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Bahía de Asunción

Site Facts

Country, State, Province/Region:

Paraguay, Central Department

Relative Location:

North of the City of Asunción, in the Municipality of Asunción


25°16'1" S; 57°37'32" W



Basis for Designation:

More than 1% of the flyway population for Buff-breasted Sandpiper (Tryngites subruficollis).


522 hectares (1,290 acres)


January 2008

Site Owner/Steward:

Municipality of Asunción (land), Secretariat of the Environment of Paraguay (water)

Site Partners:

Guyra Paraguay

Population within 100 km:

1 million


Hugo Enrique Cañiza
Director of Environment
Municipality of Asunción

Alberto Yanosky
Executive Director
Guyra Paraguay


At its January 2008 meeting, the WHSRN Hemispheric Council voted unanimously to approve Bahía de Asunción near Asunción, Paraguay, as a WHSRN Site of Regional Importance. This 522-hectare Ecological Reserve and Important Bird Area hosts more than 1% of the population of Buff-breasted Sandpiper, a shorebird species of high conservation priority. The bay’s combination of freshwater lagoons, mudflats, sandy beaches, reed beds, and seasonally inundated grasslands provides a diversity of habitats benefiting a wide range of migratory birds.

Bahía de Asunción is a relatively small bay located along the northern outskirts of Asunción, the capital of Paraguay (in the Capital District). The bay is separated from the large Paraguay River by the Banco San Miguel, a narrow peninsula of low-lying land, and lies on the border of two geographical and ecological distinct regions of Paraguay: the lowland Chaco (western part) and the Atlantic Forest (eastern part, and Asuncion city). The bay’s water level is regulated by the Paraguay River pulses, flooding the area in autumn /winter, and receding its water level during spring/ summer.

Bahía de Asunción was declared a reserve by law N° 2715 in 2005, titled “Ecological Reserve of Banco San Miguel and Bahía de Asunción.” In addition, the reserve corresponds to the Category IV of the IUCN guidelines. The Reserve is a first case of co-management between the Municipality of Asunción and the Environmental Secretariat (SEAM) – the municipality owns Banco San Miguel peninsula, and the secretariat owns the water body. Currently, they and Guyra Paraguay (national BirdLife Partner) are developing a management plan for the area.

Despite the relative small size of the area (500 hectares), a total of 269 species of birds have been recorded to date, including no less than 25 species of shorebird. Five species are of conservation concern to some extent, including four species considered near-threatened and one species considered vulnerable. Of the Nearctic shorebirds recorded here (n=19), the area is of major importance to the near-threatened Buff-breasted Sandpiper (Tryngites subruficollis). Regular monitoring of shorebirds by Guyra Paraguay since 2000 showed that over 3% of its global population uses the area during southward migration. Based on the abundant presence of this species, the area was also declared an Important Bird Area under categori A4i. Other species of Nearctic shorebirds that are common in the area during migration are the American Golden- Plover (Pluvialis dominica), Lesser Yellowlegs (Tringa flavipes), White-rumped Sandpiper (Calidris fuscicollis), and Pectoral Sandpiper (Calidris melanotos).

Birds that use Bahía de Asunción as a breeding, stopover, or wintering site share it with local people who also depend on its resources. The east and south coast of Bahía de Asunción is densely populated, with the majority of the people being extremely poor. The Banco San Miguel is inhabited by fewer people, but the community is expanding as people from the interior encroach and illegally occupy pieces of land. The area is used by the local community for fishing and hunting. To a lesser extent, recreational activities are carried out. Major threats to the area include habitat disturbance and loss, hunting, and pollution. 




Situated just 1 mile from downtown Asunción, the bay is exposed to many potential and current threats, including urban expansion, pollution, over-exploitation of natural resources, habitat destruction, and feral cats and dogs. The area is easely accesible and there is no control on activities carried out within the area.

Research & Management

Despite the rich diversity of bird species, only a handful of studies have focused on birds in Bahía de Asunción and the majority of studies that have been carried out, were focussed on waterbirds. One of the first studies carried out at the bay were those of Floyd Hayes and Jennifer Fox who conducted the first series of waterbird surveys. They conducted a total 47 censuses from 1987 to 1989, studying Nearctic shorebirds (Wilson Bull. 103: 637-649, 1991) and resident waterbirds (Hornero 14: 14-26, 1996). The first study focused on seasonality, habitat use, and flock size of all observed shorebirds. A total of 20 species of shorebirds were recorded, of which 15 were Nearctic migrants and 5 were resident species. They found that numbers of Nearctic shorebirds peaked during October–December, while numbers of resident shorebirds peaked during December–March (Hayes & Fox, 1991).

In 2000, Guyra Paraguay initiated a project supported by the National Fish and Wildlife Foundation, focusing on Nearctic migrants in Paraguay with a special focus on Nearctic shorebirds. As part of the project, regular shorebird monitoring was conducted at Bahía de Asunción. During 5 months of fieldwork carried out between September and December, an estimated minimum of 5,104 Nearctic migrant shorebirds passed through the Bahía de Asunción; it is believed that more regular monitoring would show the area to be used by more than 10,000 birds (Lesterhuis & Clay, 2001a). A total of 14 Nearctic shorebirds were recorded, including the first record of the Ruddy Turnstone (Arenaria interpres) for the country (Lesterhuis & Clay, 2001c). The study also showed that the area appeared to be of major importance to the near threatened Buff-breasted Sandpiper (Tryngites subruficollis). The highest single count recorded (140 birds) is just less than 1% of the global population, and a minimum of 539 individuals (or 3.6 % of the global population) were estimated to have passed through the bay during the initial study period. Based on these counts, Bahía de Asunción was declared an Important Bird Area (IBA) in 2003.

Guyra Paraguay continued regular monitoring of Nearctic shorebirds at Bahía de Asunción and, to date, a total of 19 Nearctic shorebirds have been recorded. Among the most abundant species are the American Golden-Plover (Pluvialis dominica), Lesser Yellowlegs (Tringa flavipes), White-rumped Sandpiper (Calidris fuscicollis), Pectoral Sandpiper (Calidris melanotos), Stilt Sandpiper (Calidris himantopus), Buff-breasted Sandpiper and Wilson’s Phalarope (Phalaropus tricolor). Species that are less common, but worth mentioning are the Upland Sandpiper (Bartramia longicauda), Hudsonian Godwit (Limosa haemastica), Red Knot (Calidris canutus) and Sanderling (Calidris alba).

In 2004 a project was developed by Guyra Paraguay entitled “Assessment of the importance of the Bahía de Asunción for the Near-threatened Buff-breasted Sandpiper”. The project was supported by the Canadian Wildlife Service and had as its main goals to evaluate the importance of Bahía de Asunción as a stopover site for the Buff-breasted Sandpiper and to gain information regarding its migration route and associated wintering and breeding grounds. During the project a total of 19 birds were trapped and banded; three of those were re-sighted within 2 weeks at Lagoa do Peixe National Park, Brazil. Based on a turnover rate of approximately 7 days, the total population that visited the bay during the southward migration was estimated to be nearly 600 birds (4% of its global population).

Guyra Paraguay has agreements with the Municipality of Asunción and the Ministry of the Environment (SEAM) for cooperative action to protect the site. Currently they are co-working on the development of a management plan (see:, which has as a main goal to secure the future of Bahía de Asunción as stopover site for migratory birds.


Hugo Enrique Cañiza
Director of Environment
Municipality of Asunción
(00 595) 21 663369

Alberto Yanosky
Executive Director
Guyra Paraguay
(00 595) 21 227777


Additional Resources


Hayes, F.E. and J.A. Fox (1991). Seasonality, habitat use, and flock sizes of shorebirds at the Bahía de Asunción, Paraguay. Wilson Bull. 103:637-649.

Hayes, F.E. (1996). Seasonal, geographical and time of day variation in resident waterbird densities along the Paraguay River.Hornero 14: 14-26.

Lesterhuis, A.J. and R.P. Clay (2001a). Nearctic shorebirds in the Bahía de Asunción, Paraguay. WSG Bulletin 95: 19.

Lesterhuis, A.J. and R.P. Clay (2001c) First record of Ruddy Turnstone Arenaria  interpres for Paraguay. WSG Bulletin 95: 68.

Lesterhuis, A.J. and R.P. Clay (2005). Buff-breasted Sandpipers in the Asunción Bay, Paraguay. CWS. Project report.