Bar-tailed Godwit

Bar-tailed Godwit Limosa lapponica is one of those species that you might only pick up if you live near the coast, on an island, or underneath a narrow migration corridor. They migrate in flocks; lone individuals are rare. Coastal lighthouses are ideal places to intercept them, and seven of the recordings here were made either right below a lighthouse, on Texel in Noord-Holland, the Netherlands, or close to one at Portland in Dorset, England.

Frequently misidentified, this is one of the more challenging waders to learn, and it has been rewarding to study. Depending where you live, learning opportunities may be limited, and it has a large repertoire of calls, some of which can easily be confused with other species. Fortunately its calls by night or day are the same, so take every opportunity to listen for and learn the calls described below, if you find yourself in their company during the day.

The dominant NFC is the kek call, so it helps to learn that one first. It will nearly always be mixed in with the other call-types when flocks migrate at night and is the only call likely to be used by a lone migrant. With enough practice it will become possible to identify Bar-tailed Godwit using any of these call-types, given good listening conditions.

kek

• short, sharp, nasal-sounding
• may be given singly, or grouped in twos or threes
• duration 33 – 82 ms (90% range; median 49 ms; n = 40)
• marked harmonic structure gives nasal timbre; second harmonic usually the strongest band; fundamental much weaker and may be invisible in sonagrams
• simple arched shape with ‘foreleg’ and ‘handle’; highest frequency often before the mid-point, ie, upward slope may be slightly shorter than downward
• intonation sounds ‘flat’ despite arched shape; pitch not changing noticeably during the call
• frequencies from 1.6 – 2.4 kHz for second harmonic (mean minimum 1.8 kHz; mean maximum 2,2 kHz; n = 40)
• clusters of two or three kek calls have slightly varied individual notes

Effects of recording quality

• Distant or poorly recorded calls show fewer harmonics as well as shorter ‘forelegs’ and ‘hindlegs’ in sonagrams.

bay-bay

• short duplet, each note rising with accent towards the end
• usually double, but one- and three-note versions exist
• rising slope usually concave, sometimes with slight drop in the middle
• second note may have different shape, eg arched or even slightly falling pitch
• nasal timbre with strong harmonics as in kek call
• strongest band is 2nd harmonic, with frequencies between 2 and 3.1 kHz excluding ‘legs’ (first note: mean minimum 2.4 kHz; mean maximum 2.8 kHz; n = 15)
• ‘foreleg’ and ‘hindleg’, with mean minimum of 2.1 kHz (n = 15)
• duration of first note 89 – 146 ms (90% range; median 111 ms; n = 15)
• duration of second note 78 – 149 ms (90% range; median 112 ms; n = 12)

Effects of recording quality

• Distant or poorly recorded calls show fewer harmonics as well as shorter ‘forelegs’ and ‘hindlegs’ in sonagrams.

husky chatter

• short, husky-sounding waves of excited chatter; more often clusters than single notes
• volatile, with waves of excitement followed by stretches of silence
• notes usually recall husky versions of kek, but other notes are longer than this
• huskiest notes have no definable pitch at all
• some notes harsh at the start, then ending with kek timbre
• note durations 49 – 156 ms (90% range; median 85 ms; n = 67)
• when discernible, pitch similar to kek
• frequencies from 1.5 – 2.7 kHz for 2nd harmonic (mean minimum 1.8 kHz; mean maximum 2.2 kHz; n = 65)

Effects of recording quality

• At a distance the harshness is reduced, and quieter calls become inauduble.

song

• nasal-sounding, two-note cycles, though first cycle may be single-note
• notes typically joined together within couplet
• small pitch difference between maximum frequency of first and second notes (or none)
• first note almost always longer than second
• either first or second can be higher-pitched in a given series
• accent is on the higher-pitched note (first or second, depending on pitch)
• pitch pattern occasionally reversed during a series (eg, first notes higher at start, second later in series)
• series durations from 1.2 – 2.8 s (90% range; median 1.8 s; n = 7)
• ‘speed’ highly variable; cycle lengths from 209 – 397 ms (90% range; median 311 ms; n = 7)

kek

• Black-tailed Godwit Limosa limosa has a very similar kep call with a nasal timbre. It averages marginally shorter and higher-pitched, but a clearer difference can be found in the shape of the call. In both species the shape is an arch or convex curve, but in Black-tailed most or all of the call slopes downwards. This difference is subtle but audible. Each note in Black-tailed has a slight downward inflection and covers a wider pitch range, whereas each note in Bar-tailed sounds rather ‘flat’ by comparison.
• Common Moorhen Gallinule chloropus has a similar-pitched and very commonly heard kek-kek-kek NFC which can cause confusion with Bar-tailed Godwit. It usually contains 2-4 virtually identical notes, which average shorter than in the godwit and are repeated in a very exact rhythm; when Bar-tailed Godwit kek notes are delivered in clusters of 2-4, the notes vary more noticeably in pitch and the rhythm sounds looser. Moorhens have a stronger fundamental giving them a slightly fuller-sounding and even more nasal voice.

bay-bay

• Red Knot Calidris canutus has nasal-sounding, rising calls at a similar pitch, which are easily mistaken for Bar-tailed Godwit. A useful feature is that they are usually given one at a time, although they can occasionally be doubled. The clearest difference is that Red Knot has notes are nearly twice as long (90% range 147 – 265 ms; median 211 ms; n = 12). In addition, the shape is more convex than in Bar-tailed Godwit, usually showing an obvious dip in the middle, so that the entire call has a V- or U-shape with the final peak much higher than the initial one.

husky chatter

• Eurasian Whimbrel  Numenius phaeopus has similar husky chatter that can be difficult to tell apart. Individual notes average one third longer in Whimbrel, and there is less separation between them. The tonal sounds emerging from the chatter are more whistle-like, being more nasal in Bar-tailed Godwit; indeed, the whole call is spread across a much narrower frequency range in the godwit. Both have their strongest energy at a similar pitch, but Whimbrel has very little energy around 1 kHz whereas the godwit has a fundamental in this range which contributes significantly to the timbre of the call.
• Eurasian Curlew Numenius arquata has similar husky chatter but it consists of less well-separated notes that average a quarter longer. The tonal sounds emerging from the chatter often resemble the quip call of Curlew, lacking the nasal quality of Bar-tailed Godwit. In addition, the main energy of the call is concentrated at a lower pitch in Curlew: 1 – 2 kHz.

song

• Black-tailed Godwit Limosa limosa has several types of song, at least two of which have been recorded in the context of nocturnal migration. One of these is easy to identify, being a repeated three-note pattern half a second long: a descending first note, a brief middle note and a rising final one (roughly W-shaped in sonagrams): kyuu-ku-week, kyuu-ku-week, etc. The other type is a very rapidly repeated two-note figure (U-shaped in sonagrams) that sounds like kyuwik-kyuwik-kyuwik-kyuwik-kyuwik…. The syllables kyu-and wik are of even length, whereas the syllables in songs of migrating Bar-tailed are usually of uneven length.

• mainly near the coast: rare inland
• nocturnal and diurnal: uses same flight calls day and night
• mostly middle and second half of the night: but recorded any time between dusk and dawn

While there are enough recordings of Bar-tailed Godwit migrating at night to describe its NFCs with confidence, the same cannot currently be said of Black-tailed Godwit. To ensure accuracy, the comparisons above have been primarily based on calls of the latter species during the day, assuming that like other waders they use the same calls at night. In particular, it is not clear whether flocks of Black-tailed use much ‘husky chatter’ during nocturnal migration. We expect so, in which case it will likely be very similar to that of Bar-tailed, but with more downward-inflected kep calls in the mix, rather than nearly symmetrical kek calls.