I would like to be able to report the exact number of nests, but as the car driver, that would not have been a safe survey to conduct.
However, the snapshot imprinted on my mind left the distinct impression that the nests were high in the branches, which is an important point for those who believe country folklore. The higher that rooks nest in spring, the better will be the weather of an ensuing summer, it is said, but if the birds build their nests lower down then you can expect the summer to be dull and dreary. The main problem with this, however, is that rooks habitually repair and re-use the nests they occupied the previous year.
In rural Yorkshire, where the bird is often referred to simply as the “craw”, there is another weather-related superstition: when they are seen perching on the dead branches of a tree it is held to be a sign of imminent rain.
There are many fine rookeries in the region, my favourite one being in Coverdale, where it is a quite overwhelming experience to stand beneath the trees listening to the very loud cawing from a couple of hundred birds in the branches overhead. Early spring, before leaves obscure both birds and nests, is the best time to do this.
There was a fashion in Victorian times to build large houses surrounded by tall deciduous trees, which were colonised by rooks so that, later, the name of the house was changed to The Rookery. A decent-sized rookery will contain up to 40 nests, so the cacophony of calls and beating of wings against leaves - particularly in spring and early summer - must have made sleep nigh impossible after the first glimmers of dawn.
A measure of just how common these large, gregarious crows have become was shown by a British Trust for Ornithology census finding of nearly 1,900 rookeries containing 63,000 nests in Yorkshire.
One collective noun for the birds is “a parliament of rooks”, although I haven’t been able to discover its origin. In winter they form huge flocks with jackdaws at dusk, prior to flying off to a communal roost, and I was once almost deafened by them in a field outside Beverley.
It was to keep rooks off newly sown crops that farmers first came up with the idea of the scarecrow. Centuries ago some people actually worked as “crowkeepers” - Shakespeare’s Lear refers to someone who “handles his bow like a crowkeeper” - and Thomas Hardy’s young Jude was hired to frighten crows.
Today, it is believed that rooks probably do as much good as harm in a field, eating the grubs and larvae of insects which attack crops. Still, we have rooks to thank for Yorkshire’s many colourful scarecrow festivals in villages like Baildon, Muston and Kettlewell.