It is wonderful to walk down the lane on to the marsh and see how, despite April’s refrigerated interlude, spring is building still. In some cases, this is literally true, not just the hawthorn hedges, which are fattening up with fresh leaves and blossom, but also the jackdaws, whichjourney back and forth with great gobbets of moss and cattle hair in their beaks. Some are so front-loaded with construction materials that one wonders how they see to navigate.

Corvids are generally great architects, and once the instinct has been unleashed it is remarkable how lavish their designs can be. The standard rook nest is a rough 15cm-deep stick platform, but recently I have come across some where the foundations are in a deeply forked situation. They have gone on until these twisting columns of sticks, which are known as “castles”’, are more than a metre tall.



In his book Birds and Man, WH Hudson tells a great story about cathedral-going jackdaws at Wells, Somerset. He claimed that some of them were hoisting up two-metre sticks and then dropping them, only to return and start again. Much as I love the man I find it hard to believe that the bird could manage what would be a relative tree trunk for the species. Yet it is certainly true that one belfry-dwelling jackdaw pair in Gloucestershire assembled a nest that was 2.5 metres in height and diameter.



More moving still are the ways in which birds can develop their building works through time. There are gyr falcons in Greenland whose nests have been renewed for so long that they have massive guano deposits in the footings. The carbon dating of some of this debris suggests that the oldest have been continuously occupied for 2,500 years.



Occasionally this avian fidelity to place acquires cultural significance. There is a steep cliff ledge in Cressbrook Dale, Derbyshire, called Ravencliffe Cave, presumably for its long occupancy. When ravens returned to the region after a manmade absence of more than a century and a half, among the first sites that they nested was on the old ledge named after their ancestors.

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