Something is amiss with the Yare valley rooks

Claxton, Norfolk At Thorpe Hall near Haddiscoe, 340 pairs of rooks once nested, but this spring there is not one

Assessing the rook population in the Yare valley has long been a favourite ritual of my springs. Since the nests are coarse bundles of sticks in the bare treetops it is easy to combine the serious census work with the season's wider pleasures: the sounds of first chiffchaffs or blackcaps, the lemon wings of male brimstone butterflies, and the year's first glamorous colour from primroses, marsh marigolds and walls of blackthorn blossom.

However, by the time I reached the third of my 30 rookeries, I sensed that this year would be different. A site that had once held 100 nests was completely empty. Thereafter, each old place revealed the new story of absence.