British Wildlife of the Week

Wren

Wherever you are in the UK, you’re probably never far away from a wren. Although many people have never seen a wren, at least not knowingly, it is far more common than other garden birds that we may be more familiar with, such as sparrows and robins. In fact, it is our most common breeding bird, with around 11 million pairs here in Britain. So how come we rarely see them?

The wren is a shy, skulking, unobtrusive bird. Because it usually hides away, rarely venturing out into the open, it is often ignored and overlooked. It roots around in crevices and crannies or at the base of bushes and shrubs, searching for small arthropods, behaving more like a small mammal than a bird. Its habit of disappearing into dark, secret cavities while roosting or foraging explains its puzzling scientific name, Troglodytes troglodytes, which means ‘cave dweller’.

If you do get a good view of a wren, however, you will see a tiny, plump, unassuming bird with a stubby, cocked tail that it holds at a jaunty 45-degree angle from its body. Weighing just 10 grams – the same as a new £1 coin – it is sometimes mistakenly referred to as our smallest bird, although both the goldcrest and firecrest are smaller, weighing only around half as much. For such a diminutive bird, though, the wren certainly has a powerful and disproportionately loud voice, and it can be heard exuberantly singing all year round, even in the depths of winter.

During the breeding season, a male wren constructs several ball-shaped nests and then shows them off to his mate as if he were an estate agent showing a client around a property. The female will reject most of these nests, choosing the one that is in the safest place and closest to the best food supply. She will then work on interior decoration, lining it with hair and hundreds of tiny feathers. Once the eggs are laid, the female usually does all of the incubating duties, whereas the male will start work on wooing a second mate.

In addition to being our most numerous breeding bird, the wren is also, perhaps, our most ubiquitous. Extremely adaptable, it can be found everywhere and anywhere, in virtually every land habitat, from woodlands and gardens to moors, coastal cliffs, and even remote offshore islands. In fact, as discovered by a British Trust for Ornithology survey, it is present all year round in at least 97% of 10-km squares across Britain and Ireland. By this fact alone, the wren can surely claim to be the most successful British bird.

Some of our island-dwelling wrens have diverged from the common mainland variety so much that they are now considered their own separate subspecies. One of them lives on the remote archipelago of St Kilda and has become a little bit larger and paler. Three other unique, endemic subspecies can be found on other Scottish islands. The differentiation of these distinct island races must have been rapid because their respective islands would have been uninhabitable until just after the last Ice Age, a little over 10,000 years ago.

One of these unique wrens lives on tiny Fair Island (located about halfway between mainland Shetland and the Orkney Islands), which is the remotest human-inhabited island in Britain, supporting a human population of just 65. The Fair Island wren, as it is called, is one of the least numerous bird forms on Earth, and also one of the most restricted: the 7.68 km² island is home to a tiny population that varies from 10 to 50 pairs.

In the next British Wildlife of the Week, we’ll be looking at a strange nocturnal bird with an eerie song that was once thought to suckle from goats until it drained them of their milk – the nightjar.