Thursday, 27 February 2014

A murmuration of starlings

Helen Baczkowska, Conservation Officer

This winter, the County Wildlife Site (CWS) nearest my home has seen a roost of starlings wheeling and flowing across the sky each evening, like smoke in caught in the wind. An hour or so before sunset, small groups of starlings wing their way across the winter tree tops, the numbers slowly growing to several hundred, as more and more groups arrive from the fields and gardens where they have been feeding. Sometimes small groups break away, dart off on a circuit of their own, then return to a flock that one moment spreads out like a streamer, then clusters tightly, constantly twisting and flowing in forms that never quite resemble any nameable shape. As I watch, the birds shoot over my head chattering, with a whisper of wings like soft rain.

Starling roost, photo by Brian Macfarlane
One reason for these circling flypasts, before settling roost in the reeds of the pond, may be the local sparrow hawk. Scientists studying the phenomena of starling murmurations think that the flocking and ever-shifting shapes are largely a response to predation, as targeting one bird out of the mass becomes impossible. Certainly, the sparrow hawk has tried to fly up out of the reeds into the flock, or to fly at them from above, but always seems doomed to failure.

The science of murmurations is incomplete, but researchers have employed sophisticated video analysis and computer modelling to study how the birds achieve the spectacular moving sky patterns. To date, the thinking is that the flock is like a liquid turning to gas, or snow before an avalanche. It is a system poised to tip, with the movement of every part affecting the whole. This is a science closer to physics than biology and the evidence seems to be that each bird reacts to even the smallest movement of the birds closest to them, this movement rippling rapidly through the flock in groups of seven – each bird affecting the seven closest to them. Research continues, for the exact science of how the changes ripple through the flock without accident or confusion remains a mystery.

Flocks of thousands of starlings are known from large reed beds around Britain, with notable winter roosts on the East Anglian coast. Many of the birds will be winter migrants, boosting the numbers of a species that has suffered a dramatic decline in recent decades; long-term monitoring by the British Trust for Ornithology (BTO) shows that starling numbers have fallen by 66 per cent in Britain since the mid-1970s. The roost on the CWS is tiny compared to some, but it demonstrates the value of even small areas of habitat and is a reminder that observing the natural world is vital in informing the management of sites. It would be easy to look at the reed-covered pond as overgrown, but it is the only local pond suitable for a starling roost. If clearance of the ponds is considered in the future, retaining some of the reed will mean there is always a winter roost for the starlings.

Starling in flight, photo by Elizabeth Dack
As evening grows darker, the starlings circle ever closer to the reeds, swooping down close, then rising again, until at last, as if on some unseen signal, they pour into their roost in a single black flow, like dark liquid through a funnel. At first, they are easily unsettled, fluttering and chattering amongst themselves, rising uneasily if I walk too close. In the morning they fill my garden hedge with the fizz and buzz of their song, reminding me that spring is around the corner and that the flock will soon disperse - at least until next winter.

Friday, 21 February 2014

Trinity Broads: February

Eilish Rothney, Warden Trinity Broads

Slavonian grebe on Filby Broad. Photo by Geoff Tibbenham
I stood on the Filby walkway in the sunshine, a cold wind freezing my fingers and making my eyes water, trying to focus my telescope as it judders in the wind. I was looking for a Slavonian grebe which was sheltering and feeding in the calmer waters right at the opposite end of the broad to where I was standing – isn’t that often the way! Slavonian grebes have stunning summer plumage and breed further north in Scotland and Northern Europe. Cold weather can drive them southwards in the winter and their arrival attracts bird watchers to the Trinity Broads. This time of year they have lost their spectacular breeding colours, showing grey-brown above and pale below. Smaller than our great crested grebe and lacking the winter remnant of  crest that these larger birds show, the slavonians have a bright red eye – if you get close enough to see it - which didn't happen today.

We have also had a red head smew and a female scaup, showing well on Ormesby Little Broad and I took a lunch-break with my Monday conservation volunteers last week to sit in the sunshine (yes it is always sunny here!) to enjoy the views. The arrival of these special winter visitors is often a harbinger of harsh weather further north and moving this way, I hear the forecasts of more rain and then snow and my numb fingers witness to dropping temperatures. Many birds come and shelter here for the winter, I can see over 85 shoveller, numerous tufted duck and pochard. A pintail was seen on Sunday along with seven goldeneye (on Rollesby Broad). We have also had regular sightings of bittern and, as well as marsh harriers, buzzard and peregrine have frequented our air-space and perched to survey their kingdom from broadside trees.
To visit Filby and Ormesby Little Broad park at the car park west of Filby Bridge (Acle side) on A1064.

Thursday, 13 February 2014

Species of the month: marsh harrier

Ed Parnell, Norfolk Wildlife Trust

With its impressive four-foot wingspan the marsh harrier is one of the largest and most spectacular birds of prey to be found in Norfolk. 

Marsh harrier, photo by Mark Ollett
The male has distinctive black and grey upperwings, which contrast with their chestnut back; females and young birds are a more uniform chocolate brown, with a creamy head and face. In flight they have a distinctive silhouette, holding their wings in a shallow, streamlined ‘V’.

Winter is an excellent time to see these magnificent birds as they drift languidly across the marshes and reed beds of the coast and Broads, scaring up flocks of waders and ducks in the process. However, given their chequered history, the species’ current relative abundance shouldn’t be taken for granted.

Marsh harriers were widespread in the UK prior to the eighteenth century, but extensive wetland drainage, egg collecting and persecution meant that their numbers fell dramatically and, by the end of the nineteenth century, the species no longer bred in England. Hopes were raised in the 1920s as the Broads were recolonised, but despite spreading into surrounding areas the species declined once again during the 1960s, as a result of poisoning by pesticides such as DDT. By 1971, only one pair remained in the whole of the UK.

Today, the species has made a remarkable comeback with around 450 pairs found across the UK. Around 75 of those are found in Norfolk, many of which are thought to have made their way over from the burgeoning Dutch population. The species now also over-winters in the county in sizeable numbers with the largest gatherings found roosting at NWT Hickling Broad, viewable from a special raised bank at Stubb Mill. Other birds of prey occurring at this site include the smaller and sleeker hen harrier and the merlin (the UK’s smallest falcon), along with almost the entire UK population of common cranes – on a fine winter’s afternoon the Hickling roost offers a spectacular wildlife spectacle. 

Marsh harrier in the Norfolk broads, photo by Mali Halls
To watch marsh harriers in cosier surroundings you could also head to NWT Cley Marshes, where you can usually enjoy great views of the birds gliding low over the reeds from the comfort of the reserve’s panoramic café.

Marsh harriers start to come in to roost from mid-afternoon at Hickling. Park in the NWT Hickling Broad nature reserve car park (NR12 0BW) and follow directions to Stubb Mill. A small charge applies to non-NWT members. NWT Cley Marshes is found just east of Cley village on the A149 coast road (NR25 7SA). There is free parking and entrance to the visitor centre and café, though a small charge applies to adult non-members for entry on to the reserve.

For more stunning images of marsh harriers, please visit our online gallery