Eurasian Whimbrel

On most occasions, Eurasian Whimbrels Numenius phaeopus migrating at night are immediately recognizable thanks to their characteristic pi-pi-pi-pi-pi-pi flight call, the same one they use during the day. Nevertheless, things are not always as easy as they seem.

Mistaking a Little Grebe Tachybaptus ruficollis for a Whimbrel is everyone’s rite of initiation into one of the enduring mysteries of nocmig:  that two species can sound disturbingly similar despite being distant both visually and taxonomically. We will explain how to tell the difference.

When Whimbrels migrate nocturnally in flocks, the challenge increases. There may be few or even no pi-pi-pi-pi-pi-pi calls, and in their place may be other calls that invite confusion with Eurasian Curlew N arquata or Bar-tailed Godwit Limosa lapponica.

In spring and to a much lesser extent in autumn, migrating Whimbrels may occasionally sing briefly. This song is a simple one they also use when landing to claim a feeding territory.

To gain experience with the less well-known call-types in a nocturnal context, we suggest taking any opportunity to listen to Whimbrels at a roost during the migration period. Often there is a great deal of whistling and harsh chattering and an almost total lack of pi-pi-pi-pi-pi-pi calls. Here is an example from the Netherlands.

pi-pi-pi-pi-pi-pi

• quick series of short, clearly articulated piping notes,
• sounds like a ‘trill’ or, less often, has a slightly rattling quality
• median of 6 notes per series (90% range, 3 – 12 notes; n = 50)
• series as a whole level, gently arched or slightly descending
• arch-shaped individual notes
• maximum frequency of arch 2.5 kHz (mean; ±0.9 kHz; n = 50) measured at one note in the middle of the series
• in more than 50% of calls, there are clear ‘forelegs’ before some or all of the notes, with mean starting frequency of 1.5 kHz; the more prominent they are, the harsher or more rattling the call becomes

Effects of recording quality

• Clearer calls show more clearly any ‘foreleg’ that may be present.
• Very distant calls may appear to have fewer notes, the last one being too faint to hear or to show in sonagrams.

short whistle

• slightly rising short whistle
• usually single but sometimes given in short, loosely connected series
• when more than one, first whistle longest
• slightly rising overall; shape variable but usually slightly convex, ie, with hint of an arch, more easily seen with zoomed in frequency scale; in a sample of 20 calls, 16 convex, 2 straight, 2 concave
• duration 130 – 385 ms (90% range; median 185 ms; n = 21)
• slightly lower-pitched than pi-pi-pi-pi-pi-pi
• frequency 1.5 – 2.5 kHz (mean max 2.2 kHz; mean min 1.9 kHz; n = 21)

Effects of recording quality

• Clearer calls may appear slightly more arched, due to the extremities showing more clearly.
• More distant calls may appear slightly flatter and shorter, due to missing extremities.

husky chatter

• short, husky-sounding waves of excited chatter; more often clusters of notes than single ones
• volatile: delivery constantly speeding up and slowing down
• extremely variable individual notes, but often recall husky versions of ‘short whistle’ and ‘pi-note’
• huskiest notes have no definable pitch at all
• typical note harshest at the start, resolving into a short, husky, slightly rising whistle
• note durations 70 – 237 ms (90% range; median 127 ms; n = 55)
• when discernible, pitch similar to ‘short whistle’, ie, greatest concentration of energy between 1.8 and 2.3 kHz

Effects of recording quality

• At close range the harshness is greater.
• At a distance the calls sound less harsh, and quieter ones become inaudible.

short songs

• sequence of three types of sound: low straight whistle, modulated whistle, pi-pi-pi-pi-pi-pi-like trill
• relative proportions of three sections highly variable in nocturnal migration context; final section in particular has extremely variable length
• duration 3.1 – 6.4 s (90% range; median 4.5 s; n = 10)

pi-pi-pi-pi-pi-pi

• Little Grebe Tachybaptus ruficollis has an NFC is very similar to the pi-pi-pi-pi-pi-pi of a Whimbrel. The main differences are: 1) that it is usually preceded by a couple of quiet, higher-pitched tip notes, the last of which often forms the first note of the trill; 2) the median number of notes is nearly three times that of a Whimbrel; 3) the pitch descends rapidly from the level of the tip notes, then settles at a lower pitch, whereas in Whimbrel the pitch descends either gradually over the whole call or only towards the end, and at the start it may ascend slightly; 4) the shape of the individual notes is an inverted V, (or an A without the crossbar), not an arch as in Whimbrel.
• Common Cuckoo Cuculus canorus females have a bubbling NFC that is quite similar. Differences include that the cuckoo’s NFC 1) rises then falls in pitch more noticeably over its entire length; 2) has a slight but noticeable deceleration towards the end; 3) has individual notes where the rising ‘foreleg’ dominates over the arch at the top, the strongly rising pitch in each note creating the ‘bubbling’ quality.
• Terek Sandpiper Xenus cinereus is only a problem in comparison with very short, 3-note NFCs of Whimbrel, usually solitary ones. Terek has each note more audibly rising in pitch and less arch-shaped. It also has maximum frequency around 400-500 Hz higher than Whimbrel.

short whistle

• Eurasian Curlew Numenius arquata has a similar whistle which, however, differs in being roughly twice as long. It is also markedly lower-pitched, with mean minimum frequency nearly 500 Hz lower and mean maximum frequency 200 Hz lower. Curlew calls tend to have a concave shape; Whimbrels a convex one.
• European Golden Plover Pluvialis apricaria has a similar whistle but longer and nearly 1 kHz higher-pitched with a slightly descending, not ascending contour.

husky chatter

• Eurasian Curlew Numenius arquata has very similar husky chatter. The most helpful difference is that the tonal sounds emerging from its chatter are lower-pitched and sound like muffled yelps of a puppy. They closely resemble the quip of Curlew, which is a similar call but lacking husky timbre, also given in flocks.
• Bar-tailed Godwit Limosa lapponica is also a major pitfall when it comes to husky chatter. Individual notes average one third shorter, and there is more separation between them. The tonal sounds emerging from the chatter are more nasal-sounding in the godwit, due to a marked harmonic structure; indeed, the whole call is spread across a much broader frequency range. The strongest band is usually the second one up, at 1.8 – 2.2 kHz, but the third one up is only slightly weaker. At close range, a weaker fundamental around 0.9 – 1.1 kHz becomes visible, this being far more prominent than any similar-pitched element in Whimbrel chatter.

• anywhere: over towns, forests, deserts, offshore, but more likely at the coast
• nocturnal and diurnal: uses same flight calls day and night
• recorded any time between dusk and dawn