Leg colour: Olive-tree has dark blue-grey or sometimes olive-grey legs. The Tankatara bird has rather pale pinkish yellow legs, contrasting with the darker and greyer feet. The latter pattern looks to be typical of Upcher’s and Eastern Olivaceous. Furthermore, I don’t think the legs and feet look strong enough for the brutish Olive-tree (but probably too robust for Eastern Olivaceous).
Colouration and face pattern: While worn adult Olive-trees can look a touch browner, I really think the Tankatara bird was way too warmly toned for an Olive-tree. I’m hesitant to stare at the face pattern too long, because I think this is rather variable between individual birds, even of the same species. Also, at certain angles shadows can cause problems, and if the dark feather bases are visible the whole pattern changes. Check out the two images presented here for example. That being said, Olive-tree typically has a more distinct blackish spot in front of the eye that often seems to break up the very prominent white eye-ring in the front, leaving only a thin ring of bare skin surrounding the eye and bold white flashes above and below the eye. The Tankatara bird has a more continuous and less eye-catching eye-ring, plus a smudgy dark band in front of the eye. In profile view, Olive-tree has dark ear coverts and sometimes some mottling on the malar region, that contrasts strongly with the whitish throat. In the Tankatara bird, the ear-coverts are quite pale, and blend almost imperceptibly into the throat region. . I don’t see the dark-centered undertail coverts that are sometimes present in Olive-tree (the longest undertail covert in the Tankatara bird does seem diffusely darker though, but the vent is mostly just nice and white). The bird does have slightly contrasting paler creamy buff fringes to some of its greater coverts and primary coverts, but I would expect considerably more contrast in an Olive-tree.
ABOVE: Note how the perceived darkness of the lores (in front of the eye) changes as the bird turns its head, because the dark feather bases become visible at some angles. Very subtle variations like this make me hesitant to base identification on face patterning. Photo by Michael Mason: of the same side of the same bird on the same morning.
ABOVE: In summary, these are the most important distinctions between the Tankatara Warbler and Olive-tree Warbler (below). Photo by Michael Mason.
ABOVE: An Olive-tree Warbler in a similar state of wear as the Tankatara Warbler. Photo by Malcolm Wilson.
Okay, so what the heck is it then?
Basically, there are two options. Two warblers that migrate to E Africa, of this size, with prominent pale wing panels, that wag their tails about and have pinkish-orange lower mandibles: the migratory elaeica race of Eastern Olivaceous Warbler (EOW) and Upcher’s Warbler (UW). Distinguishing between these two can be a real challenge – particularly if they are in rather worn plumage like the Tankatara bird. If you don’t believe me, just check out the millions of contracting comments on Facebook regarding this bird! Perhaps it is wise to first look at the age of the mystery bird. At this time of year, juveniles that hatched around June would be in fresh plumage, while adults would be quite worn after the breeding season. The Tankatara bird is fairly worn, although it still shows much of the pale edging to the feathers that will eventually get worn off almost completely. This suggests it is an adult bird, or second calendar year at the youngest. And what is it doing down here at the southern tip of Africa in August, when it should be fattening up for migration somewhere in Asia? Good question. The best theory I can muster is that this bird is a so-called reverse migrant, that somehow found its way south instead of north when it was supposed to return to its Asian breeding grounds in about March. It then spent the (southern) winter here, and was only discovered now (perhaps because it became more conspicuous at the changing of the seasons?). Who knows.
So can we identify it? Fortunately there are literally thousands of photos of the bird floating around on the Internet, in addition to many video clips and some sound recordings. There have also been lively and highly educational discussions by experts from all over the world (plus some quite dramatic politics, which I won’t get into in too much detail here). I personally spent an hour or two with this bird in the field as well. One of my ideas with this post is to summarize and collate the many disparate, ephemeral and transient comments that have been posted on Facebook and other channels. And objectively try to identify the bird based on the literature and expert input. But don’t take my word for it – this is just my personal opinion, and it is not in my capacity of a member of the SA Rarities Committee or any other official body. Make up your own mind based on the evidence.
I think the Tankatara bird is an Upcher’s Warbler. Here’s how I got to that conclusion:
Behaviour: To me, the movements of the Tankatara bird generally appeared slow, purposeful and ponderous, and its flight slow, heavy and low. It spent the majority of its time either low down in scrub or working along the outer edges and tops of bushes. It also spent a lot of time on the ground or hopping about on rock piles. It was remarkably unconcerned at the presence of hordes of birders, and foraged right out in the open for extended periods. Based on my very limited experience with EOW, and the literature, this sort of exhibitionist behaviour is more typical of UW and EOW. To me, EOW is a rather small, fast-moving, frantic thing, which generally sticks to the upper levels or canopy of tall bushes or small trees. It may descend to lower levels or even briefly alight on the ground, but for the most part is stays hidden in thicker vegetation. The tail movements of the Tankatara bird were also, in my opinion, generally slow and showy, unlike the constant nervous downwards tick of EOW but in line with UW. That being said, tail movement should only be seen as a supporting character. It depends on the bird in question, and the context. Tail wagging is said to be more subdued away from the breeding grounds. . Video clips illustrate behaviour best. Check out these, to start with:
Size: This is obviously difficult to judge in the field, but the Tankatara bird appeared rather big and heavy to me – I would say definitely bigger than a Reed or Marsh Warbler, though not by much. EOW is a smallish (slightly smaller than a Reed Warbler), lightly built bird, with a wing length of around 66 mm, and a mass of 7-16 g (lean weight 8.5-10.5 g). UW is a considerably bigger bird, with a wing length of around 76 mm; it is also a little heavier on average with mass 9.5-17g (lean mass 10.5-13.5 g).
Shape: The Tankatara bird is a closer fit to UW than EOW in my opinion. Compared to EOW, it has a heavier, fuller and broader-looking tail, a steeper crown (without the thin, long-nosed look of EOW), a short, thick neck, stronger legs and a more bulky body. However, at times it did transform into a sleek, skinny creature such as when stretching for insects.
Colouration: To be honest, I am not sure what to make of this. Having no experience with UW, it is difficult to evaluate the subtleties of grey and brown colour shades, particularly as the apparent colour changes dramatically depending on feather wear, light and angle. I would have expected a UW to be paler and more pure grey, whereas the Tankatara bird showed a warmer, more olive-tinged tone that would perhaps fit better with EOW. That being said, a search through hundreds of photos online suggests that colour is extremely variable and there is much overlap between the two species.
Wing panel: EOW may show a fairly prominent pale buff-tinged wing panel formed by the edges of the secondaries and lower tertials, but I would think that the very striking, full, whitish (not buff) panel on the Tankatara bird points more towards UW than EOW. Furthermore, EOW often shows particularly prominent white tips to the secondaries, which form a vertical white line on the folded wing; this is not the case in the Tankatara bird.
ABOVE: Feast your eyes on that white wing panel – it’s almost silvery! Too prominent for a typical EOW if you ask me (?). Photo by Dave Deighton.
ABOVE: Distribution of Upcher’s Warbler Hippolais languida. This species is monotypic. Upcher’s Warbler breeds in a small area of C Asia and the Middle East and winters in dry regions of NE Africa, extending only marginally south of the equator. In Africa, it typically frequents very dry country and occurs at low densities. Its scarcity probably makes it the less likely option for vagrancy to the southern tip of the continent, statistically speaking. I hope the IUCN Redlist website will forgive me for copying this off there – check out their amazing work!
ABOVE: Distribution of Eastern Olivaceous Warbler Iduna pallida. This species was formerly lumped with Isabelline Warbler Iduna opaca (=Western Olivaceous) which breeds in Iberia and N Africa and winters in W Africa. Getting back to E Olivaceous, there are 5 subspecies of which 4 (reiseri, laeneni, pallida and alulensis) breed in NC and NE Africa and are more or less resident (darker blobs on the map). However, birds from Europe (elaeica) are long-distance migrants that winter in E Africa. They are fairly common in Africa and extend to Tanzania, where they occur in various woodland types. It is this latter race that is a potential vagrant to Southern Africa. I hope the IUCN Redlist website will forgive me for copying this off there – please support them!
ABOVE: Size. Upcher’s is left, and Eastern Olivaceous right. Note also the darker, greyer plumage of the UW compared to the more sandy, olive-toned upperparts of the EOW. Many EOWs seem to have a faint orangey wash on the ear-coverts too. Photo by Shai Agmon.
ABOVE: Colour. As you read through this post, pay attention to how drastically the perceived colour of the Tankatara bird changes, depending on the light, angle and no doubt the camera settings! Photo by Michael Mason.
Face pattern: UW and EOW appear extremely similar in e.g. colour of the lores, length and prominence of the supercilium, pale eye-ring etc. I wouldn’t risk an identification on this. One thing that may point more towards UW for the Tankatara bird, is the fact that it has pale ear-coverts that contrast very little with the whitish throat – effectively just grading into the throat without colour contrasts. Some EOWs seem similar, but many have darker, often richer brown ear coverts, that contrast more with the white throat.
Call: The Tankatara bird was not particularly vocal, but Andre Marais did mange to record a series of calls, which you can listen to below. EOW is sometimes said to utter its repeated tack call each time it dips its tail. I think this probably context-specific, but it was not the case in the Tankatara bird. I’m not sure that call will be all that helpful – it comes down to the difference between a tack and a tzack and a tchak. The first file below (labeled as Upcher’s) is the Tankatara bird.
ABOVE: I fear that with this limited sample from the Tankatara bird, together with the variability in the alarm-type calls of these warblers, the vocalisations will probably not solve this mystery for us. Sonograms don’t help much, and often the difference is much clearer to the ear than it is to the eye. The Tankatara bird’s rather hoarse tzhack is plotted on the left. This sound is finer than the deep, Great Reed Warbler-like chack of Olive-tree (first two elements) but the latter species can at times produce higher, sharper calls that are very like Upcher’s. Upcher’s also has some variability, as you’ll hear in the Xeno-Canto embeds above. Finally, EOW typically has rather high, fine calls, but some are extremely similar to both the Tankatara warbler’s and Upcher’s.
Tertial spacing, primary projection and wing formula: In the Tankatara bird, the tips of the middle and longest tertials were definitely closer together. This is a standard feature of UW, while in EOW the tertials are evenly spaced. However, some EOW can apparently also show this character on the rare occasion. Thus not conclusive, but does point more towards UW than EOW. In terms of primary projection…this worries me a little for an ID as UW, as the Tankatara bird appeared to have rather short primary projection, closer to reported values for EOW. To clarify, primary projection is the length of the wing-tip visible beyond the exposed tertials; it is approximately 70% in UW and 50-66% in EOW. I measured one photo of the Tankatara bird (below) at 63%. But in the same breath, my measurements for EOW was 60% and for UW 72% – but in reality, you’re really talking about a few millimetres, and measuring from photos is an inexact science. Perhaps someone who doesn’t have two little toddlers in the house, and thus has some free time and concentration, can measure a larger series for us? In both species, 6-7 primary tips should be visible beyond the tertials, so there’s not much help there. Wing formula is extremely similar between the two, except for EOW’s longer P1 and shorter P10 (i.e. next to the outermost secondary). Not exactly of much use unless you have the bird in the hand. What I did discover though, is that there appears to be a slight difference in the shape of the rear edge of the bunched secondaries on the folded wing. In UW the longest tertial covers the secondaries entirely, or sometimes extends slightly past to create a little overhang (though nowhere near the prominent kink of Olive-tree Warbler; see above). In EOW the secondaries are proportionately longer, and typically 2+ tips of the inner secondaries extend beyond the longest tertial. This means that there is a tail-ward bulge, vs. the flat vertical edge in UW. The Tankatara bird was closer to UW in this respect. However, this feature depends to a large extent on how the wing is held; often the secondaries/tertials are sort of drooped to the side over the tertials, which complicates things. While we’re talking about this area of the bird, keep in mind that EOW often shows pale tips to its secondaries, forming a vertical white band.
ABOVE: The tips of the middle and longest tertials were closer together in the Tankatara bird. You can see that the longest tertial completely covers the secondaries, with the innermost (i.e. the one directly below the tertial) falling a little short. Photo by Michael Mason.
ABOVE: The same applies for Upcher’s Warbler, and structurally the UW in this photo seems extremely close to the Tankatara bird. I have to admit that I stole this pic from a very useful ID blogpost by Jem Babbington, which you can see here.
ABOVE: Conversely, the three tertials are evenly spaced in (most) Eastern Olivaceous. If you look at the left wing, you can see that the longest tertial (count three from the small top one) does not cover the secondaries; tips of two secondaries are visible. Photo from Lamsdell.blogpost.co.za
ABOVE: Primary projection in Upcher’s. Note also the unevenly spaced tertials, and the prominent pale panel on the secondaries.
ABOVE: Primary projection in the Tankatara warbler. Again, unevenly spaced tertials and a prominent pale panel. Photo by Trevor Hardaker.
ABOVE: Primary projection is slightly shorter in E Olivaceous (though variable). Because the secondaries are longer than the tertials, I wasn’t quite sure where to measure to.
Length of first primary: In both species, the first (outermost) primary or P1 is tiny, and partly or completely hidden by the primary coverts. However, in UW P1 is 4 mm shorter than the primary coverts, or up to 2 mm longer, so would not be visible normally. In EOW P1 is 3-6 mm longer than the primary coverts, so is often visible as a small dark wedge below the primary coverts and bases of the primaries. In all the hundreds of photos of the Tankatara warbler, I cannot see any prominent P1 peeking out. This is definitely indicative of UW rather than EOW.
ABOVE: In UW P1 (shown here in red) is usually obscured by the primary coverts, while in EOW it extends a few mm beyond the primary coverts.
ABOVE: Even on this spread wing, I cannot really make out a P1. This is the Tankatara bird. Photo by Stan Blumberg.
ABOVE: This is really the only shot of the Tankatara where I think I can a see a sliver of the tiny P1. Photo by Wilma Meiring.
ABOVE: In this EOW (another gorgeous shot by Daniele Occhiato), you can quite clearly see P1 projecting beyond the primary coverts as a small dark wedge below the base P2.
ABOVE: This very useful photo of EOW shows many of the important features distinguishing this species from UW. Note the relatively pale tail, the narrow white fringing on T6, the evenly spaced tertials, the slightly darker ear-coverts, the yellowish instead of pinkish bill and the longer P1. Photo from Lamsdell.blogspot.co.za.
Tail: In the literature, the dark tail of UW is often stressed as an ID character, no doubt in part due to the bird’s habit of fanning and swinging the tail around which draws the eye. In EOW the tail is somewhat darker brown, but not tending towards dark grey-black distally as in Upcher’s. Being in worn plumage, the Tankatara bird did not have a strikingly dark tail, although it was clearly considerably darker than the uppertail coverts and the rest of the dorsal plumage. The actual tail feathers are also broader in UW than in EOW, which is difficult to judge, but I think that the Tankatara bird did seem to have rather broad rectrices. Lastly, the white on the tail was very pronounced in the Tankatara bird, and extended to the tips and partly on the inner webs of at least T6, T5 and T4. On T6, the white curves around in a broad arc, forming a broad chevron-shape that is asymmetrical: broader on the inner web than on the outer web. As far as I can tell from the literature and from pictures, this is indicative of UW, as EOW has only a narrow white tip on the inner web of T6.
ABOVE: Note how dark the tail looks compared to the uppertail coverts – this depends a lot on the angle and light, but I still think it is too dark for an EOW. The very strong contrast with the white outer webs of T6 is striking (perhaps a touch more diffuse and contrasting less with the paler tail in EOW?). Photo by Jorrie Jordaan.
ABOVE: If you look closely, you can see that the white on the inner web of T6 is quite broad, forming a big chevron-shaped blob on the inside tip of T6. This is the T6 on the left side of the tail. T6 on the right was more worn, and the big tip has fragmented a little. Photo by Tim Booth.
ABOVE: Again, note how dark the tail is and how much in contrasts with the rump and uppertail coverts. There are clear white tips to T6 and T5 and a little on T4 as well. Photo by Trevor Hardaker.
ABOVE: The tail looks a little paler and browner in this strong direct light. Note that the big feather on the right is T5 not T6; the latter is paler and more worn with a bigger white tip, and can be seen just peeking out below the broad T5. Photo by Wilma Meiring.
ABOVE: Upcher’s Warbler tail – looks a lot like a Karoo Scrub Robin actually! This tail is fresher and less worn than the Tankatara bird, but you can make out the same pattern with broader white blobs on the inside tips of T4-T6. Photo by Jem Babbington.
ABOVE: An EOW to compare. The tail is overall slightly paler and the white on the inner web of T6 is not expanded, merely continuing as a narrow fringe around the feather. Photo from Lamsdell.blogspot.co.za.
Bill: UW has a marginally longer and stronger bill than EOW. In UW bill length is 18.2 mm on average, in EOW 16-16.5 mm average. I am not sure that such a tiny difference would be helpful in the field, but the Tankatara bird did give me the impression of being quite heavy-billed. In some photos the bill of EOW looks particularly thin and quite clearly decurved. Conversely, that of UW often looks slightly deeper at the base and more convex when seen from the side. I am not sure whether either of these two extremes really fit the Tankatara warbler. The lower mandible tends to be more pinkish in UW compared to yellowish in EOW. The lower mandible had a distinctly pink base in the Tankatara bird, with a yellower tip. My friend Noam Weiss, a ringer from Israel, also pointed out that the inside of the mouth is orange in UW, but more yellowish in EOW. This is a subtle distinction to see in the field or from photos, but I would still say the mouth was more orange-tinged in the Tankatara bird.
ABOVE: The base of the lower mandible was decidedly pink, although the very tip of the bill was yellower. Photo by Tim Cockcroft.
ABOVE: The inside of the mouth looks more orange in the Tankatara warbler, suggestive of UW instead of EOW. Photo by Michael Mason.
ABOVE: The bill of UW looks more robust, and often a little bulging when seen from the side (not really decurved). There is a pink tinge to the lower mandible, at least at the base. Photo by Daniele Occhiato.
ABOVE: A perfect profile shot showing the bill shape of the Tankatara bird. I think it looks fairly bulky with a slight bulge at the base – more like UW than EOW, but that might be splitting hairs. Photo by Michael Mason.
ABOVE: The bill of EOW is rather delicate, with a yellowish base, and often looks slightly decurved. Also note the crown shape, with a flatter, long-nosed look. Photo by Daniele Occhiato.
||May point to Upcher’s
||May point to EOW
||Fairly deep, slow tail wagging; lifting of tail; occasional fanning or circular swinging
||Apparently short primary projection
|Wider white chevrons on tail tips
||Uneven tertial spacing
||Warm brown tones to upperparts
|Dark, broad, heavy tail
||Longest tertial level with longest secondary
||Number of primary tips visible
|Very prominent whitish wing panel
|Pink base to bill
||Relatively strong, longish bill without a slight decurve
|Forages on the ground for extended periods
||Apparently large size and bulky shape and slow movements
|Orange inside mouth
||Tameness; foraging in the open
||Open, scrubby habitat (?)
A few more images…just for posterity and fun
ABOVE: Summary of features of the Tankatara bird. Steep forehead. Rather long and strong bill, with pinkish base. Prominent pale wing panel. Tail darkens towards tip. Pale ear-coverts. I would be very keen to hear from anyone that can explain the bar formed by the pale tips to the median coverts? A bit of a mystery. Photo by Michael Mason.
ABOVE: Summary of features of Eastern Olivaceous Warbler. Slightly flatter crown with long ‘nose’. Slighter bill with yellower base and sometimes a slight decurve. Darker ear-coverts, often washed richer brown. Longer P1 extending beyond primary coverts. Looks more delicate and less robust than Upcher’s or the Tankatara bird. Photo by Juha Sjöholm, http://straybirder.blogspot.co.za.
ABOVE: The features of this Upcher’s Warbler are essentially the same as listed under the Tankatara bird above. It is a little more worn, but even so, the pale wing panel is still obvious. Could the rictal bristles be a touch stronger than on EOW? Now I’m really splitting hairs. Image from a highly recommended blog on the ID of Upcher’s: see it here.
ABOVE: The very first image that I saw of this bird, from Jo Balmer himself. Actually a BOC shot of this was the first image I saw, on Whatsapp. This certainly got my heart racing!
ABOVE: Looking very big and brutish, with that broad dark tail – this image probalby swung the vote from EOW to UW for most people. Justin, send me the edited one when you get round to it please? Photo by Justin.
ABOVE: The Tankatara bird looking rather slim and olive-brown – more like an EOW. Photo by Lynette Rudman.
ABOVE: A really beautiful shot of the Tankatara warbler by Stan Blumberg.
ABOVE: The Tankatara warbler by Jorrie Jordaan.
ABOVE: The Tankatara warbler on the ground. Photo by Foden Saunders.
ABOVE: The bird got into some interesting positions during its pursuit of midges. Photo by Jorrie Jordaan.
ABOVE: Could this be te apparently diagnostic glide peformed before landing? Perhaps, or just a well-timed photo. By Wilma Meiring.
So there you have it. My reasoning for why the tantalizing Tankatara warbler is Southern Africa’s first Upcher’s. But I want to stress that this is just my opinion, and I would love to hear from you if you opposing view or counter-arguments, or if there are any features that I overlooked. I also have to apologize for stealing so many of your photos off Facebook and random blog posts and image galleries. With this being such a hot topic at the moment, I wanted to publish my thoughts as soon as possible. Desperate times call for desperate measures! If you do want me to take down a picture, please don’t hesitate to get in touch. But thank you to everyone who made their images available. In particular, a big thanks to Michael Mason, Dave Deighton, Dewald Swanepoel for his detective work, Jem Babbington for his meticulous observations, and to Daniele Occhiato – who must rank as one of the world’s top bird photographers.
This has certainly been one of the most stimulating identification challenges we’ve ever experienced in the SA birding community! Thank you also for the valuable input from those in the know, but particularly Etienne Marais, Killian Mullarney, Hadoram Shirihai, Yoav Perlman, Jonathan Meyrav, Noam Weiss, Paul Frensch, Thibaut Chansac, Harry Hussey, Niel Baker, Lee Evans, Miguel Demeulemeester, Forrest Rowland, Frederic Jiguet, Trevor Hardaker, Michael Mason, Lynette Knott Rudman and Biochat.