Tales of the riverbank

Contrary birds, sand martins. As soon as you write about their disappearance they return, flying in the face of the weather. Because it's still cold here - though at least the sun has appeared to celebrate May Day.

There they were, as if they'd never gone away, when I walked through the River Field today. There must have been at least ten of them zigzagging over the water. Tiny brown crescents of movement, they flutter more than fly, reminding me of moths rather than birds. They're much smaller than swallows, with pale bellies and a dun band around their necks connecting the dark bands of their underwings.

The river bank in the field is sandy and eroded, leaving low, crumbling cliffs. Perfect for sand martins to nest in - if they're not washed away. One or two of them were prospecting for likely places to start burrowing, gripping onto the cliff-face with their scratchy little feet that seem too small for their bodies. Every winter the flooding river scours the banks, destroying last year's tunnels, and the sand martins are forced to start the whole laborious business again. The burrows can extend over two feet into the sand, and with just their beaks and feet to dig with progress is slow, perhaps a couple of inches a day.

The Allan Water is a good place to see sand martins, as it gently meanders through arable and pasture land. The air above the fields can sometimes offer rich pickings for these aerial grazers of tiny flies and gnats. Numbers have been good in recent years, after big population crashes in the sixties and eighties. But the crashes were linked to drought in their birds' wintering grounds in the Sahel, not habitat loss here. Don't think 'so not our fault this time' too soon though. Climate change - something we all have an influence on - could make such droughts more frequent, and agricultural 'improvements' over here to make food cheaper for us, threaten to reduce invertebrate numbers on, and above, farmland. Sand martins are on the Amber list, meaning their population trends are causing concern.

So despite them making me eat yesterday's words I was very glad to see them in the field today, ducking and diving defiantly over the river. Will it be the swallows' turn tomorrow to make me look an idiot?