Wren: bird song and calls

By James Duncan

Communities and Wildlife Officer

Wren (Troglodytes troglodytes)

The Wren, a species of contrast. On the one hand it's a tiny little bird, only a fraction larger than the Goldcrest, it's minute size matched by the simplicity of its name. On the other hand it packs a voice with huge punch and boasts a UK population large enough to make it our most numerous breeding bird. You may not always be aware of its presence, but familiarise yourself with its song and its abundance becomes clear. In fact, it's likely the Wren's lifestyle that disguises the true range of its population - though they will sometimes roost communally to keep warm (essential to protect against high winter mortality) it's a highly territorial species that largely lives a sheltered and solitary life. The Wren of course can be found all over the country in all manner of terrain. We may consider them to be birds of landscape-scale habitats, such as woodland, but ultimately this isn't truly correct. The Wren is really a master of the subterranean. It can be found where there are cracks and crevices, fallen branches and bushes, rocks and boulders, banks and walls, cliffs and wasteland. In fact, wherever you go, with the exception of the highest mountains, the Wren can be found. Its scientific name of troglodytes is even indicative of its habits, referring to the bird as a 'cave dweller.' It has conquered such a variety of environments that it's now known we have not just one UK species, but six subspecies. Four of these are distinct island specialities - the Shetland, Outer Hebrides, St Kilda and Fair Isle Wrens. Of course the Wrens aren't restricted to the UK - they're a hugely successful family of nineteen genera, with many species that occupy almost every part of the globe. It's fair to say the Eurasian Wren is certainly loved by us as we voted it our fourth favourite bird in the same national poll that gave the Robin top billing. 

Whilst the Robin sings for the majority of the year, the Wren perhaps trumps it for it rarely having a day off. It's truly an all round singer and its song is the one most likely to be heard on any given day. The Wren seems to sing with real soul and gusto, remarkably consistent with its personality of fizzing intensity. It moves rapidly, endlessly alert, almost mouse like, whilst the furious flurry of its tiny little wings seems to resemble a buzzing insect more than any bird species. The territorial nature of the Wren tends to result in cascades of song emerging from undergrowth, as rivals attempt to out-compete each other with the intensity and volume of sound. The one feature that is perhaps most noticeable about their song is indeed the sheer power for their size. There is no other UK bird species of such diminutive stature that utters such a jubilant repertoire.

Listen to the song in this video below -

The song may be repeated a number of times per minute, usually lasts between five to seven seconds and comprises a series of high-pitched, ringing, metallic notes interspersed with little 'trills' that sound somewhat like a soft 'machine-gun.' These trills tend to be predominantly within the second half of each verse. It has an 'explosive' nature to its delivery as there's no lead-in or out. Whilst wrens will often sing from cover to avoid detection, it's not unusual to see them perched, singing loudly and proudly from a prominent position. Interestingly, studies from both the Universities of Costa Rica and Salamanca have shown that environmental sounds in urban areas have increased the complexity of Wren vocalisations. It seems that some urban birds now sing longer notes, faster trills and at higher frequencies. It's possible that this could perhaps be a response to either increased background noise or higher population densities in such habitats. It should also be noted that many birds develop their songs from what they hear around them, and changes in complexity may also arise from the vastly more diverse and wide-ranging soundscape in our towns and cities. 

The song may well seem at odds with the size of the bird, but the reason the Wren is able to produce quite such a serenade is due to its physiology. In fact, the physiology of all birds. They're able to produce the most complex vocalisations in the animal kingdom owing to the syrinx, the bird's voice-box. The syrinx is located at the other end of the windpipe from the human larynx and is dual chambered. Put simply, unlike us, birds do not sing only when exhaling, allowing them an ability to produce contrasting notes almost simultaneously. 

Wrens also exhibit a couple of commonly heard calls. The first is a punchy, rattling "tik-tik" that can be uttered either individually or strung into a succession of rapidly repeated notes.  They're not unlike Robin calls, though they're longer, lack the 'elasticity' and have a much more squeaky quality. The series of notes tends to become more pronounced and vigorous should the Wren become more agitated.

Listen to this call below -

The call may often be interspersed with another, the more common alarm call, given typically in response to predators. This trill is somewhat more subdued and can be replicated by producing a 'rrrr-rolled R,' produced by blowing air over your tongue. Owing to the type of sound it's often a little harder to locate the direction of its delivery, another aid to avoiding detection by predators. It can be transliterated as "zrrrrr."

Listen to this call below -