I confess I’m not really sure if they’re ravens, carrion crow or rooks — I haven’t got close enough to use my excellent RSPB bird books to distinguish them — but I do know that in a valley I regularly visit in the Morvan in Burgundy, there’s lots of one or more crow species, and they seem to interact in interesting ways, forming, particularly in winter, quite large groups that swoop around at dusk, raucously dominating the neighbourhood.
So when I saw Mark Cocker’s Crow Country, it was clearly a book that I’d not only read, but read in France. Which is what I’ve just done, and it’s left me with a strong desire to learn more about my local corvids, because I’m sure there’s a lot to be discovered.
The fact that Cocker describes himself as a “nature writer” did give me some pause — the more literary end of nature writing tends to leave me cold — but although some passages of Crow Country were a bit too far down the poetical side for my taste, overall I found it a fascinating account of the natural history of rooks and jackdaws in Britain, and gave me plenty of information about their French cousins.
The key line of the book is Cocker’s attempt to understand rook behaviour, and particularly their spending part of winter in large, sometimes enormous, mass roosts. He starts with their rookeries (breeding centres), the reasons for which are well established.
“In the nesting season, the abundant supply of worms is the key to the rook’s success. The onset of the breeding cycle in earliest spring is timed to coincide with the maximum availability of prey for the chicks. But the food items aren’t spread evenly, they’re clustered randomly…It’s thought that rooks have evolved to share resources and capitalise on the shifting and temporary abundances by pursuing a feeding strategy of follow-my-leader…. Each bird discovering a food hotspot faces the disadvantage of competition from neighbours, but it is more than compensated by the opportunity, on all occasions when it is less successful, to share the good fortune uncovered by others.”
That’s from late February to June, the nesting season, but the rest of the year, Cocker gradually concludes, they are roosting, often split between a late summer/early autumn roost and a later one – the latter reflecting a large concentration of birds. Roosts are usually in the middle of woods, even though these are birds that feed in grasslands (they’ve been recorded flying up to 32km to feeding grounds for the day – “as the crow flies”!), and he concludes that protection from weather, uninterrupted nights (they’re usually in very calm places) and perhaps to some degree predators (although there’s few of these now) , are an important part of the roosting behaviour.
But the biggest advantage for rooks in these huge gatherings is, he concludes, like in rookeries, the spread of information. It is, however, ore complicated than that. In the Yare Valley roost he studied, numbers ranged from 10,000 to 40,000 at the year’s peak, numbers depending to a large degree on continental European visitors, who leave snow-covered territories for warmer western wintering grounds.
“For non-resident naive individuals the primary value might lie in following resident birds out to otherwise unknown feeding sites. The resident population may thus enjoy a dominant status in the froost and occupy more central locations in the trees. They can monopolise the best perches for thermal protection or defence against predators.”
It’s well known that corvids are intelligent – the Caledonian crows having shocked researchers by inventing tools – but Cocker also finds real world examples. There’s the M4 rooks who’ve learnt to get to waste at the bottom of bin bags by gradually tugging them up the side of their frame, holding the bulked plastic under one foot, and those birds who’ll bury food for later consumption. (For jays this is standard, for rooks seemingly more learned behaviour.) So we learn in the Aberdeenshire vernacular a self-seeded tree is “craw(rook)-sown”.
Cocker explains how rooks mainly eat insects and arthropods in the upper topsoil, particularly worms, which explains theiir distribution as a bird of pastures and cropland. (Although they’ll also eat small mammals, eggs and grain.) They stab 5-6cm into the ground, then uses Zirkeln, open-billed probing, to find their prey. Forest is not for them.
“They occupy vast swathes of the Mongolian and Manchurian grasslands, right through to the outskirts of Beijing and the shores of the Yellow Sea. To the west they’ve conquered the immense oceanic expanses of Russia and Asian grassland from about 160E to a point half a world away on the Baltic coast. …Rooks were dependent on the westward spead of stock grazing and cereal agriculture … to make their own entry into Europe. So when you next pass a rookery remember to stop and listen. Amond the spring-summoning cacophony you’ll hear the faintest echo of a Neolitic axe.”
Some history: in Britain rookeries were traditionally associated with grand houses and the landed gentry, no doubt because the birds like to nest in large and ancient trees. He quotes (with some doubt) the tale recorded by Bishop Edward Stanley from France: “When their dreadful Revolution broke out… the country people, amongst other causes of dissatisfaction with their superiors, alleged their being fond of having rookeries near their houses; and, in one instance, a mob of these misguided and ignorant people proceeded to the residence of the principal gentleman in their neighbourhood, from whence they dragged him and hung his body upon a gibbet , after which they attacked the rookery, and continued to shoot the Rooks amid loud acclamations.”
But I learn rooks have only relatively recently spread to France, and their natural borderlands must not be far from me – in the “southern half of the country” – perhaps around Macon, about two hours south from the Morvan, generally considered the start of the south, the ground is too dry and hard for their key feeding technique. (Although Cocker visits a small island of rooks in northern Spain around the city of Leon, an unusually wet area, finding in the ancient place names signs they’d been here for many centuries, and notes a second anomoly in that Virgil talks in his Georgics of rook weather lore and their breeding, from an area where ravens are now found only as summer visitors.)
Along the way, Cocker tells the story of corvid research in the UK, which starts with Hugh Gladstone, author of Birds of Dunfreeshire (1910), who “mapped all the rookeries in the county and traced evidence for some back to the 1650s”. And he quoted one Mrs Pollock, writing about 1866 of her childhood memories “On a summer’s night (put early to bed!) I have lain by the nursery window, watching them flying home… the sky would be black with the, their flight overhead would occupy at least an hour and a half… it looked like a river”.
Along his rook journey, Cocker takes some interesting byways. I was particularly taken by his account of the story of a favourite piece of nodule flint. “Flint like this is composed of re-deposited silica from trhe exoskeletons of marine creatures such as sponges and sea urchins. They lived once on the bed of a broad warm tropical sea in the Upper Cretaceous and were contemporaries of their weird paddle-limbed reptile giants known as ichthyosaues and pleiosaurs. As the sea urchins died their deposits of silica drizzled on to the saebed, where they oozed or leached through faults in the accumulating sediments of chalk. Over millions of years they metamorphosed into continuous beds of ‘tabular’ or scattered piece of ‘nodule’ flint.”
And in tracing this history, he encounters telling tales of lost abundance. He quotes the Reverend Richard Lubbock who saw a change from 1816: “When first I remember our fens they were full of Terns, Ruffs and Redlegs [redshanks], and yet the old fenmen declared there was not one tenth part of what they remembered when boys.” (p. 92) So Cocker notes that while two huge field surveys of British birds, in 1968-72 and 1988-91 are taken as baselines “is that really where we should begin to caculate the fortunes of our wildlife.”
You have to say that’s a very good question, not just about bird life, but all of our natural environment.