Getting to Grips with Curlew Sandpiper and Dunlin in Autumn

 

There comes a time in every birder's life when you have to face the frightening prospect of looking at small waders…and early autumn is that time. From early August into September, Ireland sees large numbers of waders moving into and through Ireland on their migration from their northern breeding grounds. These include species like godwits and shanks but it is the small waders (or ‘smalls’ as we birders fondly call them) that offer the greatest challenges. Why? The problem is that there are many species that fit into the category and they all fundamentally appear alike.

 

The commonest of the ‘smalls’ is the Dunlin while the very similar Curlew Sandpiper is a regular and common autumn passage migrant. The key to understanding their identification is in getting to know Dunlin. In fact getting to know Dunlin makes the identification of every other member of the ‘small tribe’ easy. However, that it not as easy as it sounds because there are several races of Dunlin. Some have longer bills and seem larger than others. Of course, as with all waders, there is the added complication that Dunlin vary greatly according to their age. So, even within a group of Dunlin, there are some birds that look very different from the others. However, there are very obvious differences between Curlew Sandpiper and Dunlin and that’s what we’re concentrating on here.

 

So, what do both species have in common? Both have black legs and decurved black bills. On Curlew Sandpipers both the legs and bills are longer than on Dunlin but, as already mentioned, some Dunlin (especially the race known as alpina) can show quite long bills. So bill length, while a useful feature, should not be the sole feature to look for when you think you have found a Curlew Sandpiper.

 

ADULT SUMMER DUNLIN

ADULT CURLEW SANDPIPER MOULTING FROM SUMMER PLUMAGE

 

In early autumn, looking through flocks of smalls will reveal lots of adult birds and both species are easy to identify when in adult summer plumage. Dunlin show neat black belly patches, a streaked breast and face and, depending on the race, bright rufous to reddish-brown mantles. Even when moulting from summer to winter, the birds will usually show some black on the belly (if only they kept that plumage all year around…life would be so much easier!). Curlew Sandpipers are totally different to Dunlin in summer plumage in that they become like mini-godwits adopting brick-red underparts with black, red and white upperpart feathers. Adults when first returning in autumn will still usually show some of their summer plumage and are easy to identify among the Dunlin flocks. So, adults of both species are easy to tell apart when in, or moulting from, summer plumage.

 

 

CURLEW SANDPIPERS HAVE LONGER LEGS THAN DUNLIN AND CAN SOMETIMES WADE CHEST-DEEP IN WATER

OR SOMETIMES EVEN SUBMERGE THEIR HEADS COMPLETELY WHEN FEEDING

  
DUNLIN TEND TO FEED IN SLIGHTLY SHALLOWER WATER  

 

The real problem is with the identification of juvenile birds (birds born this summer). Before looking at plumage lets look at the birds’ jizz…their personality. Curlew Sandpipers appear more elegant than Dunlin. They seem to stand more upright, have longer necks than Dunlin and their longer legs give them a taller stance. Having long legs also allows them to wade into deeper water than Dunlin and within large flocks, they are sometimes the birds wading chest deep in water. When feeding they can often submerge their heads under the water. They have longer more decurved bills than the longest billed Dunlin and also have slightly longer wings than Dunlin which adds to their elongated, elegant jizz. To my eye they also seem more methodical in their feeding behaviour. By comparison, Dunlin seem more hunched, with shorter legs and a more rapid, busy feeding action. Birds can’t be identified on jizz alone, so examining the plumage is critical.

 

JUVENILE CURLEW SANDPIPERS HAVE CLEANER FACES AND UNDERPARTS THAN DUNLIN

 

JUVENILE DUNLIN CAN APPEAR TO HAVE QUITE ‘MESSY’ UNDERPARTS AND BROWNER, LESS DEFINED FACE PATTERNS

 

It is important to remember that many of the birds you see from August onwards will be starting to moult from their warm-coloured juvenile plumage to their first ever winter plumage. As a result, many will show some grey feathers on the mantle and wings (so concentrate on the warmer-edged, darker juvenile feathers). However, in all stages of juvenile plumage, Dunlin always have very ‘messy’ underparts with heavy streaking on the brownish breast extending as black spots and smudges onto the whitish belly and lower flanks. Even as they develop more winter-like plumage, they can still show some spotting on the belly. By comparison, Curlew Sandpiper appears very clean and pristine on the underparts with a ‘peach’ wash across the breast, very faint streaking on the sides of the breast (sometimes faint streaks on the centre of the breast) and a clean white, unmarked belly and flanks. Even as the birds begin to moult, the streaking is confined to just the breast sides and they often still show a faint peach wash.

 

Looking at the heads of both, the clean white supercilium on Curlew Sandpipers make the crown appear more capped and sharply defined while the pale brownish supercilium of Dunlin makes the head appear less contrasting. Overall, the face of a Dunlin is brownish while on Curlew Sandpiper the white chin and white supercilium gives a much ‘cleaner’ impression. In summary, the face of a Curlew Sandpiper is cleaner than in Dunlin with ‘crisper’, more defined features.

 

FROM BEHIND, JUVENILE DUNLIN SHOW WHITE V’S ON THE BACK

JUVENILE CURLEW SANDPIPERS SHOW AN ‘ANCHOR’ PATTERN ON SOME SCAPULARS AND WING-COVERTS
AS BIRDS MOULT, GREY WINTER FEATHERS REPLACE DARKER JUVENILE FEATHERS AS ON THIS DUNLIN

The patterns and colours of the upperparts are also very important. Juvenile Dunlin show a warm brown mantle with black streaking and several white stripes forming narrow white V’s on the back. The scapular feathers (the big feathers between the back and the wings) have black centres with rufous and white edges. The wing coverts have greyish centres and pale brownish edges and appear quite plain. On Curlew Sandpipers, the upperparts are a colder greyish brown tone and lack the white V’s on the back. In fact all of the upperpart feathers have neat pale edges giving a very scalloped or scaly appearance. Some of the scapular feathers and the wing coverts have pale centres with a dark central line and a dark tip almost forming an ‘anchor-like’ pattern inside each feather. By comparison to the upperpart feathers on Dunlin, Curlew Sandpipers are very strikingly marked.

 

EVEN WHEN THE WINGS ARE DROOPED, THE WHITE RUMP ON A CURLEW SANDPIPER IS EASY TO SEE

Finally, in flight the birds are easily recognised as Curlew Sandpipers have a clean white rump which is very obvious even at a long distance. Dunlin show a dark broad line extending from the back, down the middle of the rump and onto the tail. This gives the rump a dark-centred, white-edged appearance when the bird flies. If seen well, the longer legs of Curlew Sandpipers extend just beyond the tail in flight while the legs of Dunlin never extend beyond the tail.

 

JUVENILE CURLEW SANDPIPER, ONE OF THE MOST ATTRACTIVE WADERS TO LOOK FOR IN AUTUMN

 

Curlew Sandpipers are one of the most attractive waders to occur in Ireland each autumn. With a little practice, they can be very easily picked put among the Dunlin flocks. The great thing is that they are usually with Dunlin so direct comparisons between the two species can be made. In some years we experience very high numbers. So, enjoy them while we have them because by October most of them will be well on their way to their African wintering grounds.

 

Text & Images © Eric Dempsey