COMUNICACIONES

First record of the Lesser Sand Plover (Charadrius mongolus) in Argentina: a new species for the country and for South America

 

Arnaud Le Nevé ^1,2 and Mauricio Manzione ³

¹ Direction Régional de l'Environnement, de l'Aménagement et du Logement des Pays de la Loire. 5 rue Françoise Giroud, CS 16326, 44263 Nantes cedex 2, France.
² 6 rue de l'Olivraie, 44200 Nantes, France. le-neve.arnaud@orange.fr
³ Administración de Parques Nacionales. Alsina 1418, 6° piso, oficina 610, C1088AAL, Buenos Aires, Argentina.

Received 23 June 2011
Accepted 26 December 2011

 

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ABSTRACT

In this communication we provide the first record of the Lesser Sand Plover (Charadrius mongolus) in Argentina and South America. An adult male of the species in breeding plumage was observed and photographed on 30 March 2011 at Punta Rasa, Buenos Aires Province, Argentina. The diagnostic plumage features of the bird refer to the mongolus subspecies group.

KEY WORDS: Charadrius mongolus; First record; Punta Rasa; Vagrant.

RESUMEN

Primer registro del chorlito mongol (Charadrius mongolus) en Argentina: una especie nueva para el país y para América del Sur.- En esta comunicación se ofrece el primer registro del Chorlito Mongol (Charadrius mongolus) para Argentina y para América del Sur. Se observó y fotografió a un individuo macho adulto en plumaje reproductivo el 30 de Marzo de 2011 en Punta Rasa, provincia de Buenos Aires, Argentina. Las características del plumaje indican que se trataría de un individuo perteneciente a una subespecie del grupo mongolus.

PALABRAS CLAVE: Charadrius mongolus; Errante; Primer registro; Punta Rasa.

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Waders constitute a large bird group with worldwide distribution which exploit diverse habitat types. In particular, plovers are represented in all biogeographic regions except Antarctica and almost all areas support several species. Plovers belong to the family Charadriidae, which includes 10 genera and 68 species. They dwell in open habitats, both wet and dry, including a great variety of wetlands, coastal shorelines, grasslands, tundra, steppes and semi-deserts (del Hoyo et al. 1996). The genus Charadrius encompasses 33 species around the world (del Hoyo et al. 1996), 8 of which are cited for South America (Remsen et al. 2011) and 5 for Argentina (Narosky and Yzurieta 2010).

The Lesser Sand Plover (Charadrius mongolus) is a Palearctic species that breeds in steppes and deserts, predominately at high altitudes in the Northern Hemisphere (Marchant and Higgins 1993). Two different subspecies groups make distinctive migratory movements. The atrifrons group, including the atrifrons, schaeferi and pamirensis subspecies, breeds in Central Asia and winters in a wide area that encompasses Malaysia, Indonesia and western Pakistan. Charadrius mongolus pamirensis also breeds in Central Asia, but its wintering area includes western India, the Arabian Peninsula, eastern Africa, South Africa and Namibia. The mongolus group, including the mongolus and stegmanni subspecies, breeds in eastern Siberia and migrates to the China Sea, Philippines, eastern Indonesia, Melanesian islands and Australia in winter (del Hoyo et al. 1996, Cramp et al. 2001). According to Garner et al. (2003) and Taylor and Message (2005), these two subspecies groups could be separate species, but the Association of European Records and Rarities Committees still considers them only one species (Crochet et al. 2010, Crochet and Joynt 2011). During the non-breeding season, the species is strictly coastal, foraging on sandy beaches, mudflats, estuaries and mangroves (Pizzey 1991, Smith 1991, Marchant and Higgins 1993, del Hoyo et al. 1996).

The Lesser Sand Plover is an uncommon visitor to the outer Aleutians Islands and to extreme northern Alaska where it has already bred (AOU 1998). There are less than 15 records of the Lesser Sand Plover in North America (excepting those from Alaska). It has been recorded in New Jersey and Rhode Island on the eastern seaboard, in Ontario on the Great Lakes, in Louisiana, the Gulf Coast and Florida (Curtis 2007). According to the South American Classification Committee the Lesser Sand Plover has not been recorded in South America up until March 2011 (Remsen et al. 2011).

The first record of this species for Argentina and South America occurred at Punta Rasa (36°18'S, 56°46'W), San Clemente del Tuyú (central-eastern Buenos Aires Province). It is located in the confluence of the fresh waters of the Río de la Plata estuary and the Atlantic Ocean. This area has extensive intertidal mudflats, tidal saltmarshes and a network of tidal creeks (Scott and Carbonell 1986). This site is classified as an Important Bird Area (Coconier 2007), especially for shorebirds such as Grey Plover (Pluvialis squatarola), American Golden-Plover (Pluvialis dominica), Twobanded Plover (Charadrius falklandicus), Hudsonian Godwit (Limosa haemastica), Lesser Yellowlegs (Tringa flavipes), White-rumped Sandpiper (Calidris fuscicollis), and Red Knot (Calidris canutus) (Coconier 2007).

One Lesser Sand Plover was observed by Arnaud Le Nevé on a small sandy bank which had just emerged at the beginning of low tide, at Punta Rasa on 30 March 2011, towards the second half of the morning. The observation was made during 2 h, with a telescope (30x) and photographed by digiscoping, until a short range of 15-20 m, after a slow and gradual approach. The bird foraged on the wet sand in a flock of waders including 9 Red Knots, around 20 Two-banded Plovers, 20 White-rumped Sandpipers, 4 Ruddy Turnstones (Arenaria interpres), 2 Greater Yellowlegs (Tringa melanoleuca), 3 Grey Plovers and 1 American Golden-Plover. The Lesser Sand Plover was the most friendly bird of the flock and was still there when the viewer departed around 11:00 h. It did not fly nor call. Despite the efforts of local birdwatchers the bird was not seen again.

Both Greater Sand Plover (Charadrius leschenaultii) and Lesser Sand Plover have subspecies which exhibit overlapping characters, making them difficult to identify or even indistinguishable (Hirschfeld et al. 2000). But in this case, the breeding plumage and good conditions of the sighting (minimum distance, sunny weather) leave no doubt on the identification of the species. The bird was similar to the Two-banded Plover in size and the head was relatively small and round (Fig. 1). Rufous and brown tones were intense. Moreover, it showed a broad orange-rufous breast extending into orange-brown along the flanks. In comparison, the Greater Sand Plover, already seen in Central Asia by the observer, is a bigger bird with a large and angled head and less or no orange on flanks.

Figure 1. Lesser Sand Plover (Charadrius mongolus) observed at Punta Rasa, San Clemente del Tuyú, central-eastern Buenos Aires Province, Argentina. The relatively small size (A) is comparable to the Two-banded Plover (Charadrius falklandicus) and excludes the Greater Sand Plover (Charadrius leschenaultii). The broad orange-rufous breast extending into orange-brown along the flanks and rear flanks (A-D), the white forehead divided by a narrow black line (B, C) and the narrow black bar between white throat and clear-cut orange-rufous chest-band (A-C), are diagnostic characters for the mongolus subspecies group. The prominent dark central tail feathers, raised by the wind, are visible under the wing (D), and are also a character for the mongolus group. The relatively long wings entirely covering the tail feathers, the relatively thin bill (D) and the wider darker lines of the face mask (B), may correspond to Charadrius mongolus stegmanni.

The correct identification of the subspecies could provide the information necessary to establish the origin of the bird. Moreover, Garner et al. (2003) suggest that differences in characters and breeding ranges between the subspecies groups are distinct enough to regard them as separate species, and encouraged further research to address the taxonomic issues. The nearest point of its distribution area is the region of Cape Town in South Africa, which is 6650 km away from Punta Rasa. Nevertheless, the subspecies observed in Argentina does not correspond to the population wintering in South Africa (Charadrius mongolus pamirensis) but to those wintering from China to Australia and breeding in east or north-east Siberia (Charadrius mongolus mongolus or Charadrius mongolus stegmanni). The irregular dusky orange to greyish-brown marks along the flanks, extending to the rearmost flank feathers, is characteristic of both Charadrius mongolus mongolus and Charadrius mongolus stegmanni and is absent in the remaining subspecies (Garner et al. 2003, Taylor and Message 2005). The subspecies from the atrifrons group can show an extension of the orange breast pattern onto the flanks in breeding plumage, sometimes to about two-thirds of the way down the flanks, but there is no greyish-brown component to these markings. In addition, the subspecies from the mongolus group have a broad dark tail band due to the two large dark prominent central tail feathers that clearly contrast with the upperparts, as shown by figures 1A and 1D, whereas the other subspecies have a tail pattern in which the sandy-brown tones are relatively uniform with the rest of the upperparts (Garner et al. 2003). The obvious and extensive white forehead, divided by an indistinct narrow black line and the narrow black bar between white throat and clear-cut orange-rufous chest-band also indicate a bird of the mongolus group (Fig. 1). The black frame (not brown as in the female) on the face, the broad orange-rufous chest-band and orange collar on the lower nape may indicate a male (Garner et al. 2003). Variations in the proportions of the wings, tarsus and bill define the main differences between Charadrius mongolus mongolus and Charadrius mongolus stegmanni (Cramp et al. 2001). Unfortunately, these characteristics are not obvious from the photos. However, the long wings (entirely covering the tail), the relatively thin bill (Fig. 1 and also noted in the field) as well as the wider darker line of the face mask (Hirschfeld et al. 2000), may correspond to Charadrius mongolus stegmanni. In connection with this identification, Curtis (2007) concluded that the Lesser Sand Plover in Florida likely corresponds to this same subspecies.

ACKNOWLEDGEMENTS

We thank Violette Le Féon and Marta Telesnicki for reading and commenting on this note and Eugenio Coconier, Philippe Briand and Mark Pearman for providing relevant bibliography and advice. Also we thank Mark Pearman for his careful examination of the text.

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