It could be just a clod of mud, there, in the green field churned by cows.
We’re on the sea wall looking inland at the most easterly point on the Isle of Sheppey in Kent.
And just to the right of the white thing that could be a broken plastic bottle but before that scattering of dried grass is the smallest bird of prey in the UK.
To the naked eye it is indistinguishable from the clods but unmistakeable through the telescope.
Brown upper parts, about the size of a blackbird, a pale chest with dark vertical streaks and hunched shoulders, with ‘eyebrows’ that meet at the bill. It’s a merlin – either a female or a youngster – and it’s only the second we’ve ever seen.
This part of Sheppey, the marshes that make up Swale National Nature Reserve, is ranked as one of the best sites in the entire south-east for spotting merlins and other wintering raptors.
These are birds of prey that breed in the colder north – of the UK but also further up towards the Arctic – and overwinter here.
The other headline species is the hen harrier – the male an almost regal silver – which is much persecuted by gamekeepers. Short-eared owls are also a possibility and rough-legged buzzards can also appear – but only to the very fortunate.
It is bitingly cold this Sunday morning. The forecast is 6C that, with the wind, will feel like 2C. There are hundreds of brent geese here – neat, compact birds, largely black – that honk and gobble almost turkey-like to each other as they fly overhead in wobbly Vs.
It’s high tide and hundreds of oystercatchers roost huddled together on what’s left of the shore, a mass of black that waits for the sea to peel back from the mud so as to resume digging invertebrate from the sludge.
Beside them, dunlin scrum together – tiny waders that are dull-brown-dun-brown above and white below. And among them are one or two grey plover – although there is nothing ‘grey’ about these pot-bellied, short-billed cousins of lapwings that dazzle like elvish silver when the light falls right upon them.
But it is this merlin we had hoped for. It sits on the ground, bopping its head up and down. Is it looking for prey?
They feed on small birds, such as meadow pipits, often chasing them on the wing. And there are plenty of pipits here, fluttering up from the sea purslane with a ‘tseep’.
The merlin bobs some more then flies low, left, tail briefly fanned. But not for long. No more than a few yards. It lands back among the dried grass and the clods.
It carries out four, five, six more of these short flights. Each time our breath catches – has it picked out a prey? Will we see it in full chase?
After 20 minutes it takes flight again but this time making height, up into the cold air, away up to our left – a silhouette against the grey, flapping on a killer’s wings before soaring down and out of sight into the purslane of the marshes.