Think of a heron. Hunter of the shallows. Hunched, static, by the waterway. Stalking the gravelly banks of the Thames. On the gable end of the house next door, sizing up my newt-filled pond with a gimlet eye. Flying ponderously, a stop-frame animation, legs trailing like a ballerina’s. Always alone.
I thought, if you want to see birds in groups, take a kit of pigeons, circling the weather vane on the school, a murmuration of starlings, billowing like smoke over the hill, a mutation of field fares, filling the beech hangar with their noise, a charm of goldfinches, like a shoal of fish above the estuary, a clamour of rooks and jackdaws, commuting to their roost.
There is a collective noun for herons, a sedge or siege. But grey herons en masse? No, they don’t like company. Breeding season is the only time you see more than one at the same time, when they nest at close quarters in trees.
Or that’s what I thought. But I have seen it happen, more than once, a beautiful and mysterious congregation in a field by the Thames. Always in late autumn and early winter, just after dusk.
A main arterial route out of London, the A316, passes through Richmond-upon-Thames. Travelling south west, the last half mile of road before the River Thames rises on a massive embankment to join the elegant span of Twickenham bridge, opened in 1933.
North of the embankment is the Old Deer Park, a great expanse of grass that once belonged to the Royal estates at Kew. It is municipal land now and there are sports pitches and, near the river, the flood waters can engulf acres for days at a time.
One soggy evening in late autumn, I was cycling home after work along the embankment. It must have been getting on for 5pm. The traffic was heavy both ways under the orange street lamps. I looked out towards the meadow, into the darkness and, what I saw made me laugh aloud in surprise.
Slender figures, like anorexic ghosts, their breasts pale in the gloom beyond the cast sulphurous light. Three of them. No, five. Hah! Ten. No, twenty. Spread out, like socially inept guests at a cocktail party, perhaps five yards separating each from the other.
That was the first time. I saw them many times after. If I cycled steadily past, I got a good view of them – the most I counted was 36 – between the leafless cherry trees on the embankment. If I stopped, they spooked.
What were they doing there? It had to involve food. The rough bank and the mown grass at its base would be teeming with slugs and snails, amphibians and even small rodents. Maybe the street lighting helped them to hunt.
I got in touch with Richard Bullock, Biodiversity Officer of WWT London Wetland Centre at Barnes, to see what he made of it. He said they often migrate at night, so their night vision is likely to be good, but that the artificial light would have helped them out. Grey heron are wide-ranging, opportunistic eaters and invertebrate food can make up a quarter of their diet. He had seen three or four together hunting at night on the playing fields at Barn Elms and so many herons in one place on the Old Deer Park suggested a rich source of food. Mild weather means that invertebrates become more available during the evenings, especially after rain, when earthworms, beetles and other invertebrates come to the surface. The waiting birds (my birds, I thought, stupidly) would be there waiting.
A siege of herons. It did look a bit like a siege, this wan legion standing in formation beyond the walls. I could imagine it taken up in folklore about strange goings on beside the Thames. Not herons, but spirits of the dead, in silent protest against the interminable ravages of the internal combustion engine. Or ghosts of fallen soldiers rising from the scene of a long-forgotten battle. Or witches morphing for an arcane seasonal ritual.
The reality was far more straightforward and more wonderful. Abundant food. Intelligent life. Using a man-made, artificially-lit hill to nab some easy prey. These big, handsome birds, determinedly wild, are somehow making the best of the city – they even breed in colonies in the trees of Regent’s Park, right in the heart of London.
They don’t need us, far from it, but they walk among us, and sometimes, if we’re lucky, we catch them from the corner of our distracted eye.