AudioMoth recording of nest relief. Not edited for length, so that the actual duration of events is shown, hence gap between vocalisations. After hearing the male flight call (0:02), the female churrs to the male from the nest (0:03) and gets two calls in response (0:09 – 0:11). Nothing is then heard until 1:30, when the female again ‘churrs’ and immediately gets a flight call back, then very close flight calls from the male and a wing clap (that sounds somewhat hollow due to the noise reduction I have applied) 1:33 -1:36 as he approaches the nest, dropping in at 1:46. The female tremolo gets more excited, rises in pitch and stop abruptly at 1:43. Movement in the nest is heard before a softer call and wing claps at 1:46. Another dry churr occurs at 1:56 and a loud call, which sounds male, not clear of the scenario here, female may have left the nest and the male is vocalising from the ground. We first became aware of female churring when a nest camera recorded this behaviour a couple of years ago. Stulcken (1962) describes the female churring at nest relief and Glutz & Bauer (1980) refer to a ‘brief and subdued variant’ given by the female at the nest, so this behaviour has been long established, if not well known.
Since we recorded this in 2020, we have now recorded several more instances of this. In 2021 too, for the first time, I have heard this in the field, and recognised it for what it was. I was watching from a forestry track, where a nest was nearby, perhaps 10m or so. I must have heard this sound previously, but not realised it was the female.
I found a good description of this in Bird Life Glimpses, by Edmund Selous (1905);
‘As it (the male) comes nearer, it is evidently recognised by the sitting bird, who churrs in response, but so softly that human ears can only just catch the sound.’
Here are some further examples of the sound. At one nest, although this was recorded on three successive nights, it is not invariably given.
Interestingly, Selous goes on to discuss whether females churr in the same way as males, asserting that they do. However, he is in fact describing a different sound and not ‘true’ churring. Despite the difficulties (referenced here) of relying on text to convey bird sounds, it becomes clear that he is describing what we refer to colloquially as ‘purring’;
‘In regard to the two sexes churring, thus, in unison, I can assert, in the most uncompromising manner, that they do so, having been several times a witness of it, at but a few steps’ distance, and in broad daylight, I may almost say, taking the time of the year into consideration. The eyes, indeed, are as important as the ears in coming to a conclusion on the matter, for not only is the tail wagged in these little duets, but with the first breath of the sound, the feathers of the bird’s throat begin to twitch and vibrate, in a very noticeable manner. Various authorities, it is true, either state or imply that the male nightjar alone churrs, or burrs, or plays the castanets, however one may try to describe that wonderful sound, which seems to become the air itself, on summer evenings, anywhere where nightjars are numerous. But these authorities are all mistaken, and as soon as they take to watching a pair of the birds hatching their eggs, they will find that they were, but not before, for there is no other way of making certain. It is true that the churr thus uttered, though as distinct as an air played on the piano, is now extraordinarily subdued, of so soft and low a quality that, remembering what it more commonly is, one feels inclined to marvel at such a power of modulation. But it is just the same sound ” in little ” how, indeed, can such a sound be mistaken ? and, after all, since a drum can be beaten lightly, there is no reason why an instrument, which is part of the performer itself, should be less under control. What is really interesting and curious is to hear such a note expressing, even to one’s human ears, the soft language of affection for it does do so in the most unmistakable manner.’
From Bird Life Glimpses
George Allen, 1905