From early spring to the middle of summer, the song of the Yellowhammer is (still) a familiar sound in the Czech countryside, as in much of Central Europe. In words, it can be described somewhat clumsily as "tsi-tsi-tsi-tsi-tsi-dzee" or more poetically as "a-little-bit-of-bread-and-no-cheese". You can listen to recordings of its song such as this one on xeno-canto. A useful way of picturizing bird song is to plot its sonogram, in which the horizontal axis denotes time, the vertical axis frequency, and the blackness of the picture indicates the volume of the sound. For a Yellowhammer song strophe, this typically yields a picture that looks like this:

In the left part of the picture, you see the part described in words as "tsi-tsi-tsi-tsi-tsi", which is called the opening phrase. In it, the Yellowhammer alternates two elements many times (in this example 18 times) after each other. In the right part of the picture, you see the part described in words as "dzee". In this example, it consists of two syllables and actually sounds like "dzee tsiep". This part of the song is called the endphrase.

The opening phrase can be sung in many different ways that to our ears sound similar (though not exactly the same) but that in sonograms can easily be told apart. I call these different ways of singing the opening phrase songtypes. In my study area, in the year 2016 alone, I have recorded about 48 different songtypes, many of which are unique to a single individual, but some of which are shared more widely. Usually, an individual has a repertoire of 1-3 songtypes. Usually, one way will be used for about half a minute (but this varies a lot between individuals) before the bird switches to another songtype (provided it has a repertoire of at least 2). If you listen carefully to a Yellowhammer, it is easy to recognize the moment when it switches to a different songtype. It takes a good musical ear, however, to be able to remember and recognize birds from their way of singing the opening phrase. Personally, I can recognize only a single bird by ear, which is special because it has a songtype that it is falling in pitch, while most birds sing the whole opening phrase at more or less the same frequency. Although many birds seem to have their own unique songtypes (at least within my study area), it is also quite common for birds to copy songtypes from their neighbors. Sometimes, in the sonograms you can still notice subtle personal differences in the way various birds interpret a songtype, but sometimes the only way to tell such birds apart is because the rest of their repertoire is different.

The endphrase is less useful for individual recognition, although also here there are personal differences. However, the main reason why the endphrase is interesting is that this part of the song gives rise to large scale dialects that can cover areas that are tens or even hundreds of kilometers across. Lucie Diblíková, Pavel Pipek, and Tomáš Telenský of the Charles University of Prague have initiated a citizen science project that has produced a fascinating world map showing the distribution of these dialects. Quite often (roughly half the time), the endphrase is left out completely, and even if it is sung, it is often not sung completely. If the endphrase is sung in full, then in most dialects it consists of two syllables. In western dialects the first syllable can be very short (as in the poetic description "no-bread") and can sometimes be left out. In easter dialects (such as in my study area), the second syllable is optional and most of the time left out. In my study area, 13 out of 29 birds never sing it, while the remaining birds sing it perhaps only 5-10% of the time. If the second syllable of the endphrase is sung, then it is possible to recognize the dialect from it. Of my 29 birds, 14 sing the dialect BE (using terminology of the map) one sings BlBh, and one sings BC (which is the bird named Arie whose sonogram is shown above). Although BE is clearly dominant in my study area, less than 3 kilometers to the east, BC seems to be dominant, so Arie may have immigrated from there.

Yellowhammers have one more way of "singing" that has not been studied very much. This is very different from the song described above. Instead, male Yellowhammers often sit for a long time on their favourite singposts repeating, at a measured rate, a call that sounds like "dzip". In fact, if you listen carefully, you will notice that they often more or less regularly alternate two calls, something like "dzip ... tsp ... dzip ... tsp ... tsp ...". Although this does not sound very impressive, it seems to have a function that is fairly similar to that of normal song. Maybe the use of this type of singing is just to draw attention and then let the bright yellow plumage of the male, combined with a conspicious sitting post in the top of a small tree or bush, do the rest of the work in advertizing the territory. When I approach a normally singing bird too close, it often switches to this type of singing. This may mean that the call is in part an alarm call, but maybe it just means that the Yellowhammer switches to a softer way of singing to avoid being detected by me.