London Colney News

The first time I visited our nature reserve - it was an impenetrable forest. I looked from the Shenley Lane entrance, and there was a bramble thicket. What was noticeable was the large number of wrens flying around.
I went there earlier this year. The thicket still stands ,and there are still wrens flying around - descendants of the ones I saw in 1975. London Colney owes a lot to the Nature Conservancy and other volunteers who manage the reserve, and have made accessible to all the many natural treasures there. The wren’s top is chestnut, and its belly is rather lighter. On both surfaces there are darker stripes. There is a pale flash behind each eye, but the most noticeable feature is the tail, which is permanently cocked upwards.
There is only one variety of wren in Europe, and they live all over Europe. There are minor sub-species living on various off shore islands - which are generally larger, and brighter coloured. Wrens eat insects , spiders and small invertebrates. By choice they nest in shady places and in large thickets. Possibly the wrens liking for holes and caves gave rise to its scientific name “troglodytes troglodytes”.
Most birds are reasonably faithful to each other. A pair will build a nest, mate, produce a family, and care for them. Promiscuity is rare, although several species, as well as cuckoos lay their eggs in other birds’ nests. The wren is the exception. When a male wren reaches sexual maturity, he seeks an area with lots of bushes, and where he knows many insects live close by. He will build several nests. They are always dome shaped with a side entrance - to make a cosy nest. Often nests are quite readily visible, but he’ll build the first one which is well hidden, and lined with feathers. When the nests are finished, he’ll start singing loudly, to attract a female. The first to appear, he’ll show her the nest he’s built, and he’ll care for her and the chicks in their early days. But after a while, he gets restless, and starts seeking a new partner. He’ll install her in another of his nests, and care for her and her chicks, until he gets a roving eye - and seeks another partner. A healthy male can have five families in one season. You’ll ask, what do the female wrens get out of this arrangement? The first gets considerable help starting her family. But subsequent partners get less help. Presumably, if the male is particularly vigorous - he’ll choose a site for his nests where there is lots of nearby food, so later partners have a chance of raising a family otherwise could not have got.
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Being small, wrens are very susceptible tD me cold. They eat high energy food. When winter comes, they seek a hole in wall, or a tree, hand several wrens will settle together, keeping each other warm. During the long, cold winter of1962/3 - the British wren population crashed to a quarter its normal size - but within a couple of years, because of wrens’ promiscuous habits, the population was back to its normal levels.
In spring, there are about ten million pairs of breeding wrens in Britain - so it is quite a common bird. Old bird books will tell you the wren is Britain’s smallest bird. This is no longer true. Since the planting of pine forests in southern England, fire crests and cold crests have moved in. Both species are smaller than the wren, but you will only see them at the edgea of a pine plantation - while you can find wrens all over Britain.
Robin Cooper