Rows and relations in the rookery

A READER who regularly emails me with news updates about his local wildlife tells me that a nearby rookery has become very noisy lately.

I’m not surprised. Rooks tend to spend most of the winter roaming around the countryside in search of food, often in the company of jackdaws and increasingly adding urban areas to their itinerary. But, like other members of the crow family, they breed early in the year, so some time in January they return to the rookery.

Rooks use the same nest year after year, which is quite unusual among birds. But the nests get damaged by winter storms and have to be repaired. The basic structure is woven out of twigs and the birds nearly always break the twigs off a growing tree with their powerful beaks, very seldom picking up ones that have fallen to the ground. Rook colonies are, in general, extremely civilised places and the birds show a high degree of community spirit. But this does tend to break down a bit at this time of year because when birds fly off to prospect for the right twig to repair that damaged side of the nest, other birds will steal twigs from it while it’s unattended.

The foraging birds return and a very noisy row breaks out as they accuse their neighbours of theft. This may all sound a little bit anthropomorphic but remember two things. First, rooks are extremely intelligent. It’s estimated that their tool using ability, with their beaks, is greater than that of a chimpanzee with its hands and captive rooks have demonstrated extraordinary problem-solving skills. Secondly they have, by bird standards, an extremely large vocabulary. It’s difficult to say how large, particularly as some of the “words” are not vocalisations but expressed in body language and mandible clapping. Based on my own observations I would give them a vocabulary of around 20 words. That may not sound like much, but by bird standards it’s huge.

The first eggs will be laid in late February or early March and there are usually between three and five of them. They will be incubated for 16 to 18 days and both parents feed the young, which fledge and leave the nest on the 32nd or 33rd day.

While I was researching the subject of rookeries I came across a strange story. A lady reported an eccentric pair of rooks that tried to build a nest at some distance from the colony. The other rooks repeatedly destroyed the nest and eventually killed the pair. I don’t know if I believe it, but if it’s true it throws an interesting light on the inner workings of a rook colony.

WREN (Troglodytes troglodytes)

The wren is not quite our smallest resident bird, that distinction belongs to the goldcrest, but it is the shortest. It looks even shorter because its slim tail is usually cocked upright, at 90 degrees to its body. It’s possibly our most widespread species with a huge range of habitats varying from urban gardens to raised bogs, high mountains and offshore islands. It’s also extremely noisy, with a loud and complex song and a rather narky alarm call.

Small birds suffer from the cold more than larger ones and hypothermia is a major cause of wren mortality. But they will use their nests to roost in, which is very unusual, and these domed structures with a small entrance hole are very well insulated. And, although they’re normally very territorial, in cold weather they will forget their differences and huddle together for warmth at night.

One cold February in England 61 birds were found sleeping together in a nest box.