Fewer and fewer Red Knots arrive in San Antonio Oeste. They are the migratory birds that stand out because they make the longest journey to unite the Canadian Arctic with the south of Tierra del Fuego: They travel about 32 thousand kilometers a year. And the Bay of San Antonio is one of his stops on such a long journey.
Before, flocks of 20,000 specimens arrived, but now they are around 1,300, a figure that is the most outstanding data provided by scientists who are dedicated to the study of the reddish sandpiper species: it is in danger of extinction.
The migratory behavior of these birds and its possible changes are being investigated through the use of small devices, that emit signals that will be captured in different points of the extensive geography that they cover. It seeks to specify what produces these fluctuations in the populations of the species.
In the month of June, Red Knots are in the Arctic and are breeding. Before arriving, they made a stop at Bahía San Antonio, Río Negro
The initial numbers, which were given some time ago, showed that 50% of the population of these birds passed through the San Antonio Bay and stayed making a stopover, in a stay of a maximum of 45 days in which they rested, they doubled their weight and had finished moulting their plumage.
Today the scale persists, but the figures indicate that only 25% of the total pass through the area, which is located in an area of great tourist impulse within the east of Rio Negro.
“There could be many reasons for them to see each other less. There are some that cannot be explained, and others that can be assumed, such as the increase in birds of prey such as peregrine falcons. The presence of hawks causes the entire flock that passes through here to change their behavior, to avoid a possible attack. And this not only happens because the birds of prey could eat some of them. The shorebirds are very perceptive, and they directly change their migratory strategies if they perceive a threat,” said biologist Patricia González, from the Inalafquen Foundation, in San Antonio Oeste, in dialogue with Black river.
Another reason is the possible existence of disturbances on the beach that are generated just when the ideal window of time for birds to feed begins. If these disturbances persist over time, the birds will move to other areas where the food may not be as good in energy quality, but where they are calm when it comes to feeding.
Red Knot flocks have dwindled from 20,000 to 1,300. find out why
“If birds of prey are around at those times or there are threats such as the presence of dogs or other incidents, the red knuckles lose the opportunity to eat. They feed on marine invertebrates such as mussels, clams and polychaetes (similar to worms), which are not available homogeneously along the entire coast nor are they always within reach of their beaks, because they eat in intertidal zones, which are available when the sea comes down. Therefore, if at that time they lose access to food, they are left, directly, without eating, ”said the biologist.
In addition, everything that can happen to the species is linked to the extensive migratory route that they travel. Each point of the route can harbor some condition that generates a specific affectation, which ends up disturbing the flocks. For this reason, the strategies that are designed at a scientific level are generally addressed jointly.
what they investigate
“Red Knots arrive from Tierra del Fuego and migrate north to the Arctic to breed. To determine if the migratory routes are changing in the last ringing campaign we did, which was during this month of April, in the Mar Grande area, we put tiny transmitters called nanotags on some of them, which emit signals captured by some towers arranged for this purpose, to investigate behaviors, ”González said.
Experts from other points are involved in this research project, such as Yves Aubry from Environment & Climate Change, from Canada, and Enver Ortiz López from the Corbidi Center for Ornithology and Biodiversity, from Peru. In addition to a vast team of professionals from the area who worked on the banding, such as Natalia Martínez Curci from the Institute of Marine and Coastal Research (IIMyC), Verónica D’Amico and Marcelo Bertellotti, among others.
“When the birds pass near sites with towers located throughout the continent, their presence is detected, but only until they moult and lose the nanotag,” he specified. During the procedure, the birds that were recently captured, the specimens were identified with a ‘flag’, to individualize them and then enable their follow-up. “We also weigh them. In general, they were found in good condition, with very few specimens delayed in their migration,” said the expert.
What they do in San Antonio Bay
Red Knots arrive every year starting in March at the San Antonio Bay Protected Natural Area. They come from Tierra del Fuego, where they kept their gray, non-breeding plumage, which they later begin to shed for the red with which they will be seen later. They prepare for breeding in the Arctic. At the stop they make in San Antonio Bay, they rest and eat to double their size, and prepare for their next stopover north.