ birds, as featured on the reserve’s website. But what of the third? Marsh harriers have nested here regularly since 2009 (with a few sporadic successes prior to that). Today, they breed in good numbers;
2019 was their most successful season so far, with 20 or more young fledged from 17 nests. And they’re starting to expand.
“Marsh harriers are beginning to breed again in other parts of the Somerset Levels,” says Steve Hughes, site manager at Ham Wall. “This suggests that the number of birds in the Avalon Marshes may be reaching capacity and they’re now looking for new areas to nest in.”
As I’ve focused my binoculars elsewhere, the marsh harrier’s presence has quietly grown, something that naturalist and author Stephen Moss, who leads birdwatching tours on the Levels, acknowledges. “People come on our tours to see the starlings, bitterns and egrets,” he told me when I joined him on a walk at Westhay Moor – managed by Somerset Wildlife Trust, of which Stephen is the president – last November. “But they fall in love with marsh harriers in the process. They really have become one of Somerset’s stars.”
Back at the reed bed, romance is definitely in the air. Several times, the male marsh harrier climbs high, turns and then tumbles downwards like a lovestruck lapwing. This dramatic display – evocatively known as
‘skydancing’ – is performed by other harriers and it’s a thrilling bit of theatre. One April, I watched a marsh harrier matinee at Strumpshaw Fen in Norfolk that featured three males all dancing in the same patch of sky.
The climax of this courtship ritual is the famous mid-air food pass – something that I’ve only witnessed once. Or almost witnessed. Three years ago at Ham Wall, my friend James and I saw a pair of marsh harriers approach each other. The male bird held his position in the air with a kite-like tilt of the tail, his legs dangling. Squealing, the female flew beneath him and then, at the last moment, flipped upside down with talons extended. The male let go of his parcel of prey for his prospective partner to promptly... drop. “Butterclaws!” quipped James, beside me.
This breathtaking behaviour is not just for show. By provisioning his mate with prey, the male harrier ensures that she’s in prime condition for egg-laying, which usually begins in late April. And it doesn’t end there. Hidden away on her reed-bed nest, the female relies on food deliveries throughout incubation – which takes 31–38 days – and for the first two weeks after the four or five chicks have hatched. Add in the fact that the male might well be supplying food to another female, for marsh harriers are routinely bigamous, and he’s got his work cut out until well into the summer months.
The items on a marsh harrier’s menu are many and varied. Everything from insects and amphibians to small mammals and the chicks of waterbirds are taken by the male. The female
“Squealing, the female flew beneath him, then flipped upside down with talons extended”
bird, being larger, can target more substantial meals – including moorhens, water rails and wading birds – to feed her growing brood. Once, I saw one struggling to carry what must have been a metre-long grass snake. The marsh harrier’s hunting maxim is ‘low and slow’. It quarters the ground like a barn owl, floating above the reeds on those long, V-shaped wings, looking and listening intently for movement below – their owl-like facial discs assist with this. Surprise is their key to success: they can turn on a sixpence and drop down on to their quarry in an instant.
Until recently, most marsh harriers migrated to north and west Africa at the end of the breeding season. Now, they’re overwintering in the UK in ever-increasing numbers. Visit the East Anglian fens to see tens of birds coming into their communal roosts. In Somerset, the Levels host up to 40 harriers in winter.
Here’s something to celebrate at last: a conservation success story and a bird of prey back where it belongs, on the wetlands of the west. I’m going to make a special effort this year to seek out these captivating raptors and I urge you to do the same. Watching them could seriously improve your spring.