Streaked Locustella warblers in autumn can be the stuff of nightmares. Near-impossible to flush, whirring away low and fast and then disappearing, never to be seen again, they give a whole new meaning to the word ‘elusive’. Their plumage is sombre and complex, and the identification features are small and subtle, so that even if there is time to raise your binoculars and ‘lock on’ to one, your chances of nailing an identification are not high. Truly, these birds can reduce grown men to tears!
Nevertheless, two species of these confounding warblers are among the most highly sought after of all autumn migrants. They can also be the stuff of dreams. The combination of maddening behaviour and potential rarity means that every encounter with the two is a heady mix of excitement and frustration, and to the connoisseur of ‘small, brown, streaky birds’ this genus contains some of the ultimate prizes.
In autumn, three species are on the radar: Grasshopper, Pallas’s Grasshopper and Lanceolated Warblers. The other (unstreaked) Locustellas – Savi’s and River Warblers – present a different range of ID issues and are beyond this article’s scope.
Once our own breeding Grasshopper Warblers have faded away in August, any autumn Locustella will be a migrant from Europe or beyond and will therefore most likely be found on the east coast. At such times, Grasshopper Warbler is still the default species, but Lanceolated and Pallas’s Grasshopper Warblers are doubtless overlooked.
Grasshopper Warbler
This is a relatively common breeding bird in Britain and across northern Europe and western Asia, though it is familiar to most as a singing bird in spring, not as a skulking autumn migrant. The smaller form straminea occurs east of the Urals.
Pallas’s Grasshopper Warbler
This is a much more eastern species, breeding only in central and eastern Siberia, and wintering in SouthEast Asia. A number of forms have been recognised and, given the variety in the appearance of those reaching Britain, it seems likely that more than one is involved.
Formerly a great rarity, this species is now nearannual between mid-September and mid-October, though the Northern Isles dominate. There are at least 46 records, but only 11 away from Shetland.
Lanceolated Warbler
This species breeds across Siberia and winters in South-East Asia. However, it is extending its breeding range westwards and now breeds as close as Karelia, in north-west Russia, with spring singers regularly recorded in neighbouring Finland.
Lanceolated Warblers are annual in Britain between mid-September and mid-October, though in tiny numbers, with Fair Isle the classic location. Elsewhere this is a very rare, though presumably overlooked, bird. Of some 130 records to date, only 22 have been away from Shetland.
Finding a Locustella
In autumn any of these three species is a ‘good bird’. Finding one, however, is a challenge. Their ultra-secretive nature means that almost all will go unnoticed. They are only ever regularly found in places which combine minimal cover and high search effort. Away from Shetland, however, your task is considerably more difficult and there are only two real strategies. The first is to find somewhere coastal as open, bare and barren as possible. Ignore all your experience of migrant hunting and mental images of welcoming sycamores and sallows and look for somewhere a warbler should hate.
Then you need persistence. A Locustella warbler will never just hop out and perch in the open as you walk past. Instead, you need to put on your walking boots and methodically walk the ground, concentrating on a whole range of ‘micro-habitats’ – ditches, tufts of grass, patches of weeds, the bases of walls and so on. Any slight anomaly in flat ground may hide a bird – to find a Locustella, think of where you might hide if you were a mouse. Although you can do this alone, there is some merit in a more co-ordinated approach by two or three like-minded companions, as this will maximise your chances of flushing a bird.
Then, very occasionally and if you are lucky, a dark, whirring shape will fly up f rom your feet. What do you do now? The first thing is to be sure that what you have just found really is a Locustella. Normally the bird’s rapid, low and whirring flight and abrupt drop into cover will be sufficient pointers, but an ability to run fast on the ground under vegetation and disappear completely, defying any further flushing attempts, will be further confirmation. If any view on the ground is achieved, look for the slightly curved outer wing and the extra-long undertail coverts – both unique to Locustella and additional evidence that you haven’t glimpsed, for example, a Sedge Warbler or a Dunnock.
Getting views
Unfortunately, many attempts at identification beyond this point end in failure, with the bird immediately lost. The sad reality is that a high percentage of Locustellas will remain forever unidentified. Much, however, depends on the habitat. Locustellas are not necessarily afraid of people – they are largely oblivious, just making use of whatever cover is available. On Shetland, they often walk about in the open in thick grass, but elsewhere in Britain, where there is always much denser habitat available, this is a much less likely scenario.
Here you have two options, though neither guarantees success. The first involves attempting to ‘encourage’ the bird into a viewable position (best of course with a couple of companions), but this approach has a high failure rate. A couple more flight views might result, but the bird then usually goes to ground and resists any further attempts at observation.
The other approach is to stand back and hope that the bird emerges, though this may or may not be successful. Should you get views, however, it is important to focus on the important characters quickly, as highlighted in the following photographs.
FITEEN: Lanceolated Warbler (Hong Kong, China, 26 October 2009). This ‘field guide perfect’ bird is the same as that featured in photo 11. Here it can be seen that the amazingly heavy blackish ‘drop-shaped’ marks on the upper breast and upper flanks also extend to the rear flanks and undertail coverts. Though most are not as striking as this, the other features of the species are also easily seen here: the brown rather than olive hues, the stoutish bill, the heavily streaked crown and mantle, crisp tertial contrasts, short, narrow tail, a very short primary projection and heavy ‘blobs’ on the uppertail coverts, all reminiscent of the end of a mascara brush. Its mouse or shrew-like jizz is apparent even in the hand, emphasising its willingness to creep away from an observer rather than take flight.
THREE: Lanceolated Warbler (Unst, Shetland, 12 October 2009). This in-the-hand juvenile shows the almost ‘baby pipit’ look of Lanceolated Warbler – a function of a slightly short bill and well-streaked crown. The short, narrow tail, short primary projection and upperparts streaking are also shown to good effect, as is the crisp contrast in the tertial fringes, while the ‘necklace’ of upper breast streaking is reasonably well defined. The completely fresh plumage in autumn ages the bird to its first calendar year, as adults at this time have worn and fresh primaries with sharp points on the tips of the worn feathers. The paucity of streaking on the underparts is another indication of age.
TWO: Grasshopper Warbler (The Garrison, Scilly, 8 October 2005). This unusually good view of a migrant Grasshopper Warbler in autumn shows its features to perfection. It is a soft olive-brown above with very limited crown and mantle streaking – indeed ‘Groppers’ can at times appear almost unstreaked above. The tail is moderately long and quite broad, the bill is fine and the primary projection is medium to long. The underparts are essentially plain with slightly darker flanks, the uppertail is concolorous with the mantle and the border between the tertial centres and the fringes is slightly ‘blurred’ and lacking in contrast. Note also that the eyering is rather prominent.
FOUR: Pallas’s Grasshopper Warbler (Hong Kong, China, 11 September 2008). This trapped juvenile is of the richly coloured eastern subspecies minor. The bird looks quite large and ‘heavy’, the bill is long, stout and almost thrush-like, the head is ‘heavy’, the primary projection is medium to long and the tail is long, broad and paddle shaped. As for plumage, it shows sharp contrasts – a dark, well-streaked crown, reasonably prominent supercilium, very dark, well-streaked, almost ‘oily-looking’ upperparts, crisp bright white fringes to the tertials, broadening very slightly at the tip to form a characteristic ‘pip’ on the inner web, heavy drop-shaped centres to the uppertail coverts, a contrastingly dark tail and sharply defined dusky white tips to all but the central tail feathers. There is also a pronounced yellowish suffusion to the underparts.
FIVE: Grasshopper Warbler (Suffolk, 6 September 2009). This juvenile shows typically plain-looking upperparts with minimal crown and mantle streaking. This species has pale fringes to all the upperparts feathers, giving a more mottled than streaked appearance. It also has a longish, quite broad tail and quite a long primary projection, prominent eyering, ill-defined tertial fringes, weakly marked centres to the uppertail coverts and a brown wash (not streaks) across the breast. The dark-centred wing feathers are often less contrasting and bright than in the rarer species. Note that not all Grasshopper Warblers are olive – this one is quite brown.
SIX: Lanceolated Warbler (Unst, Shetland, 7 October 2010). This juvenile Lanceolated Warbler looks typically small and ‘creeping’. Its overall colour is warm brown with no olive, its tail is short and so is its primary projection. To complete the identification, note the ‘necklace’ of fine streaking across the upper breast, the well-streaked mantle with, as in Pallas’s Grasshopper Warbler, the dark feather centres reaching the feather tips and aligning in rows. Also visible are crisp, well-defined tertial fringes. Note also the crisply contrasting wing markings with solid dark feather centres and paler fringes.
SEVEN & EIGHT: Pallas’s Grasshopper Warbler (Fair Isle, Shetland, 23 September 2010). This juvenile Pallas’s Grasshopper Warbler shows off its main identification points all at once. Its demeanour is ‘aggressive’, with a stout bill and wedge-shaped look to the head. It has a reasonably well-marked face pattern, well-streaked crown and mantle (with the dark feather centres reaching the feather tips and aligning in rows), white ‘pips’ just visible on the inner webs of the tertial tips, a slightly ‘warm-looking’ rump, heavy uppertail covert ‘blobs’ and a contrastingly dark tail. The wing is visible in detail here, notably the blackish tertials with their browner and paler edging, and the white tips are subtle but present. The dark-centred, paler brown-bordered theme continues onto all the other fresh wing feathers, and as in the other two species this uniformity of feather is a good indicator of age; the moult will be completed over the winter, thus making first-summer birds indistinguishable from adults in the field. Note that white in the tail tips is always invisible on the closed tail. The undertail coverts (above right) are plain and have the yellowish underparts tint continuing right to their very tips. A glimpse of the weak breast band can also be just about seen on this individual.
ELEVEN: Lanceolated Warbler (Hong Kong, China, 26 October 2009). This adult
Lanceolated Warbler is an easy one! Its shortish, quite stout bill, ‘cold’ brown upperpart hues and well-streaked crown are all easily visible but, given the strength of this individual’s breast streaking, noting these other features is somewhat academic. Not all birds, however, show such dark, blackish ‘dropshaped’ marks across the breast and down the upper flanks – most are more sparingly streaked with just a narrower gorget of finer streaks; a very few are almost entirely unstreaked and so more reminiscent of Grasshopper Warbler in this respect.
NINE: Grasshopper Warbler (Suffolk, 26 July 2009). Though not the most helpful view, this juvenile Grasshopper Warbler shows a longish, quite slim bill, rather bland face, prominent eyering, barely steaked crown and completely plain underparts with no hint of upper breast streaking; note, though, that some birds can show slight streaking in this area. There is also a pronounced olive cast to the upperparts and soft yellowish hues in the underparts – both features entirely typical of this species and absent in Lanceolated Warbler. This very young bird also shows the remnants of its fledgling gape line at the rear of its bill.
TEN: Pallas’s Grasshopper Warbler (Fair Isle, Shetland, 23 September 2010). This Pallas’s Grasshopper Warbler is harder to identify from this photograph, but though perhaps deceivingly hunched up, it still shows a ‘heavy’ structure, strongish bill and a comparatively well-marked face pattern. Yellowish underpart hues are frequent, if not typical, of this species in juvenile plumage, and this bird also shows, as do many, light upper breast streaking. Little can be seen of the rest of the upperparts here or the bird’s rear end, but the tail feathers do appear quite dark. This image also underlines its secretive and stealthy habits.
TWELVE: Lanceolated Warbler (Unst, Shetland, 12 October 2009). This photograph shows a juvenile with more typical upper breast markings formed by a gorget of quite fine streaks. Though some are more heavily marked than this (see photo 11), some individuals may be much less streaked. Note also the shortish bill, the ‘cold’ upperpart hues lacking olive (deduced from the crown and nape seen here), the lack of any kind of prominent eyering and the characteristically cute ‘baby bird’ look of this species. Later in the winter and spring, this bird will begin to moult in its nominal lanceolations, the marked streaks so clearly shown by the adult bird.
THIRTEEN: Grasshopper Warbler (Kuwait, 29 August 2008). This more typical view of a Locustella nevertheless gives enough information to identify it. Its long, slim outline with a longish, slim bill, longish tail and longish primary projection all strongly suggest Grasshopper Warbler, while its rather bland face pattern, mottled rather than strongly streaked mantle, plain-looking upper breast and weak tertial contrasts are more than enough confirmation. Its rear flanks are, however, much more strongly marked than normal and more reminiscent of Lanceolated Warbler.
FOURTEEN: Pallas’s Grasshopper Warbler (Lake Baikal, Siberia, 21 June 2008). This striking adult in many respects looks more like a Sedge Warbler than a Grasshopper! Pallas’s Grasshopper Warblers reaching Britain have presented a variety of appearances, presumably reflecting a number of origins (and therefore subspecies): some are strikingly contrasting, as here, with strong face patterns, others much darker and ‘oilier’, and yet others still more uniform and confusingly similar to Grasshopper Warbler. This bird’s heavily streaked crown and mantle, with pale nape/ neck sides, strong greyish-white supercilium, dark, white-fringed tertials, heavy uppertail covert markings and dark tail would certainly attract attention.