Identification of Spotted Sandpipers out of breeding plumage

Transcription

1 Identification of Spotted Sandpipers out of breeding plumage D. I. M. Wallace Plate $ i INTRODUCTION The Spotted Sandpiper Tringa macularia, now generally treated as a full species once more (e.g. Vaurie 1965), presents no identification problem in its breeding plumage. Immatures and adults in winter plumage, however, are widely held to be indistinguishable in the field from similarly aged Common Sandpipers T. bypokmos. As noted in The Handbook, the definite identity of some individuals is difficult to establish even on the museum bench. The fact, therefore, that during seven records of Spotted Sandpipers out of breeding plumage were accepted {Brit, Birds, $9: 288, 60: 318, 61: 541, 62: 469) warrants discussion. This need was first noted by the late D. D. Harber and he asked me to help meet it. I have used his and my notes on the 1965 bird, and J. L. F. Parslow and F. R. Smith have supplied me with full details of those in 1966 and These four records, all from the Isles of Scilly, were as follows: (1) St Agnes, 23rd September to 28th October 1965 (trapped on 24th September and 15 th October) (2) Tresco, 3rd September to 1st October 1966 (trapped on 21st September) (3) St Agnes, 23rd to 25th September 1966 (4) Gugh and St Agnes, 6th to 21st September 1967 All four arrived in September and three made the extended, presumably recuperative, stays so often associated with American waders in Scilly. All were noticeably tame, and could usually be approached to within a few yards. Migrant Common Sandpipers were about the islands each year at the same time as the Spotted Sandpipers. Notes on the Spotted Sandpipers of 1968 and 1969 are not included, though I saw the St Agnes/Tresco bird of 1968 and one on near-by St Mary's in 1969 and could find no unusual features on either. GENERAL APPEARANCE AND VOICE It must be understood that all four birds could have been taken at a glance and even after extended observation for Common Sandpipers. Their shape and size, behaviour and habitat selection in no 168

2 Identification of Spotted Sandpipers 169 way indicated that they were of a different species. Only on detailed examination at short range could observers recognise the plumage differences that separate the two species. More useful was their vocabulary; though they called less frequently than migrant Common Sandpipers their notes were generally very distinctive, being quieter and more varied and having a different tone. PLUMAGE CHARACTERS A digest of the many notes and sketches of all four, together with feathers, feather drawings and photographs of the first and feather drawings of the second, shows the following features to be diagnostic (or at least indicative) of the Spotted Sandpiper: Bill colour Essentially horn with noticeably dark, almost black tip and (on 1 and 2) a fleshy-orange or yellowish base to lower mandible, thus showing a trace of the breeding dress pattern. The Common Sandpiper's bill is dark brown. Head and face Lores and ear-coverts uniform, not streaked; orbital ring white, very striking due to poorly marked supercilia (see plate 31b). The latter mark is shared by some Common Sandpipers. Upper-parts Mantle cleaner and greyer in tone, lacking any warm brown, appearing almost uniform. Some feathers showed faint subterminal bars but the widely dispersed shaft streaks and cross-bars of autumn Common Sandpipers were absent. In contrast, wing-coverts evenly barred blackish and greyish-white. At short ranee and under most lights, this difference between mantle and wing formed a most striking field-mark. It is clearly portrayed in Taverner (1949) and Peterson (1947, i960). Though the wing-coverts of immature Common Sandpipers are also barred, the marks are closer in colour (dark brown and buff). The barring is apparently also less marked in winter adults and none of the Common Sandpipers closely observed in Scilly, nor any specially examined in Berkshire (by J.L.F.P. on 12th September 1966) and in southern Nigeria (by the author in the winters of 1968 and 1969), exhibited the marked contrast between mantle and wing-covert plumage shown by the Spotted Sandpipers see plate 31 and Voous (i960). Undir-parts Chin pure white, throat also white becoming sullied with greyish olive-brown at breast and near chest-patches, the latter unmarked save for a few faint streaks (see plate 31b). Unfortunately no accurate comparison of these areas with those of Common Sandpipers was possible in the field but an examination of skins indicates that the differences (fig. 1) are constant. Legs Distinctly yellowish, varying from fleshy yellow-brown through pale greenishyellow to bright ochreous-yellow (on 2). The legs of all four were much more brightly coloured than those of the Common Sandpipers, whose legs were usually an inconspicuous grey-green.

3 1 7 o Identification of Spotted Sandpipers Upper wing in flight Wing-covert barring not obvious, but a white trailing edge to the secondaries and inner primaries noticeable in the field, except on the second bird on which, however, it was discerned when in the hand. Plate 51a (of the 1965 bird) shows that this was merely a thin edging on all but the inner two feathers, but at close range in the field it was clearly visible. It is consistently illustrated by Peterson (1947, i960, 1961). Common Sandpipers on Tresco and St Agnes in October 1965 did not show this pale edge in the field, though the normally marked areas of white on the inner secondaries were visible as illustrated in the Field Guide, etc. This character probably results from the dark inner secondaries heightening the contrast of the white trailing edge. Upper tail in flight Outer feathers (on 1 and 3) much blotched with black or brown chevrons, Fig. 1. Common Sandpiper Tringahypeleueos (left) and Spotted Sandpiper T.macularia. Note the latter's greyer, more uniform, mantle contrasting with strongly barred wing-coverts, almost unstreaked breast-patches, pure white throat and chin, conspicuous eye-ring, bill pattern and yellowish legs (see pages ) making the sides of tail appear barred to the very edge (see plate 31c). Thus at least two birds did not have the tail 'outlined' in white as in the Common Sandpiper, and all appeared darker-tailed. From the detailed analysis of the above characters, it appears that all four birds were in immature or first-winter plumage. This conclusion is not quite so rash as it may seem; Dresser (1903) isolated most of these features 70 years ago. The slight but distinct differences are shown (in standing birds) in fig. 1 and (in flight) in fig. 2. CALLS Fifteen transcriptions of the four birds' calls were made. These were mainly flight calls, but a distinct alarm note was also heard: Flight calls Notes of two or three syllables were frequently recorded. The former were more common and were written without a terminal consonant only once. They may best be rendered as teep-teep (with variants from sooeet-sooeet to swee-me), completely lacking the ringing, whistling quality of the Common

4 Identification of Spotted Sandpipers 171 Sandpiper's flight call, being much quieter and less strident and even suggesting Meadow Pipit Anthus pratensis to some ears. The tri-syllabic call may be transcribed as weet-loo-eet (with variants from tit-it-met to cheep-cbeep-cbeep). It was phrased like the tri-syllabic call of the Green Sandpiper T. ocbropus but was much more muted. Fig. 2. Common Sandpiper Tringa bypoleucos (left) and Spotted Sandpiper T. macularia. They share a white wing-bar, but the latter's darker inner secondaries accentuate the narrow white trailing edge. Note also the more extensive barring on its outer tail-feathers, the tail aooearine eenerallv darker (see oaees I Alarm call When closely pressed, the first bird tittered another distinctive call, a disyllabic tho-it (usually repeated). Common Sandpipers on Ttesco and St Agnes in October 1965, in Berkshire in September 1966 and in southern Nigeria in the winters of 1968 and 1969, were listened to with great care by observers fresh from the Spotted Sandpipers of those years, but no calls other than the classic tsee-wee or tsee-me-wee were heard. Thus, with the exception of the second bird which gave a swee-wee call, the vocabulary of all four individuals differed distinctly from that of migrant Common Sandpipers. Peterson (i960, 1961) noted the call of the Spotted Sandpiper as 'a d.e&tpeetot pee-met! oxpee-weet-n>eet~n>eet-weef,&n& incidentally Taverner (1949) gave Pewit and Peetweet as local names in Canada. With plumage characters diagnostic only in the most favourable circumstances, voice is the best distinction. Unfortunately The Handbook missed this clear dichotomy, otherwise we might have noticed autumn and winter Spotted Sandpipers long ago.

5 17 2 Identification of Spotted Sandpipers ACKNOWLEDGEMENTS Many observers contributed to the successful identification of the Spotted Sandpipers discussed in this paper. Chief among them were those who trapped the first and second birds, namely J. R. Mullins, B. Marshall, C. S. Waller, P. J, Grant, and the late D. D. Harber, and R. F. Thearle, M. Kendall and S. C. Joyner, Other major contributions came from R, H. Charlwood, who took the photographs on plates 5 la and 31c, D, B. Hunt, R. J. Johns and J. L, F. Parslow. The Rarities Committee also helped, and I am particularly grateful to R. Wagstaffe who examined skins during the circulation of the four records analysed in detail and agrees with the conclusions in this paper. SUMMARY Previous statements that in immature and winter adult plumages Spotted Sandpipers Tringa macukria are not separable in the field from Common Sandpipers T. bypokwos have not been borne out, at least in the case of immatures. Experience of recent records on St Agnes and Tresco, in the Isles of Scilly, shows that certain diagnosis is possible. It is clearly worth examining any autumn or winter Common Sandpiper that sounds at all unusual. If it has a dark-tipped bill, a white chin and clean throat, barred wing-coverts contrasting with a uniformly greyish mantle, and yellowish legs, and shows in flight light trailing edges to uniformly dark secondaries and strongly barred tail sides, it is on the evidence presented here a Spotted Sandpiper. Confirmation by trapping is nevertheless recommended. REFERENCES DRESSER, H. E A Manual of Palearctic Birds. London, p PETERSON, R. T A Field Guide to the Birds. Boston, Mass. p. 93, plates 27 and 32. i960. A Field Guide to the Birds of Texas, Cambridge, Mass. p. 99, plates 27 and A Field Guide to Western Birds. Boston, Mass. Second edition. p. 109, plate 29. TAVERNER. P. A. loio. The Birds of Canada. Toronto, o &&. 2-1%. VAURIE, C. A The Birds of the Palearctic Fauna. London, vol 2. Voous, K. H. i960. Atlas of European Birds. London, plates 139 and 140. D. I. M. Wallace, c\o Nigerian Breweries, Box JJJ, Lagos, Nigeria

6 PLATE 31. Spotted Sandpiper Tringa macularia, Scilly, September Left, note the clean appearance, uniform upper-parts and barred wing-coverts {photo: D, I. M. Wallace). Above and below, the same bird in the hand, showing the barred wing-coverts (which contrast with both scapulars and tertials), the white trailing edge to the secondaries (faintly continued on to the primaries) and the strongly barred outer tail (pages ) {photos: R. H. Charlwood)