Mystery Calidris Sandpiper from Florida

See update (6 Aug 2005) at the end of the commentary section with a rather similar, albeit considerably longer-billed bird photographed in the Netherlands on 24 May 2001 by Norman Deans van Swelm.

This small Calidris sandpiper was photographed by Wayne Richardson on Marco Island, Florida, USA on 16 May 2005. It associated with Semipalmated Sandpipers, providing a good indication of size. Wayne considered it to be bigger than Western Sandpiper and smaller than Dunlin. His initial thought was an alternate-plumage White-rumped Sandpiper, but there the bird lacked a reddish base to the lower mandible and more importantly, lacked a white rump!! Baird's Sandpiper was considered based on size, however, review of the literature and reference photographs did not support this identification. In particular, it is evident that the primary tips fall short of the tail, which would be atypical for Baird's Sandpiper. The confusing mixture of features strongly suggest a hybrid, and guesses to the most likely pairing should make for interesting discussion. Whilst aware that the off-spring of some interspecfic pairings, e.g. Aythya ducks, can look more like another species than either parent, Wayne holds to the view that White-rumped Sandpiper is 'in the mix'.

As will be discussed below, the most parsimonious combinations seems to be Dunlin x White-rumped Sandpiper but it is worth keep other possibilities in mind such as Dunlin x Western Sandpiper or White-rumped x Western Sandpiper.

Fig. 1. Calidris sandpiper sp., 16 May 2005, Marco Island, Florida. Photo copyright Wayne Richardson©, all rights reserved.

Fig. 2. In flight - Calidris sandpiper sp.(right) with Semipalmated Sandpiper (left) notice the dark uppertail coverts and central retrices. 16 May 2005, Marco Island, Florida. Photo copyright Wayne Richardson©, all rights reserved.

Fig. 2. Calidris sandpiper sp., 16 May 2005, Marco Island, Florida. Photo copyright Wayne Richardson©, all rights reserved.

Fig. 4. Calidris sandpiper sp. with Semipalmated Sandpipers, 16 May 2005, Marco Island, Florida. Photo copyright Wayne Richardson©, all rights reserved.

Fig. 5. Calidris sandpiper sp. with Semipalmated Sandpiper, 16 May 2005, Marco Island, Florida. Photo copyright Wayne Richardson©, all rights reserved.

Wayne also noted the following:

- Frequented a small 'backwater' pool on a sandy spit. It was above the tide line and surrounded by knee high sea grasses etc.
- Very territorial & was continually chasing off the Semipalmated Sandpipers;
- Much smaller than any American race of Dunlin, although perhaps approaching schinzi in size. Judgment based on comparison with Semipalmated Sandpipers, Turnstone, plus Semipalmated & Wilson Plovers.
- It had a soft twittering call & was quite vocal.
- Thought processes on encountering the bird was 'Oh, a White-rumped', but when it flew & I saw it had a dark rump assumed it had to be a Baird's.

Shorebird expert Dennis Paulson gets the ball rolling with the following comments:

"The bill looks too long and droopy for either White-rumped or Baird's and makes me wonder if Dunlin might be in the parentage. It's also quite large, I think larger than either W-r or Baird's, and approaching Dunlin size. Were there Dunlins there so you could see that it was smaller? One of the hybrids involving White-rumped Sandpiper (I can't recall the other parent) was named as "Cooper's Sandpiper," and this bird may share some of the characteristics of Cooper's. Your bird doesn't show any characteristics that make me think of Baird's, but the heavily striped breast and upper sides and reddish edges on the scapulars and tertials are reminiscent of White-rumped."

In a posting to ID-Frontiers, Kevin McLaughlin of Hamilton, Ontario drew clear parallels between this bird and one that he and others studied in Ontario:

Hi to all. There is a striking similarity between the Florida sandpiper and the bird identified by myself as an apparent Dunlin X White-rumped Sandpiper in May 1994 and photographed by Alan Wormington and others at Hillman Marsh, Ontario, north of Point Pelee. That observation, published in the April 2000 issue of ONTARIO BIRDS, is referenced [in the hybrid shorebird section below]. There are a number of things similar between the two and these are nicely displayed by Wayne Richardson's excellent photos, along with those of Alan and Robert L. Waldhuber.

BILL : The length and structure are quite alike with the colour black to the base. I am struggling to decide if the Florida ( hereafter MI - Marco Island ) bird may have an ever so slightly thicker bill base. Not absolutely certain. Bill colour on both birds is black, and , if I may venture, perhaps a "shinier " black on the HM bird.

HEAD PATTERN : The head of the MI bird is generally darker but much like the Hillman Marsh ( hereafter HM ) bird in pattern. Both have a streaked crown with some rusty suffusion throughout. The MI bird is more densely streaked through the lores and the auriculars, which contributes to the darker look of the head overall. The oval shaped suffusion of rust in the auricular region seems more noticeable on the HM bird.

EYEBROW : Both birds have a vague, well streaked eyebrow, more heavily streaked in the MI bird.

UNDERPARTS : The pattern of dark markings on the underparts anterior to the legs, if not identical, is very similar, and a fascinating feature ! The upper breast and throat are heavily streaked dark brown or slate. This gives way to copious round slate spots on the lower breast and side of the belly. In both birds there are some lengthwise streaks on the flanks above the legs.

UPPERPARTS : Another compelling similarity. The MI bird has scapulars which are somewhat more abraded compared to the HM bird. The essential pattern is much alike with blackish or slate centers combined with broad gray tips along with a variable amount of russet tinging to the gray sides at the base. Generally speaking, the HM bird is more profusely shaded with rust on the upperparts, particularly on the upper scapulars and tertials. The scapular pattern carries through to the mantle feathers with even broader gray fringes in this area.

COVERTS AND PRIMARIES : The HM bird possesses very abraded and faded brownish gray coverts and primaries, placing it in its second calendar year. I am not sure how to assess the MI bird on this feature from viewing the photographs.

PRIMARY LENGTH : All photographs of the HM bird show primaries which stop a millimetre or two short of the tail tip. On shots taken from above, the faded brown wing tip contrasts to the slate tail tip. The MI bird has a very comparable ratio involving tail tip to wingtip.

TERTIALS : Quite similar in the two. Dark centers with distinct pale fringes, the HM bird having somewhat more rust.

RUMP - UPPERTAIL : The flight shot of the MI bird displays a very dark rump and uppertail, along with a tail consisting of dark central rectrices and paler gray outers. The HM bird has more white on the outer uppertail but also possesses a thin black bar extending down the centre of the uppertail coverts joining the slaty rectrices. The one photo in my possession showing this also shows a grayish rump.

LEG COLOUR AND LENGTH : As with the bill the legs are black in both birds. I am not convinced that there is any palpable difference in leg length. As I have itemized above, there is a striking resemblance between the HM and MI birds. Characters shown by these two individuals lead me to entertain the potential that the parents in both cases may have been White-rumped Sandpiper and Dunlin.

Dear Angus,
The unidentified sandpiper shown on your website made me remember a Dunlin my son Charles and I found in May 2001 here in the SW Netherlands (see Fig. 6). In my opinion this long-billed individual is an American bird C. a. hudsonia and very similar to a bird photographed by Richard Chandler and
shown on the cover of British Birds some years ago.

Fig. 6. Apparent Dunlin, The Netherlands, 24 May 2001.Compared to the florida bird, the bill is obviously longer and more Dunlin-like. However, the two birds share similar rows of dense spotting on the breast and extening onto the flanks (somewhat hidden by wing). Three scapulars show dark centers with a hint of orange color in the fringes. The crown and ear coverts are also warmer than the base color. Photo copyright Norman van Swelm©, all rights reserved

Our bird shows a few breeding plumage mantle feathers which look similar to the ones on your unidentified calidris. The majority of Dunlins in late May are in full breeding plumage, the last to leave here in the Dutch delta are breeders from the Taimyr Peninsula C. a. centralis. However some individual waders are known to breed in apparent winter plumage i.e. Knot though their plumage must have undergone a partial pre-nuptial moult as well. As you can see from the pictures the plumages of both our and the Florida bird show little or no wear. Although the two birds differ somewhat I wonder if the Florida bird is a Dunlin rather then a hybrid of sorts. All the best, Norman Deans van Swelm.


Many thanks to Dennis Paulson for bringing this wonder bird to my attention and of course to Wayne Richardson for his stunning photographs. Thanks also to Norman Deans vans Swelm for the bringing the Dutch Dunlin (?) to our attention and providing his very useful photograph.

Known Shorebird Hybrid Combinations

Careful scrutiny of shorebirds around the world suggests that hybridization between Charadriiformes is not quite as exceptional as it was once thought. Here is a listing of know or well justified hybrid combinations. I'd appreciate hearing about other combinations or appropriate articles.

(1) Cooper's Sandpiper ('Calidris cooperi') was described by Baird in 1858 based on a specimen collected on Long Island, New York, U.S.A. in May 1833. A similar bird was collected in Stockton, New South Wales, Australia, in Mar 1981. Evidence suggests this is a Curlew Sandpiper x Sharp-tailed Sandpiper (C. ferruginea x C. acuminata) (Cox 1990a; 1990b).

(2) Cox's Sandpiper ('Calidris paramelanotos'). First described from Australia in 1982. Genetic evidence established that Cox's Sandpiper is not a distinct species, but is a hybrid between Curlew Sandpiper (Calidris ferruginea) and Pectoral Sandpiper (Calidris melanotos) (Christidis et al. 1996).
Excellent photos of a fresh juvenile (and more here) from Japan on 26 Aug 2001. See Ujihara 2002 for discussion.

(3) Buff-breasted Sandpiper x White-rumped (or possibly Baird's) Sandpiper (Tryngites subruficollis x Calidris fuscicollis).

(4) Dunlin x White-rumped Sandpiper (Calidris alpina x Calidris fuscicollis). See McLaughlin and Wormington 2000 for discussion.

(5) Dunlin x Purple Sandpiper (Calidris alpina x Calidris maritima). See Millington 1994.

(6) Common Sandpiper x Green Sandpiper (Tringa hypoleucos x Tringa ochropus).

(7) Little Stint x Temminck's Stint (Calidris minuta x Calidris temminckii). See Jonsson 1996.

(8) Black Oystercatcher x American Oystercatcher (Haematopus bachmani x Haematopus palliatus frazari). A relatively common occurrence on the Pacific Coast (Jehl, 1985).

(9) Black-necked Stilt x American Avocet (Himantopus mexicanus x Recurvirostra americana). Some times referred to as an 'Avistilt' or 'Stavocet', this is a fairly regular combination. Examples from South San Francisco Bay, California June 2003; Moss Landing, Monterey Bay, California. See Principe 1977.

(10) New Zealand Black Stilt x Pied Stilt (Himantopus novaezelandiae x Hemantopus leucocephalus). Hybridization is major threat to the surviving population of Black Stilts. See Pierce, 1984.

Useful Literature

- Alderfer, J. K. (2000) Mystery Sandpiper Revisited - Buff-breasted Or Hybrid ? Birding 32(6): 535-539.

- Christidis, L., K. Davies, M. Westerman, P. D. Christian, and R. Schodde. (1996) Molecular assessment of the taxonomic status of Cox's Sandpiper. Condor 98: 459-463.

- Cox, J. B. (1990a) The enigmatic Cooper's and Cox's Sandpiper. Dutch Birding 12: 53-64.

- Cox, J. B. (1990b) The measurements of Cooper's Sandpiper and the occurrence of a similar bird in Australia. South Austral. Orn. 30: 169-181.

- Kasprzyk, M. J., R. A. Forster, and B. A. Harrington. (1987) First Northern Hemisphere record and first juvenile plumage description of the Cox's Sandpiper (Calidris paramelanotos). American Birds 41(5): 1359-1364.

- Jehl, J. R., Jr. (1985) Hybridization and evolution of oystercatchers on the Pacific Coast of Baja California. Neotropical Ornithology, A.O.U. monograph 36: 484-504.

- Jonsson, L. (1996) Mystery stint at Groote Keeten: first known hybrid between Little and Temminck’s Stint? Dutch Birding 18:24-28.

- Lane S. G. , Van Gessel F. W. C. , and C. D. T. Minton (1981) A hybrid wader? Corella 5(5): 114-115.

- Laux, E. V. (1994) Mystery Sandpiper. Birding: 66 - 68.

- McLaughlin K. A. , and A. Wormington (2000) An apparent Dunlin x White-rumped Sandpiper hybrid. Ontario Birds 18(1):8-12.

- Millington, R. (1994) A Mystery Calidris at Cley. Birding World 1994 7(2): 61-63.

- Monroe, B. L. Jr. (1991) Reconsideration of the Massachusetts Cox's Sandpiper. American Birds 45(2): 232-233.

- Pierce, R. J. (1984) Plumage, morphology and hybridisation of New Zealand Stilts Himantopus spp. Notornis 31: 106–130

- Principe W. L., Jr. (1977) A hybrid American Avocet x Black-necked Stilt. Condor 79: 128–129.

- Stepanyan L. S. (1990) A new hypothesis on the origin of Calidris paramelanotos (Scolopacidae, Aves) [Russian]. Zoologicheskii Zhurnal 69(5): 148-151.

- Ujihara, M. (2002) An Apparent Juv. Cox's Sandpiper in Japan. Birding World 15(8): 346-347.

- Vickery, P. D., Finch, D. W. and P. K. Donahue. (1987) Juvenile Cox's Sandpiper (Calidris paramelanotos) in Massachusetts, a first New World occurrence and a hitherto undescribed plumage. American Birds 41(5): 1366-1369.

Other topics in shorebird identification (complete listing here)

Eastern or Western Willet?
Age and sexing of a Bar-tailed Godwit.
Pacific versus American Golden-Plover.
Black-tailed Godwit - Islandica or limosa?
Black-tailed Godwit - identification of the asiatic subspecies melanuroides.
Red-necked Stint and Little Stint Identification.
Curlew Sandpiper or Dunlin?

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