By Magnus Robb, Lukas Pelikan & The Sound Approach

Black-crowned Night Heron

Black-crowned Night Heron Nycticorax nycticorax is the very archetype of a nocturnal migrant. It even has the word ‘night’ in its English and scientific names. Its name in Dutch is ‘Kwak’ and it has similar names in many other languages, imitating the sound of its NFC.

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Black-crowned Night Heron 
Nycticorax nycticorax 
Lake Khanka, Primorsky Krai, Russia, 00:08, 15 September 2019 (Lukas Pelikan). A flock of at least seven Night Herons migrating south at the eastern shore of Lake Khanka and coming gradually closer to the microphone (closest in the middle of the recording). An overflying Eurasian Bittern Botaurus stellaris gives its grouw at 1:10 for a nice comparison. For a detail of the recording see g) below. Background: Red-crowned Crane Grus japonensis, Von Schrenck’s Bittern Ixobrychus eurhythmus, Grey Heron Ardea cinerea and crickets. 
190915.0008LP30648Х.01

Please use headphones

The nocturnal activity and the calls Night Herons use at night have been well known for centuries. In fact, Naumann provided a description of its eponymous qwar, rich in detail, as early as 1838. He also pointed out that the ‘corax’ in its scientific name was due to the raven-like timbre of its calls and not due to any similarity of its posture to a crouched raven or crow (Naumann 1838).

Night Herons use only one type of flight call at night. Once learned, it is fairly distinctive, although sometimes anthropogenic noises, a very distant Grey Heron Ardea cinerea or Eurasian Bittern Botaurus stellaris can sound similar. However, the specific timbre of Night Heron’s qwar should always be audible.

The chances of hearing a Night Heron one night at your home – wherever it is – are not bad. Why? The grenade effect! The young Night Herons start spreading out in all directions immediately after breeding time, more than other species (Berthold 1993). Wherever you are, whether near their colonies or way north of their breeding range, in a forest or in a city, give it a go – you may hear one.

Identification

qwar calls

  • medium pitch, roughly as Grey Heron Ardea cinerea
  • timbre not particularly nasal, but more baby-voice-like: press the rear part of your tongue against your upper teeth and say “wha” in a baby voice
  • sounds frog-like, sometimes more duck-like
  • mean peak frequency 1.6 kHz (±0.13 kHz; n = 61)
  • frequency range 0.8 – 2.2 kHz (mean min 1.2 kHz; mean max 1.8 kHz; n = 61)
  • shape in sonagrams shows an arch or line with major part of the call rising in frequency (makes it sound questioning)
  • frequency arch usually starts lower in frequency than it ends; ie, minimum frequency located at beginning of call
  • arch often with one or more kinks in the course of the frequency band; a diagnostic feature when present
  • duration 121 – 233 ms (90% range; median 163 ms; n = 61)
  • mnemonic: it rhymes with “what?”

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 a) Black-crowned Night Heron Nycticorax nycticorax Sagres, Vila do Bispo, Portugal, 04:15, 19 September 2018 (GM). Single flight call of a nocturnal migrant. 180919.MR.041530.01

b) Black-crowned Night Heron Nycticorax nycticorax near Paralimni, Cyprus, 01:33, 7 September 2018 (JS). Two flight calls of a nocturnal migrant. Sonagram shows second call. Background: cockerel. 180907.MR.013312.01

c) Black-crowned Night Heron Nycticorax nycticorax Besh Barmag, Siyazan, Azerbaijan, 19:40, 3 April 2019 (BB). Single flight call of a nocturnal migrant. 190403.MR.194052.00

d) Black-crowned Night Heron Nycticorax nycticorax Ayias Minas, Akamas peninsula, Cyprus, 19:51, 19 April 2019. Three flight calls of a nocturnal migrant. Sonagram shows first call. Background: crickets. 190419.MR.195111.00

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e) Black-crowned Night Heron Nycticorax nycticorax Sagres, Vila do Bispo, Portugal, 20 September 2019 (GM). Two flight calls of two different nocturnal migrant. Sonagram shows first call, Background: European Pied Flycatcher Ficedula hypoleuca. 190920.MR.013138.01

f) Black-crowned Night Heron Nycticorax nycticorax Ebro Delta, Catalunya, Spain, 03:15, 20 September 2019. Two flight calls of a nocturnal migrant, the first of which is unusually quiet. Sonagram shows second call. Background: begging Little Egret Egretta garzetta. 190920.MR.031505.01

g) Black-crowned Night Heron Nycticorax nycticorax Lake Khanka, Primorsky Krai, Russia, 00:08, 15 September 2019 (Lukas Pelikan). A flock of Night Herons migrating south at the eastern shore of Lake Khanka. First call shown. See also a longer version of the same recording at the top of the page. Background: Red-crowned Crane Grus japonensis and crickets. 190915.0008LP30648Х.01

h) Black-crowned Night Heron Nycticorax nycticorax Ebro Delta, Catalunya, Spain, 04:48, 20 September 2019. Four flight calls of a nocturnal migrant with slightly odd timbre. 190920.MR.044558.11

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i) Black-crowned Night Heron Nycticorax nycticorax Sagres, Vila do Bispo, Portugal, 00:49, 4 October 2018 (GM). Single flight call of a nocturnal migrant. MR.004959.10

j) Black-crowned Night Heron Nycticorax nycticorax near Paralimni, Cyprus, 19:56, 24 April 2019. Four flight calls of a nocturnal migrant. Sonagram shows first call. Background: Two-spotted Cricket Gryllus bimaculatus and Middle East Tree Frog Hyla savignyi. 190424.MR.195634.01

k) Black-crowned Night Heron Nycticorax nycticorax Besh Barmag, Siyazan, Azerbaijan, 20:56, 4 October 2018 (BB). Single very harsh flight call of a nocturnal migrant. 181004.MR.205645.02

l) Black-crowned Night Heron Nycticorax nycticorax Odeceixe, Aljezur, Portugal, 21:58, 28 August 2017. Single flight call of a nocturnal migrant. 170828.MR.215830.00

Effects of recording quality

  • Calls at very close range can have additional frequency bands above and below or show more croakiness, which blurs the sonagram.
  • Distant qwar calls may show only a faint single frequency band in an apparently straight line, which otherwise would show rising parts and a kink in the frequency band.

Similar NFCs

  • Eurasian Bittern Botaurus stellaris has a lower pitched NFC, which otherwise strongly reminds of Night Heron’s qwar when pitch is difficult to assess. A good reminder is, that Eurasian Bittern’s grouw sounds descending, whereas Night Heron’s qwar sounds rising, as if asking a question. Bittern NFCs are also longer.
  • Grey Heron Ardea cinerea has a similar general pitch but its rrank is otherwise different in timbre and shape of the call. Grey’s rrank has every so often a strident or shrill timbre. It shows (depending on quality of the recording) a broad bandwidth without one clear main frequency band (often it shows two instead), whereas Night Heron has often a clear main frequency band and additionally may show a prominent rising part and kinks in the course of the frequency.
  • Little Egret Egretta garzetta is a potential confusion risk as its NFC argh, similarly pitched, is not well-known among birders. It sounds not prominently rising overall but rather gurgling and invariably croaky; sometimes even slightly descending with a hint of the diphthong ‘aʊ’. Shape appears as a diffuse block or arch and may show diagnostic frequency bands in zig-zag lines, resulting from the gurgling, slightly shivering timbre of its call.
  • Little Bittern Ixobrychus minutus is remotely similar but its NFC ker is distinctly higher-pitched (mean peak frequency is 2.2 kHz) and sounds overall slightly descending, like a miniature Eurasian Bittern.

Where and when?

  • anywhere: over towns, forests, mountains, offshore; but more likely near rivers or lakes
  • mainly nocturnal: but may start or finish migration in twilight
  • typically in the middle of the night: but recorded any time between dusk and dawn

Black-crowned Night Heron Nycticorax nycticorax Maximum estimates of calling individuals per night: low, medium and high activity. See introduction for a full explanation.

Further reading

Berthold, P 1993. Bird migration: A general survey. Oxford.

Naumann, J F 1838. Naturgeschichte der Vögel Deutschlands. Volume 9. Leipzig.