{"id":500,"date":"2017-06-04T22:20:49","date_gmt":"2017-06-04T22:20:49","guid":{"rendered":"http:\/\/caperteebirder.com\/?page_id=500"},"modified":"2017-06-04T22:29:35","modified_gmt":"2017-06-04T22:29:35","slug":"owlet-nightjars","status":"publish","type":"page","link":"https:\/\/caperteebirder.com\/?page_id=500","title":{"rendered":"Owlet-nightjars"},"content":{"rendered":"

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This article was published in Audiowings<\/em>, the journal of the Australian Wildlife Sound Recording Group, Volume 13, No. 2, December 2010.\u00a0 You can also download the article in pdf format here (684 kb).<\/a>\u00a0 You can hear the sound clips that go with the sonagrams, further down the page.<\/h4>\n

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Australian Owlet-nightjar vocalizations<\/h2>\n

by Vicki Powys 2010<\/h4>\n

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On summer nights in woodland areas, above the din of crickets comes the occasional call of the Owlet-nightjar.\u00a0 The call may last but a few seconds and occur just once every hour or so, making it very difficult to record.<\/h4>\n

Last summer I took to keeping my Olympus LS-10 pocket-sized recorder by my pillow at night, connected via a long lead to a stereo microphone placed on my verandah or under a tree outside.\u00a0 I would lie in bed and use headphones to listen in for long periods, leaving the recorder running, and if there were no calls I would simply delete that track and begin a new one.\u00a0 I used no playback and my observations were of the natural calls of the species.<\/h4>\n

I have on occasions been lucky enough to observe an Owlet-nightjar in daylight, usually peeping out of a hollow tree in the dry woodland habitat of my property in Capertee Valley in NSW.\u00a0 My place is \u2018prime Owlet-nightjar habitat\u2019 with lots of tree hollows, and with calls from as many as five or six different birds at any one time, audible from my front verandah.<\/h4>\n

Moonlight vs darkness:<\/em><\/h4>\n

Debus (1997) and Brigham (1999) found that Australian Owlet-nightjars called more and were more active on moonless rather than moonlit nights.\u00a0 This may be a defence mechanism to protect themselves from predation by larger owls which are most active on bright moonlit nights.<\/h4>\n

\u00a0\u00a0\u00a0 Not knowing this, I had expected my Owlet-nightjars to be calling well on the brightest nights, but most of my recordings, especially the call and answer routines, were made when there was no moon visible.\u00a0 They called well after a thunderstorm, and 2.30 \u2013 5.30 a.m. DST was also a good time for recording, i.e. up until the first hint of pre-dawn light.\u00a0 Sometimes I recorded good sequences 9 p.m. to midnight.\u00a0 On several occasions I have recorded Owlet-nightjars calling briefly during the day from a tree hollow.\u00a0 All of my recordings for this study were made from November 2009 to April 2010.<\/h4>\n

Identification of calls:<\/em><\/h4>\n

When you record birds but do not see them, there comes the problem of identification.\u00a0 After many months of recording and listening I sent what I thought was a representative collection of eight different Owlet-nightjar calls to a number of experts.\u00a0 [You can hear this medley of calls on the Audiowings CD].\u00a0 Steve Debus in particular was very helpful and is a noted nightbird authority.\u00a0 Bird guide Carol Probets made helpful comments.\u00a0 Thanks also to Audiowings members Dave Stewart, Fred van Gessel, Bill Flentje and Tony Baylis for your comments, and to Lisa Doucette (from Canada) who is currently studying the species in the Armidale, NSW region.<\/h4>\n

I should add that there was not unanimous agreement on the identification of all the calls, but the majority felt that the calls I have presented here are from the Owlet-nightjar.\u00a0 The fact that not everyone was in agreement may indicate that there is some regional variability in the calls of the Owlet-nightjar, and that some calls may be used more prominently in some regions, and not in others.\u00a0 If any readers disagree with my identification of these calls, feel free to say so.<\/h4>\n

HANZAB describes the voice of the Owlet-nightjar as \u2018not well known\u2019, providing sonograms for three different types of calls and mentioning Churr, Cry, Yuk, Trill, Che-ok, Hiss, Screech, Rattle and Trill.\u00a0 I could not exactly match my Owlet-nightjar calls with the sonograms in HANZAB.\u00a0 However HANZAB says that often Owlet-nightjars will answer one another, and for my own study I was intrigued by the calls and answers that I could hear, which helped me to verify in my own mind that the calls I have presented here are all from the Owlet-nightjar.<\/h4>\n

Sugar Gliders vs Owlet-nightjar:<\/em><\/h4>\n

One or two of the people who made comments said that the jik<\/em> call (Figure 1, number 6) sounded to them like a Sugar Glider.\u00a0 So far as I know there are no Sugar Gliders on my property, and certainly in many long nights of recording I have never heard any of the typical \u2018shrill yapping\u2019 Sugar Glider calls.\u00a0 I am convinced the jik <\/em>call is from an Owlet-nightjar, and Steve Debus has verified this.<\/h4>\n

Barn Owl vs Owlet-nightjar:<\/em><\/h4>\n

The hiss<\/em> call I have presented here (Figure 1, number 5) was considered by one or two people to be a Barn Owl.\u00a0 While I do occasionally have Barn Owls visit my property, I feel sure that much of the hissing that goes on here is from Owlet-nightjars.\u00a0 I recorded several sequences that begin with hissing then evolve into more typical Owlet-nightjar calls (an example can be heard on the CD), which convinced me that Owlet-nightjars do sometimes give hissing type of calls.\u00a0 Carol Probets pointed out that the Owlet-nightjar hiss seems to swell more slowly than does the Barn Owl hiss, and the latter is also more shrill.\u00a0 Lisa Doucette had never heard Owlet-nightjars hiss during her fieldwork in the Armidale region, where she uses playback for monitoring populations.\u00a0 Given my experience that Owlet-nightjars DO hiss, care should be taken when doing surveys at night as it is all too easy to tick off \u2018Barn Owl\u2019 when in fact it might be an Owlet-nightjar!<\/h4>\n

Number of syllables:<\/em><\/h4>\n

A typical sequence of calls often came in a burst of 3-6 syllables.\u00a0 An answering bird might also give 3-6 syllables but in a slightly different timbre, for example the falsetto churr <\/em>(Figure 1, number 3).\u00a0 Also, the hiss<\/em> call often occurred as 4-6 syllables.\u00a0 Some calls had a broadband hissy type of quality, while other calls were clearer, and you can see this in the sonograms where a smudgy look equals a hissy quality.\u00a0 The jik<\/em> call sometimes occurred as a longer series lasting several minutes.<\/h4>\n

Extended calls:<\/em><\/h4>\n

Everyone agreed that cut no. 7 in Figure 1 was definitely Owlet-nightjar, and that this is their best known call.\u00a0 The sound is somewhat reminiscent of a Brown Falcon.<\/h4>\n

Descending whistle:<\/em><\/h4>\n

This call is the only one I am not 100% sure of.\u00a0 It seemed to be used as part of the Owlet-nightjar call-and-answer sequences.\u00a0 I feel certain this must be Owlet-nightjar but I cannot prove it.<\/h4>\n

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It has been quite a challenge to make this study of Owlet-nightjars \u2013 with too many sleepless nights waiting for them to call!\u00a0 But now I am hooked on this intriguing, cryptic little owl, so no doubt there will be more sleepless nights for me this summer.<\/h4>\n

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References:<\/em><\/h4>\n

Brigham, R. Mark; Gutsell, Robin C.A.; Geiser, Fritz & Wiacek, Richard S., 1999: Foraging Behaviour in Relation to the Lunar Cycle by Australian Owlet-nightjars Aegotheles cristatus<\/em>; Emu 99(4) 253 \u2013 261.<\/h4>\n

Debus, S.J.S., 1997: Vocal behaviour of the Southern Boobook Ninox novaeseelandiae<\/em> and other nocturnal birds; Australian Raptor Studies 2: Birds Australia Monograph 3, pages 71-85.<\/h4>\n

Higgins, P.J. (editor), 1999: Handbook of Australian, New Zealand & Antarctic Birds, volume 4, pages 1036 \u2013 1048.<\/h4>\n

Sketch is from The Atlas of Australian Birds, RAOU, 1984.<\/h4>\n

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AUDIO<\/strong><\/h3>\n

Here are the sounds to go with the sonagrams.\u00a0 The calls are introduced, and are in the order 1-8 according to the numbers on the sonogram.<\/h4>\n\n