Oxyura vittata ( Philippi , 1860 ) ( Aves , Anatidae ) : range extension and first record from the Upper Paraguay basin , Brazil

This note extends the range of Oxyura vittata (Philippi, 1860) to the Upper Paraguay basin in the Brazilian Pantanal and presents the first record of this species from Mato Grosso do Sul state.


Introduction
The Lake Duck, Oxyura vittata (Philippi, 1860) (Aves, Anatidae), is a resident of the Chilean lowlands from Atacama south to Chiloe Island.East of the Andes, it occurs in Argentina from La Rioja and San Juan to the south to Tierra del Fuego.This species also nests along the east from Rocha to Montevideo in Uruguay (Arballo and Cravino 1999, Johnsgard 2010, Carboneras et al. 2016).After the breeding season, O. vittata, like other ducks in the Southern Cone, migrates during the winter, reaching southern Brazil, Paraguay and Bolivia (Carboneras et al. 2016).However, droughts have caused birds to detour from their regular flyway to the Falklands and Deception Island (Kear 2005, Carboneras et al. 2016).In Brazil, this species is considered an irregular visitor to Rio Grande do Sul, with records from April to August (Belton 1994), but the WikiAves Photo Archive (http://www.wikiaves.com) also documents summer records from Laguna and Joinville in Santa Catarina state and Curitiba in Paraná state.Here, we present the northernmost record to O. vittata and the first records for the Upper Paraguay basin in the Brazilian Pantanal.

NOTES ON GEOGRAPHIC DISTRIBUTION
observed among a flock of Red Shovelers (Anas platalea Vieillot, 1816) while foraging and swimming in a brackish pond, locally known as "salina" (see Medina-Júnior and Rietzler 2005).

Results
Our identification of the species follows Kear (2005) and Sick (1997) and was confirmed by experts, Alessandro Pacheco Nunes and Fábio Olmos.The observed individual was simply identified by the white stripe on the lateral of its head, which separate O. vittata from the very similar Nomonyx dominica (Linnaeus, 1766).
Oxyura vittata is a small diving duck characterized by stiff tails, and strong sexual dimorphism and display courtship (Sick 1997).Males exhibit chestnut body plumage and bright blue bills; females show a complex drab brown coloration (Sick 1997, Kear 2005).In comparison to the very similar O. ferruginea (Eyton, 1838), O. vittata is smaller with a flatter head and proportionately longer  tail and shorter bill.Males are distinguished from O. ferruginea by lacking white on the chin and having rich, dark chestnut colour that lacks true reddish tones.The head and the whole neck are black.Females have more patterned flanks than O. jamaicensis (Gmelin, 1789) and a vermiculated reddish-buff back (Sick 1997, Carboneras et al. 2016).

Discussion
Based on previous and current sources (Quezada et al. 1986, Brandolin et al. 2011, eBird 2016) database, our record extends the regular range of Oxyura vittata for 670 km from the nearest point, located in the Argentinean Chaco.For Brazil, it is nearly 1,000 km from the nearest location along the country's southern coast (WikiAves 2016) and the first documented record to Pantanal ecoregion and Mato Grosso do Sul State (Fig. 2).
In the southern province of Santa Fe, Argentina, O. vitatta was considered a rare bird at Melincué Lagoon, (Romano et al. 2015).Its wintering areas are known to be in the humid Chaco and northern Pampas (Birdlife 2015), and thus, our record likely represents a wandering migrant individual if we consider that many southern species of ducks migrate to the Pantanal.The salinas, and baías (freshwater ponds), are favoured sites for migratory waterfowl in the Pantanal floodplain (Nunes and Tomas 2008), including in Barranco Alto, where several migratory waterfowl species such as Dendrocygna bicolor (Vieillot, 1816), Coscoroba coscoroba (Molina, 1782), Sarkidionis sylvicola (H. von Ihering & R. von Ihering, 1907), Callonetta leucophrys (Vieillot, 1816), Anas baham ensis Linnaeus, 1758, Netta peposaca (Vieillot, 1816) and Nomonyx dominica (Linnaeus, 1766), with many likely coming from southern South America (Leuzinger, unpublished data).Previous observations of migratory birds in the Barranco Alto region suggest that harsh winters are important cause of southern species occurring in northern sites.Although undocumented, the winter in 2009 reached lower temperatures than usual and our record of O. vittata reinforces this hypothesis.However, additional records, as well as long term observations and temperature data, are needed to confirm this hypothesis.

Figure 1 .
Figure 1.Oxyura vittata recorded in a salina in the Nhecolândia subregion of the Pantanal in the 2009 winter.Photograph by Lucas Leuzinger.

Figure 2 .
Figure 2. Distribution map of Oxyura vittata in Brazil.Red circles: records extracted from WikiAves (2008); yellow star: the new record to Mato Grosso do Sul State and Pantanal.