Stone the crows, what’s coming next? Carrion Crow breaking walnuts
Mark E Turner
I have for the few years we’ve been living in Evesham known of the Carrion Crows, Corvus corone that reside and raise their families in and around Bengeworth Cemetery, off the Broadway Road.
During October 2010 I noticed when observing from the second floor (converted roof-space) that one or two adult crows from this clan did as the crow flies and make a regular beeline from the graveyard over our house to a large walnut tree Juglans regia to the rear of our property in a neighbour’s garden.
The nuts which appeared to be bursting from their cases since a number of recent frosts, were being collected one at a time by these birds, usually from the crown of the tree. On the morning of 18th October I saw a bird repeatedly dropping a walnut whilst in flight, down onto the car park tarmac below. Another time a crow was hammering open a walnut on a chimney stack across the road.
In the late afternoon of a cold and sunny 20th October I rushed over to observe from our back kitchen window a crow making for the walnut tree again. As the bird departed I rushed to the front living room window to see what would occur this time. The crow in its flight back to the cemetery momentarily stalled then jinked upwards and dropped its walnut only to catch it in mid-air before continuing on its course back home. The skill involved in this manoeuvre almost suggested this to be playful fun, a bit of sport typical of an intelligent being. And these birds being intelligent, resourceful as well as opportunistic have long been a fascination to me not least for their feeding behaviour.
The saga continued at 11.00 hrs on 12th November when the nut-breaking routine had shifted across to a nearby warehouse roof which is flat in its design with a slightly higher outside ledge all the way round. This gave the birds a good level of privacy to carry out their ritual. On this day a crow collected a walnut and made three attempts to break it open by dropping it onto the roof after a vertical ascent on the wing. Obviously this didn’t work and the ritual ceased. The crow then seemed to walk around in a pondering manner as if figuring out what to do next. The decision was to go and get another nut. With the walnut tree now pretty much denuded of its leaves I could watch with ease the method used to procure the fruits. Having selected a nut the crow very gently tweezered at the stalk, but it dropped straight to the ground. Another nut was selected but this time was gripped around the whole case. Back at the roof one block over, this second attempt took five aerial drops before the kernel was extracted. Fortunately for me the crow hopped up onto the raised ledge giving a good view of it from the top bedroom. The bird at first picked delicately at the snack, but then finished off by taking bigger morsels.
The episodes with the harvesting and breaking open the walnuts recall observations I’ve made at Dawlish Warren National Nature Reserve in Devon of crows dropping shellfish in a similar manner. In my battered copy of T.A.Coward’s The Birds of the British Isles and Their Eggs Series One, the author describes the same method of preparation for breaking into molluscs by dropping them onto hard ground. However, I disagree with him that they seldom vary the height from which they drop their food items if the first efforts fail. A case in point being the second walnut on the warehouse roof when on the fifth attempt the crow climbed even higher to achieve the desired result.
More recently my wife and I watched a crow in Sandford Park, Cheltenham, wading up to its belly in a slow-flowing stream and fishing out meagre meals by plunging its head below water.
Most shocking of all though was a time back in 2005 when looking across pasture in the North Cotswolds near Guiting Power, a Carrion Crow was hammering at something in the grass, raining heavy blows repeatedly with its bill on an invisible object. Imagine my horror when the invisible object turned out to be a rabbit which after several seconds of sustained beatings, leapt into life putting an end to the crow’s intentions. Whether the rabbit was stricken with disease and had been resting up and giving the impression of being dead to the crow is open to conjecture or was the crow genuinely attempting to dispatch the rabbit itself? The old saying ‘a murder of crows’ suddenly has a ring of truth about it. I would welcome anybody’s views on this matter or indeed if anyone has witnessed a similar incident.
Crows have evolved to be generalist feeders, yes, but should that read: generalist birds of prey. Perhaps evolution is still progressing.