Habitat preference and abundance of Coscoroba coscoroba and Cygnus melancoryphus in Petrel wetland (Región O’Higgins, Chile): Implications in the conservation

By Marcelo Miranda-Cavallieri, Carolina Allendes-Allendes, Camilo Matus-Olivares and Fulgencio Lisón

Wetlands are environments with a high diversity and global importance due to the ecosystem services they provide. In Chile, most wetlands are threatened, including their avifauna.

In South America, the presence of two species stands out, coscoroba swan (Coscoroba coscoroba Molina, 1782) and black-necked swan (Cygnus melancoryphus Molina, 1782), the only species of swans in this region of the continent. Despite their restricted distribution, the information regarding them is limited and unlike the species of swans of the Northern Hemisphere, of which it has been achieved establishes that their populations are increasing or are stable in number, for these two species, the information on the size and trends of the populations is quite imprecise, therefore the conservation status of South American swan species is not well known.

Coscoroba Swans by Christopher Mathers – WWT

Both species are highly dependent on wetlands to maintain their populations and are recognized as susceptible to rapid habitat loss, especially in Chile, where they have an irregular distribution, and many of these ecosystems are unprotected. Despite this, studies on their habitat preferences and the seasonal variation of their populations are scarce especially in urban wetlands. Therefore, the knowledge about abundance patterns and seasonality of these species is essential to develop appropriate conservation and management plans.

Pair of Black-necked Swans with cygnet by Febe van Tonder / WWT

Therefore, to contribute to improve their conservation status, it is important to know the environments to which they are directly associated within the wetlands and to understand the relationships with their habitat.

In this study, three years of abundance monitoring of both species were carried out in the Petrel wetland, a coastal wetland in central Chile.

Abundance prediction using model averaging from the best-ranked regression models by species. The relation between the best-adjusted environmental variables and the abundance of C. coscoroba (A, B y C) and C. melancoryphus (D).

The results show that the Petrel wetland is an important site for the conservation of South American swan populations, with an abundance average of 38.5 ± 18.8 individuals of C. coscoroba (peak of 60 ind.) and 11.6 ± 12.4 individuals of C. melancoryphus (peak of 40 ind.).

These swan species avoid sites close to urban areas and show a preference for habitats distant from anthropogenic activities. The detection probability of swans was influenced by minimum and maximum temperature and wind speed. The vegetation aquatic and riverine are key variables to the abundance of these swans. Our large monitoring highlights the importance of Petrel wetland for the conservation of southern swans and provide value information about their abundance patterns and the population dynamics of C. coscoroba and C. melancoryphus. These data support the need to develop conservation and management plans for this wetland.

The full article can be found here