Why soundbirding ?

Why soundbirding ?

The aim of this collaborative website is to provide keys to improve our knowledge on acoustic bird identification and promote the use of acoustic approaches in citizen science.

Seeing and hearing are neither substitutable nor complementary. Focusing on sounds rather than on visuals really means exploring new dimensions in bird detection and identification. Sometimes, sounds will barely comfort the visual approach, sometimes they will completely outperform it. Here are a few reasons to explore soundbirding :

Birders on Ouessant island (France) waiting for a very vocal yet hidden Red-breasted flycatcher (Ficedula parva) to come out. ©Stanislas Wroza
  1. Seeing through bushes
  2. Birding at night
  3. Identification of birds in flight
  4. Sound phylogeny and dialects
  5. Strengths and limits of the sound approach : what can we really expect ?

1. Seeing through bushes

As my favourite birding saying goes:

“There are two sides on a tree : the side you can see and the side where the bird is”

Birds often move deep into bushes or high up in the trees. And when we get a glimpse at them, the probability of identifying them correctly highly depends on parameters such as the lightning conditions, viewing angle, duration of the observation, distance to the bird… Even with good pictures, some birds remain unidentified.

Sound has the power to overcome these obstacles. Bird calls are loud enough to cross many physical barriers, and are (almost) not distorted by the environment. In rains or in blinding sun, at dusk or in mid-day, close or distant, behind that branch or deep into that bush, a “chip” note is a “chip” note. Each species has its own call, that is (almost) not depending on any external parameters, so that the detection of the bird and its identification generally happen simultaneously. As soon as the bird has called, it has delivered to you its identity. Just get the spectrogram and this will ensure in most cases a 100% identification.

In practice – of course – things are a bit more complicated than that. Still the fact is that, with sounds, you can “see” birds that are hidden deep into a dense reed bed or a dark forest and identify them without even knowing where they are. That’s like some kind of supernatural powers isn’t it ?…

This famous Siberian rubythroat that has wintered in the Netherlands in 2015-2016 spent most of its day close to the ground and hidden in bushes, but the bird was advertising its presence by singing in mid-winter ! ©Stanislas Wroza

2. Birding at night

For most people, birding at night is a crazy idea. The best thing you might see is a flying by owl crossing the beam of your flashlight. Hopefully you might identify it based on size and flight. With sounds now, neither your eyes nor the daylight are necessary to go birding. The night is filled by an unexpected variety of songs and calls, often different from what you can hear during the day.

Midnight is your best luck to hear rails, crakes, owls and a variety of migrating birds such as thrushes or shorebirds. Sound birding enables you to explore this often neglected dimension of birding.

American woodcock (Scolopax minor) : a night bird that is typically more often heard than seen. ©Stanislas Wroza

3. Identification of birds in flight

Most songbirds are difficult to identify in flight. Even with a good camera (and a lot of dexterity !), visual identification of passerines in flight remains a challenge because you will often miss that particular obvious little feature on the back that is not visible on your picture.

Luckily enough most of them produce a loud sound while flying over us. The flight call – produced while taking off or during migration – is often diagnostic and enables a 100% identification in many cases. Hence, soundbirding is unarguably the best approach for the flight migration of passerines. During spring or fall migration, just find an open place and you will get over 30 species flying over.

On the left the only picture I could get of a Richard’s pipit (Anthus richardii) flying over me in Picardie (France). You can’t really identify the bird based on this. On the right, a 100% identifiable spectrogram of a Richard’s pipit. © Stanislas Wroza

4. Sound phylogeny and dialects

4.1 Divergent evolution in sounds

Sometimes the evolutive history of vocalization can be more perceptible than the evolution of visual phenotypes. This is the case for some tricky birds like warblers.

For some of them, sound can even be the only diagnostic criterion, or at least the easiest way to tell the difference. One good example down here in France is the much discussed Iberian chiffchaff (Phylloscopus ibericus) /Common chiffchaff (Phylloscopus collybita collybita)/ Siberian chiffchaff (Phylloscopus collybita tristis) (Soundbirding article about their vocal identification here)

Just compare these three songs :

While the songs are fairly different, a visual identification, when even possible, is tricky.

Iberian chiffchaff (Phylloscopus ibericus). © Pierrick Devoucoux
Common chiffchaff (Phylloscopus collybita collybita). © Thibaut Chansac


Siberian chiffchaff (Phylloscopus collybita tristis). © Stanislas Wroza


4.2 Dialects

Divergent evolution in sounds can occur so fast that difference may be perceptible among different populations of the same species : just as humans have regional accents, some bird species develop distinct, area-specific dialects. This generally arises when populations of the same species are isolated by geographic barriers such as mountains, water, or wide areas of unsuitable habitat. These local dialects are then inherited by the next generations, which do not hear any other songs than those from their fathers and other local males. After many generations, the songs within one isolated population may be well-defined and significantly different from those of other populations.

This is very perceptible with crossbills, that are proven to have many local dialects. These are so complicated that it is sometimes difficult to know whether two populations should really belong to the same species. Sound divergence occurs at both specific, regional and individual level

Hence soundbirding may enable to gain accuracy, by identifying not only the species, but sometimes also some subpopulations, offering promising prospects for researchers.

Scottish crossbill (Loxia scotica). Still a controversial species, it was distinguished from other crossbills by its scottish accent ! ©Stanislas WROZA

5. Strengths and limits of the sound approach : what can we really expect ?

5.1 Sound and raritys.

Sound and visual birding are not substitutable nor perfectly complementary. Unavoidably, your attention will be mainly focused on either listening or watching. On a more technical level it would be fairly difficult to carry a scope and handle a microphone at the same time.

So if you’re looking for raritys on the coast, you will be more likely to find something in your scope or binoculars than hear a rarity in your microphone. If you’re looking for breeding songbird surveys, or interested in monitoring passerine migration, then a more sound-oriented approach is probably the best choice to maximize the detection probability

Having said that, what can we really identify ?

One of the most striking example of tricky sound identification I’ve witnessed was Julien Rochefort’s first ever documented little bunting for Paris area.

On the 15th of September 2008 Julien saw a small passerine migrating over the forest near Fontainebleau. With his microphone pointed at the bird he could record a dozen of tiny “tsip” flight calls. As you can listen below, this call was pretty insignificant and would probably not catch the attention of most birders. Julien didn’t identify the bird on the field but investigated very closely the spectrogram and could reach the conclusion that the only matching species was little bunting

It took a lot of time for this bird to be accepted as a little bunting by the rarity committee. Yet, this shows that under favorable circumstances (good recording quality, several calls and a good knowledge of the species involved) a vagrant might be identified in migration, even if its call doesn’t sound like much.

Little bunting. ©Stanislas Wroza

5.2 Pitfalls in sound identification

To conclude, it would be illusory to think that everything can be identified. If you look for raritys on sonograms, you’re going to be frustrated by spending way more time analyzing spectrograms without reaching any conclusion than enjoying birds. Having said that, we can still expect to identify most of the birds that produce flight calls provided we never forget those four major pitfalls :

  • Seasonality of bird vocal activity
  • Individual variations
  • Dialects
  • Signal quality

Read the next page of “The quick guide to soundbirding” : About bird songs 

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