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 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.