RICHARD WILLIAMSON Nature Trails...Swarming oak-rollers provided fine feasting

The dry summers of drought made birds very thirsty on the downs with no water at all along the chalk hills. But it helped nestlings to survive because green oak-roller moth caterpillars (Tortrix viridana) swarmed in June giving some fine feasting for the nestlings.

In the 1976 drought which was far more severe than anything in recent times, Tortrix caterpillars stripped almost every oak tree in the land of all their leaves so that by mid June we had the bare oaks apparently in midwinter outline.

Then all the trees grew a second crop of fresh green leaves at the expense of girth increase. Have a look at the annual rings of felled trees and many will show the 1976 narrow gauge lines.

Tortrix moths are very nice-looking little things with pale green wings and about half an inch in length. They resemble cream-bordered green pea moths but are not related. You can tell those from the oak-roller by the white rear wings and a cream line on the leading edge of the forwings.

We used to see green peas when we were children in the osier willows around the duck decoy on my father’s old farm at Stiffkey in Norfolk. I have a clear memory of feeling as though I was in paradise at the age of six with the willows breaking out in leaf overhead in bright sunshine and then Canadian troops on manoeuvre across the farm firing live rounds from machine guns over my head and the willow leaves falling around me like green rain. It was quite thrilling.

If that happened today I would be able to see the green pea caterpillars rolled inside the leaves as they fell from the trees. As it was, I did notice that marsh tits and blue tits scurried down from the treetops to my own low level while the firing continued ten feet above. We used to see the green pea moths in flight but had not known much of their life history.

This year I guess blue tit hatching will not be so prolific. I have already seen newly-hatched chicks dead in nests due to the heavy rain and lack of feeding potential from their parents.

Blackbirds, robins and song thrushes have done well though because parents can find abundant worms on the wet lawns and leaf mould. Crows have done well because pheasants have abandoned their nests.

If we get a dry spell the frying pan birdbath will again come into its own and I shall enjoy again the sight of crossbills, siskins, bullfinches, goldfinches, black-cap warblers and the rest of the tribe of garden birds that provide such a spectacle outside my kitchen window as I do the washing up.