versión On-line ISSN 1850-4884
Hornero v.18 n.1 Buenos Aires ene./ago. 2003
The first record of Dunlin (Calidris alpina) in Paraguay and a summary of South American records of the species
A. J. Lesterhuis 1,2 and R. P. Clay 1,3
A Dunlin (Calidris alpina) in full breeding plumage was discovered at Laguna Ganso in the Paraguayan Chaco on 29 June 2001. This bird represents the first record of the species for the country and for the interior of South America. Although primarily a species of higher northern latitudes, there are a number of previous records from coastal South America.
Key words: Calidris alpina, Dunlin, first record, Paraguay, South American records.
Primer registro del Playerito Vientre Negro (Calidris alpina) y un resumen de los registros sudamericanos para la especie
Un Playerito Vientre Negro (Calidris alpina) en plumaje nupcial fue observado el 29 de junio de 2001 en Laguna Ganso, en el Chaco Paraguayo. Esta observación representa el primer registro de la especie para el país y también para el interior de América del Sur. Si bien es una especie que se encuentra principalmente en las altas latitudes del Hemisferio Norte, existen varios registros anteriores provenientes de la costa de América del Sur.
Palabras clave: Calidris alpina, Paraguay, Playerito Vientre Negro, primer registro, registros sudamericanos.
Received 24 April 2003, accepted 6 August 2003
The Dunlin Calidris alpina has a circumpolar Northern Hemisphere breeding distribution, and winters widely on the coasts of North America, Europe, North Africa and southern Asia. However, only in Africa does the species regularly occur south of 20°N, and there are few records south of the Equator (Hayman et al. 1986). Here we detail the first record of Dunlin for Paraguay and the interior of South America, and briefly review other South American records of the species.
On 29 June 2001, AJL found an adult Dunlin in breeding plumage at Laguna Ganso (22°34'48"S, 59°35'29"W), a saline lagoon in Presidente Hayes Department, western Paraguay. The bird, which was also seen by H del Castillo, A Esquivel and A Spiridonoff, immediately drew attention through its clear black belly patch. It was feeding along the shoreline of the shallow lagoon, associated with a mixed flock of approximately 100 Collared Plover Charadrius collaris, 22 White-rumped Sandpiper Calidris fuscicollis and 14 Stilt Sandpiper Micropalama himantopus. A search of the same area the following day failed to relocate the Dunlin, and it was not recorded during fieldwork in the same area on 18 July 2001.
The Dunlin was slightly larger than nearby White-rumped Sandpipers, with a noticeably more hunched, short-necked and short-winged stance, and a longer, all-black bill with slightly drooping tip. The bird was in full breeding plumage, with broadly fringed reddish-brown upperparts, reddish crown and neck, and a clear black belly patch, contrasting with the white flanks and thighs. A clear white band separated the black belly patch from the streaked breast, a feature considered characteristic of the subspecies pacifica (Hayman et al. 1986). Distant photographs, clearly showing the hunched stance and black belly patch, have been deposited in Guyra Paraguay.
Laguna Ganso is part of a large complex of largely saline wetland habitats formed by the paleochannels and meanders of the Riacho Yacaré Sur, an area approximately 111 km2 in extent that forms an important migration stopover site for Nearctic shorebirds (see Lesterhuis and Clay 2001). In June and July 2001, this area was also found to hold noteworthy concentrations of oversummering shorebirds of eight Nearctic migrant species, in addition to regionally important numbers of Collared Plover.
Of the nine commonly recognized subspecies of Dunlin (Gils and Wiersma 1996), two breed in North America and winter in the southern United States, México and Central America. Calidris alpina hudsonia breeds in central Canada and migrates to the south-eastern United States and eastern Mexico, while Calidris alpina pacifica breeds in south-west Alaska and winters in the western United States and Mexico (van Gils and Wiersma 1996). Both Calidris alpina hudsonia and Calidris alpina pacifica have been recorded in Costa Rica and Panama (Hayman et al. 1986, Ridgely and Gwynne 1989, Stiles and Skutch 1994, Canevari et al. 2001), and both could be expected to occur in South America as vagrants. While the first documented record of Dunlin in South America was an adult male of the subspecies Calidris alpina hudsonia (Greenwood 1983; Copenhagen Univ. Mus., Cat. No. 36029), all other subspecifically identified records refer to Calidris alpina pacifica (Table 1).
Table 1. Records of Dunlin Calidris alpina in South America.
The southernmost record concerns a bird observed at Mar del Plata, Buenos Aires Province, Argentina, on 12 March 1981 (Kieser 1982). Although the observer considered the bird to be juvenile moulting into first-winter plumage, the time of the year and several of the reported plumage details (e.g., "numerous bold dark roundish spots on the belly" and "primaries dark with very narrow and abraded pale edges") suggest a bird moulting into breeding plumage. While most records pertain to lone individuals, small flocks have been recorded in both French Guiana (Tostain and Siblet 1992) and Ecuador (Ridgely & Greenfield 2001). The series of boreal summer records in the Bay of Paracas, Peru, during 1978-1979 (Petersen et al. 1981) sets an interesting precedent for the first Paraguayan record (Table 1).
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