Whistles, chirps and chattering: a lesson in bird song
Wandering around, it seems as though there has been a dramatic change in noise on the reserve. With the whooper swans dwindling in numbers, their honks have become more muted against the whistles, chirps and chattering of songbirds.
Most passerines are songbirds, meaning they have a specialised vocal organ (the syrinx) that enables them to produce complex melodies and calls. If you listen closely, you can begin to dissect the calls and gain an idea of why birds have different ones. For example, the arrival of predators can often provoke alarm calls, which warn others of a predatory threat nearby. Discovery of food supply may sometimes result in a different call, drawing in more foraging birds, which is presumed to reduce the individual risk of predation (Podos & Webster, 2022).
What, then, are the specific advantages of sound, particularly in comparison to visual signals? Visual signals come with several limitations, especially in low-light conditions or darkness. However, poor visibility isn't just a problem at night - it can occur at any time in dense environments like forests or reed beds. Consider trying to spot a small bird flitting through woodland. One moment it's visible, the next it's gone! Yet, if it calls or sings you can still hear it even though it’s out of sight (Catchpole & Slater, 2003).
We have many different songbirds at WWT Caerlaverock, from chaffinches to song thrushes to wrens, you’ll always hear their melodies. But how different are the songs? Here are two sonographs comparing a great tit and a skylark which are commonly found on the reserve.
Figure 1. Sonograph from a great tit.
Figure 2. Sonograph from a skylark.
The call of great tit shown in Figure 1 is very distinguishable with only two syllables, making a “tee-cher, tee-cher” sound. Figure 2 is the continuous call of a skylark, which can carry on for several minutes. In comparison to a great tit, their call sounds like a cascade with hundreds of similar pitched syllables jumping around your ears, which you can see reflected in the sonograph. Mnemonics are a really good way of picking up bird song!
When you walk around the reserve, let the birds be your guide - tuning in might just change the way you see (and hear) them.
Words by Madisyn Pett
Feature image of great tit by Alex Hillier
References
Catchpole, C. K., & Slater, P. J. (2003). Bird song: biological themes and variations. Cambridge university press.
Podos, J., & Webster, M. S. (2022). Ecology and evolution of bird sounds. Current Biology, 32(20), R1100–R1104.
Skylark song https://xeno-canto.org/explore?query=skylark&dir=0&order=dt
Great tit song https://xeno-canto.org/species/Parus-major
