ARTICLES ON HAWAIIAN BIRDS AND BIRDWATCHING

During October 2002 a small Calidris species was observed at the Kii Unit of James Campbell National Wildlife Refuge on O'ahu in the Main Hawaiian Islands. The bird was observed on a number of occasions and was photographed by Mike Silbernagle with a digital camera through a telescope. There was some discussion as to the identification of the bird, with observers split between Semipalmated and Western Sandpiper. Although the photograph is slightly fuzzy the details in the picture allow the bird to be identified as almost certainly a male Western Sandpiper. Peter Donaldson, who was one of the observers of the bird, provided some behavioural and plumage details not visible in the accompanying photograph. Western Sandpiper is a scarce but more or less annual visitor to the Hawaiian Islands, whereas Semipalmated Sandpiper is a rare migrant, with few confirmed records. Red-necked Stint and Least Sandpiper have also been recorded from the Islands, with Red-necked Stint occurring annually and Least Sandpiper occurring less commonly but still regularly. Other similar species are Little Stint, Long-toed Stint and Temminck's Stint none of which have occurred in the State yet, although all three are possible vagrants in the future. This short article gives reasons for the identification of the Kii bird as a Western Sandpiper. An article on Stint and Peep identification can be found on the Identification Articles pages.

Identification Features

Legs:

The legs are all-dark/black and this can help eliminate Least Sandpiper, Long-toed Stint and Temminck's Stint, although rarely they can show all-dark or partially-dark legs. This really leaves us with Semipalmated Sandpiper, Western Sandpiper, Red-necked Stint and Little Stint. After identifying the bird as either Western or Semipalmated Sandpiper I was informed by two observers that they observed some webbing between the toes, which would of course rule out Red-necked Stint and Little Stint, and leave us with Semipalmated Sandpiper or Western Sandpiper and it is these two species that the rest of the article will focus on, although the other species may be mentioned for comparison.

The legs appear very long in the photograph and more akin to Western Sandpiper, only female Little Stint and both sexes of Western Sandpiper exhibit longer legs than Semipalmated Sandpiper.

Mean Tarsus Length of four Calidris

	Male	Female
Semipalmated Sandpiper	21.3	22.1
Western Sandpiper	21.8	23.4
Red-necked Stint	19.7	19.9
Little Stint	21.2	21.7

"tarsus" is length from middle point of joint between tarsus and tibia at rear of leg, to join between tarsus and middle toe at front of leg.

Bill:

The very broad base to the bill is a good pointer towards Semipalmated Sandpiper, but is also exhibited on many Westerns, although on lone individuals the breadth of the base can be hard to ascertain properly, especially from one photograph, as in this case. The bills of the Stints usually appear less broad. The bill of the bird in the photograph is short and stubby and although the bill lengths of Semipalmated Sandpiper, Western Sandpiper, Red-necked Stint and Little Stint can overlap the bill of the latter two species is usually slightly finer and not so stubby - another pointer towards Western or Semipalmated Sandpiper for the Kii peep. Although the photograph is slightly fuzzy the bill length appears to be at least twice the loral distance, which favours Western Sandpiper over Semipalmated Sandpiper. Expansion at the bill tip is not noticeable and this is (usually) lacking in Western Sandpiper and Little Stint, but present in Red-necked Stint and Semipalmated Sandpiper, although it is hard to discern the exact pattern of the bill-tip in the photograph. In Western Sandpiper the bill is usually much more finely-tipped than the bird appears in the photograph, although male Westerns do not show such a fine tip as females, and the Kii bird is within the range for this species.

Above right: Western Sandpiper, Kii Unit at James Campbell NWR, O'ahu, October 2002, © Mike Silbernagle/USFWS.

Bill Lengths of Western and Semipalmated Sandpipers

SEMIPALMATED
Adults	Male = 16.6-20.2 (mean: 18.6)	Female = 18.4-22.8 (mean: 20.2)
Juveniles	Male = 15-19 (mean: 17.8)	Females = 18-21 (mean: 19.7)

Geographical Variation from across North America = bill and wing lengths increase west to east. Bill lengths shown below:

Adults in Alaska	Male mean: 17.3	Female mean: 18.9
Adults in Central Canada	Male mean: 18.0	Female mean: 19.5
Adults in Eastern Canada	Male mean: 19.6	Female mean: 21.3

WESTERN
Adults	Male = 21.7-25.3 (mean: 23.1)	Female = 23.8-27.8 (mean: 26.7)
Juveniles	Male = 21-24 (mean: 22.5)	Female = 23-30 (mean: 26.1)

If we take these figures as accurate for most of the population (these figures are based only on a small sample size) then if the Kii peep is in fact a juvenile then the smallest Western would be a juvenile male with a bill of 21 but the largest juvenile Semipalmated would be a female of 21, showing no overlap in bill length. Only the longest-billed adult female Semipalmated Sandpipers could have a longer bill than the shortest-billed adult male or juvenile male Western Sandpipers.
If it is then assume (of course perhaps wrongly) that a bird turning up in Hawai'i is likely to come from Alaska, rather than the more eastern populations in Canada, the bill size of the largest Semipalmated Sandpiper of either sex is 18.9 (female), this then falls well short of the shortest billed Western Sandpiper, juvenile males with a bill length of 21, thus making all the Westerns measured longer-billed than the Semipalmateds.

If the Kii peep is an ADULT then the longest billed male Semipalmated is 20.2, far shorter than all ages and sexes of Western. If the bird is an adult female the longest bill length is 22.8, shorter than all female Westerns, but not male Westerns.

The mean bill lengths for the three "groups" left are Female Semipalmated: 20.2, Male Western: 23.1 and Juvenile Male Western: 22.5, showing that the mean bill length is still far shorter in Semipalmated than in Western. If we take the extreme measurements (not the means)of the Westerns (adult male and juvenile male) the measurements are: Adult Male = 21.7 and
Juvenile Male = 21. This leaves an overlap between the longest billed Semipalmated (22.8) and the shortest billed Westerns as 1.1 and 1.8 respectively.

From these data it can be seen that the majority of Westerns almost always show a longer bill than Semipalmateds, with only a small minority in the overlap range.

As for the shape of the bill, Westerns, whether long-billed or short-billed individuals, (almost) always exhibit a bill which becomes finer towards the tip, whereas Semipalmated shows a wider bill end. It has often been quoted that Western bills droop at the tip, but this is only really true of females, which exhibit longer bills than males. In Semipalmated it is often said that the bill ends in a "blob" or widens at the tip, and although this is true in many cases it is not a 100% diagnostic feature. Semipalmated Sandpipers also often show a slight kink near the bill tip (about three quarters of the way to the tip) but this can also be missing or not very obvious on some birds, and is unfortunately not viewable in the photograph either due to the poor quality of it or because it is not present (ie. because it is a Western Sandpiper).

Bill Length in the four Calidris mentioned

Semipalmated Sandpiper	Bill length typically short, 1.5 - 2 times loral distance
Western Sandpiper	Bill length typically long, 2.5-3 times the loral distance
Red-necked Stint	Bill length short, 1.5 times loral distance
Little Stint	Bill length longer, 2 (or more) times loral distance

Right: Semipalmated Sandpiper © J.A. Spendelow

Note the broad bill base, straight-edged upper bill, slightly bulbous tip (very hard to see if in the field on this individual I would imagine) and the slight kink on the lower mandible at about the three-quarter mark. Also note the loral distance: bill length (just over 2 times the length if measured correctly).

Plumage:

Unfortunately in the bird in the photograph some of the tertials appear to have been lost on the left side of the bird and this has exposed the primaries and so it is not really possible to measure how much primary-tip exposure there would be on a bird with full plumage. Stints/Peeps undertake a complete wing and tail moult from July through to February in their first summer and from August onwards when adult. Juveniles undertake a partial wing and tail moult in their first winter from December through to April.

The bird's plumage in the photograph appears to be plain on the back with just a limited amount of streaking and no bold "braces" on the back or highly coloured feathers on the wings or mantle, thus leading to the conclusion that the bird is either a moulted first winter juvenile or adult winter. It is well-known that Western Sandpipers tend to moult earlier than Semipalmated Sandpiper, and so birds occurring in the United States are often in a more advanced (and even completed) moult state than Semipalmated, but of course there is also overlap here, particularly if it involves juveniles, which having only been born that year moult later than adults which have not bred or reached the breeding grounds early and have then left earlier. It should also be remembered that the Western Sandpipers that are going to winter locally begin post-juvenile molt rapidly and can be into a basic plumage quite early in autumn, whereas those that migrate further (and this presumably could include those that visit Hawai'i) may have a longer moult period.

The greater coverts appear to have largely dark centres with only a narrow pale edge. Semipalmated Sandpiper tends to show much more extensive dark centres to the coverts than Western Sandpiper and this may have indicated the species identity as a Semipalmated Sandpiper. Western Sandpipers usually exhibit only a fine dark streak in the feather centre, lacking the more extensive dark centre of Semipalmated. However, having said that, the feathers are rather hard to discern properly in the photograph and appear plain overall with the central portion unclear.

Although the bird could have moulted to first-winter plumage by the occurrence date (October) it would probably mean that the bird would not have progressed so far in its moult by that date if it was a Semipalmated Sandpiper, however first-summers and adults could show this moult state by October. If it is a Western Sandpiper then it is quite likely to have moulted to this plumage by this date. The missing tertials would fit into the equation of a moulting bird, as would the plain upperpart feathering.

Non-breeding adults may moult their complete plumage by the end of June onwards and in most cases is completed by the end of September, however the moult of primaries and tail feathers may be protracted and not completed until the end of February.

The breast streaking is quite marked at the breast sides but it is unclear whether the streaking extends right across the front of the bird. Little Stint does not usually show a complete band of streaks whereas Red-necked Stint and Semipalmated Sandpiper can show variable breast bands and so this feature is only of limited use in this photograph. Western Sandpiper also shows limited streaking at the sides, but sometimes meeting on the breast front..

Right: Western Sandpiper, Kii Unit at James Campbell NWR, O'ahu, October 2002, © Mike Silbernagle/USFWS.

The bright colouration of the face and breast sides would seem to fit more closely with Red-necked stint, especially if this is an adult bird completing its moult to winter plumage, with just a few remaining head feathers remaining to moult. Western Sandpiper may also exhibit some rufous around the face, but this would usually have been moulted on a juvenile or even adult Western by this stage (going by the rest of the plumage). Most adult Semipalmateds do not show such rufous colouration although, as in many other features, some juveniles can. The photograph is taken with a digital camera however and the colours in the photograph have been enhanced slightly and appear more rufous than in life, which was confirmed by observers of the bird.

General Features of the four species discussed

	Semipalmated Sandpiper	Western Sandpiper	Red-necked Stint	Little Stint
Primary Projection	Short with two or three closely spaced primary tips	Very short with one or two closely spaced primary tips.	Much as Little Stint	Long with three or four primary tips and two wide spaces
General Shape	Much as Little Stint	Rather large-headed and square-cut, with long tapered body, flat-backed and round-shouldered, with long-looking legs.	Round-headed with steep forehead and bulky body with long attenuated rear-end	Small headed with slightly sloping forehead and round-bodied

Vocalizations can help in the id of these peeps but of course photographs do not show that, they also only give a brief snap-shot of the bird's overall appearance, structure and behaviour.

This bird can therefore be identified as an almost certain Western Sandpiper. However, it is important to remember that many peeps, especially in winter plumage, are extremely hard to identify and some should probably remain left un-named. In recent years there has been a wealth of new id criteria and these have certainly helped to make identification easier.

Checklist of points why the bird is a Western Sandpiper

1). The bird has webbing between the toes, a feature shared only with Semipalmated Sandpiper in the small peeps.

2). The legs are all-black and appear long.

3). The bill is deep-based, slightly curving, has no notches or kinks and gently narrows towards the tip.

4). The bird has completely moulted the underpart and upperpart feathering (except perhaps a few streaks on the breast sides), consistent with the earlier-moulting Western Sandpiper, rather than the later-moulting Semipalmated Sandpiper.

5). Overall shape and appearance.

Peter Donaldson stated that "when I saw the bird feeding, it was very active, making frequent short runs followed by rapid shallow probing with its bill". A feature sometimes noted for Semipalmated Sandpiper is the Plover-like feeding action of individuals, where they run a short while then probe, although this is not a diagnostic feature but it does highlight the need for detailed notes on behaviour as well as plumage when encountered with any unfamiliar or puzzling bird, as the "jizz" can often be of help in an eventual identification.

As a final postscript, it turns out that a "classic" Western Sandpiper in almost identical plumage was seen at the same site just a week later, but was described as having a bill at the "longer" end of the range of Western and looking different from this bird (with a bill at the short end of the range), and so presumably there were two Western Sandpipers in the vicinity.

Left: juvenile Semipalmated Sandpiper © Urban Olsson

Note the short, quite blunt-tipped bill, with a hint of a kink, dark eye stripe and ear-coverts, prominent supercilium, dark crown and dark-centred feathers. Also note primary projection.

Thanks to Peter Donaldson for some descriptive notes on the Kii peep, Mike Silberbnagle for the photograph, Doug Pratt for notes on the Western Sandpiper seen at Kii later in the month and Jason Rogers and Dan Roberson for comments on the identification of the bird.

Useful links on Semipalmated and Western Sandpipers http://www.greglasley.net/semipal.html http://www.ups.edu/biology/museum/SESAphoto.html and http://www.ups.edu/biology/museum/WESAphoto.html http://www.birdsofoklahoma.net/Semipalsp.htm http://www.montereybay.com/creagrus/mtymiss07.html

References

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BEAMAN, M and S. MADGE. 1998. The Handbook of Bird Identification for Europe and the Western Palearctic. Christopher Helm. London.

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NATIONAL GEOGRAPHIC SOCIETY. 1999. Field Guide to the Birds of North America. 3rd Edition. NGS, Washington D.C.

ODDIE, W.E. and MARR, B.A.E. 1981. Identification of Semipalmated Sandpipers and Little Stints in autumn. British Birds 74: 396-398.

PRATER, A.J.;MARCHANT, J.H. and VUORINEN, J. 1977. Guide to the Identification and Ageing of Holarctic Waders. BTO Guide 17. Tring, U.K.

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Christian Melgar, Worthing, West Sussex. 2002.

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