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Our last day was the mix of both satisfaction and failure we had gotten used to. The day started promising. Once again, the sky shone a range of blue and white, all brilliant, the only haze from crashing waves. Fortunately, the most powerful waves spawned by the cyclone offshore abated, so instead of a series of 4 or 5 breaking waves in the surf, we saw only 2 or 3, and they were smaller. We found a flock of about 45 knots not long after riding south. We set the net, which almost immediately got washed over by a rogue wave. We quickly reset as the 45 knots separated into two groups, one each north and south of the net. Stephanie and Antonio “twinkled” or slowly moved birds from each group toward the net, and soon we had 35 birds lingering exactly where we needed to catch them. I fired the net, but we failed to see a rope tangled around the net in our quick reset. We watched the birds fly away once again.
We spent the rest of the day trapping until sunset but with no luck. We had to return to Porto Allegre and our flight home the next day, so our fieldwork was over. And so, as usual, we started thinking about dinner and a beer.
That night we ate cuts of sheep raised on the farm barbecued on a traditional indoor barbecue. The farm’s manager, Julian, supervised the barbecue while Renato and Julia served cold salads and carved the meat. We celebrated the birds, Lagoa do Piexe, ASA, and the owners. We drank beer and homemade Cachaca, a spirit distilled from sugar cane and very popular in Brazi. At almost 50% alcohol, the drink quickly sent me to bed, but the younger members partied on into the night. As one would expect, the following morning turned into a bit of chaos as we had to separate equipment and pack for the long trip home. But before long, we were on our way to the city and the airport.
Mateus describes how Renato Collares de Brum Marantes ( ASA co-owner)and Caubi Gomes de Lima ( Farm Worker) barbecued the meat. Photo by Stephanie Feigin
We ran out of time to catch more birds and attach the remaining transmitters, but Antonio continued collecting data on beach characteristics and measuring prey availability along the beach. He also trapped another 20 more birds.
We achieved our main goals on this trip. At first glance, it was all our experimentation with cannons and nets. We made set after set, gradually learning the limits of the net and training Antonio and his team.
We also had to learn about the birds. We were early in the stopover period, intentionally to track birds from the beginning of thier stopover and establish thier weights on arrival. We did that, although admittedly, the data was meager. Still, of the birds we caught, we found weights ranging from 120 to 150 grams. On Antonio’s catch and the catch we made in 2019, both made later in April, we found the knots had gained as much as 100 grams, with some birds weighing in at 240 grams. This was an essential part of our learning, how much did birds gain, and what were the starting weights. The tracking data taught us even more.
The lore about the LDP, starting with Brian Harrington in the early 80s and the others who followed, placed the Lagoon as the vital feature attracting knots and other shorebirds. It does provide a key habitat used by the birds to roost, and when freshly inundated with seawater from the ocean or fresh water from the inland watershed, the Lagoon also provides foraging. It serves many other resident species similarly, like the Chilean Flamingo.
But our preliminary data suggests the key feature attracting birds to LDP is the beachfront and its unusual productivity. We only suspected this during our previous fieldwork in 2019. This area of the Atlantic coast stands out from all other places because the tide range measures less than 2 feet. Delaware Bay, for example, has a 6-7 feet tide range, while Bahia Lomas in Tierra del Fuego has a 30 ft tidal range. We saw little tidal change during our ten days in LDP because rogue waves masked all. The absence of a significant tide may result from the two converging tidal currents offshore. The Brazilian current, a southern hemisphere analog of our Gulf Stream, runs against the Malvinas Current current from the southern ocean. They merge and form a westerly flowing continuation of the Brazilian current.
The Falkland ocean current meets the Brazilian ocean current just offshore of Lagoa do Piexe making the area offshore one of Brazil more productive fisheries
Not only does it influence the tide swing but productivity as well. The area of convergence is one of the most productive fisheries in Brazil. This productivity finds its way to the beach in the form of abundant clams, in some areas so thick you can watch waves of them rise up out of the swash of a retreating wave and then slowly dig back into the sand like the wave of standing and sitting football fans in a stadium. The productivity of the offshore waters led to a dramatic overharvest in the last decade, but the Brazilian government shut down the fishery in 2018. Jair Bolsonaro’s government stayed the ban in 2020, but the future remains uncertain. In the meantime, land-based trawl fishers have seen dramatic increases in their catch.
The telemetry data from the satellite transmitters opens up an entirely new view of what is vital to the birds, based on their location as they moved from day to day, in some cases hour to hour. This extraordinary intimacy with the knot provides an unprecedented opportunity to outline the area of importance and revisit the protection of this stopover in the future.
The issue is moot now because, through no fault of Brazilian conservation, the knot population has plummeted. In 1986 there were 65000 knots in the Tierra del Fuego wintering population, and all went through LDP. On one aerial flight in 1981, Brian Harrington saw 20,000 knots. Now we are lucky to see a few hundred in the same area. They are lucky birds, though, because the area remains as productive now as it was then. We hope our data will allow a reconsideration of what is important because maybe one day, the birds will come back. Who can say?
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Red knots photographed by Antonio Brum near the end of his stopover in Lagoa do Piexe Brazil
