On August 4, 2003, a master bander named Bjorn Carlsen placed a small aluminum leg band on a juvenile common tern at a nesting colony on Petit Manan Island, off the coast of Maine. The band bore the inscription "CALL 1-800-327-BAND USFWS WASHDC" and a unique nine-digit number.
On May 18, 2026 — nearly twenty-three years later — the same band was recovered on the same island, on what was almost certainly the same bird, by Carlsen's daughter Astrid, who has continued the long-running banding effort at the colony.
The bird's recovery makes it one of the oldest known common terns. Its life history, encoded in its band and recovered three times across two continents and twenty-three years, is now part of the Bird Banding Laboratory's database of over seventy-eight million banding records and four million recoveries.
The Bird Banding Laboratory was established in 1920 at what is now the US Geological Survey's Patuxent Wildlife Research Center in Laurel, Maryland. A parallel program in Canada, now coordinated through the Canadian Wildlife Service in Ottawa, was integrated with the US lab early in its history. The two programs together issue the bands worn by every legally banded bird in North America.
The work is done almost entirely by volunteers — currently about two thousand permitted banders across the United States and Canada. Each must pass a rigorous certification process, demonstrating proficiency in mist-netting, bird handling, species identification, age and sex determination, and banding technique. Master banders supervise sub-permittees and apprentices.
Becoming a master bander typically takes five to seven years of apprenticeship. The investment is substantial and the work is largely uncompensated.
What the program produces is the foundational dataset for North American bird migration biology. Almost everything we know about where individual birds go, how long they live, and how their populations connect across the continent comes, directly or indirectly, from band recoveries.
The longevity records published periodically by the lab read like an ornithological gazetteer of extreme persistence. A Laysan albatross banded as a breeding adult in 1956 was still nesting at Midway Atoll in 2024 — making her at least seventy-three years old, and the oldest known wild bird in the world. A common tern banded in 1969 in Massachusetts was recovered alive in 2005 in Connecticut, having presumably migrated to South America and back thirty-six times. A bald eagle banded in Maine in 1977 was recovered dead in 2014, having lived thirty-seven years.
These individuals are exceptional. Most banded birds die in their first year. But the records of the long-lived individuals tell us what is biologically possible for these species, which is itself useful information.
What the band recovery data have shown about migration, in aggregate, has revised much of what was once assumed about avian movement.
The discovery in the 1930s and 1940s that small songbirds — warblers, vireos, thrushes — were making twice-yearly nonstop flights across the Gulf of Mexico, often in single overnight crossings, came from banding recoveries. Before the data, the prevailing hypothesis was that these birds were island-hopping along the Caribbean rim. The bands, recovered along the Gulf coast on mornings after weather fronts, showed that they were not.
The discovery that Arctic terns were the longest-distance migrants in the animal kingdom came from banding data, eventually supplemented by satellite tracking. The terns' circuits — from Arctic breeding grounds to Antarctic waters and back, approximately seventy thousand kilometres per year — were established by band recoveries decades before the satellite work confirmed them.
The recognition that many songbird populations have specific, geographically constrained wintering grounds came from banding. The Cape May warbler, for instance, was shown through band recoveries to winter almost exclusively in the Greater Antilles, despite breeding across a broad swath of boreal Canada. The wintering bottleneck has implications for conservation that no breeding-grounds survey would have detected.
More recently, banding data combined with stable isotope analysis have produced detailed connectivity maps for many species — showing not just where a species winters, but which specific breeding populations winter where. The work has revealed that many species exhibit strong migratory connectivity, with specific breeding populations using specific wintering grounds, while others mix freely.
Astrid Carlsen, continuing her father's work at Petit Manan, is part of a much larger ongoing colony-banding effort along the Maine coast coordinated through Project Puffin and several allied seabird recovery efforts. Together these programs have banded approximately one hundred and twenty thousand seabirds since the late 1970s. The recovery rate is low — perhaps three percent — but the recoveries that come back have transformed understanding of seabird life history, dispersal, and migration in the Northwest Atlantic.
The work has costs. Mist-netting and handling birds, even with the best protocols, occasionally results in injury or death. The lab tracks these mortality rates carefully. They are low — typically under half a percent — but they are not zero, and the program requires its banders to weigh the scientific value of their work against the welfare of the individual birds.
Most banders accept this tradeoff. Some do not, and there is a small but vocal community within ornithology that argues banding should be replaced where possible with non-invasive techniques. The argument has merit. Camera-based identification, environmental DNA, and acoustic monitoring have begun to substitute for banding in some contexts.
But the band on a bird's leg remains the gold standard for individual identification across the bird's lifetime. Until something replaces it that works equally well across all species and contexts, the bands will continue.
The lab estimates that approximately twelve thousand banded birds are reported by the public each year. Most reports come from hunters who recover banded waterfowl, from windowstrike collisions, from feral cat predation events, or from observers who manage to read a band number through a spotting scope on a foraging shorebird.
Each of these reports adds a data point. The hunter in Arkansas who calls in the band number on a mallard he shot. The homeowner in Tucson who reports a band on a dead American kestrel under her window. The birder at Bombay Hook National Wildlife Refuge who reads a coded leg flag on a red knot through a Swarovski scope and emails the record to the lab.
These reports are aggregated. They go into the database. They are queried by researchers preparing population assessments, conservation status reviews, and migration studies.
Astrid Carlsen recorded the recovery of her father's tern band in the colony's notebook, photographed the band, and called the recovery in to the lab. The bird, retrieved briefly from the colony, was alive, in good condition, and incubating a clutch of two eggs.
It was released. It returned to its nest. As of the date of this writing, it is still on the colony, presumably tending to chicks now hatched.
Bjorn Carlsen, who placed the band on the bird as a juvenile in 2003, died in February 2024. He did not live to learn that the bird returned. Astrid, who is forty-one, will probably band birds at the same colony for another thirty years, give or take her own longevity.
The work, like the migration of the birds it tracks, continues across generations.
