Migratory birds arriving from Antarctica
The Urban Coastal Reserve (R.C.U.) of Río Gallegos "protects a representative sample of marshes and muddy intertidal flats. In addition, one of its important functions as a natural system is a place with high richness in food sources that constitutes a place of rest and feeding for thousands of shorebirds during their seasonal movements, as well as a final destination for other species ", slogan Nature Guide edited by the South Environment Association. (1)
Thus, the seasonal movements of these birds, the Patagonian and hemispheric migrants, populate the coastal landscape of our city of different species according to the time of year. We have already developed here the characteristics of some of the species that visit us in winter and we will continue with them, but in this case describing two particular visitors since they migrate between the Antarctic Islands, Antarctica and the continent.
The Common Giant Petrel (Macronectes giganteus) is the largest bird we can see in the estuary, it measures approximately 87 cm and with the wings spread it reaches almost two meters. Currently, in terms of its conservation status is in the category of "minor concern" of the International Union for the Conservation of Nature (IUCN) and in the category of "vulnerable" according to the Argentine Republic.
The specimens observed in the area are generally juveniles, whose plumage is completely black and with a noticeable peak of ivory to greenish color. The adults move progressively towards a whitish gray, beginning with the head and then extending to the chest and the rest of the body. It could only be confused with the Dark Giant Petrel (Macronectes halli) who differs in the absence of a red spot on the beak (observable only at close range) and whose presence in the area is accidental.
The giant petrel has been observed gliding over the water and the coast, moving its wings slowly or resting seated in the sea. It feeds by perching on the surface of the water or submerging up to a couple of meters to capture all kinds of dams or fishing boat debris. Sometimes, it takes advantage of dead animals, acting as a scavenger and also predates other live animals. He is very aggressive when he must defend his food. He remains almost all his life in the sea, except for the few occasions when he approaches the land to feed or when he nests.
It does not nest in the area, it does so on oceanic islands free of terrestrial predators. The specimens of the estuary probably come from the colonies of the Georgias and Malvinas Islands, Antarctica and the islands near the Chubut coasts.
The Antarctic pigeon
The Antarctic Dove (Chionis alba) is a carrion bird that lives in the sub-Antarctic regions of South America, as well as in the Antarctic Peninsula. It does not belong to the family of pigeons. It is so named only because of the great resemblance, without ceasing to be a close relative. It is not a species in danger of extinction, maintaining good conservation of the populations.
This bird measures 35 cm, it is robust; totally white with short and thick beak, pink with black tip. The males are slightly larger than the females, although the difference is imperceptible if the pair is not seen as a whole. In short flights it seems clumsy, with its legs hanging, but when it moves over the open sea it flies more energetically and folds its legs.
It lives on the rocky shores of the Antarctic Peninsula, Falkland Islands and sub-Antarctic islands. It can also be seen in the Patagonian coasts, as is the case of the Río Gallegos estuary, and there have even been reported sightings in the Torres and Castillo Grande islands on the Atlantic coast of Uruguay.
It feeds mostly carrion, eggs and waste. It usually visits colonies of seals, penguins, cormorants and other species in order to steal food and eggs. It is also often seen in the vicinity of Antarctic bases, fishing ports or beaches, looking for waste and food debris. The Antarctic dove is very confident, is found alone or in scattered groups, walks very slowly or runs jumping. It is usually seen standing still on some stone.
It nests exclusively in Antarctica and nearby islands, among the rocks near the coast. The nest is a depression in the ground surrounded by grasses and other plants, where it deposits three white eggs with spots and sprinkled with dark brown. The chicks are fed by both parents until they learn to fly. It breeds in Antarctica and the South Atlantic Islands as: Georgia, Sandwich, Orkney and Shetland; in the winter, it migrates north along the coast, when it is possible to spot it on the coast of the estuary, and it reaches Uruguay and southern Brazil; it is also seen in Chile.
1-"Guide to the Nature of the Urban Coastal Reserve of the city of Río Gallegos". Martina Mc Namara, Santiago Imberti, Carlos Albrieu and Silvia Ferrari. South Environment Association. Rio gallegos. 2008