December 8, 2014

part two: special:

Broad-billed Sandpiper

text by Abu

 ( link to previous post: part 1 )

2. Broad-billed Sandpiper. © M. Putze

As promised earlier, in this post Birding Mongolia will publish lots of Broad-billed Sandpiper pics, all taken at Buir Nuur in June 2014 during the Swamprunner Tour 2014!

Broad-billed Sandpiper Calidris falcinellus (formerly in genus Limicola) breeds discontinuously across the tundra from northern Scandinavia to the delta of the Kolyma River at the East Siberian Sea. Western breeders belong to the nominate subspecies, but the here-dealt-with birds are of the brighter coloured subspecies sibirica which breeds from Taimyr eastwards. All photos presented here illustrate spring birds of the latter, which is regarded to be the only subspecies migrating through Mongolia, usually in low numbers.

In this wader, females are bigger and have a longer bill than males. Unfortunately, these are average differences and one should be very careful in sexing a single bird. Even in hand, only those individuals with the most extreme measurements can be sexed! We got the impression that the males had not only broader, but also rustier feather fringes. On the breeding grounds the males take care of the chicks after a while. But would the rather minor difference in plumage, if it really existed, be enough to cause a benefit during breeding? That could be tested on the breeding grounds only.

Picking out a flying Broad-billed Sandpiper from a mixed flock will be possible under the most favourable circumstances only. Look for its streaked upperparts (keep in mind that e.g. the much smaller Long-toed Stint shares this feature as well as the longer legged and bigger Pectoral Sandpiper, the latter with not more than two records from Mongolia, yet) and its well striped face. The mostly dark colouration of the breast (just like in Pectoral in some, others with paler breast) continues down along the flanks, sometimes reaching to the undertail-coverts. But only faintly so. This, combined with the almost complete lack of toe projection, will be your best clues. The underwing is not fully white but to see the details during the bird’s whirling flight will prove to be impossible. Nevertheless, picture 3 shows all the details of the underwing and also shows how the breast streaking runs along the flanks in very narrow arrowheads.

3. Underwing of a male Broad-billed Sandpiper.
© A. Buchheim & T. Langenberg

4. Frontal view of the same male Broad-billed Sandpiper.
© A. Buchheim & T. Langenberg

5. Upperside of the same male Broad-billed Sandpiper.
© A. Buchheim & T. Langenberg

In pictures 4 and 5 the same bird can be seen. This one really has lots of orange on its breast and a solidly orange cheek patch. It further has a rather narrow supercilium (said to be broader in sibirica than in falcinellus). This bird is very short-billed and hence is more likely a male. Of course we took all basic measurements and with a mere 27 mm its bill is way too short for any female. Some of these very short-billed males, which look so different from our common image of the species, can be mistaken for other species though it is hard to say for which. Nevertheless they show not only the characteristic bill shape with a broad base (name!) and the down-down tip but also the typical head pattern.

Of the two birds we caught this was the more colourful individual as shown in picture 6. Even a few median coverts showed broad reddish fringes as well as all scapulars, the mantle feathers and the two central rectrices (cf. picture 8). Note that these birds have a rather narrow wing stripe formed by the white tips of both those of the greater coverts and those of the primary coverts (picture 5).
Compare the two birds by checking the pictures below (male picture 6 and female 7; both could be sexed by their measurements).

6. Male Broad-billed Sandpiper.
© A. Buchheim & T. Langenberg

7. Female Broad-billed Sandpiper.
© A. Buchheim & T. Langenberg

8. Comparison (composite) of the tail feathers
of a male (left) and a female (right) Broad-billed Sandpiper.
© A. Buchheim & T. Langenberg

Now check out the pictures from the field. Surely not all are as colourful as one would expect. There are always some birds in larger flocks which have just buff fringes to the feathers (pictures 11 and 13). But although the fringes are on average broader than in nominate birds, it turns out that sibirica is a weakly defined subspecies only. However, how many individuals cannot be identified at subspecies level remains unclear. Also note how long-billed some females are (pictures 10, 11 and 16) and that the breast can look surprisingly pale in a few individuals (pictures 12 and 15). The split supercilium is most easily seen when the head is turned towards the observer (pictures 12-14). Broad-billed Sandpipers have a short neck which gives them a distinct shape. While searching for food this short neck probably makes them hold their bills almost vertical very often (pictures 11, 12 and 14).

9. Broad-billed Sandpiper. © A. Buchheim

10. A quite colourful and very long-billed, thus very likely a female,
Broad-billed Sandpiper. © A. Buchheim

11. Another female(?) Broad-billed Sandpiper. © A. Buchheim

12. The split supercilium is clearly visible; also note the rather
pale breast of this Broad-billed Sandpiper. © A. Buchheim

13. Broad-billed Sandpiper showing the split supercilium at
its best, this bird has rather narrow fringes and is less colourful.
© A. Buchheim

14. Broad-billed Sandpiper with a very broad upper supercilium.
© Thomas Langenberg

15. Another pale-breasted variant of Broad-billed Sandpiper,
note that the reddish fringe of the central tail feather is visible here.
© A. Buchheim

16. Female (left) and male (?) right Broad-billed Sandpipers,
here, the putative male is more colourful than
the accompanying female. © A. Buchheim

17. Broad-billed Sandpipers. © A. Buchheim

18. A Broad-billed Sandpiper with a really
nice orange cheek patch. © Thomas Langenberg

This post is intended as a training for our readers and we hope that it will enable more birders to find them amongst other waders under all viewing angles, just by shape or by their feeding postures. So go out birding!

19. Mixed flock of waders swarming over Buir Nuur.
© A. Buchheim

20. Flock of Broad-billed Sandpipers.
© M. Putze

21. Flock of Broad-billed Sandpipers.
© M. Putze

More on other waders and other birds we saw at the site will be reported later, so keep on checking Birding Mongolia!

1 comment:

Bolormunkh said...

Looking forward to the main highlights, anyway your trip itself is entirely enjoyable experience. Thanks for the report. Keep up and take care until you came back.