TAWNY OWL (Strix aluco) - Chouette hulotte
Summary
A fairly common bird of forests found up to 1500m a.s.l. in Switzerland. Nocturnal habits make it hard to see but most people can recognise this owl’s hoot:
The Tawny Owl is found throughout the Western Palearctic region with a separate east Asia population. About a dozen sub-species have been described across this range with two colour morphs - a brown one (which is mostly in western Europe) and a grey one, the latter more common in colder areas and mountainous regions.
In Switzerland, it is found in all forest/ woodland types up to about 1500m, but becomes more patchy in distribution as you get higher. This is the archetypical woodland owl, reasonably common throughout Europe, where it also occurs in wooded farmland and mature urban parkland. It is sedentary and pairs will occupy territories over a number of years.
In English the call is usually verbalised as "too-whit, too-whu", which most children know even if they have never heard one. But this is wrong and mixes two kinds of call - it may have its origins in the song for winter which closes Shakepseare's play "Love's Labour's Lost": …….”Then nightly sings the staring owl, Tu-whit; Tu-who, a merry note….”
The "tu-whu" part of Shakespeare's description is probably the common advertising call, which is a low-frequency series of 3 notes best verbalised as "hoooo-hu-huhohooooo", with that final "hooo" prolonged and resonant and tremulous. It is a strong sound and, in the quiet of the night, can carry a long way - this bird was about 50m away when I recorded it with my parabola. It is a long piece but gives a true reflection of the timing of the strophe, and the 50 - 60 seconds of silence between calls. You can appreciate the qualities of the sound: the first note rises and falls, then after a pause this is followed a very brief second note, leading straight on to the third which is more prolonged and tremulous with almost a rasping quality to it:
There are other noises in that last piece: rustling sounds are the feet of a small herd of Chamois in the dry leaves. They were slowly moving away from my approach, around 1.38 - 1.44, then at 2.06 are some clear calls from overhead that sound rather like a Coot flying about.
The sonogram below shows two calls extracted from that last piece where I have focused just on the lower frequencies. The main energy is around 800 Hz, but there are many harmonics above that. In the sonogram, in addition to the fundamental notes, you can also see the first harmonic at 1600Hz. Note how the first note rises from about 750 Hz to 850 Hz before falling back again; the second note arrives after a pause of 3-4 secs and is so brief it can be missed; the third note is modulated and the vibrato effect is clearly seen:
This advertising call is for both territorial defence and communication with a mate. A beautiful sound, almost like an ocharina, and may be the most important in the repertoire of this species. Galeotti & Pavan (1991) made a detailed study of 140 calls from 17 identified individuals: they found a set of 7 measures taken from the spectrogram which enabled them to identify individuals correctly on 99% of occasions. Tawny Owls are highly territorial, and pair bonds can last for several years, knowing exactly where your mate is in the dark, and distinguishing them from competitors or invaders, makes individual identification from sound pretty important.
Some of the literature will identify this advertising call as “the male call”, but both birds of a pair will use it in their interactions. In fact, as far as I can tell, there seems to be very few definitive “male” or “female” calls. They both seem to communicate in much the same way, the main difference being that the female calls tend to be at a slightly higher pitch than the male calls, and sometimes they are of a rougher or more coarse nature (Robb etal 2015). The higher pitched call of the female is quite clear when heard side by side, but in isolation it is nearly impossible to tell them apart (at least for me!). Here is a brief advertising hoot conversation between male and female where you can see and hear the difference:
Male and female hooting, the female starts at 4 secs and completes the full sequence, the male starts about a second after her and completes his sequence, so the second part is an overlap of the two.
Here is another example where the coarseness of the higher pitched female is clear:
So that is the most easily recognised advertising hoot as delivered by the male and female. This back and forth calling can last for hours at night.
But back to the myth again………the "tu-whit" part of Shakespeare's description. This is probably a rendition of a more explosive call that sounds like "ke-wick". They use it to locate each other, and sometimes females will use it to respond to a male song, so it is often referred to as a “female song”, but again, both birds are capable of making this sound. Here is a recording of a single bird calling:
It is a far-carrying shreik of a call, much higher pitch than the hoots. The “kewick” (“tu-whit”) nature of it is created by it starting at about 1.2kHz, descending rapidly to 1.0 kHz before sweeping up to 1.4kHz:
This call can be used as a contact call between a pair, but the female will also use it as a “soliciting” call from the male, when she may be demanding food, or attention, or something else. Here is quite an amusing piece where the female uses the “kewick” call insistently directed at the male, flying in closer to him, then he answers in a rather subdued manner (to my ears) with a modified version of his advertising hoot. Listen carefully, I think there may be a third owl much further away who answers the female’s soliciting call:
Very similar to the “kewick” call is what Robb (2015) calls the “distance” call. Like a very rapidly delivered “kewick” this is usually aimed at intruders, telling them to keep their distance, so probably more often used by the male. Here is an example from a bird calling around dawn. I am not sure who the intruder might have been, but probably not the farmyard rooster crowing in the background….
I started this section on “kewick” calls stating that both birds will use it, here are two birds calling close together, one with a lower note I think is the male, and the higher note the female. Although I must say that I did not actually see them:
One more call which I can add here is known as “pulsed” hooting. This soft low call, a characteristic of other Strix owls (Robb 2015), seems to be used mostly in autumn and winter (again by both sexes) and is often associated with nest hole inspection (see Galeotti update of Cramp et al):
These birds lead complex lives, active during darkness, defending fairly fixed territories, maintaining pair bonds over several years. There is always tension in the air when any fierce raptorial male and female come together, the male usually taking the main share of territory defence, but the larger female nest guarding and feeding young. So, all sorts of noises can emerge when they are together, trying to attract, but not get too close. Here is a bird whose advertising hoot became a single elongated note immediately followed by two rapid beaks snaps - usually a warning or annoyance signal:
This complex relationship between the members of a pair, or between them and competitors, for territory or romance, can result in all sorts of noises described by Southern (1970) as “caterwauling”. I am not sure if this matches what he was hearing, but is the sort of reality you may face with these birds in the wild. See which parts of this you can now identify (there is a small mammal running around near the microphone):
Finally, as a precautionary tale, recording nocturnal birds is an arduous and sometimes risky business that can be full of surprises……..
Tawny Owl studies © Frank Jarvis
