Where is that ‘tack, tack, tack’ sound coming from?
of male cicadas make their sound while in a stationary position, but have you
ever noticed one flying around while calling? If so, you are probably hearing
an ambertail or tree-ticker. Or, if you are in southern Western Australia, you
may well be hearing the legendary Duke, a species that can be notoriously
difficult to observe. Apart from these particular cicadas, not many insects
make sounds on the wing. Whistling Moth (Hecatesia
fenestrata) is one other example. These moths fly in high circles, making a
strange, high-pitched, rattling or grinding sound.
[The male Black Tree-ticker starts calling while stationary, then launches into flight, calling vigorously and scouting for females]
My November feature for ‘Cicada of the Month’ is Southern Ticking Ambertail. So far, this species has been found in inland southern New South Wales, the Australian Capital Territory and around Adelaide in South Australia. Populations occur in open forest and woodland in association with eucalypts. In this species, the males fly actively, making a sharp ticking sound, similar to an electrical pulse passing through an electrified fence (which may be audible when earthed). They call once the temperature warms to above 20°C in the morning, again at intervals throughout the day provided that the temperature does not become too hot (i.e. >30°C), and again from late afternoon. The males are also often active in the summer twilight when the weather is balmy and are often attracted to artificial lights.
[Southern Ticking Ambertail cicada (male) ]
You may be wondering why males of these cicadas fly around so actively when calling, while others sit still? Cicada calling songs are produced for the sole purpose of mate attraction. With almost no exceptions, the males produce the call. Each species essentially has unique call signature, which allows females to recognise the call of their species amongst background sounds, including the calls of other cicada species. In larger cicadas, the males often occur in big aggregations and the females fly in once they recognise the call of their species. By contrast, in the majority of smaller cicadas (including the ones that fly like Southern Ticking Ambertail), the males are more actively involved in mate localisation then the females. To facilitate this, the males have brief pauses encoded into calling songs. This allows them to listen for the precisely-timed response (a soft wing-click) of a nearby female. Males of many small cicada species tend to move singing stations fairly frequently in order to position themselves in an area where they might have a reasonable chance of elucidating and detecting a response from a female. This brings us back to the original question, which was: why do some species fly around when calling? In effect, this is just a behaviourally extreme version of moving between singing stations frequently, whereby the males instead move constantly while listening for a female response. This has the advantage of allowing males to cover much more territory when looking for females. At the same time, it uses a lot more energy than being stationary, so males tend to fly and sing in short bursts, particularly in hot or unusually cool weather. Once a female is detected, a calling male will stop scouting, swoop in and move quickly to locate the female, before mating takes place.
[Wave plot of the calling song of Southern Ticking Ambertail showing the characteristic sharp ticking pattern. Listen to a sample from this species here]
The distribution of Southern Ticking Ambertail between the eastern half of southern New South Wales and Adelaide is not well understood. Julianne Vincent of Adelaide has kindly shared some photographs of this species from Adelaide here and here. If you encounter this species or any other fascinating small cicada in your area, please take a recording on your smartphone and contact me by leaving a comment on this post, via the contact form or via Twitter. Specimen samples and photographs will also be very welcome. Keep listening and tell me about your encounters with the sounds of summer!