Tag and Release: Tiny Tech Traces a Rare Bird's Path

As it turned out, three of the 47 red knots initially fitted with data-loggers on the Delaware Bay that year were recovered the following spring. It may sound like a puny recovery but given that this was the first attempt to release and recapture geolocator-equipped red knots from the Bay, each bird was celebrated as a success. Among them was Y0U, leaving the Delaware Bay at the end of May, 2009, flying to James Bay, Ontario, and then on to Southampton Island, Nunavut, Canada to (hopefully) nest. The southbound trip later that summer included some surprises, presumed to be the result of severe storms that year, including a “backward” northern flight from New Jersey to Cape Cod and a stop in the Lesser Antilles, before wintering in northern Brazil. Though Y0U's geolocator stopped recording prematurely on the Brazilian wintering grounds, it was re-captured on its northward migration through the Delaware Bay on May 14, 2010. In all, Niles and his team estimated that this particular shorebird had covered more than 17,000 kilometers—that’s 10,500 miles—over the course of the year.

Subsequent studies have told similar stories about the few red knots captured, fitted with geolocators, and re-captured throughout the hemisphere. Similar, but not exactly the same. As the same research team in a later study involving eight red knots recovered on Cape Cod put it: “To date, all studies of shorebirds using geolocators have changed our conceptions about their migration strategies and the sites they use. This study is no exception. It has revealed previously unknown stopover and wintering sites and a surprising lack of commonality between the eight focal birds in their migratory pathways.” While in theory geolocator-outfitted red knots serve as proxies for an entire subspecies, thus far each bird has had its own, surprising story to tell. While these surprises are valuable, they also indicate a need on the part of scientists for more research until stronger patterns emerge. As the study concludes: “it will be very difficult to reach firm conclusions about the [migration] strategies of the whole population without a lot more data.”

Data-loggers have added more than surprises, however, providing continuity and meaning to known migratory stopovers. Research sites that were once brief windows onto the phenology of shorebirds have become part of a more fluid, connected narrative. As Niles recently blogged from Brazil: “Even the most seasoned shorebird biologist is thrilled to follow one bird’s movement as it leaves its Arctic home and muscles thousands of miles to one or more stopover sites on its way to a comfortable winter. Our team sees these birds in many of these places, including Delaware Bay, Cape Cod, Georgia’s barrier islands, the Caribbean leeward islands, and San Antonio Oeste, Argentina, to name a few. Our experience at these stopovers puts flesh on the bones provided by the geolocators so we can knit together a journey, an experience, a life of a wild animal.” Which means that even the newest geolocation technology is being used for a classic kind of research. Today’s style of natural history would indeed have been recognizable to wildlife biologists in the Biological Survey a century ago—though the miniaturized Space Age tools and cutting-edge computer modeling may have astounded them.

Valuable and meaningful geolocator results notwithstanding, the intended and unintended consequences of these hybrid technologies and human/nonhuman collaborations remain to be seen. This is particularly apparent when it comes to conservation, the ostensible reason for all this research. Shorebird study at major stopovers like the Delaware Bay intensified greatly in the 1990s in response to a new, large-scale fishery on the East Coast: trawling and hand-harvesting Atlantic horseshoe crabs to be used as bait in the eel and conch fisheries. In addition, and subject to much press of late, has been the use of horseshoe crab blood in the biomedical industry. This industry has come under strict regulation in the United States, particularly in New Jersey, because eggs laid by spawning horseshoe crabs each spring are the primary, exquisitely-timed food source for shorebirds on their northward migration through the Bay. The proposed “threatened” status for rufa red knots under the Endangered Species Act is just the latest effort by environmental activists and many biologists to restrict the horseshoe crab harvests on behalf of the birds.

Geolocators have enriched the story, but have perhaps not yet added clarity. What will knowing the previously only guessed-at migratory paths of the few, recovered red knots mean for conservation, particularly as it relates to more precise understanding of populations, stopovers, and “critical habitat” for a threatened subspecies? For that matter, what if anything can these data-loggers add to debate over the livelihoods of horseshoe crab fishers and biotech workers, or to concerns about offshore energy sources on the Atlantic coast? As is so often the case in environmental controversy, questions about the quantity and quality of data, and their utility in public dialogue, defy easy answers.

In the meantime, the shorebird teams continue to piece together migration and population details in concert with their technology-equipped research subjects. The doubts about releasing, and hoping to re-find, red knots with data-loggers mirror the larger anxieties of watching flocks come and go from the Bay more generally.

I recall standing at Mispillion Harbor, Delaware, with members of the British Trust for Ornithology in late May 2009. It was around 7:30 in the evening, dusk, and we were watching a flock of shorebirds depart for their northern nesting grounds. An incredible phenomenon, but one tinged with uncertainty. This year's cohort of rufa red knots, presumably Y0U among them, have already departed the Bay and are nesting in the Canadian arctic. The question, as cyclical as migration itself, remains: what will we find next year?

Presented by

Kristoffer Whitney is a fellow in the Holtz Center for Science and Technology Studies at the University of Wisconsin-Madison.

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