Birdsong has evolved over immense periods of time, and with Australia’s Robins, you can hear that evolution in the songs these birds sing today.

Where we live in southern Australia, there are four closely related, ‘red-breasted’, Robin species (note these are Australian Robins of the Petroicidae family – unrelated to the European or American Robins):

The Rose Robin, Petroica rosea, found in dense, wet forests
The Flame Robin, Petroica phoenicea, which prefers more open areas in heavy forest
The Scarlet Robin, Petroica boodang, common in open woodland
and the Red-capped Robin, Petroica goodenovii, found across the drier inland of the country.

You can see that each of these species are adapted to successively drier habitats.

Over geological time, Australia has gradually ‘dried out’, with the wetter forest types that formerly covered much of the continent now being largely restricted to coastal and highland areas. Thus the wetter forests are the older habitat, and the drying inland a new habitat to which Robins have adapted.

So I’m surmising that the wetter forest species, the Rose Robin, is probably the ‘oldest’, and the others have evolved from that species, leading to the Red-capped Robin being a more recent species adapted to a drying continent.

If so, then each ‘drier country’ species may be expected to have evolved successively. You can see a graduation in their plumage patterns, such as the successively larger size of the forehead ‘flash’, the darkening of the back and the deepening red of the breast color.

I was curious to find whether this was also reflected in their songs – whether you could hear evidence of a successive development in their song structure.

Here are the songs of these four Robin species:

As you can hear, each has a fairly recognisable, and quite pretty, little song. To assist appreciating what is going on in each bird’s song, I’m presenting sonograms of each.

The Rose Robin has what could be called a di-phonic melody, there are two melodic components to it, a higher pitched one, and a lower, the song weaving these together to create a lilting pattern.

The Flame Robin’s song doesn’t show these two clear upper and lower components. Instead they have been integrated into a more singular melodic line, although still showing a lot of rising and falling, ‘lilting’ movement.

By the time we get to the Scarlet Robin however, the single melodic line has ‘levelled out’ to being almost on one pitch.

So you can see a successive relationship quite clearly in the songs of the Rose, Flame and Scarlet species, which each have a similar dainty, twittery song.

However, the Red-capped Robin seems at first to have an utterly different song. It still has that dainty quality, but rather than the melodic ripple of the other red Robins, it is comprised of two repeated syllables. When you look closely at a sonogram, each syllable is actually a rapid trill, with chipping, ‘grace-notes’ before and after.

Is the Red-capped Robin’s song actually related to that of the other red Robins, when it sounds so different?

Lets go back to the Scarlet Robin’s song. If you look closely at the sonogram (and you can just hear it too if you have ‘quick’ ears), you will see a tiny pair of trills hiding among the sonic structure. One is almost not there at all, but the other is clear enough. It is the same trill structure as the Red-capped. And you can also find that the melodic components in the other Robin’s songs have de-volved to those little ‘grace-notes’ that bookend the Red-cap’s trills.

So you can both see and hear a progressive relationship in the songs of these four closely related Robin species that matches the changes in their chosen habitats.

Australia has other related Robin species, for instance the yellow robins, which look and sound quite different and are thus likely to be less closely related to the ‘red’ robins, and the Hooded Robin, who’s song does show similar structures and can easily be seen as just a ‘red’ robin that has lost its ‘red’.

What this leads to is an appreciation that, when you are outdoors surrounded by birdsong, you are hearing not just a unrelated variety of avian vocalisations, but a soundscape that has evolved.

It may not be evident until you listen closely, but you can actually hear the evolutionary history of our planet in the birdsong around you.

Tweet

Birdsongs often sound like simple, twittery noises to our ears, but what do birds hear? It is difficult to know of course, but the first thing to notice about birdsong is that is often incredibly complex sonically.

To give you an idea of this, I’ve taken the song of a Superb Fairy Wren. Their song may be described as a loud, brisk, merry reel, often like a tinny alarm clock (from Graham Pizzey’s ‘Field Guide to the Birds of Australia’). It just sounds like a scratchy, ripple of notes – very characteristically a Wren!

You can hear two song phrases on the first part of our sound sample. (Pause when they’ve played – and read on!)

Here is a sonogram of that 3 second burst of song. (A sonogram is like a picture of what you’re hearing, with time (in secs) on the horizontal axis and frequency (kHz) on the vertical.)

Just look at it. You can see that this wren is putting a wealth of sonic acrobatics into his song – far more than we are aware of to just hear it.

(Click on the image to view it larger if you like. By the way, some of the fainter lines below are from background birdsong, Robins and Magpies)

Why don’t we hear this complexity? Probably because we have a different perception of the world around us than a Wren probably does. To get a ‘Wren’s-ear listen’, we can slow the sound down.

How slow? Well, a wren has a possible lifespan of around ten years. They rarely get that old due to high mortality, so that is a potential lifespan. You could say that they live their life in around an eighth the time we do. So I thought; what happens if I slow down their vocalisations by eight times? This would drop it several octaves and bring it more into our human hearing range – and also slow it down to our pace of mental comprehension.

The result is pretty extraordinary, I think you’ll agree. Here is an expanded sonogram of the whole song. Click to expand, and you’ll probably want to play the sound sample again and follow it on the sonogram.

I was amazed to hear what this Wren is actually doing, and how, well, ‘human’ the phrasing is. At this speed, you may may be tempted to actually imitate what this Wren is singing with your own voice. If you try, you’ll realise it is not that easy – there is a lot of sonic subtlety in there.

Indeed – it is comparable with the amount of subtlety that we articulate in our singing and speaking.

Which leads to the question; how much of the acoustic information and variety in a Wren’s song is actually intended? In other words, a part of it’s communication? It is obvious that birds need their songs to survive, and that they respond to them in acutely subtle ways – but how much is conscious for them?

Just to compound the puzzle, consider this.

While each three-second Wren song sounds superficially the same to us, they are actually very different. Here is a sonogram of the second song phrase, and you can see it is different to the first.

They are each comprised of very different sonic patterns. When you make a sonogram of them or slow them down, you can see and hear these different phrases. So Wren songs are like snowflakes – each one unique.

Are we just witnessing the variability of nature, an artefact, a ‘can’t quite do it the same twice’ phenomena? Or is this a vital part of Wren survival? Nature is not usually wasteful, so is all this detail just ‘acoustic junk’, or actually an intentional part of Wren communication?

Instinctively, I lean toward the latter. I reckon it means something to Wrens. It is tempting to imagine that each of their songs is like a human sentence; saying something with a unique meaning. But I feel it is more likely that, if it is intended, then it is more akin to our way of singing a song, where we hear the song as one expression, even though it is comprised of many melodic phrases. It is also likely that it is a marker of individuality and virility; ‘this is my song, and see how varied and fine it is!’

But I am guessing. I am no researcher, and I don’t have answers to my own questions. For me, these observations just highlight how little we know about the amazing lives of even a common garden bird like our Fairy Wrens.

So the next time you are hearing birdsong in your garden or woodland, consider what they may be saying to each other. It may be more than you think.

Tweet

We’ve just had a succession of 40 degree days. I’m talking Celsius (that’s over 100 degrees Fahrenheit), and yes, I’m writing from the Southern Hemisphere – Australia.

The cicadas have begun singing in the eucalypt forests around us, and the other morning I put my microphones out for a few hours to capture their choruses. For those of you locked in the depths of the northern winter, have a listen while you read on, it may warm your spirits!
Multi-species cicada chorus in the Australian bush by Listening Earth

Now on to ‘I and the Bird’ #116 – the hot, the cool, the mysterious and the exotic!

Lets stay in warm climes to begin, visiting Panama in search of elusive Ground Cuckoos, Ecuador for an emotional encounter with a Crimson-mantled Woodpecker, and a gallery of truly stunning images of birds from Costa Rica.

While we’re in latin America, wade through the mud for a day with a research team studying Flamingos on a lake shore in the Bolivian high Andes.

Off to Africa next, and a new quest; to sight one of Tanzania’s endemic skulkers, the secretive and rarely-seen Spot-throat.

In Australia, we brave inclement weather hoping to hear the ethereal dawn song of the Tawny-crowned Honeyeater.

Now let’s go way cool… For many of you, winter is bringing the challenges of birding on chilly days, but the promise of finding a winter wonderland of birds.

It is a good time to view waterbirds, and look out for seasonal visitors that have arrived to over-winter.

Strolls by icy watersides give pleasure to many birders, bringing with them sightings of Gulls, waders and Mallards, both Red-winged and Brewer’ Blackbirds, plus Goldeneye, Eurasian Wigeons and, well, more Gulls!.

In Denver, a short riverside walk leads to a collection of lovely waterbird images, and possibly a new addition to the birder’s lexicon; ‘Colatteral Duckage’. On the waters of New York Bay, gulls continue to fascinate with their graceful flight.

In Austria, Mute Swans float serenely on Achensee, prompting these thoughts on photographing white-plumaged birds in a winter landscape. Also out on the water, this Cormorant may have bitten off a little more than it can swallow!

Of course one doesn’t need to venture far to enjoy the birdlife, even in winter. The bird feeder just outside is always a good place to view interesting behaviour and interspecies interaction – it also inspires an opportunity for bird sketching.

As wonderful as photographs can be, a talented ornithological artist can capture something special of a bird’s character, as these studies of an American Bald Eagle show. Even using only monochrome pencil, an insightful artist can illuminate their subjects and bring them to life.

Christmas bells were heard at the end of this day spent searching for raptors, and new year’s morning brought the first bird sightings of the new year.

For another birder, a day spent Owling leads to a dilemma over the right thing to do.

Winter also brings some unexpected encounters, such as this Brown-headed Nuthatch at Lake Norman.

Here though is a sighting that is just plain baffling; the Desert Finch is a native of Kazakhstan – what is it doing in Arkansas?

Which brings us to the mysterious.

A flow-motion ‘mystery’ photo of a Golden-crowned Sparrow has now been conclusively identified, but is still fascinating for the abstract patterns created by moving plumage.

On the subject of identifying species, consider this cautionary tale about being overconfident in your bird id, in this case a Turkey Vulture – especially when you didn’t actually see the bird! While with Turkey Vultures; here a group of them take over a cell-phone tower.

Finally, to the exotic… and what could be more exotic than species previously unrecognised by science? This fascinating article presents a wrap up of newly-described species for 2009.

May 2010 bring you many beautiful moments and delightful discoveries in nature.

Tweet

‘Bill-clicking’ is a widespread behaviour, and is sometimes combined with normal vocalising, as with the flock calls of White-winged Choughs, where a bill-click subtlely precedes a mournful descending whistle (listen for it on track 11 of our ‘A Morning in the Australian Bush’ album).

The distinctive slapping of wings in flight by Crested Pigeons or the haunting whistle of wind through the feathers of Hornbills are other examples of non-vocal sound generation.

I’ve even heard a female White-winged Triller Lalage sueurii distinctly ‘coughing’, or more accurately using what sounded like a very throaty exhalation to create a soft ‘hissing’ sound.

Here is a recording of it.

(You may have to turn the sound up – it is a very soft sound, almost lost in the ambience of the landscape. You can hear it as two ‘hisses’, the first just after the prominent song, and the second softer about 3 seconds later.)

However recent research indicates that the Club-winged Manakin Machaeropterus deliciosus is in a league of its own. These small birds live in the mountain rainforests of Ecuador and Columbia in south America. In a process similar to how crickets and cicadas call, the male vibrates its short wing feathers to create a brief tone around 1500Hz. Unlike some of the sounds I’ve mentioned earlier, the Manakin’s sound is a fully-realised ‘birdsong’, used by the male to attract the female in the species’ communal breeding display.

Other closely-related Manakin species also create mechanical songs, but the Club-wing is the most ‘musically’ articulate. It’s ability is not only an extraordinary evolutionary development, but one of the clearest examples of how a bird can use its body rather than its voice to ’sing’. Click here for a short National Geographic video showing how they do it.

See also: Wikipedia article and New Scientist article describing recent research.

Tweet

Here is a picture that illustrates what I am talking about. This shows the waveform of a recording from our recent album ‘Frogs, Frogs, Frogs!’. Time flows horizontally from left to right, and the amplitude (volume) of the sounds registers vertically. It shows about 10 seconds from track 16; ‘Striped Marsh Frogs (Southern race)’. These frogs have a sharp and quite loud clicking sound, and you can see each frog ‘click’ as a vertical line, where the volume of each frog (there are several calling here) is indicated by the height of the line.

What is remarkable is that the volume of the clicks from each frog is nearly identical. I have drawn some lines on this waveform to indicate the calls of individual frogs.

Thus you can see that when a frog makes its call, it has little control over the volume or expression of its vocalisations in a way that we take for granted. Considering that amphibians are a primitive family of animals, and have limited vocal apparatus, this is understandable.

Of course individual frog sounds do vary quite considerably, but this is often a factor of their body temperature, derived from the ambient environmental temperature. Sometimes these variations, affecting pitch and frequency of calling, can be so great that frogs of the same species can sound like another altogether. An example of this can be heard also on the album: compare the spotted marsh frogs heard in the background during tracks 5 or 8 (rapid “uk-uk-uk” calls), with the chorus of them on track 14. You can hear the lower pitch and slower rhythms very clearly, its the same species, but you’d be excused for thinking it wasn’t.

And just to give an example of racial differences, compare the ‘click!’ sound of the southern race of the striped marsh frogs we were looking at earlier, with the tennis-ball-like ‘whuck!’ of their northern cousins (track 5).

So given their ‘limited’ vocalising abilities, what makes frog sounds so appealing to us? Well, for me, lots of things, principle among them rhythm and texture. The tones of different frog species can be fascinating; chiming, bleating, clicking, croaking, moaning, laughing, whistling, purring… there is an endless variety to frog sounds. They seem to do everything – except curiously “rrri-bit”, I’ve yet to hear a frog do the classic “rrri-bit”!

Frogs also set up great polyrhythms. These rhythms are important and purposeful, a part of frog’s evolutionary survival strategy. In a dense frog chorus, complex overlapping and interlocking rhythms allow each individual frog to be heard, while simultaneously confusing predators who may be trying to locate one frog by its call.

The frog choruses on our ‘Frogs, Frogs, Frogs!’ album were recorded in diverse habitats across Australia, from tropical rainforests in the north, to the outback after rains, and bush waterholes in the east and south. Each chorus has something that may appeal to you, from the familiar calls of pobblebonks that open the album, to the extraordinary moaning of western spotted frogs that conclude it.

Both are included in a sound sample from the album, which you can listen to here.

‘Frogs, Frogs, Frogs!’ is available for exclusive download from the Listening Earth wesbite.

Tweet

Every two years, the Australian Wildlife Sound Recording Group gathers for a workshop, and in October of 2007 we met for a week of talks and social events, on a bush property near Mount Walsh National Park in SE Queensland. Many in the group are amateur nature recordists, and together we are an odd mob, but there is always a lot of knowledge, experience and good humour shared.

On this occasion we had the honour of hosting two guest speakers from the USA: Don Kroodsma is one of the world’s leading researchers into birdsong and avian vocal behaviour, and Greg Budney is the head curator at the Macaulay Library of Wildlife Sound at Cornell University.

For me, meeting with Don Kroodsma was inspiring. As professor emeritus at the University of Massachusetts, and having spent the last 40 years researching birdsong in the field, he has some very interesting things to say about how and why birds sing.

Don has recently published a book entitled ‘The Singing Life of Birds’, and I took the opportunity of reading it around camp at Lawn Hill (a good use of shady trees on hot afternoons).

At the gathering, I took Don aside for an hour and sat him down under another of those shady trees for a discussion about the science and aesthetics of listening to birdsong. As we talked, the birds sung around us. You can listen to what Don has to say about our feathered vocalists by downloading our discussion here (mp3 file, size 63Mb, right click & save to desktop).

Don’s ‘The Singing Life of Birds’ is a fascinating and delightful read. It is poetic, thoughtful and full of insights. We bought a copy from the splendid Andrew Isles Natural History Bookshop in Melbourne (AU$50), but it is also available via Amazon.com.

The book includes an audio CD to accompany the text, and I guarantee that after reading what Don has to say, you will never listen to a bird singing in quite the same way again.

A related book that I also read on the road, and can thoroughly recommend, is Don Stap’s ‘Birdsong’. It is writen from the perspective of a non-expert, as he accompanies some of the world’s leading researchers (including Don Kroodsma) in their field work. It is as much a book about the people who study birdsong as it is about the birds themsleves.

Giving a good overview of current knowledge of birdsong, it is an easy read, and makes a good prelude to delving into Don’s work. (It is also available via Andrew Isles, or online sellers such as Amazon, where I see you can buy both books as a special deal)

Tweet

]]> http://www.listeningearth.com.au/blog/a-fresh-perspective-on-listening-to-birdsong/feed 0