Birdwatch: without ash, wither rooks?

Like black bin bags caught in the tops of the tallest trees in the village, the rooks are back at their rookeries. Here on the Somerset Levels their habit of gathering together to breed makes them one of the most visible of all our birds. That is proving very helpful as I cycle around my parish and beyond to survey rookeries for the British Trust for Ornithology and the Somerset Ornithological Society.

I usually hear rooks before I see them: uttering a volley of guttural cries, noticeably less harsh than their cousin, the carrion crow. As the nature writer Dominic Couzens puts it, a rook sounds like a crow who has been on an anger management course.

What surprises me is that large swathes of the levels have no rookeries at all. I mostly come across them along the main roads, in clumps of ash – by far the tallest tree in this soggy, low-lying landscape. But now that ash dieback disease is ravaging our countryside, their preference for these particular trees could prove to be these birds’ downfall. For, if the ash goes, where else will the rooks find to nest?

The only other widespread tree here on the levels is the willow, whose tightly packed twigs are not suitable for these bulky birds to build their nests. Perhaps in a decade’s time, if I repeat the survey, there will be no rookeries – or rooks – here at all.