Thursday, 7 April 2016

Secrets of a small rookery, part three: Crow Culture

Wheatfield with crows by Vincent van Gogh (1890), oil on canvas


What is a crow to you, reader? The answer will vary depending on who you are, where you live and the ways in which - and the extent to which - you connect with your environment.

To many people, crows are a noisy, messy, annoying family of birds with unpleasant voices who attack bins and rubbish sacks, steal songbird chicks from nests, steal farmers' crops and generally cause a nuisance. To others they are intelligent creatures, innovative problem-solvers - fascinating to observe and a source of immense pleasure. I am firmly rooted in the latter camp.

In about 1995, while walking along the Ouse riverbank between Newhaven and Piddinghoe in East Sussex, I witnessed a group of several Carrion Crows manoeuvring a square of plywood, which looked like an old drawer-base that had been washed along the river and stranded on the high tide line. One crow wrestled the square of wood down the riverbank and into the water, where it floated. Each crow in turn then flew into the air and attempted to land on the floating wood, not very successfully, and suggesting an appearance of novice surfers, but obviously able to take an idea and put it into practise. This level of enquiry on the part of the crows was remarkable to observe. Whether they were playing or attempting to gain some advantage, perhaps by using the floating wood as a fishing platform, I could not speculate about, but it convinced me that crows are clever birds.

Soler & Møller (1990) demonstrated that Magpies (Pica pica) learnt to detect Great-spotted Cuckoo (Clamator glandarius) eggs when their nests had been parasitised in areas where the two species had coexisted for some time. The ability to detect these eggs was reduced in areas where coexistence was more recent and, where their ranges did not overlap at all, there was no recognition. Magpies had developed the ability to recognise cuckoo eggs through learning experiences and had tweaked their behaviour accordingly. Other victims of brood-parasites, such Reed Warblers (Acrocephalus scirpaceus) and Dunnocks (Prunella modularis), have shown no such recognition of Common Cuckoo (Cuculus canorus) eggs. The New Caledonian Crow (Corvus moneduloides) is a well-documented problem-solver, tool-maker and tool-user (Hunt, 1996). Crows are clever birds and their intelligence has impressed and captured the imagination of the humans in their midst.

To many human cultures crow species are a defining cultural reference: gods or messengers of gods, spiritual beings who may deliver the souls of the dead to the afterlife. They are emblematic, their image having been used in aboriginal art including cave paintings and aboriginal names and costumes, heraldic coats of arms, place names (Rookery Hill, Rookery Way and The Rookery are all about a mile away, as the crow flies, from where these words are being written) and in numerous other creative works. We have exploited crows in our culture and crows have adapted to exploit us too. This entwined relationship can be termed cultural coevolution.

Ravens scavenging a wolf kill-site carcass
Here is an example of cultural coevolution: the automobile is one of the defining images of the American Dream. Perhaps there is an inevitability, therefore, that the American Crow (Corvus brachyrhyncos) has adapted its own culture in response to road vehicles. Traditionally, Ravens (Corvus corax), Magpies (Pica pica) and other corvid species adapted and evolved to scavenge the carcasses of hunted animals which they locate by flying and searching across the landscape, perhaps following packs of wolves or humans to a kill-site. Roadkill could be considered to provide the same opportunity, particularly in areas where kill-sites are less common now than they were in the past, so it is not much of a cultural shift on the American Crow's part to follow roads, which cut like rivers through the landscape, searching for dead deer, rabbit or birds. American Crows have also been observed picking dead insects from the fenders of stationary cars. These behaviours should still be considered as a cultural response; they have been observed in North America (Marzluff & Angell, 2005), but probably also occur wherever crows and humans with cars coexist. In Japan in 1975, Carrion Crows (Corvus corone) were observed at a driving school placing shelled walnuts before the wheels of parked cars so that they would be cracked open as the cars drove over them and away. This behaviour has been adopted by observant crows and has since spread some miles along the Hirose River region (Nihei & Higuchi, 2001).

Further reading provides a wealth of examples which demonstrate the effect that crows have had on European culture, and particularly so on our languages, which will be the subject of part five of this corvine compendium.

I think the relationship between crows and humans, whether it is welcomed, tolerated or despised, dates all the way back through human history, back beyond the 150,000 or so years that Homo sapiens has walked across the world, even back beyond the seven million years since our evolutionary trajectory branched away from our closest extant relatives, Bonobos and Chimpanzees. Crows have been on the wing all this time - they evolved (I think) in the Eocene Epoch about 50 million years ago, although the species we share the world with today are more recent. At the end of the last ice age ten thousand years ago, Hunter-gatherers would doubtless have been in close contact with Ravens, who followed or possibly even led humans along the migration routes towards the great herds of ungulates, where we might have revered the birds, tolerated them or chased them off from a kill. As farming practises spread from the Middle-east westwards across Europe and into Britain about six or seven thousand years ago, we would have put down roots and found ourselves closer to other crow species such as Rooks and Jackdaws, who colonised the fringes of the land cleared by our ancestors and who plundered the insect pests which devoured our ancestor's crops and then helped themselves to the same crops as they ripened.

Four seeds in a hole,

One for the Rook, one for the Crow,

One to rot and one to grow.



During the past few thousand years of civilisation and warfare, battlefields strewn with dead soldiers would have been a happy hunting ground for Ravens, Carrion Crows and Magpies. Survivors who witnessed the battlefield-fallen being pecked and torn apart in a corvine feeding frenzy could be forgiven for holding a fear or awe of those birds whenever their paths crossed.

Gallows-crows
The same crows would have perched upon gibbets and gallows and it is easy to imagine them gathering ahead of a public execution - observant and intelligent birds would learn to recognise the signs, the noise of excitable crowds. The black, ravenous birds would understandably have become symbols of judgement, both human and divine judgement.

The crow or raven might have been the influence of the beak-shaped mask worn by plague-doctors in Europe during the 16th and 17th centuries. The costume of a waxed or leather cloak was topped with a mask and beak. The beak was filled with straw and aromatic herbs and oils - all to filter and protect the plague-doctor from miasma (putrid air), which was considered until modern times to be a vector of disease. Even Florence Nightingale is alleged to have believed in misama theory, but the Nightingale is a different bird altogether. The beaked mask of the plague-doctor is still a chilling sight.

We have shaped crows' culture and they have shaped ours. It is no wonder that crows became symbols of fear, death and perdition. It is via this background that crows and crow-culture have become braided into our language.

Plague Doctor costume

References:

Hunt, Gavin R. 1996. Manufacture and use of hook-tools by New Caledonian Crows. Nature 379: 249-25.

Marzluff, John M. and Angell, Tony. 2005. In the Company of Crows and Ravens. Yale University Press: New Haven.

Nihei, Y. and H. Higuchi. 2001. When and where did crows learn to use automobiles as nutcrackers? Tohoku Psychologica Folia 60: 93-97. 
Soler, M. & Møller, A.P. 1990. Duration of sympatry and coevolution between the great spotted cuckoo and its magpie host. Nature. 343, 748-750. 

No comments:

Post a comment