So why do starlings form such large flocks in the evening before they roost?
Starlings do this for many reasons: grouping together offers safety in numbers which means they individually protect themselves from predators like the sparrow hawk and peregrine falcon; predators find it hard to target any one bird in the middle of a hypnotising flock of thousands (rather like fish shoals); they also flock to keep warm at night and to exchange information, such as the whereabouts of good feeding areas.
When and where on the Wimpole Estate?
- Autumn roosts usually begin to form in November, though this varies from site to site and some can begin as early as September.
- More and more birds will flock together as the months go on and the number of starlings in a roost can swell to around 100,000 in some places – at Wimpole we have approximately 10,000.
- Early evening, just as the sun is going down, seems to be best, just before dusk. However they can be earlier if the sky is cloudy and the light dimmer.
- They are roosting in the Octagon pond which is full of reeds and drop straight in before spreading out among the reeds, they also make a tremendous noise!
Why are there so many when numbers have been crashing?
Despite the increasing size of the starling flock at Wimpole, starling numbers generally have fallen dramatically over the last few decades. I remember seeing a huge flock in Leicester Square in London and apparently there used to be huge flocks in many cities. I have no idea why they have crashed in and around cities but modern farming practices which have caused the ripping up many permanent pastures, the loss of livestock especially in the shires (once upon a time each parish might have had up to 1000 sheep plus cows and other livestock and certainly in the east these have made way for fields and fields of rape and wheat) and the use of livestock chemicals like wormers but also arable farm insecticides have certainly contributed to the decline. The starling population has fallen by over 80% in recent years, meaning they are now on the critical list of UK birds most at risk.
Here on the Wimpole Estate starling numbers have been increasing year on year especially since the arable in-hand farm went organic. Wimpole also has a large amount of permanent pasture and its own livestock to boot. It is also notable that the arable ley grasslands along with Jacob’s (we call him the flying shepherd, well no, he doesn’t fly himself silly!) South African Dorper sheep that graze these arable leys in the winter months have also seen more and more starlings where there were none.
This is a nice article from the Telegraph by Daniel Butler 23 Feb 2009
‘As the Shropshire sky gradually deepens from yellow to orange and finally angry red, so the noise levels build above the reed beds. A swirling, chattering,flock of starlings swirls above the wetlands of Whixall Moss on the Welsh Border, shimmering dark then light as it drifts like a plume of smoke from some monstrous pyre. Back and forth it twists like an out-of-place tornado before suddenly, when it is almost too dark to see, the flock streams to earth and is gone.
“Numbers build up slowly near the roost over the afternoon as small groups of birds return from foraging in the area,” explains Paul Stancliffe of the British Trust for Ornithology. “By late afternoon there is a huge swirling cloud. It’s all about safety in numbers – none wants to be on the outside, none wants to be first to land.”
A “murmuration” of starlings, as this phenomenon is known, must be one of the most magical, yet underrated, wildlife spectacles on display in winter. Impenetrable as the flock’s movements might seem to the human eye, the underlying maths is comparatively straightforward. Each bird strives to fly as close to its neighbours as possible, instantly copying any changes in speed or direction. As a result, tiny deviations by one bird are magnified and distorted by those surrounding it, creating rippling, swirling patterns. In other words, this is a classic case of mathematical chaos (larger shapes composed of infinitely varied smaller patterns). Whatever the science, however, it is difficult for the observer to think of it as anything other than some vast living entity.
Until recently such sights were common over London. Indeed, in 1949 so many roosted on the hands of Big Ben that they stopped the clock. Sadly, such invasions are a thing of the past, but Rome is currently subject to a vast influx of several million birds each winter. This produces spectacular swarms, but the problems associated with the roosts are not so wondrous. Starling droppings are extremely acidic and the authorities are worried about the damage to ancient ruins, while car owners have to pay out millions of euros for resprays.
The logic behind this spectacular behaviour is simple: survival. Starlings are tasty morsels for peregrines, merlins and sparrowhawks. The answer is to seek safety in numbers, gathering in flocks and with every bird trying to avoid the edge where adept predators can sometimes snatch a victim.
Flock sizes vary around the year. During the breeding season, groups are rarely more than a few birds gathering at a good food source, but in late summer juveniles begin to congregate and are soon joined by adults. These flocks are in turn swollen by continental birds fleeing the harsher winters. During the Seventies a particularly large murmuration of one and a half million birds regularly gathered near Goole in East Yorkshire, but the current flock of around 5,000 at Slimbridge is more typical.
During the day, big flocks disperse into smaller foraging groups. The search for calories is now critical and grouping allows each to put more effort into finding food, safer for scores of watchful eyes. These tend to scour rough pasture for insects, but they punctuate these bouts by preening and chattering in tree tops or on telephone wires where there is good all-round visibility. In late afternoon, however, the smaller groups move back to the main roost, flying up to 20 miles to coalesce in ever-growing numbers. By dusk this murmurating cloud can number thousands or even millions of birds.
Sadly, starlings have recently declined sharply; the breeding population is down by some 73 per cent since 1970. It is not clear what lies behind this fall, but it is probably due to the loss of suitable nest cavities and a decline in the rough pasture where they find most of the insects which form the backbone of their diet.
To put this drop in context, however, a shortage of literary references to the birds before the 18th century suggests they were comparatively uncommon even two centuries ago. Certainly their Welsh name adern y eira (“snow bird”) suggests they were regarded as winter migrants. It seems that they expanded rapidly after the Industrial Revolution, probably aided by milder weather and better food thanks to agricultural improvements.
There is another glimmer of hope. In 1890, an American eccentric, Eugene Schieffelin, decided to introduce all the birds mentioned in Shakespeare to his native land. He released 60 starlings in Central Park and the birds have thrived, spreading as far as the Pacific. There are now 200 million and thus, in years to come, it seems we are as likely to see murmurations over New York as a Shropshire peat bog.’