Adapting their song to the environment they find themselves in is just one of the remarkable characteristics of this wonderful bird
Scientific name: Turdus merula
UK numbers: 5.1 million pairs / 10-15 million wintering
Diet: Insects, worms and berries
Here’s an admission – the Blackbird’s is my favourite birdsong in all the world. I find the virtuoso notes and the wondrously unhurried delivery not just pleasing on the ear, but on the psyche, too.
It is soothing. There are times when, during a particularly stressful day, I have put on a recording of a singing Blackbird and allowed it to wash away life’s frustrations. Try it; it works.
There is no doubt that the Blackbird is one of Britain’s finest songsters. Each phrase is a discrete production, with a significant pause from the last, and no phrase is immediately repeated (making it very different to the Song Thrush’s song.) Listen carefully and you might notice that each phrase begins with glorious contralto fluty notes, but ends much less tunefully, with a squeak or chuckle.
These endings vary enormously, and allow for a dash of mimicry, not always of another bird, but even bells or human voices. Each individual male Blackbird (the females don’t sing) has a repertoire of at least 100 song-phrases.
Studies of Blackbird song have also revealed something unusual – individuals get better as they get older. Their repertoires increase with novel input – they will sometimes incorporate copied phrases from first-year birds – so a three-year-old Blackbird will have a richer vocabulary compared with a younger bird. In most other species that have been studied, such as the Chaffinch, the song is set in the individual’s first year and doesn’t become enriched. In theory, therefore, you could get a clue as to your local Blackbird’s age if you listened thoroughly enough, with younger birds having simpler songs! The sheer variety among individuals should also mean that, with practice, you could learn the songs of the birds around you.
It isn’t only the richness, variety and tone of a Blackbird, though, that makes it such a pleasure to listen to. Another factor, which also confers deep resonance to us humans, is that the song is a staple of the built environment – it’s enjoyable because it’s there. Some of the world’s most gorgeous songs – that of the Hoopoe Lark is a good example – are tucked away, virtually unheard, into rarefied habitats, such as desert. They can only be enjoyed by the few, not the many (to misquote that famous phrase). Not the Blackbird, that of the constant euphonious spring soundtrack of the concrete sprawl.
The Blackbird has been a staple of the urban environment in Europe for a remarkably long time, since the start of the 19th Century, 200 or so years. Had you been allowed to predict its ecological future back then, you probably wouldn’t have picked it as a pioneer; it is a bird seemingly at home in deep deciduous forests, where many individuals still thrive. Yet, some birds managed to swap the boughs for the balconies, and the rustle of leaves for the human hubbub. It was a remarkable feat of adaptation and, since the populations in town and country don’t seem to differ much genetically, a remarkable feat of plasticity in behaviour.
Today’s urbanised sprawl provides enormous challenges for wild animals, and many are not up to it. Those that are, though, don’t stay exactly as they are; some of their behaviour changes. In the case of the Blackbird, it breeds at much higher densities in towns, as if it were aping the human arrangements. There are more positive differences, too. The breeding season is extended, and Blackbirds in cities are less prone to migrate away in winter (as they would in many European locations) because there is more food available and, of course, it is invariably warmer than in the countryside.
There are two factors prevalent in cities, though, that are particularly challenging for wild animals. The first is light pollution, and the second is noise pollution. The two together can mess up a bird’s diurnal and annual rhythms and interfere with its ability to communicate.
Take light pollution. Towns and cities are artificially lit up 24-hours a day. Yet most animals, including Blackbirds, use the natural ebb and flow of daylight to determine their annual cycles, such as breeding, moulting and migration. Their lives are fine-tuned to a daily rhythm of sunrise and sunset.
For example, the switch from reduced daylight to increased daylight in December sets off a cascade of hormones in the blood that prepares Blackbirds and other animals for breeding.
There is plenty of evidence that artificial lights in urban environments have an effect. For example, urban Blackbirds are known to advance the growth of their testes by up to a month in (experimental) conditions of night light. Blue Tits are known to lay eggs 1.5 days earlier in artificially lit territories as opposed to unlit ones, and even the opportunities for extra-pair copulations are enhanced!
The dawn chorus also starts earlier in cities, and the effect is enhanced on cloudy days, when the city lights reflect off the clouds and make it brighter.
On the other hand, artificial noise, especially the almost continuous rumble of traffic, will have the greatest effect on social interactions between animals. This is another factor that strongly affects dawn singing – more, in fact, than artificial light. In the case of Blackbirds, scientists in Leipzig measured the onset of dawn song across a spectrum of habitats, from a city park to the town centre, and found that in spring it could start up to five hours earlier in the most urbanised parts, although the last bird in the urban parks was usually about three hours behind the city singer.
Not surprisingly, the dawn chorus is also fragmented. In the park, most birds started singing at about the same time, whereas in the urban areas they started at widely differing times.
Several studies have suggested that birds alter their singing times simply to avoid traffic rumble. This has been proven in Robin populations, where singing in the middle of the night is common. One might guess that it could have other implications, not measured as yet.
One change that the urban lifestyle does cause is the nature of the song itself. For example, a study in Vienna found that Blackbirds in the city sang at a higher pitch than their peers in the Vienna Woods and had shorter intervals between phrases. For example, the most frequent elements in the songs of forest Blackbirds were between 1.8 and 1.9kHz, whereas the favoured elements in urban Blackbird songs were pitched at between 2.2 and 2.3kHz. This has been replicated for other places and for other species. This is assumed to mitigate against the relatively low-pitched hum of traffic, but the picture is more complicated than that.
Blackbirds in cities don’t just sing higher pitches, but they sing louder – a combination of a higher number of high-pitched elements, with greater intensities. The Vienna urban birds could gain as much as 6dB by using the higher pitches (the average was 2.5dB.) That means that, against the roar of the traffic, a forest bird could transmit its song as far as 30m, whereas a city bird, with its greater pitch and amplitude, could broadcast its notes as far as 43m.
This is a remarkable feat of adaptation. The fact that a bird can change something as fundamental to its fortunes as song, the key to keeping a territory and attracting a mate, just to cope with human-induced noisiness, is truly wondrous. Indeed, it can only enhance your sense of wonder as you listen to the melodic phrases.
And it so happens there is another change that has been measured in urban Blackbirds, as opposed to their countryside equivalents. It turns out they are more resistant to stress. So, the Blackbird you are listening to in order to calm you down, has already calmed down itself.
Sleepless in Town – Drivers of the Temporal Shift in Dawn Song in Urban European Blackbirds, Anja Nordt *and Reinhard Klenke, PLoS One. 2013; 8(8): e71476., Published online 2013 Aug 7. doi: 10.1371/journal.pone.0071476
Bird song and anthropogenic noise: vocal constraints may explain why birds sing higher-frequency songs in cities, E Nemeth, N Pieretti, SA Zollinger et al, Proceedings of the Royal Society B, 2013 – royalsocietypublishing.org & https://doi.org/10.1098/rspb.2012.2798