by Matthew Cobb

I used to run a field course for second-year university students at Saint-Auban in the foothills of the French Alps. My favourite bit of the course was when we would drive out at dusk into a deserted valley (seen in the picture below, taken from a nearby peak) and observe the local animals as they emerged from the forest. We would regularly see lowland hare, fox, roe deer and, if we were very lucky, wild boar.

In the parts of the valley that are dominated by heathland, out of sight on the photo, we would encounter the eerie nightjar. Often, the first sight of this amazing bird would generally be the gleam of its red eye, reflected in the car headlights. For reasons that I don’t think anyone understands, nightjars tend to sit in the middle of the road, playing chicken with any oncoming car. Maybe they are warming themselves on the tarmac, and as a nocturnal/crepuscular bird they are blinded by the headlights and just sit tight until the last possible moment.

The male nightjar will perch on a branch – often in a pine tree – and sing, a bizarre churring sound that, once heard, is never forgotten. Why they sing like this is not clear, but it carries long distances and also spreads in all directions – it is often very difficult to localise. This would be advantageous both for attracting a mate and for territorial purposes – the latter seems particularly important in nightjars.

I presume the  structure of the song is related to the geography of the heathland where they live, with lower wavelengths travelling further and not being absorbed by dense woodland. There may also be an element to the song which encodes the male’s fitness in some way.

In Asian nightjars, the song seems to be a defining feature of the species and is a reliable way of differentiating otherwise similar species, as shown in this 2008 article, which includes the identification of a new species, partly on the basis of its song. It turns out that you can reliably identify individual birds on the basis of their song.

This French video shows you what the song is like. In French, the nightjar is l’engoulevent (the wind-swallower). You’ll notice that it carries on singing for ages – it seems to be able to do this by singing as it is inhaling as well as when it exhales.

Now this site’s favourite cryptic bird has received the ultimate accolade – it has been featured on BBC Radio 4’s excellent series, Tweet of the Day, which we have mentioned here before. This is a 2-minute daily radio slot featuring birds from the UK, with their song and some brief details about their ecology. I can’t embed the programme, so you’ll have to click on this link to listen on the BBC site (a screenshot is below).

Go ahead – you’ll learn some stuff, and the sound will transport you to warm summer nights in France, and the sounds and smells of the mountains.