Rooks

The East of England boasts one of nature’s most remarkable sights. Up to 80,000 rooks gather at a wood in Norfolk, making this the biggest rookery in Britain - maybe even the world. Every morning and evening the birds fly in and out of the rookery en masse, making it an incredible spectacle.

The RSPB has requested we remove details of the whereabouts of the roost, since there is not the local infrastructure for large numbers of visitors.

Gamekeeper of the estate Joe Callum keeps an eye on the rookery.

“They just belong here,” he says. “They’re even mentioned in Doomsday Book.”

Rooks belong to the corvid family which also includes crows, ravens, magpies, jackdaws, and jays. Characterised by a bare, greyish-white face, thinner beak and peaked head. These birds have a cawing ‘kaah’ call.

Rooks are very sociable birds. They feed and roost in flocks in winter. The rook is the only species of crow to nest colonially in rookeries. These structures are home to an extended family of rooks for about six months of the year.

The size of a rookery is often dictated by the availability of food nearby - rooks rely on invertebrates and healthy worm populations on the farmland around them.

According to Norfolk based Mark Cocker, author of Birds Britannica, numbers of rooks are increasing, and the birds have no natural predator. But they don’t have the best reputation.

“Well it’s a very beautiful scene when they all fly. The birds gather every day to sleep in roost for protection, the mass resolves and they all fly as one organism,” says Mark Cocker. “Hitchcock has a lot to answer for. Black is the colour of evil … so they are often seen as omens of doom.”

Jennifer Westwood, an author and expert on superstition and folklore who lives in South Norfolk, explains why rooks feature heavily in folklore:

“They are mysterious because they are so clever. Folklore suggests they are the cleverest bird. In some countries it was suggested they sat in circles or parliaments, and debated. In East Anglia it’s considered very lucky to have them near your house, and if they go then it’s a bad sign - the family is about to fall on bad times.”

But local farmer Richard Hurst from Ormsby isn’t a fan. He is aware that their numbers are on the increase and he says they lay waste to about 35 per cent of all his seed crops, and eat sky lark chicks. He arranges for the birds to be shot to keep the numbers down.

Whatever your view, rooks are fascinating creatures. Professor Nicky Clayton at Cambridge University has been studying the birds for some years:

“The reason we’re interested in rooks is because they are highly intelligent, highly social and it’s often thought that our type of brain is key to high intelligence. We’re finding they have a completely different type of brain that gives different but still high intelligence. That’s exciting for all kinds of reasons. These studies have found that some corvids are not only superior in intelligence to birds of other avian species (perhaps with the exception of some parrots), but also rival many nonhuman primates.”

Increasingly, scientists agree that it isn’t physical need that makes an animal smart, but social necessity. Group living tends to be a complicated business so for individuals to prosper, they need to understand exactly what’s going on. So highly social creatures like dolphins, chimps, and humans tend to be large-brained and intelligent.

Like apes, many birds employ tools to gather food, but it isn’t clear whether birds like rooks appreciate how these tools work. It may be that they simply discover their usefulness by accident. One thing is clear - these birds are amongst the brainiest of our avian population.

Source: http://www.bbc.co.uk/insideout/east/series9/week_nine.shtml

Some good quality photos, video and audio.

Visit Mangoverde

The Rook is one of our most familiar and widespread birds. With nearly one million pairs in Britain, it is only absent from upland areas and from treeless islands off the west coast of Scotland, though it has been able to find suitable trees to nest on Shetland and on Lewis in the Western Isles …

Visit Birds of Britain for more information

The study was carried out in 2000–2002 around 6 rookeries. Rooks foraged in numbers from 1 to 132 birds (n = 417); flocks of less than 10 individuals were dominant. The type of crop influenced the size of a foraging flock. Most of the rooks were recorded within 0.5–1 km of the rookery, while the greatest distance of a foraging ground from the rookery (x– = 2833.3 m) depended on the size of that rookery. Spring corn, meadows and pastureland were of the greatest significance in the rooks’ foraging area. Winter corn and root crops were avoided, while wasteland areas were visited intermittently.

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Protect the birds or reduce the bird strike rate>

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In a free living rook (Corvus frugilegus) a well differentiated squamous cell carcinoma without keratinization arising from the oesophageal mucosa was found. This tumour had grown around the right main bronchus and so caused marked respiratory distress.

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Sleep and wake states were monitored polygraphically in the rook Corvus frugilegus, under the natural photoperiod and temperature. The indices of sleep and wake states in the rook were similar to those described previously for birds in general. The appearance of sleep episodes was confined to the dark part of the photoperiod.

Slow wave sleep (SWS) showed a tendency to increase during the course of the night, while paradoxical sleep (PS) showed the opposite trend. The distribution of short SWS episodes were clustered into two groups, one group occurred in the period following the onset of sleep and the other, less prominent group occurred towards the end of sleep. The longest episodes of SWS appeared in the second half of the night, whereas those of PS appeared after onset of sleep.

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The occurrence of avian mycobacteriosis in the rook (C. frugilegus) was investigated in the years 1966-1985. A total of 188 birds captured at three localities of the Czech Republic were subjected to patho-morphological examination and to culture examination. Patho-anatomic lesions were observed in five rooks (2.6%), M. avium was isolated from 10 rooks (5.3%). Positive findings occurred in each examined locality.

Rook sensitivity to M. avium infection was tested by experimental infections. After intramuscular infection with M. avium suspension macroscopic tuberculosis lesions were found out at the place of puncture, histological lesions in liver and spleen at the beginning of the trial (days 12-35). Mycobacteria were isolated from particular organs and tissues, more frequently at the beginning of the trial.

Peroral infection by feed contaminated with liver of tuberculous fowl failed to induce tuberculous lesions, while a proof of M. avium from the organs was the only one after 157 days. The contact of the rook with the tuberculous fowl did not lead to the origin of tuberculous lesions after 238 days nor were the mycobacteria proved in the rook tissues.

In comparison with e.g. the house sparrow, tree sparrow and pheasant, the rook is very resistant to M. avium infection according to the results of experimental infections. A relatively frequent occurrence of tuberculous processes or of mycobacteria in the rook captured in the open area is probably conditioned by a possibility of repeated, frequent contacts of the rook with the contaminated environment during its longer life.

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Droppings from 112 urban rooks (Corvus frugilegus) were cultured for the presence of Listeria sp. Overall, 46% of rooks sampled harboured one or more Listeria species. Of all birds examined, 33%, 24% and 8%, respectively, were infected with Listeria monocytogenes, Listeria innocua and Listeria seeligeri.

Differentiation of L. monocytogenes and L. seeligeri carried out by several phenotypic typing methods proved the diversity of strains and the major role of rooks which widely contribute to spreading this bacteria in our environment. The results also suggest that the ability to recover specific Listeria strains from the same sample is at least partially dependent on the methodology. These findings reinforce the need for strain-specific typing of multiple L. monocytogenes isolates from the same sample.

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Although animals (particularly tool-users) are capable of solving physical tasks in the laboratory , the degree to which they understand them in terms of their underlying physical forces is a matter of contention. Here, using a new paradigm, the two-trap tube task, we report the performance of non-tool-using rooks. In contrast to the low success rates of previous studies using trap-tube problems , seven out of eight rooks solved the initial task, and did so rapidly. Instead of the usual, conceptually flawed control, we used a series of novel transfer tasks to test for understanding.

All seven transferred their solution across a change in stimuli. However, six out of seven were unable to transfer to two further tasks, which did not share any one visual constant. One female was able to solve these further transfer tasks. Her result is suggestive evidence that rooks are capable of sophisticated physical cognition, if not through an understanding of unobservable forces , perhaps through rule abstraction. Our results highlight the need to investigate cognitive mechanisms other than causal understanding in studying animal physical cognition.

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