Author: Magnus Robb
The first time I heard nocturnal flight calls of a Great Spotted Cuckoo Clamator glandarius was quite unforgettable. It was 24 May 2001, and I was at Durnalık, near Gaziantep in southern Turkey. I had been recording White-throated Robins Irania gutturalis until nightfall, and was preparing for a night in ‘Hotel Volkswagen’ when I heard a series of strange wails. They were quite long, descending, given at regular intervals, and I could hear clearly that they were moving across the night sky. In some ways they reminded me of calls of Little Owl Athene vidalii, but such a determined, long-distance flight would be completely out of character for a little owl and besides, the sound was not quite the same. I’m not sure how long it took or quite how the penny dropped, but I was very excited when I realised what I had just heard was a Great Spotted Cuckoo. For years the experience resonated as one of those sounds I’d have loved to record, but missed. Not for ever though.
In March 2009, not long after moving to Portugal, I went out recording one night along the river Tagus where it forms the border with Spain. I believe it was Eurasian Eagle Owls Bubo bubo that I was after, but from my vantage point on top of a little cliff I could also hear whistles of Eurasian Otters Lutra lutra, thudding footsteps and grunts of Wild Boar Sus scrofa, flight calls of Little Grebe Tachybaptus ruficollis and Northern Lapwing Vanellus vanellus, various amphibians and even some fish. The first wails of the Great Spotted Cuckoo were very distant. What followed was different from the sequence I had heard eight years previously. The wails were essentially the same, but they were followed by a long, descending chuckle. All in all, the two-parts together suggested some diabolical caricature of a gull’s long call, but it was clearly higher-pitched. The first call was far off to one side and the last was way over on the other. The bird was clearly flying a long distance, and it did not call again.
Great Spotted Cuckoo Clamator glandarius, Alares, Idanha-a-Nova, Portugal, 20:26, 7 March 2009 (Magnus Robb). Nocturnal flight calls of ‘wails & chuckle’ type at 0:01, 0:29, 1:01 and 1:39. Background: high metallic clicks of European Free-tailed Bats Tadarida teniotis, whistles of Eurasian Otters Lutra lutra, hooting, devils’s cackle and soliciting call of Eurasian Eagle Owls Bubo bubo, and croaking of Mediterranean Tree Frogs Hyla meridionalis.
Since then I have recorded Great Spotted Cuckoo nocturnal flight calls (hereafter referred to as NFCs) on many occasions. From the east margin of the Tagus estuary and further inland, these are among the commonest NFCs I record, but only during the first half of the year. In the Sound Approach archive there are currently around 30 recordings spanning the entire period when adults are present in Iberia: late January to early July. Besides Portugal, I have also recorded them in Morocco and Spain, and Arnoud has recorded one of the same call types in Turkey in early March, although that bird seemed to be perched. Calls belong to three main types, which I will describe in order of prevalence from the commonest to the rarest.
Great Spotted Cuckoo Clamator glandarius adult, Almodôvar, Castro Verde, Portugal, 10 April 2014 (René Pop).
‘Wails & chuckle’ series
My first nocturnal recording and most subsequent ones were of the ‘wails & chuckle’ type. The first part of this call consists of an average of 3 wails (range 1-5), and the latter part is a rapid chuckle consisting of an average of 17 individual units (range 7-33). The individual wails rise sharply at the start then descend slowly, giving a raptor-like effect. See the table below for more detailed analysis.
My single best recording of a ‘wails & chuckle’ series is fairly typical, although the wails are relatively low-pitched and the number of chuckle-notes is on the low side.
Great Spotted Cuckoo Clamator glandarius, Rosmaninhal, Idanha-a-Nova, Portugal, 04:36, 4 June 2013 (Magnus Robb). Single ‘wails & chuckle’ series in nocturnal flight. Background: Red-necked Nightjar Caprimulgus ruficollis and Eurasian Scops Owl Otus scops.
Nocturnally calling Great Spotted Cuckoos appear to fly rather high, allowing the sound to carry far. It is always worth listening for second and subsequent series, which may not come for well over a minute. On average, however, the gap between the end of one series and the start of the next is 47.5 seconds (range 22.7 – 111.2). Here are two further recordings with several series each.
Great Spotted Cuckoo Clamator glandarius, Minas de São Domingos, Mértola, Portugal, 20:35, 12 March 2012 (Magnus Robb). ‘Wails & chuckle’ series in nocturnal flight, at 0:02, 1:19, 2:18, 3:06 & 3:48. Note that the cuckoo can still be heard at 4:15, long after the closest series. However, this final call is a ‘long series of wails’ (see below).
Great Spotted Cuckoo Clamator glandarius, Rosmaninhal, Idanha-a-Nova, Portugal, 22:56, 13 May 2012 (Magnus Robb). ‘Wails & chuckle’ series in nocturnal flight, at 0:01, 0:43, 1:20, 1:59, 2:35 & 3:24. Background: Iberian Green Frog Pelophylax perezi.
Table 1 shows mean measurements of typical two-part ‘wails & chuckle’ series taken from 17 individuals, all recorded at night either in Portugal or just over the border in Spain. For each individual I measured the mean from as many series as were present in the recording. The table shows the means of all 17 individual means. The ‘range’ shows the extent of variation across all calls recorded.
|N = 17|
|Total call length |
|Nr of wails|
|Max freq wails |
|Nr of chuckles|
|Length of chuckle |
|Gap until next series
|3.57 - 7.72|
|1 - 5|
|1.280 - 1.866|
|7 - 33|
|1.02 - 4.66|
|22.7 - 111.2
Rarely, a Great Spotted Cuckoo passing overhead at night giving series of wail-chuckles at, say, 40 second intervals will include one without a chuckle at the end. Two of the 17 individuals that I analysed included a single series like this. The number of wails is still typical for that individual’s ‘wails & chuckle’, but the chuckle is simply not there, as if something distracted the bird mid-series. By contrast, I have never recorded a chuckle at night that was not preceded by one or more wails (but see ‘chatter calls’ below).
’Long series of wails’
The second commonest type of Great Spotted Cuckoo NFC is simply a long series of wails. These are exactly like the ones at the start of a ‘wails & chuckle’ series, or indeed a ‘wail & no chuckle’ series, except that there are many more of them. The average number of wails from 12 individuals that I have recorded was 7.63 (range 5-9). Here is a recording I made in Morocco last year, with ‘long series of wails’ of two individuals. Great Spotted Cuckoo is only an irregular breeder in Morocco, so these were probably migrants heading for Iberia, a possibility supported by the atypical wetland habitat and the early date when I recorded them.
Great Spotted Cuckoo Clamator glandarius, Oued Loukkos, Larache, Morocco, 05:13, 6 February 2016 (Magnus Robb). Wail series of two individuals (judging from the different shapes of their wails) in nocturnal flight, the first at 0:03 and the second at 0:49 and 1:45. Background: Mallard Anas platyrhynchos, Western Swamphen Porphyrio porphyrio, Red-knobbed Coot Fulica cristata, Eurasian Coot F atra, Black-winged Stilt Himantopus himantopus and Western Marsh Harrier Circus aerugineus.
Lacking a give-away chuckle, this call type could easily be mistaken for the aggressive song of a Little Owl A vidalii; the repetition rate (average of one wail per 1.13 sec) is very similar. However, the cuckoo’s NFCs wails are more drawn out and clearly descending in pitch (in Little Owl they are more arch-shaped), as well as being marginally lower-pitched (average max freq 1612 Hz). Also, if you hear more than one series of ‘wails & chuckle’, separated by an average gap of 49 sec, you will usually notice that they come from different directions: the bird has clearly moved. While multiple Little Owls could create a similar illusion, continued listening would reveal that each caller stays within its own fairly small territory.
Arnoud once recorded ‘long series of wails’ while trying for Turkish Fish Owls Bubo semenowi in southern Turkey. In this case the series were longer than usual, possibly because the bird was perched and could manage a longer series without becoming out of breath. Assuming that this is indeed the same call type, it is our clearest example so far.
Great Spotted Cuckoo Clamator glandarius, Akseki, Antalya, Turkey, 06:39, 14 March 2010 (Arnoud B van den Berg). ‘Long series of wails’ from a perched individual at dawn, presumably a migrant. Background: Song Thrush Turdus philomelos and European Robin Erithacus rubecula.
Just for comparison, here is a recording of aggressive song from at least four different Little Owls in Portugal.
Little Owl Athene vidalii, Rosmaninhal, Idanha-a-Nova, Portugal, 22:45, 6 March 2009 (Magnus Robb). Aggressive song of at least four individuals. Background: Mediterranean Tree Frog Hyla meridionalis and Iberian Green Frog Pelophylax perezi.
Several observations suggest to me that the ‘long series of wails’ is to be expected from Great Spotted Cuckoos on migration. Arnoud’s recording was made in a part of Turkey where the cuckoo is not known to breed, and on one of the earliest dates it has been recorded in the country. As already mentioned, I have also recorded this call type very early in the year in Morocco where the species is only an occasional breeder, and my only two January NFC recordings from Iberia have been of ‘long series of wails’. As for ‘wails & chuckle’, so far we have only recorded them on the breeding grounds, where they may serve as an advertisement call for unpaired individuals.
Sometimes it is possible to hear both types of NFC described so far, ‘wails & chuckle’ and ‘long series of wails’, from the same individual. I have recorded several examples documenting this, including the third in this article, above. It is still unclear whether only one or both sexes give these calls.
Table 2 shows measurements of ‘long series of wails’ from 12 different individuals in flight. For each individual I measured the mean from as many series as were present in the recording. The table shows the mean of these 12 individual means. The ‘range’ shows the extent of variation across all calls recorded.
|N = 12 |
|Total call length|
|Nr of wails|
|Maximum frequency of wails in kHz||Gap until next series
|3.78 - 9.51|
|5 - 9|
|1.407 - 1.866|
|36.8 - 139.5
Once, I recorded a call very similar to a ‘long series of wails’ from a juvenile. This was a bird that I had been observing and recording for a couple of hours, begging and being fed by Eurasian Magpies Pica pica. It was not clear what caused it to change from begging calls to a ‘long series of wails’ but this only happened once, at a moment when no adult magpie was close by. The six wails were fairly quiet and had a harsher timbre than in adults, especially the first two of the series. Unfortunately the recording was spoiled by a bee, but here it is for the sake of documentation.
Great Spotted Cuckoo Clamator glandarius, Segura, Idanha-a-Nova, Portugal, 10:09, 2 July 2009 (Magnus Robb). A single begging call morphing into a series of harsh wails, similar to a ‘long series of wails’. A bumble bee gate-crashes the recording. Background: Eurasian Golden Oriole Oriolus oriolus and Barn Swallow Hirundo rustica.
‘Chatter’ calls and ‘chatter & wails’ series
The third type of Great Spotted Cuckoo NFC is rare, at night anyway, and I have only recorded it twice. Fortunately, one of those occasions I got a good recording. This contains two series, each consisting of a chatter followed by series of wails. An obvious difference from the usual ‘wails & chuckle’ is that here the wails come at the end. In addition, the chatter differs from the usual chuckle in its stuttering, irregular rhythm.
Great Spotted Cuckoo Clamator glandarius, Alares, Idanha-a-Nova, Portugal, 20:43, 4 March 2011 (Magnus Robb). Two series of ‘chatters & wails’ in nocturnal flight, the first at 0:01 and the second at 1:01.
The only other time I recorded something similar at night was on the surprisingly late date of 8 July, when most adults have already left the country and many juveniles are still being reared by their corvid foster parents. The recording contains a single series of chatters but without any wails.
Great Spotted Cuckoo Clamator glandarius, Rosmaninhal, Idanha-a-Nova, Portugal, 02:23, 8 July 2012 (Magnus Robb). A single chatter call at night. It is not clear whether this bird was flying or not.
Despite being rare at night, chattering calls like this are among the commonest sounds of Great Spotted Cuckoo during the day, eg, forming part of their courtship display. The literature is not clear, or convincing, on whether the call belongs to one or both sexes: a puzzle still to be solved by careful observation.
In fact there is much more to puzzle about with Great Spotted Cuckoo calls. What kind of message are the birds trying to communicate with their NFCs, and to whom? Why do the callers appear to be flying such long distances, as if migrating, through most of the five to six months that they are north of the Sahara? Is the commonest call, the ‘wails & chuckle’ series, really only used on the breeding grounds, and only by unpaired birds as suggested above? A rich subject for a PhD, if anyone is creative enough to find ways to answer these questions!
Night flight calls of other cuckoos
Black-billed Cuckoo Coccyzus erythropthalmus and Yellow-billed Cuckoo C americanus are often detected migrating through the USA at night thanks to their flight calls. Here are links to recordings of both at www.xeno-canto.org, recorded by Paul Driver.
As for Common Cuckoo Cuculus canorus, it is often possible to hear the song of males at night, and sometimes briefly in flight, but in my own experience this is only on the breeding grounds. On the other hand, I once recorded a nocturnal bubbling call of a female in Oman, where the species is not known to breed. I think we can safely assume this was a migrant heading north.
Common Cuckoo Cuculus canorus, Al Hajar mountains, Al Batinah, Oman, 03:21, 26 April 2013 (Magnus Robb). Bubbling call of a female, presumably while migrating.
As far as we know, this is the first time anything has been published about nocturnal flight calls of Great Spotted Cuckoo. If anyone can direct us to other information on NFCs, or other study looking at calls of this species in any detail, we would be interested to read it, and will provide a reference or link for other interested readers.