Part 10: The sound approach to birding

When I imagine my name in British Birds (‘BB’), I always see it after the words ‘White’s Thrush 17th October, Studland village’ so, ‘M Constantine pers comm’, in Pennington & Meek’s (2006) paper on ‘The Northern Bullfinch invasion of Autumn 2004’ wasn’t quite what I wanted. Particularly because I couldn’t remember communicating with either of the authors, although as it turned out, Arnoud had told them about a Northern Bullfinch I recorded in Finland. I wish I had been in contact with the authors directly, as it is an interesting paper, discussing an unknown ‘trumpeting’ call which was picked up all over Europe. There’s a single page on sound, where the distinctive call is discussed at length and then a three-page discussion at the end, all best summed up by the authors echoing previous brave souls who tried to write about bird sounds: “the wide range of descriptions and comparisons used by observers only served to emphasise the variations in human perception”. 

Pennington and Meek ask the following questions. Where have the birds making this call come from? Why had so many of those that they had corresponded with never, or only occasionally, heard the distinctive trumpet call before? Was the sound diagnostic of Northern Bullfinch? They concluded that “this call is not diagnostic of Northern Bullfinch”, “that birds giving such a call had been recorded in northern and western Europe before”, and that the birds most likely originated in European Russia, with any heard further west in the breeding season “possibly lingering from previous influxes”. What makes the piece most interesting is that it illustrates so well the problems of investigating puzzles like this without a framework to make sense of the sounds. To conclude the book lets try to answer the same questions using ‘The Sound Approach to birding’. 

We are more fortunate than they because we can start with an unequivocal example of a known Northern Bullfinch making the sound that everyone is talking about. On the 1st of November 2004, Arnoud recorded a first-year female Northern Bullfinch at the ringing station in the Kennemerduinen national park near his home in the Netherlands (CD2-93). It had been measured and identified to subspecies, ringed, photographed and released, and was calling three metres up in a dead tree, six metres away from him. We can see from the frequency of this call in the sonagram that it’s perfectly within normal hearing limits, so it’s not being misheard. If birders were missing them in the past, this had more to do with not listening out for them, rather than the sound being missed. We know that the same sound is used in flight, because we have a recording of calls of another female (CD2-94) as it migrated along the Dutch coast, passing within a few metres. As we have demonstrated, there is nothing unusual in a bird using the same sound in different circumstances. Both birds were recorded in quite favourable acoustics, with negligible degradation of the sound at such short distances. If you listen carefully you can hear a slight Doppler effect as the migrating bird flies past the mic. 

Now we have to consider ageing and sexing, as a first-year female may well sound different to an adult male. We can check this with a recording made at a migration hotspot in Sweden, where we recorded this male Northern Bullfinch perched on top of a tree (CD2-95) making a very similar sound to what we heard in the previous two recordings. In the collection, we also have other recordings of Northern Bullfinch of both sexes giving these calls, both first-years and adults. 

By now it becomes clear that having real recordings to listen to and discuss is much more fruitful than having to guess the sound from comparisons such a “phone ringtone”, a “far-away train horn” or a “rather electronic version of a car horn”. The ‘trumpet call’ has a most distinctive tone, and is quickly distinguished from calls commonly produced by smaller Eurasian Bullfinch subspecies. The ‘classic’ bullfinch sound for western European ears is typified by equivalent calls of pileata of Britain and Ireland (CD2-96a), but note that europoea of western central Europe can have different and rather distinctive calls for flight and maintaining contact (CD2-96b), at least in coastal areas of the Netherlands. Comparing sonagrams, we learn that not only do these calls sound distinctively different; they also have quite different structures (the BB paper had no sonagrams).

Next, let’s consider rhythm and timing. Northern Bullfinch ‘trumpet calls’ are sometimes used in stereotyped combinations with one or more other types of call. In CD2-97, doubled calls very similar to trumpet calls alternate with two other types of buzzing notes in a regular sequence. Bullfinches of both sexes are known to produce these ‘sequence calls’, and our collection reveals that they can be heard at various times of the year. The repeated nature of ‘sequence calls’, given by perched, often solitary bullfinches of all subspecies, suggests a parallel with chaffinch ‘rain calls’, reminding us of the possibility that what we thought was a call may sometimes be used as part of a song.

When reading the BB paper, you get the uneasy feeling that the authors and most of their correspondents assumed that Northern Bullfinches have just one or two calls, rather than a whole repertoire of sounds that can be used in many ways. Listen to a couple of other calls in the non-breeding repertoire of Northern Bullfinch (CD2-98). BWP lists 17 types of call and song, with extensive notes on the behavioural context in which they have been heard.

Interesting though these other calls are, as birders we know that we can often identify birds quite successfully when we just know one of their sounds. This works because outside the breeding season, and especially in winter conditions, most birds only use a small part of their total repertoire. Sexual attraction, rivalries and caring for young are no longer the main issues; the priority is to stay with friends and keep out of danger. At such times, birds behave less extravagantly to conserve energy. A much smaller repertoire of calls fulfills their needs, and certain calls will now be used much more often. This may be one reason why the ‘trumpet calls’ of Northern Bullfinches attract our attention during migration and winter. Listening to and analysing our own recordings of Northern Bullfinches made in Finland and Lapland from 2001 to the present, and to Finnish sound publications like Luonto Soi (Hallikainen 2001) and Lintumme Laulavat (Birdlife Finland 2001) we find that in some areas the ‘trumpet call’ is used throughout the year although during the breeding season it probably forms a smaller part of the total vocal output. So if Finland and Lapland form part of the normal range of ‘trumpeter bullfinches’, why were so few Finnish birders familiar with these calls? Who knows, but having been on three winter recording trips to Finland, in temperatures as low as -18ºC, I can tell you that even hardened Finns wearing three layers of thermal underwear don’t like to stay outside too long in the winter. 

At this stage we can sum up a couple of our conclusions. Although we have no reason to dispute that the ‘trumpet call’ is used by Northern Bullfinches from further east (Antero Lindholm has recorded ‘trumpeters’ in Komi, European Russia), it appears that this sound is used regularly by Finnish birds, and its occurrence seems too widespread to be explained by birds “possibly lingering from previous influxes”. We would agree that it had been noticed before 2004, as we had previously recorded it ourselves, both in Finland and during autumn migration in the Netherlands. As to whether this sound is diagnostic for Northern Bullfinch, we have listened to and analysed many Eurasian Bullfinches of other subspecies, and we have yet to find it outside this taxon. So while we would agree that not every Northern Bullfinch uses this call, other bullfinches don’t. In other words it is diagnostic. 

However, as always, it’s not quite that simple: now we need to bring a little caveat into the discussion. One of the features of Northern Bullfinches that made them very popular with bird keepers in the past is that they can be taught to mimic other sounds very easily. Ludwig Koch, in his Encyclopedia of British birds (1957), wrote that Northern Bullfinch was imported into England as a cage bird and that “this is the bullfinch seen for sale in shops”. Northern Bullfinches were regularly taught to sing complicated songs with the help of a musical box or penny whistle. Research has also shown that bullfinches learn their calls from their father, and Bergmann & Helb (1982) tell us that parent bullfinches can also pass on songs learned from humans to their young. As in certain other finch species, it has also been discovered that individual pairs of bullfinch share their own distinctive calls; a bird can pick out and respond to its mate in among a crowd of others. So while the ‘trumpet call’ seems to be diagnostic of Northern, other bullfinches are probably capable of learning it.

Conclusion

The Sound Approach to Birding is dedicated to Peter Grant. I first met him in Mallorca where he was tour leading. He was chairman of the British Birds Rarities Committee at the time and an editor of British Birds. I was very keen to learn, and he was a great teacher. After his tour leading duties, he would sit with Mo and me drinking wine and teach us about moult, topography, and identification. Through him I came to meet Killian, Arnoud and indirectly Magnus. This book was to be a pamphlet like his The New Approach, and through his example I looked and listened to bird sound and read the science behind it as in the same way he had approached gulls. He died of cancer at Easter in 1990, and as I conclude the book I am again in Mallorca and it is Easter 2006.

It could have as easily been dedicated to Magnus Robb, as the power house of The Sound Approach, had he not had so many accolades throughout this publication. Sometimes when he’s deeply immersed in sound recording, I think he models himself on Orpheus, poet and musician, who protected the Argonauts from the Sirens with his music. According to myth, Orpheus taught the birds to sing, but Magnus, who thinks about such deep things, believes that the ancient Greeks got it the wrong way round, and the birds taught us to sing. Personally, sitting in these mountains puzzling over the differences between songs of both rock thrushes, I realise that the birds are teaching me to listen.

To conclude, see if you can hear Magnus sigh as nature tries to disrupt his efforts to record a beautiful song of Ménétries’s Warbler S mystacea while at the bottom of a steep rocky wadi in Turkey.

As I reach the end of the book my hope is that it will help popularise bird sound identification. During one of the long sessions of work together, Magnus asked me to define what I meant by popularise. “I would like to be able to talk to someone other than you about it, Magnus.”