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The next day, Sunday, April 2nd, we awoke to a sky of turbulent clouds, part of the wide spiral of clouds created by the cyclone more than 500 miles offshore. The winds blew cool from the northwest at about 20 knots. We needed to spend the morning preparing charges for the cannons, test-firing the nets, and gearing up for catching later in the day. We brought our 3 cannon small mesh net, measuring 23 by 10 paces but using Viriginia’s cannons. They were machined 40 years ago by Virginia Petry’s Ph.D. supervisor, who copied the design brought to him through a collaboration with Brian Harrington, formerly of Manomet Bird Observatory. Unlike our own cannons copied from Clive Minton’s design, where the projectile slides into the cannon and is fired by a removable cartridge we load with black powder and an igniter, Virginia’s cannon projectile fitted over the canon and was fired by a charge nestle in a cavity within in the solid metal cannon We used the cannons in our last trip but also brought one of ours which are more powerful gram for gram of powder. We test-fired the three cannons at 23 grams powering our three cannon’s small mesh net. Video of the net pulled out by the projectiles proved the power sufficient.
While we stayed at the ASA farm, we were able to test our equipment including text-firing our nets. Photo by Stephanie Feigin
We used igniters purchased from a fireworks store, but the wires were too short and required a bridge wire that proved a weak spot when the rogue waves washed the bases of the cannons. The wave would leave the powder and igniter dry because the cavity holding both sat high at the mouth of the cannon. The wire connection would always be short, however. Ultimately we had to waterproof the joint, but like a bad ankle, it always gave out at the wrong time.
Mateo and Antonio loading cannons while trapping Lagoa do Piexe.
Our second net was from Viriginia’s kit, roughly 16 paces by 8, or about half the area of the small mesh net. It was much lighter, however, making it more valuable than the small mesh net for firing into the wind, the wider mesh making it less affected by the wind.
We had a third net, a box net named for the metal box containing it. Clive and I created the box net as an alternative trapping method for use on the Atlantic Coast of NJ and in the gulf coast of Texas. Only small flocks of shorebirds string out along long shorelines in those places, so fast setting is critical. The box bet contains two small cannons with smaller-than-normal projectiles and a small net measuring eight by ten paces. To use the box net, we would charge the projectiles with a 9-gram load of black powder in s a small hole drilled into the projectile’s head. We would load the cannons, furl the net into the box, and then search for birds. Upon finding a small group, we would jump out of the truck, dig a small hole, set the net’s corner stakes, run a wire to the firing box, and try to move the birds into the catch area. If all goes right, which is rare.
Julia Finger, Antonio Brum. Mateus Luís Haas and Larry Niles talk about where to set the box net. The net is inside the metal box held together by two small black powder cannons.
At the same time, Stephanie and Antonio charged the satellite trackers to ensure the tiny battery had a full charge when placed on the birds. These $2000 transmitters demand a lot of care to ensure they are ready in the field. The tiny battery must be fully charged before deployment, which is difficult on cloudy days. To attach the devices to the bird, Stephanie uses techniques developed by Pam Loring of the USFWS, suturing the device to the knot’s back. We will also take a blood sample to determine gender and a covert feather to assess ratios of carbon and nitrogen isotopes characteristic of where the feather was grown, usually the wintering area. Finally, Edison Luiz Durigon of the University of Sao Paulo and his team will collect swabs of the bird’s mouth and cloaca to test for Avian influenza.
A sunbird transmitter on a red knot. The tiny solar panel powers the satellite transmitter longer than its attachment to the bird, which depends on the method.
We rode the beach of Lagoa do Piexe that night and found over 200 knots roosting in the dry inlet of Lagoa do Piexe. The birds joined a flock of about 5000 semipalmated sandpipers, white-rumped sandpipers, a few hundred black-necked stilt, and American oystercatchers. The sun set behind them, so we saw the birds silhouetted with the golden sunset.
The inlet was recently overwashed because offshore, an unnamed low-pressure cell chugged away at about 50 mph. It generated random but powerful waves that washed through the dry channels of the inlet. The productivity of the LDP depends on these occasional rushes of salt water through the inlet. It mixes with the Lagoon’s fresh water from a small watershed that includes the LDP peninsula and a small portion of the mainland. The Lagoon nurtures a large population of small shrimp harvested with nets by local fishers. It is staple in all the restaurants in the area.
The sun sets on a remnant of wet lagoon where red knots and other North American migrants mix with more South American migrants like Chilean Flamingoes.
A low pressure system off the coast of Lagoa do Piexe blew gusts of over 100 mph and whipped up waves that washed ashore at random intervals. These rouge waves bedeviled our nets until the last day of field work.
But the inlet has been primarily dry over the last year, and much of the lagoon waterline has shrunk to a historically small area. On our way out to the beach, we crossed two bridges over dry waterways that were both flooded the last time we visited in 2019. The shrimp fishery has died along with the livelihoods of many small commercial fishers. Drought plagues this whole state. It has already punished most farmers of the state, who primarily produce corn, soy, and wheat for the international markets. Worse still, the prolonged drought could be the future because of climatic changes in moisture patterns that bring rain throughout Brazil. Brazilian scientists postulate the increased logging of the Amazon rainforest has disrupted atmospheric moisture movement patterns leaving much of southern Brazil in drought.
The flock we watched before a golden sunset promised a good chance of catching birds tomorrow.
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The dry bed of the Lagoa do Piexe Lagoon seen from high dunes of the Park
