Things that go plik in the night

Nocturnal autumn migration of Ortolan Bunting Emberiza hortulana in Dorset, England, and southern Portugal

Magnus Robb, Nick Hopper, Paul Morton & The Sound Approach

Ortolan Bunting Emberiza hortulana is not an easy migrant to observe in Britain. Most birders would be delighted to find just one during any given autumn. The majority of records come from well-watched migration hotspots in early autumn, especially on the eastern and southern coasts of England. These days it is very unusual for any site to host more than one on the same day. According to the Dorset Bird Reports, the annual county total in recent years has ranged between 3-9 birds (2008-2013). Our all-night sound recording of nocturnal migration has started to paint quite a different picture. In August and September 2016, we detected Ortolan a total of 31 times at two sites in Dorset, England: Poole Old Town centre and Portland Bill. Most of these were likely to have involved different individual birds, except perhaps during two nights where there may have been some repeat detections from potentially disoriented birds. What does seem clear however is that Ortolan is a more regular visitor than we had previously thought.

This study explains how we reached such a conclusion. We have divided it into two parts. The first is about identification and how and where we became familiar with Ortolan Bunting calls. When analysed, recordings of migrants during the day turned out to contain eight distinct call-types, six or possibly seven of which we have also recorded during the night. We give many examples from both night and day, and also of potential confusion species. The second part will tell the story of each author’s listening station, document night migration of Ortolans at each one, and consider the differing amounts of information in recordings, as well as the problem of assessing the number of individuals involved. We will conclude part 2 by asking why Ortolan should be so prominent among nocturnal migrants despite being so difficult to detect during the day, and sharing with you our astonishment at this phenomenon.

Part 1 Ortolans night and day – identifying them by call
Part 2 Nocturnal migration of Ortolans in Dorset and southern Portugal

 

Part 1. Ortolan night and day – identifying them by call

Of the three authors, MR has been recording Ortolan Bunting calls for longest, after developing a passion for sound identification of passing migrants while living in the Netherlands in the late 1990s and early 2000s. In the low countries, there is a tradition of birders visiting migration watchpoints, especially along the North Sea coast. At these points, observers watch and listen to autumn migration on a scale that can often be very impressive. The main focus here is on passerines, unlike famous migration bottlenecks such as the Strait of Gibraltar, or Eilat in southern Israel, where the focus is on soaring birds. In recent decades the popularity of migration counting in the Netherlands rose rapidly, as a quick look at the Dutch-founded international website trektellen.nl shows. On a typical October day in 2016 around 50 Dutch watchpoints were entering their counts on this website.

Anyone visiting such a migration watchpoint for the first time is likely to be impressed by the ability of experienced observers to name tiny dots passing by, largely based on their calls, and many will want to learn how to do the same. When MR started, he sound recorded most of the calls he was hearing, something that virtually nobody else was doing at the time. He soon built up a library of migrant calls, comparing them with published recordings and his own ones of birds not actually migrating, in order to make their identification as secure as possible. In 2000, MR co-founded the Sound Approach and these recordings became part of the Sound Approach collection.

In the Netherlands, Ortolan Bunting is a regular migrant passing in very small numbers. Under the right weather conditions, it is not unusual to hear more than one passing during a morning’s migration; 10 sites have had counts in double figures, and the national day record stands at 47 (De Nolle near Vlissingen, Zeeland, 7 September 1992). So with patience, it is possible to build up experience of Ortolan in migration flight. It is more difficult to find them foraging during the day but when MR did, he recorded them extensively, as a way of checking that the birds seen less well during migration flights had been correctly identified. In the meantime he and other members of the Sound Approach team recorded Ortolan in many other parts of its range, both during the breeding and migration periods.

In 2009, MR moved to Portugal, where he was disappointed to find that passerine migration observable by day was on a smaller scale than in the Netherlands. When parenthood also made him less free to travel to migration hotspots, he tried his luck with nocturnal migration in his back yard instead. This soon became a new obsession when he realised that surprising numbers of Ortolan Buntings were flying over his house on early autumn nights. Up to October 2016, MR has retained 106 recordings of Ortolan in nocturnal migration, most of them over his house in Cabriz, Sintra, but also at various other sites.

In Portugal, Ortolan Bunting is more numerous in autumn than in the Netherlands. Besides being a locally common breeder in upland terrain in the northern half of Iberia, a large part of the European breeding population passes through the peninsula in autumn. Still, most birders would be delighted to encounter an Ortolan during a morning’s birding in autumn and few would suspect how many are passing at night.

In August 2015, PM showed MR a mystery call he had recorded one night over his garden in Lytchett Matravers, Dorset, and MR immediately recognised it as an Ortolan. PM recorded another individual a month later from the same location, and with both NH and PM detecting them in 2016 from newly set up listening stations, the Dorset total of night migrating Ortolan recordings now stands at 33. We will explain more about the circumstances of these recordings in part 2, but first here is how we are identifying these birds as Ortolans.

 

Ortolan Buntings usually give more than one type of flight call

Ortolan Buntings use a surprising variety of calls during migration flights. One of their most peculiar characteristics is the way they deliver these calls, especially when undertaking longer flights. The calls are delivered as a ‘medley ‘of different types, often at fairly regular intervals. A more varied diurnal sequence might be plik…. plik…. plukpluk… tslew… tslew… pluk… tew… tew… plik… At night the gaps between calls are longer, sometimes 10-20 seconds, but the call types used in the dark are derived from exactly the same set used during the day.

When an Ortolan flies past on migration, it may be audible for 30 seconds or longer, depending on how soon it is picked up, whether special listening equipment is being used to amplify the sound, and how quiet the surroundings are. On one occasion in the Netherlands, a friend phoned MR from 1 km to the north and told him a day migrating Ortolan was on the way. Knowing which direction to aim, he picked it up with his Telinga parabolic microphone nearly a minute before it arrived. Listen to it approaching gradually, in the company of migrating yellow wagtails Motacilla, Meadow Pipits Anthus pratensis, Dunnocks Prunella modularis and a Common Reed Bunting E schoeniclus. We have only excluded the first 10 seconds, where you would struggle to hear the Ortolan. Most of the calls here could be described as plik or pluk.


Ortolan Bunting Emberiza hortulana, IJmuiden, Noord-Holland, Netherlands, 09:46, 10 September 2006. One migrating along the Dutch coast. Background: Meadow Pipit Anthus pratensis, yellow wagtail Motacilla, Dunnock Prunella modularis and Common Reed Bunting Emberiza schoeniclus. 060910.MR.94605.11

We have classified flight calls of Ortolan Bunting into eight types, all of which we have recognised in more than one individual. Five are common (four of these also at night) and three are rare. Here is a brief summary. Click on the name of each call to read about it in detail, listen to both day time and night time examples, and also to other species that sound similar.

Plik v common day & night fairly consistent arch shaped, narrow frequency range
Pluk v common day only consistent low frequency, sharply rising
Tew common day & night more variable descending, steepest at top, monosyllabic
Tslew common day & night more variable descending, distinctly disyllabic
Tsrp common day & night very variable single pitch, fairly high, hint of roughness
Puw rare day & night fairly consistent low, fairly level, bullfinch-like
Tup rare day & night fairly consistent low, descending, chaffinch-like
Vin v rare day & night fairly consistent single pitch, low, brief, nasal

 

Five call-types commonly heard from migrants

Plik is the commonest call of migrating Ortolan Buntings both day and night. It is distinctive; nothing else sounds quite like it. While there is considerable variation in pitch the shape is remarkably consistent. What all plik calls have in common is their short duration and narrow frequency range, making the call sound to human ears as if it has a single pitch, not rising or falling. In sonagrams, however, it appears as an arched shape with mean peak frequency of 4.4 kHz and a mean total duration of 35 mS (38 mS in our nocturnal examples). For a table of measurements scroll down. The call starts with a steep descending line of variable length and strength. Where this ends, it forms an acute ‘angle’ with the arch to its right. The rising ‘left side’ of the arch – a fairly straight line sloping up to the right – is the call’s most prominent and least variable feature. From the top of the arch – the call’s second ‘angle’ – a more gentle slope descends to a greater or lesser degree, forming its right side. The first angle is always sharp, and the second may be sharp or more rounded. Listen to an example of a diurnal call sequence with several plik calls. Below it is a sonagram and corresponding sound file showing six variations of this call type recorded during the day.


Ortolan Bunting Emberiza hortulana, Cabo Espichel, Setubal, Portugal, 08:02, 17 September 2010 (Magnus Robb). Several plik calls in flight.


Ortolan Bunting Emberiza hortulana. Six variations of plik calls recorded by day. 1) Cabo Espichel, Setúbal, Portugal, 08:02, 17 September 2010 (Magnus Robb) 2) Sagres, Vila de Bispo, Portugal, 08:22, 17 September 2008 (Magnus Robb) 3) Ponta de Erva, Vila Franca de Xira, Portugal, 07:55, 22 September 2010 (Magnus Robb) 4) Vedi, Ararat, Armenia, 15:37, 14 May 2011 (Magnus Robb) 5) Planalto de Mourela, Montalegre, Portugal, 10:35, 22 May 2015 (Magnus Robb) 6) IJmuiden, Noord-Holland, Netherlands, 07:51, 29 August 2007 (Magnus Robb)

 

At night, plik is by far the commonest Ortolan Bunting call we have recorded. Plik was present in 83 out of 141 recordings of nocturnally migrating Ortolans. Listen to an example of a nocturnal sequence. Below it is a sonagram and corresponding sound file showing six variations of this call type recorded at night.


Ortolan Bunting Emberiza hortulana, Cabriz, Sintra, Portugal, 01:19, 8 September 2012 (Magnus Robb). Sequence of plik calls from a passing nocturnal migrant.


Ortolan Bunting Emberiza hortulana. Six variations of plik calls recorded by night. 1) Cabriz, Sintra, Portugal, 01:19, 8 September 2012 (Magnus Robb) 2) Portland Bill, Dorset, England, 23:27, 25 August 2016 (Nick Hopper) 3) Cabriz, Sintra, Portugal, 03:02, 26 September 2011 (Magnus Robb) 4) Cabriz, Sintra, Portugal, 23:21, 3 September 2012 (Magnus Robb) 5) Cabriz, Sintra, Portugal, 04:35, 6 September 2012 (Magnus Robb) 6) Sagres, Vila do Bispo, Portugal, 23:12, 3 October 2009 (Magnus Robb).
Things that go plik in the night Part1 Sonagrams

 

European Goldfinch Carduelis carduelis has a call similar to Ortolan Bunting’s plik, although it normally uses this call in combination with others. Goldfinches usually move around in tight flocks, and we have never recorded one migrating at night, despite it being such a common species.


European Goldfinch Carduelis carduelis, IJmuiden, Noord-Holland, Netherlands, 3 October 2005 (Magnus Robb). Plik-like calls of a single individual migrating. Note the variation in pitch and rhythm, giving a bouncing effect. On odd occasions when a single goldfinch repeats only its most plik-like calls, these are likely to be given in twos as well as singly, and with much shorter gaps than an Ortolan Bunting. Background: Dunnock Prunella modularis.

The following table compares measurements of plik calls recorded by day and by night. We limited the diurnal sample to birds identified both visually and aurally. For nocturnal plik calls, we chose the 18 clearest recordings from each country (PT for Portugal and UK for Dorset). Where there was more than one plik call in a recording we calculated the mean of up to three of the clearest ones. For each measurement we give the mean, standard deviation and range.

 

 Diurnal allPT nocturnalUK nocturnal
Sample size171818
Start frequency4354 ± 566
(2839-5210)
4470 ± 348
(3899-5105)
4499 ± 423
(3573-5108)
Frequency angle A3362 ± 519
(2512-4075)
3562 ± 338
(2904-3986)
3728 ± 390
(3070-4298)
Frequency angle B4328 ± 430
(3489-4857)
4405 ± 298
(3924-4804)
4443 ± 297
(4075-4968)
Freq B/Freq A1.299 ± 0.09
(1.151-1.435)
1.242 ± 0.09
(1.131-1.426)
1.211 ± 0.07
(1.069-1.336)
End frequency

3741 ± 518
(3070-4605)
3830 ± 361
(2919-4393)
3935 ± 297
(3433-4522)
Total duration

35 ± 3.79
(29-43)
38 ± 6.13
(29-48)
38 ± 4.65
(28-45)

 

Pluk is the second commonest call type of migrant Ortolan Buntings during the day. Curiously, we have never recorded it at night. Pluk calls are low-pitched with a sharply ascending contour, the fundamental typically rising from 2 to 3.5 kHz in just 16 ms. This is the only Ortolan call likely to be doubled or trebled rapidly, and it is usually the first call we hear after flushing an Ortolan (they also pluk during longer flights). Pluk is one of the least variable calls, although occasionally we have recorded calls intermediate between plik and pluk. Listen to a typical example of pluk calls given just after taking off. Below it is a sonagram and corresponding sound file showing six variations of pluk calls recorded by day.


Ortolan Bunting Emberiza hortulana, IJmuiden, Noord-Holland, Netherlands, 17 September 2003 (Magnus Robb). Pluk calls shortly after taking off, with three plik calls.


Ortolan Bunting Emberiza hortulana. Six variations of pluk calls recorded by day. 1) IJmuiden, Noord-Holland, Netherlands, 17 September 2003 (Magnus Robb) 2) Sagres, Vila do Bispo, Portugal, 08:24, 17 September 2008 (Magnus Robb) 3) Cabo Espichel, Setúbal, Portugal, 09:24, 11 October 2010 (Magnus Robb) 4) Chokpak, South Kazakhstan, Kazakhstan, 2 May 2000 (Magnus Robb) 5) Soguksu, Kızılcahamam, Turkey, 8 May 2001 (Magnus Robb) 6) Dadia, Evros, Greece, 2 May 2002 (Magnus Robb)
Things that go plik in the night Part1 Sonagrams

 

Of interest, the corresponding calls given by Ortolan Bunting’s closer relatives – species that give similar medleys of calls – are subtly different. These species are much rarer than Ortolan in a western European perspective. Here are low-pitched take-off calls of several from this group, plus the equivalent call of Yellowhammer E citrinella.


Cretszchmar’s Bunting Emberiza caesia, Wadi Dana, Jordan, 30 April 2004 (Magnus Robb). Various calls of a male, starting with the equivalent of Ortolan Bunting’s pluk.


Grey-headed Bunting Emberiza buchanani, ‘Van Hills’, Van, Turkey, 2 June 2002 (Magnus Robb). Calls when taking off, equivalent to Ortolan Bunting’s pluk.


Cinereous Bunting Emberiza cineracea semenowi, Nemrut Dag, Adiyaman, Turkey, 29 May 2002 (Magnus Robb). Low-pitched calls in flight, equivalent to Ortolan Bunting’s pluk.


Black-headed Bunting Emberiza melanocephala, Akseki, Antalya, Turkey, 11 May 2001 (Magnus Robb). Low-pitched calls in flight, equivalent to Ortolan Bunting’s pluk.


Red-headed Bunting Emberiza bruniceps, Chokpak, South Kazakhstan, Kazakhstan, 2 May 2000 (Magnus Robb). Low-pitched calls in flight, equivalent to Ortolan Bunting’s pluk.


Yellowhammer Emberiza citrinella, IJmuiden, Noord-Holland, Netherlands, 6 November 2003 (Magnus Robb). Calls when flushed.

 

Tew is a common call-type used by migrant Ortolan Buntings both night and day. It is highly variable, and future studies may show that it can be divided into further types. What all tew calls have in common, however, is that they descend rapidly in pitch over a wide frequency range, more steeply at the start than at the end. A good feature to look for in sonagrams, when present, is one or more obvious kinks somewhere along the line where the slope changes. These help to distinguish Ortolan’s tew from similar calls of several other species. To the human ear tew always sounds monosyllabic. Similar calls that are audibly disyllabic are best classified as tslew. Listen to an example of a tew call recorded from a passing spring migrant, seen and heard by many observers. Below it is a sonagram and corresponding sound file showing six variations of tew calls recorded by day.


Ortolan Bunting Emberiza hortulana, Breskens, Zeeland, Netherlands, 08:02, 13 May 2007 (Magnus Robb). Tew and tsrp calls of one passing a ‘migration station’ by day.


Ortolan Bunting Emberiza hortulana. Six variations of tew calls recorded during the day. 1) Breskens, Zeeland, Netherlands, 08:02, 13 May 2007 (Magnus Robb) 2) Chokpak, South Kazakhstan, Kazakhstan, 2 May 2000 (Magnus Robb) 3) Vedi, Ararat, Armenia, 15:37, 14 May 2011 (Magnus Robb) 4) & 5) Soguksu, Kızılcahamam, Turkey, 8 May 2001 (Magnus Robb) 6) Cabriz, Sintra, Portugal, 06:44, 1 October 2011 (Magnus Robb)

At night there were tew calls in 45/141 recordings. When they occur they are often repeated in sequences. This example from Poole Old Town has four tew calls. Below it is a sonagram and corresponding sound file showing six variations of tew calls recorded by night.


Ortolan Bunting Emberiza hortulana, Poole Old Town, Dorset, England, 03:08, 25 August 2016 (Paul Morton). Three tew calls of a passing nocturnal migrant.


Ortolan Bunting Emberiza hortulana. Six variations of tew calls recorded during the night. 1) Poole Old Town, Dorset, England, 03:08, 25 August 2016 (Paul Morton) 2) Cabriz, Sintra, Portugal, 03:02, 26 September 2011 (Magnus Robb) 3) Poole Old Town, Dorset, England, 02:00, 24 August 2016 (Paul Morton) 4) Portland Bill, Dorset, England, 23:29, 25 August 2016 (Nick Hopper) 5) Cabo Espichel, Setúbal, Portugal, 01:06, 3 October 2015 (Magnus Robb) 6) Sagres, Vila do Bispo, Portugal, 22:42, 14 September 2011 (Magnus Robb)
Things that go plik in the night Part1 Sonagrams

 

The most likely confusion species for this call-type include ‘yellow wagtails’ (eg, Blue-headed Wagtail Motacilla flava), Lapland Longspur Calcarius lapponicus and Common Reed Bunting. We have recorded all of these as nocturnal migrants.


Blue-headed Wagtail Motacilla flava, Vila Real de Santo António, Algarve, Portugal, 08:31, 5 September 2009 (Magnus Robb). A small flock migrating. Some of the lower-pitched flight calls towards the end of the recording sound fairly similar to tew calls of Ortolan Bunting. Most flight calls of yellow wagtails are clearly higher-pitched, however, and descend most steeply towards the end of the call, whereas Ortolan shows the steepest descent at the start. Also, any ‘steps’ or ‘kinks’ tend to be in the upper half in yellow wagtails, but in the middle or lower half in Ortolan.


Lapland Longspur Calcarius lapponicus, IJmuiden, Noord-Holland, Netherlands, 28 September 2002 (Magnus Robb). Tew calls of an autumn migrant. These were recorded by day, but by night there can be a very real danger of misidentification. Although Lapland’s rattle or Ortolan Bunting’s plik or other call types immediately solve the identification, when we only hear tew, identification can be really challenging. Listen for a slightly higher pitch in Ortolan, and in sonagrams, look for the ‘kink’ that is often present in Ortolan, but lacking in Lapland.


Common Reed Bunting Emberiza schoeniclus, Nore og Uvdal, Trolltjörnstölan, Buskerud, Norway, 06:44, 5 July 2001 (Arnoud B van den Berg). Psieuw calls of a male. These are actually quite different from Ortolan, being both higher-pitched and having a much longer duration. Arguably, they are more likely to cause confusion with the disyllabic tslew call.

 

Tslew is another call type with a descending overall shape, commonly used both day and night. It differs from tew mainly in that it sounds clearly disyllabic. The first syllable is around 5 kHz, and sonagrams show that it usually has a slightly ascending shape. The second syllable lies between 3-4.5 kHz and is much more variable. It can descend from the first syllable like a tew call, or it can be completely separated from it and arch-shaped. Very often it actually overlaps in time with the first syllable, indicating that each was made with a different syrinx (birds have two vocal organs, one for each lung). In the following recording of a bird migrating on an autumn morning there are several tslew calls among a rich medley of other call types. Below it is a sonagram and corresponding sound file showing six variations of tslew calls recorded by day.


Ortolan Bunting Emberiza hortulana, Sagres, Vila do Bispo, Portugal, 08:26, 17 September 2008 (Magnus Robb). A rich medley of calls, including tslew from a migrant passing during the day.


Ortolan Bunting Emberiza hortulana. Six variations of tslew calls recorded during the day. 1) Sagres, Vila do Bispo, Portugal, 08:26, 17 September 2008 (Magnus Robb) 2) Chokpak, South Kazakhstan, Kazakhstan, 2 May 2000 (Magnus Robb) 3) IJmuiden, Noord-Holland, Netherlands (Magnus Robb) 4) Cabo Espichel, Setúbal, Portugal, 09:33, 3 September 2010 (Magnus Robb) 5) Sagres, Vila do Bispo, Portugal, 08:24, 17 September 2008 (Magnus Robb) 6) Berlenga, Leiria, Portugal, 11:19, 28 September 2011 (Magnus Robb)
Things that go plik in the night Part1 Sonagrams

 

At night there were tslew calls in 27 of our 141 recordings. When we record them they are often given in sequences. For example, there were six consecutive tslew calls in the following recording from Portland Bill; another from Poole Old Town also had six. Below this is a sonagram and corresponding sound file showing six variations of tslew calls recorded by night.


Ortolan Bunting Emberiza hortulana, Portland Bill, Dorset, England, 22:55, 25 August 2016 (Nick Hopper). Several tslew calls of a nocturnal migrant on a night of intense Tree Pipit Anthus trivialis migration.


Ortolan Bunting Emberiza hortulana. Six variations of tslew calls recorded during the night. 1) Portland Bill, Dorset, England, 22:55, 25 August 2016 (Nick Hopper) 2) Cabriz, Sintra, Portugal, 02:02, 17 September 2012 (Magnus Robb) 3) Cabriz, Sintra, Portugal, 03:02, 26 September 2011 (Magnus Robb) 4) Poole Old Town, Dorset, England, 02:00, 24 August 2016 (Paul Morton) 5) Poole Old Town, Dorset, England, 02:46, 7 September 2016 (Paul Morton) 6) Cabriz, Sintra, Portugal, 05:49, 18 September 2015 (Magnus Robb)
Things that go plik in the night Part1 Sonagrams

 

Very few other species have calls similar to the tslew of an Ortolan Bunting. One that can sound a little similar at times is Eurasian Siskin Spinus spinus. We have only heard it once as a nocturnal migrant and that was less than 100% certain.


Eurasian Siskin Spinus spinus, IJmuiden, Noord-Holland, Netherlands, 09:01, 18 November 2007 (Magnus Robb). Social calls of a solitary migrant passing on autumn migration. Siskin will usually mix other calls in its flight sequences, making misidentification as an Ortolan Bunting highly unlikely.

 

Tsrp is the last of the calls commonly heard both by day and night. This is perhaps the most difficult Ortolan Bunting call to identify. Tsrp calls are so varied in shape that future studies may show this ‘type’ to be several. What all have in common, however, is that they are relatively high-pitched, monosyllabic and delivered on what sounds to the human ear like a single pitch: their inflections, which we can see on sonagrams, are not obvious to the ear. The whole call fits within a fairly narrow frequency range, typically centred around 5 kHz. Most have a slight huskiness, reminiscent of a Dunnock, and this is what sets them apart from plik calls. Listen to an example of diurnal tsrp calls in flight. Below it is a sonagram and corresponding sound file showing six variations of tslew calls recorded by day.


Ortolan Bunting Emberiza hortulana, Sagres, Vila do Bispo, Portugal, 08:21, 17 September 2008 (Magnus Robb). A medley of calls including many tsrp from a migrant in flight during the day.


Ortolan Bunting Emberiza hortulana. Six variations of tsrp calls recorded during the day. 1) & 2) & 4) Sagres, Vila do Bispo, Portugal, 08:21 & 08:24 & 08:26, 17 September 2008 (Magnus Robb) 3) Breskens, Zeeland, Netherlands, 08:02, 13 May 2007 (Magnus Robb) 5) Sagres, Vila do Bispo, Portugal, 10:23, 10 September 2010 (Magnus Robb) 6) Vedi, Ararat, Armenia, 15:37, 14 May 2011 (Magnus Robb)
Things that go plik in the night Part1 Sonagrams

 

At night there were tsrp calls in 44 out of 141 recordings of passing migrants. Usually tsrp is given in the presence of other call types, and if plik is among them the mystery is soon solved. When plik is missing, it can be more difficult to identify. The following recording had MR stumped for a long time, and were it not for the tslew call also in this sequence, he might still be guessing. Below it is a sonagram and corresponding sound file showing six variations of tsrp calls recorded by night.


Ortolan Bunting Emberiza hortulana, Barão de São João, Lagos, Portugal, 21:14, 5 October 2009 (Magnus Robb). A series of tsrp calls with one tslew from a nocturnal migrant.


Ortolan Bunting Emberiza hortulana. Six variations of tsrp calls recorded during the night. 1) Sagres, Vila do Bispo, Portugal, 21:14, 5 October 2009 (Magnus Robb) 2) Cabriz, Sintra, Portugal, 01:38, 13 September 2013 (Magnus Robb) 3) Poole Old Town, Dorset, England, 03:34, 30 August 2016 (Paul Morton) 4) Portland Bill, Dorset, England, 22:44, 5 September 2016 (Nick Hopper) 5) Cabriz, Sintra, Portugal, 05:38, 18 September 2015 (Magnus Robb) 6) Portland Bill, Dorset, England, 21:55, 25 August 2016 (Nick Hopper)

Possible confusion species for this call-type include Tree Pipit A trivialis, Dunnock and Yellowhammer. All are regular nocturnal migrants.


Tree Pipit Anthus trivialis, Shizzafon Kibbutz fields, Arava Valley, Israel, 08:00, 2 December 2001 (Killian Mullarney). Tip calls of a wintering individual. These are similar in pitch and duration to the tsrp of Ortolan Bunting, but more simple and pure-sounding.


Dunnock Prunella modularis, De Cocksdorp, Texel, Netherlands, 06:25, 6 September 2016 (Magnus Robb). Calls of a migrant at dawn, at first perched then flying off. Individual calls longer than tsrp of Ortolan Bunting, and often doubled in a way that excludes Ortolan.


Yellowhammer Emberiza citrinella, IJmuiden, Noord-Holland, Netherlands, 31 October 2002 (Magnus Robb). Dzheu calls of a passing migrant. Much coarser (more heavily modulated) than most Ortolan Bunting calls, although one visually confimed Ortolan did give a single call that was almost identical.

 

Three call-types more rarely heard from migrants

Puw is only occasionally used by Ortolan Buntings during migration, both by day and by night. However, a very similar call is common during the breeding season in situations where the nest or brood is under threat. This is a very low-pitched whistle reminiscent of a bullfinch Pyrrhula. In our recordings of migrants, the call usually descends from around 3 to 2.5 kHz and has a mean total duration of 64 mS (n=7 individuals). Listen to an example of puw calls used by a migrant during the day. Below it is a sonagram and corresponding sound file showing three variations of puw calls recorded by day.


Ortolan Bunting Emberiza hortulana, Sagres, Vila do Bispo, Portugal, 08:21, 17 September 2008 (Magnus Robb). A medley of calls, starting with puw, from a migrant in flight during the day.


Ortolan Bunting Emberiza hortulana. Three variations of puw calls recorded during the day. 1) Sagres, Vila do Bispo, Portugal, 08:21, 17 September 2008 (Magnus Robb) 2) Madzharovo, eastern Rhodopi mountains, Bulgaria 09:58, 3 June 2009 (Arnoud B van den Berg) 3) Planalto de Mourela, Montalegre, Portugal, 10:35, 22 May 2015 (Magnus Robb)
Things that go plik in the night Part1 Sonagrams

 

At night there were puw calls in only 4 out of our 141 recordings of passing Ortolan Buntings, and we have not yet recorded this call type in Dorset. Listen to an example of puw calls in a rich nocturnal medley of other call-types recorded in Portugal. Below it is a sonagram and corresponding sound file showing three variations of puw calls recorded by night.

Ortolan Bunting Emberiza hortulana, Cabriz, Sintra, Portugal, 05:49, 18 September 2015 (Magnus Robb). Medley of puw and tslew calls of a nocturnal migrant.


Ortolan Bunting Emberiza hortulana. Three variations of puw calls recorded during the night. 1) Cabriz, Sintra, Portugal, 05:49, 18 September 2015 (Magnus Robb) 2) Cabriz, Sintra, Portugal, 04:13, 13 September 2013 (Magnus Robb) 3) Cabriz, Sintra, Portugal, 03:26, 3 September 2016 (Magnus Robb)
Things that go plik in the night Part1 Sonagrams

Puw calls in isolation could be mistaken for a Eurasian Bullfinch Pyrrhula pyrrhula, although we have yet to hear a bullfinch migrating at night.


Eurasian Bullfinch Pyrrhula pyrrhula, Durlston, Dorset, England, 10:47, 6 October 2008 (Magnus Robb). Calls of a male just before taking off. Bullfinch calls are much longer than puw calls of Ortolan Bunting, so when comparing recordings directly it is easy to tell them apart.

 

Tup is another call only rarely used by Ortolan Buntings during migration, both day and night. This is a low-pitched, rapidly descending whistle strongly reminiscent of the flight call of a Common Chaffinch Fringilla coelebs. In our recordings, it descends from around 3.5 to 2.7 kHz, within a mean total duration of 47 mS (n=8 individuals). Perhaps puw and tup are merely longer and shorter versions of the same call. A larger sample of both may confirm or deny this possibility. Listen to an example recorded during the day. Below it is a sonagram and corresponding sound file showing three variations of tup calls recorded by day.


Ortolan Bunting Emberiza hortulana, Sagres, Vila do Bispo, Portugal, 08:26, 17 September 2008 (Magnus Robb). A rich medley of calls including tup, from a migrant passing during the day.


Ortolan Bunting Emberiza hortulana. Three variations of tup calls recorded during the day. 1) & 2) Sagres, Vila do Bispo, Portugal, 08:26 & 08:24, 17 September 2008 (Magnus Robb) 3) Madzharovo, eastern Rhodopi mountains, Bulgaria 09:58, 3 June 2009 (Arnoud B van den Berg)
Things that go plik in the night Part1 Sonagrams

 

At night there were tup calls in just 4 out of 141 recordings of migrating Ortolan Buntings. The bird in the following recording would probably have been mistaken for an early migrating Common Chaffinch had it not given some other Ortolan call types as part of its flight call medley.


Ortolan Bunting Emberiza hortulana, Cabriz, Sintra, Portugal, 00:26, 9 September 2015 (Magnus Robb). Tup and tslew calls of a nocturnal migrant.


Ortolan Bunting Emberiza hortulana. Three variations of tup calls recorded during the night. 1) Cabriz, Sintra, Portugal, 00:26, 9 September 2015 (Magnus Robb) 2) Odeceixe, Aljezur, Portugal, 01:31, 31 August 2016 (Magnus Robb) 3) Cabriz, Sintra, Portugal, 02:19, 19 September 2016 (Magnus Robb)
Things that go plik in the night Part1 Sonagrams


Common Chaffinch Fringilla coelebs De Nolle, Zeeland, Netherlands, 11:30, 8 November 2011 (Magnus Robb). Flight calls of a bird passing on migration flight.

 

Vin is a strange little nasal call that we have recorded twice from migrants during the day, and twice at night. We have also recorded an identical call on the breeding grounds. This is a short, low-pitched, uninflected call with strong harmonics that give it a nasal timbre. Listen to an example from the breeding season, followed by one of a diurnal migrant.


Ortolan Bunting Emberiza hortulana, Planalto de Mourela, Montalegre, Portugal, 10:35, 22 May 2015 (Magnus Robb). Vin call and another rapidly rising call given by an Ortolan that approached the recordist. It may have had a nest close by.


Ortolan Bunting Emberiza hortulana, Sagres, Vila do Bispo, Portugal, 08:21, 17 September 2008 (Magnus Robb). A medley of calls, starting with vin, from a migrant in flight during the day.

Both times when we recorded vin at night, the caller was distant. In this example, the clearest call also coincides with a distant dog’s bark. Compare the calls in the sonagrams below, where the nocturnal example is the third in the row, following diurnal examples from each of the two recordings above.


Ortolan Bunting Emberiza hortulana, Cabriz, Sintra, Portugal, 00:26, 9 September 2015 (Magnus Robb). A medley of calls from a nocturnal migrant, starting with a vin call.


Ortolan Bunting Emberiza hortulana. Two diurnal and one possible nocturnal vin call. 1) Planalto de Mourela, Montalegre, Portugal, 10:35, 22 May 2015. (Magnus Robb) 2) Sagres, Vila do Bispo, Portugal, 08:21, 17 September 2008 (Magnus Robb) 3) Cabriz, Sintra, Portugal, 00:26, 9 September 2015 (Magnus Robb)
Things that go plik in the night Part1 Sonagrams

 

If anything, vin resembles a very short version of the ‘trumpet’ call given by some Northern Bullfinches P p pyrrhula, but other call types given as part of the Ortolan Bunting’s medley should soon put any such ideas to rest.


Northern Bullfinch Pyrrhula pyrrhula pyrrhula, De Nolle, Zeeland, Netherlands, 10:50, 8 November 2005 (Magnus Robb). ‘Trumpet’ calls of a female migrating with Brambling Fringilla montifringilla. Vin calls of Ortolan are much shorter.

Conclusion

By now we hope it is clear that the nocturnal flight calls we have identified as Ortolan Bunting are fully compatible with six or seven of the eight call-types we have recorded from migrants during the day. Nocturnal Ortolans can be identified with higher confidence when we hear more than one of these call-types, and this is in fact what nearly always happens. When we only hear plik, we can still identify the bird with a high degree of confidence. When we only hear one of the other three common nocturnal call-types, we have to be more cautious, considering the possibility of confusion with several other species that occur regularly as nocturnal migrants.

In eastern Europe, there are several other species of bunting that deliver their flight calls in a similar ‘medley’ style. These include Red-headed Bunting E bruniceps, Black-headed Bunting E melanocephala, Cinereous Bunting E cinerea, Cretzschmar’s Bunting E caesia and Grey-headed Bunting E buchanani. The Sound Approach has recordings of flight calls of all these species, and none appear to match any of Ortolan Bunting’s eight flight call types exactly. However, we do not know them nearly so well, as they are vagrants in our own countries. We hope that in future we will be able to gain more experience of these species in a migration context, to help exclude the highly unlikely possibility that we have been recording any of them at night in Dorset or Portugal.

Which of their eight flight calls were the Ortolan Buntings in Dorset in 2015-16 using? On which dates are those birds occurring, and at what times of night? Was 2016 a freak year? Are there any particular weather conditions when more Ortolans can be heard? What might explain why these birds are being detected in greater numbers during the night than during the day? We will discuss these questions in part two, which is currently under preparation, so watch this space.

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