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FIREFINCH is a fantastic app to the birds of Southern Africa. As I am one of the creators of the app, I might be a little biased. Amongst many other features that sets FIREFINCH apart from any existing apps, is that it features regular articles on birding-related topics. Your app will automatically load this new content. So far we’ve talked about giant penguins, falling off cliffs in search of owls, how to ID frigatebirds, birds that use lava to warm their eggs and many, many more topics. In fact, to celebrate the 50th FIREFINCH post (which we call Dawn Chorus articles), I’ve duplicated the post here. If you enjoyed this article, why not try out FIREFINCH?

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Today I want to invite you to share in a very intimate birding encounter. To spend ten minutes with an incredibly beautiful, characterful, talented and charming little bird. It’s a bird you’ve seen many times before. Chances are there’s one outside your window right now. But this one is special. I consider him a personal friend. It’s a long story…

It started when Lockdown hit. Seeing as that I couldn’t go to the birds, I thought I would bring the birds to me. With a lot of patience and a whole lot mealworms, I gradually won the trust of a pair of Cape Robin-Chats that live in my garden in Langebaan on the West Coast. Every time I tossed them some worms, I would make a loud tsk-tsk sound. They quickly started associating this audio cue with food, and over the course of three weeks or so, they became increasingly tame. So much so that they would land on my outstretched hand or come hopping into my office to ask for a snack. The ultimate proof of their trust is when they started nesting just outside my office’s sliding door. 

Even now, three years later, they still come to investigate when I make the feeding time sound. And they are still completely unafraid. It sounds silly, but their acceptance makes me feel more appreciated than any human compliment, accolade or rank.

Waking up, SA-style
Many South Africans wake up to the pleasant musical stylings of a Cape Robin-Chat every morning. I call them the ‘shopping list’ birds: each phrase starts with the same note, so it’s like the bird is reading a shopping list and needs two of everything. 

Two…dozen eggs.
Two…litres of milk.
Two…loaves of bread.

This basic song structure may be completely devoid of imitations, or may be richly peppered with borrowed notes. The late Terry Oatley, a man who had a lifelong passion for robins, recounts a delightful story in his book Robins of Africa. Over a period of eight months, noted SA ornithologist C. J. Skead kept tabs on the imitations of a Cape Robin-Chat singing outside his window while he was lying in bed. Over those months his robin imitated 36 other bird species! Sadly, the robin was found dead on the veranda of the house. The next morning, no song greeted Skead. But, three days later, a robin was once again singing. Only this time the bird did not incorporate any imitations.

In the sonogram of a Cape Robin-Chat song below, you can see how the bird mixes and matches borrowed sounds. The imitations are given in very short snippets—often just a single note—and mixed with calls of other, non-related species. In this way the bird makes up a completely new variation. Instead of having to learn multiple song variations, the bird borrows sounds from its environment to make its song richer and more impressive. Like making a playlist or mix tape to impress a girl. It’s much harder to write songs yourself, so just borrow some from your favourite bands!

But so far we’ve been talking about the main, loud, territorial song. The brave face and best foot forward song. We’re going to explore something less frequently heard and much more special, called subsong.

The term subsong was first coined in 1936. Essentially it is given by birds with low sexual motivation. It’s thus a far cry from the loud and stereotyped territorial or advertising song that you normally hear, typically from adult males during the early nesting cycle. Subsong may be given by adults during the non-breeding season or first-year birds that have not set up a permanent territory. 

Many use the term subsong to refer to the compositions of juveniles practising their vocal skills. It’s akin to the babbling a baby makes when learning to speak. To me this is something different: every year I listen to the juvenile Bokmakieries honing their skills while exploring the garden. The overall effect is recognisable as the full adult song, but much less musical and more halting, with many false notes and stop-starts. Subsong may not be full song, but it certainly involves a great deal of skill and subtle nuances that I don’t think juveniles can yet manage.

Subsong is usually given from within dense cover, often during the hotter hours of the day. It can continue intermittently for hours. My robin is subsinging as I type this, and has been doing so, on-and-off, for the last three hours. Subsong is very, very soft: following our shared adventures in Lockdown, this robin is, literally, hand-tame and not afraid of me at all. Consequently I was recording it at point blank range: within 1-2 m of the microphone (which is an overkill parabolic dish). Even at that close range and with professional equipment, the soft warbling is hardly audible. It is drowned out by any background noise, such as the boisterous local Cape Weavers. While it is singing the bill hardly opens at all, and the throat vibrates slightly.

So what does subsong sound like? Soft. We’ve established that. Fast and confident, yet calm. Almost continuous. And endlessly variable. Lots of passerine birds do it: shrikes, warblers, sunbirds, chats, you name it. It’s certainly not designed for projecting. Not aimed at another listener. When I recorded this clip there were no other robins nearby: no mates and no competitors. The bird was literally just singing to itself, while going about its daily activities and taking it easy in the shade.

So how many other birds can a robin imitate? I don’t know if we can ever have a definitive answer to that question. Robins learn throughout their lives, and you can even teach your local one some phrases. If you remind him often enough and keep him practising. 

What exactly was this robin singing? I was curious, so I decided to analyse the full recording of my friend in the garden. I chose a nice 10 minute section. Those 10 minutes took me 10 hours to analyse!

I listened, replayed, compared, plotted sonograms, measured frequencies and times, cut and pasted, listed, corrected, highlighted, imported and exported, and listened some more. At one point the robin himself came fluttering into my office, hearing his own voice being played back. So I switched to earphones.

If you’ll forgive me a bit of vanity: I’m pretty sharp on bird calls, and especially here in my local patch. But even so, I could only identify 70% of the imitations. Many of the outstanding 87 mystery phrases (of which 84 were unique) sounded frustratingly familiar, but I just couldn’t place them. It also took me a while to realise that the robin was struggling with low frequencies, such as lapwings, gulls and korhaans. In these species it only copied the higher tones, which made the imitations sound familiar but distorted. 

Another issue, is that I suspect there is a bit of second-hand mimicry happening. The neighbourhood Common Starlings are themselves excellent vocal mimics, and some of the robin’s phrases sounded like starling renditions to me. So a photocopy-of-a-photocopy effect, meaning that some detail is lost in the replication.

The other big challenge with teasing apart mimicry like this, is that the singer recomposes notes from different birds into new phrases. So you might have five different elements from 3 species all mixed up within a 2 second phrase. This robin particularly loved quickly alternating super high squeaks of sunbirds and penduline tits with lower whistles from fiscals and francolins.

The question of why birds imitate or mimic other species is perhaps a topic for another day. There are different explanations in different contexts. But in most cases vocal imitation probably serves to enrich or diversify song in order to increase repertoire size. The bigger the repertoire, the sexier the singer. A bigger repertoire is an honest signal to mates or competitors which indicates a healthy, intelligent singer. 

Much like humans would learn language, songbirds learn by listening. And repeating. Indeed, reading is a good parallel in human terms. You didn’t invent the words. You heard them around you and made them your own. You are just as proficient at pronouncing these borrowed words as the original wordsmith. You can compose different words in different orders. There will be some repeats of particular words, but most are unique. 

And perhaps that’s the best way to look at subsong: it’s like singing softly to yourself or reading a passage under your breath. No-one’s listening, but you like to keep your mind sharp and entertain yourself. A bird’s full, powerful springtime song is like speaking in front of an audience: you limit your thoughts, pick your words carefully, convey a specific message and project loudly. 

It is just incredible how much complexity is contained in a few minutes of song from this “simple creature”. It certainly kept me entertained over the weekend!