BTO: Why do gulls and other birds follow the plough at this time of year?

Black-headed gull by Tommy Holden/BTO
Black-headed gull by Tommy Holden/BTO

Gulls following the plough is a quintessential autumn scene, but what are they looking for and where do they come from? The BTO’s Graham Appleton explains.

A whole host of species are tuned in to the harvest, from house sparrows and collared doves looking for spilled grain, the last few swallows hunting for insects disturbed by combined harvesters, kestrels hovering over small mammals which have lost their cover and, of course, the birds that are waiting for the plough.

As soon as the earth is turned over, in will come gulls, lapwings, starlings and rooks, with the black-headed gulls almost touching the machinery in order to be first to spot the movement of a worm, beetle or grub. Occasionally a gull will get too close and a clod of earth will slide down to trap its wing.

The term sea-gull is not really appropriate for black-headed gulls, the standard ‘small’ gull that is the commonest one that most of us encounter. Come to think of it ‘black-headed’ is not that helpful either. The species does not have a black head in the winter time and the summer colour is a deep chocolate brown. If you see a truly black head, it’s a Mediterranean gull, but that’s another story.

Although black-headed gulls are found breeding along the coast, they are probably more at home in estuaries and around inland lakes than out at sea.

Typically, they will nest in colonies on small islands and adults will work together to deter predators. These colonies are noisy places from dawn to dusk.

A Suffolk field attracts black-headed gulls from a wide array of countries, especially as autumn turns to winter. Birds from around the Baltic dominate – Latvia, Estonia, Finland, Russia, Poland and Germany – and there are many birds from just across the North Sea and from Scandinavia, too. We know this because, when people find birds carrying rings, they report them to the BTO or directly to the organisations that run ringing in other countries. According to the latest estimates, only 130,000 pairs of black-headed gulls nest in Britain but the winter population swells to 2.2 million.

When not feeding in fields, black-headed gulls join bigger gulls on rubbish tips, steal the bread that is being thrown to ducks or take insects from the filter beds of sewage works.

It’s very much an opportunistic life-style; in wet weather, when worms are active, you’ll see them on playing fields, in the summer they’ll wheel around in the sky, catching flying ants, and they’ll get driven into gardens in the hardest part of the winter.

For the moment, however, a major focus of black-headed gull activity is their pursuit of tractors. If not swirling around in a flock in the wake of the plough, they will be quartering newly-prepared fields or lounging around in flocks waiting for something to happen.