In this blog, Matthew Feargrieve explains the general principles of shorebird identification, with an emphasis on ageing and sexing waders using plumage characteristics. For a species-by-species summary of these principles and how they can inform and enrich your observations of birds when observing them in the field, click here.
In autumn/winter, adult shorebirds (or waders) will be into their complete post-breeding moult, looking tatty, with flight feathers and tail showing gaps. Grey feathers replacing breeding feathers. The primary moult of adults spans the full period of the complete moult. In adult birds of some species, body and flight feathers are moulted simultaneously, in others body precedes wing moult (or vice versa).
Some shorebirds will undertake an autumn migration to Europe from their breeding grounds in juvenile plumage (neat looking), then undergo a partial moult on the wintering grounds (body: not remiges or rectrices) during which they typically acquire grey winter feathers (notably head, mantle and scapulars, and usually some tertials and wing coverts) and start to look like winter (non-breeding) adults.
For guidance on how the following summary of moult cycles and plumage variation applies to individual species of shorebirds, click here for our species-by-species guide.
Key features of juvenile/1w birds: moulted scapulars, mantle and body feathers, which resemble the adult winter feathers: winter adult-type feathers tend to be grey. Unmoulted juvenile feathers in winter tend to be brown and faded. The presence of these unmoulted juvenile feathers in autumn/winter indicate a first winter (1w) bird. Look for a contrast between (a) tertials, coverts (particularly greater coverts and inner median coverts) - some or most of which tend not to be moulted and so appear paler brown, with faded markings- and (b) scapulars and mantle feathers, which tend to be moulted and so appear grey in colour. The inner median coverts are the most often retained juvenile feathers in 1w waders (being protected by the scapulars) and will show buff tips/fringing.
Also in 1w birds, notching (ie jagged or dog-tooth markings around the edges of a feather), particularly faded notching, often a characteristic of a juvenile/1w tertial or covert, will contrast with adult-type feathers which tend to be plain grey or barred (Curlew tertials and scapulars being a good example).
As in passerines, flight and tail feathers tend not to be moulted by 1w waders, whereas most will moult some tertials (often inner, smaller, tertials) and some GCs and inner median coverts. So: the average 1st winter (1w) wader will have grey (adult) scapulars and mantle, possibly some greater coverts (GCs) and outer medians of the same appearance, contrasting with buff fringed or tipped (juvenile) inner median coverts and tertials, together with brown and pointed (juvenile) flight and tail feathers (ad flight feathers have rounded tips). Note that most waders moult their tail feathers centripetally (ie starting with the outer pair of feathers on either side of the tail, then moving inwards finishing with the central pair): so look for contrasts on the outermost tail feathers.
Each individual bird is different
An important point to grasp is that some 1w birds will not moult any tertials or coverts (even though in theory they are "supposed" to), only scapulars and mantle feathers, which are sometimes not enough to produce a noticeable contrast between juvenile and adult (Turnstone juvenile and adult scapulars and mantle feathers being an example, appearing similar); so you will look in vain in some 1w birds for contrasts inter/intra- feather tract.
Always bear in mind the structural characteristics of a juvenile and adult wader: in juveniles, the feathers tend to be smaller and neater, each feather tract on the wing usually being clearly identifiable (tertials, GCs, median coverts, lesser coverts and marginal coverts, scapulars and mantle feathers) creating a scalloped appearance. These tracts are less distinct on winter adult birds, which tend to have larger feathers which appear untidy and overlap one another: eg, the scapulars on an adult are large and loose and often cover the wing coverts; NB in particular, juvenile scapulars will usually not hide the small, neat rows of marginal coverts, whereas ad-type larger scapulars of 1w and winter ads will hang down over and hide the marginal coverts (frequently also the lesser coverts too). Remember that the feather tracts of some winter ads can appear neat and identifiable in orderly rows, but the feathers will be larger than a juvenile's (lacking the scalloped appearance of juvenile/1w) and will be more uniform in colour (usually grey in winter birds) and on the whole fresher looking.
Look also for worn/moulting flight and tail feathers on winter adults. Sometimes residual breeding colours on back, head or belly can indicate adults (and to this extent it can be helpful to refer back to the preceding summer adult plumage).
For guidance on how the following summary of moult cycles and plumage variation applies to individual species of shorebirds, click here for our species-by-species guide.
Finally, bear in mind the moult schedule of each species: eg a juvenile-looking Bar-tailed Godwit in December could well be still in juvenile plumage, given that 1w moult in Bar-tailed Godwits takes place Sept to Jan; whereas most 1w Turnstone will have completed their moult by Nov.
Genus-specific plumage generalities
- Calidrid juveniles have coverts and scapulars fringed whitish-buff or chestnut.
- Tringa juveniles have coverts and scapulars spotted buff or whitish.
- Charadrius juveniles have coverts and scapulars finely fringed pale buff with a darker subterminal band.
Remember that pale colours fade quicker than dark, and that buff fades to white (eg juvenile Redshank coverts which are fringed buff, fading over winter to white). White fades to yellow. Brown fades to yellowish. Grey fades to brownish, and brown fades to greyish.
Breeding Cycle impact on Plumage Characteristics
Most larger shorebirds (eg Godwits, Curlew) don't breed in their first twelve months (breeding in their third calendar year mostly, in the case of Godwits and Curlew), so 2cy (spring) birds either retain very worn 1w plumage or have a partial moult into a poor version of adult breeding plumage, later moulting in the autumn of their second calendar year into adult non-breeding (winter) plumage. Such sub-adult birds may remain in their wintering grounds or part way between wintering and breeding grounds (eg Bar-tailed Godwits, Grey Plover, Curlew Sandpiper).
In autumn, adult shorebirds moult into non-breeding plumage later than 2cy birds (can be as early as August for 2cy non-breeders, whereas ads attain non-breeding plumage around October). Eg Bar-tailed Godwits, birds seen in wintering grounds in July that are not in adult breeding plumage will be 2cy birds (born the previous year) whereas birds arriving in Aug in fresh plumage will be juveniles (migrating after older birds).
This also explains why some "adult" (ie older than 1w) winter plumage can differ between birds of the same species (Godwits and Curlew) because some (2cy birds) are moulting from a semi-summer plumage, whilst ads (3cy+ birds) are moulting from full summer plumage.
NB some species (Redshank, Greenshank, Black-tailed Godwit) have breeding plumage with upperparts consisting of mixture of breeding and non-breeding feathers, although both types are acquired during the moult to adult breeding.
Smaller shorebirds (Redshank, Dunlin) will breed (mostly) in their 2nd calendar year and will be commencing pre-breeding moult Jan-Feb. Other birds, typically (but not exclusively) larger ones, will breed in their 3cy, and some species can be seen still on their wintering grounds in the UK during their 2cy in winter- or semi- breeding plumage: Sanderling (2cy not seen in UK in summer) Grey Plover (2cy seen in UK in summer), Curlew and Godwits (2cy Black-tailed Godwits seen in UK in summer) are 3cy breeders.
For guidance on how the following summary of moult cycles and plumage variation applies to individual species of shorebirds, click here for our species-by-species guide.
Matthew Feargrieve is a bird watcher and investment management consultant. You can read his personal blog here and his business blog here. You can see his bird photography here.
