On December 30, 2017, at the age of 78, the Canadian sculptor, inventor, naturalist, and ultralight pilot William “Bill” Lishman died at his home in Port Perry, Ontario, less than two weeks after a diagnosis of leukemia. Lishman — known in his lifetime as “Father Goose,” a label coined by the Canadian and U.S. press that covered his work across the 1990s and 2000s, and the first person in recorded history to lead a flock of birds across a continental distance by flying ahead of them in an aircraft — had spent the preceding three decades of his life solving a problem that the broader behavioral-ecology community had, by the early 1990s, started to recognize was potentially insoluble. The problem was not the rescue of an endangered species from genetic bottleneck. The problem was the rescue of an endangered species’ cultural knowledge — the migratory route, the layover-stop sequencing, the breeding-and-wintering site fidelity, the seasonal timing — once the population had been reduced to a single surviving migratory tradition that, by the laws of evolutionary risk, could not be safely left as the species’ only inheritance.
In 1941, the surviving global population of the Whooping Crane (Grus americana) — North America’s tallest bird, standing approximately five feet tall in adult plumage, with a wingspan of seven and a half feet and a piercing whooping call that carries multiple miles across open prairie — reached its all-time minimum of 21 birds in the wild. All 21 birds belonged to a single migratory population that summered in the boreal wetlands of what is now Wood Buffalo National Park, straddling the Northwest Territories and Alberta in northern Canada, and wintered approximately 2,500 miles south at the Aransas National Wildlife Refuge on the Texas Gulf Coast. This was the only remaining migratory tradition the species possessed. A second, non-migratory population that had historically existed in southwestern Louisiana had been extirpated by 1950. Multiple smaller historical populations across the central and eastern United States had been eliminated through the nineteenth and early twentieth centuries by habitat conversion, hunting, and the broader cascade of agricultural-frontier displacement that had reduced the species from an estimated pre-Columbian population of approximately 10,000 birds to the single Aransas-Wood Buffalo Population (AWBP) carrying the only migratory route the species could still execute. The historical-extirpation pattern is the same pattern that eliminated the passenger pigeon, that reduced the wild turkey to remnant populations, and that reduced the broader continental avifauna across roughly the same window that produced the homing-pigeon and military-bird training infrastructure of the early twentieth century as a separate human-bird-training tradition operating in parallel.
The conservation problem the U.S. Fish and Wildlife Service, the Canadian Wildlife Service, the International Crane Foundation (founded in 1973 in Baraboo, Wisconsin by George Archibald and Ronald Sauey), and the broader continental conservation infrastructure faced after the species’ protected status was formally established was structurally different from a conventional captive-breeding-and-release recovery program. The Whooping Crane is, in behavioral terms, a culturally transmitted migrator. Adult cranes do not possess a hardwired genetic map of the migration route. Juvenile cranes learn the migration route by following adult cranes — typically their parents — across the first southbound and northbound migration of their lives, after which the route is fixed in the individual crane’s spatial memory for the duration of its 22-to-30-year lifespan, encoded in the crane’s species-specific perceptual umwelt as a sequence of landmark associations, magnetic-field-orientation cues, and visual-flyway geometry the bird will follow without further teaching. The route, the layover stops, the wintering grounds, the springtime return — all of it is learned, transmitted, and culturally inherited from one generation to the next. The 1941 bottleneck did not just reduce the genetic diversity of the species. It reduced the cultural diversity of migration to a single inherited route. If anything happened to the AWBP flock — a hurricane on the Texas coast, an oil spill in the Gulf, a disease outbreak at Wood Buffalo, a catastrophic collision event on the central flyway — the entire species could lose its only remaining migratory tradition in a single generation, in a way that no amount of post-hoc captive breeding could reconstruct without rebuilding the underlying cognitive infrastructure that supports long-distance migration in the avian brain.
The need for a second migratory population
The structural logic of the Whooping Crane Recovery Plan — first formally articulated in the 1980s and progressively refined through the 1990s and 2000s — was that the species needed at least one additional, genetically connected, ecologically separated migratory population to provide redundancy against catastrophic loss of the AWBP. The plan’s specific recovery criteria, codified in the 2007 International Recovery Plan jointly issued by the U.S. Fish and Wildlife Service and the Canadian Wildlife Service, required each reintroduced population to reach 100 individuals and 25 breeding pairs before the species could be downlisted from endangered to threatened status. The first attempt at a second migratory population — the Rocky Mountain Whooping Crane experiment of the 1970s and 1980s, which used Sandhill Crane (Antigone canadensis) foster parents at Grays Lake National Wildlife Refuge in Idaho to raise Whooping Crane chicks alongside sandhill juveniles — produced juvenile Whooping Cranes that successfully learned migration from their sandhill foster parents but subsequently failed to recognize their own conspecifics as breeding partners. The Grays Lake program was terminated in 1989. The species’ cultural-transmission problem had been demonstrated to be more complex than the original recovery planners had assumed.
What conservation biologists by the mid-1990s had concluded was that the only viable path to a second migratory population was to build the migration route from scratch — to take captive-reared Whooping Crane chicks, prevent them from imprinting on humans, train them to follow a teaching surrogate that they would associate with their species, and physically lead them across the route they would subsequently inherit as adult breeders teaching the next generation. The teaching surrogate that the planners ultimately settled on was an aircraft. The aircraft pilot was Bill Lishman. The cognitive infrastructure required for the captive-reared juvenile cranes to associate the aircraft with parental authority — and to follow the aircraft as if it were an adult crane — was effectively a cross-species behavioral imitation analogous to the broader mirror-neuron and social-learning systems documented across the animal kingdom, operating through the visual imprinting that the costume-rearing protocol was designed to channel.
Lishman’s 1988 origin and the Operation Migration trajectory
Lishman’s path to the Whooping Crane Eastern Migratory Population began in 1988, when he became the first person to lead a flock of imprinted Canada geese in flight using an ultralight aircraft over Purple Hill in southern Ontario. The geese had been hand-reared by Lishman from hatching, had imprinted on Lishman as their parental figure, and would follow Lishman’s ultralight in formation as if it were an adult goose leading the flock. The technique had been suggested to Lishman by a local naturalist who had observed geese following a boat across a Lake Scugog inlet; Lishman, an experienced ultralight pilot, recognized that the same imprinting-and-following dynamic could potentially work in flight. The 1988 demonstration flight was followed by additional refinement work across the late 1980s and early 1990s. In 1993, Lishman and his collaborator Joe Duff — a commercial photographer from Toronto who had become Lishman’s primary ultralight collaborator after meeting him at a local airfield — led 18 captive-reared Canada geese in formation from Purple Hill in Ontario across Lake Ontario to the Environmental Studies Division of Airlie Center in Warrenton, Virginia, completing the first aircraft-led continental bird migration in recorded history. Sixteen of the 18 geese survived the southbound winter; thirteen returned independently to Ontario the following spring, demonstrating that the geese had internalized the route as adult migrators capable of independent navigation.
The 1993 Canada goose migration attracted coverage from ABC News 20/20 and the broader American television-news cycle. Columbia Pictures purchased the story rights, and in 1996 released “Fly Away Home,” directed by Carroll Ballard and starring Jeff Daniels as a sculptor-aviator character loosely based on Lishman and Anna Paquin as his daughter, dramatizing the goose-migration project for a broad audience. Lishman’s company In The Sky Productions provided the story rights, the wildlife permits, the geese, the flying, and a portion of the cinematography. The film grossed approximately $32 million against a $35 million production budget, established the imprinted-bird-aircraft-migration technique in the popular cultural imagination, and provided the credibility and the operational reputation that allowed Lishman and Duff to formally establish Operation Migration as a registered Canadian nonprofit in 1994 with the explicit mission of applying the technique to endangered species reintroduction.
The transition from Canada geese to Whooping Cranes required substantially more methodological complexity. Canada geese imprint readily on human handlers. Whooping Cranes, if they imprint on humans, will subsequently fail to recognize their own conspecifics as breeding partners — the same imprinting-failure problem that had ended the Grays Lake sandhill-foster program. The behavioral plasticity that makes the imprinting failure possible is the same avian cognitive flexibility documented across multiple research streams, and is structurally why the species’ cultural-transmission system both works and breaks in the specific ways it does. Operation Migration’s solution, developed across the late 1990s in collaboration with the Patuxent Wildlife Research Center in Maryland and the International Crane Foundation, was costume-rearing: every human interaction with a captive Whooping Crane chick from hatching through juvenile flight training would be conducted by handlers wearing a full-body white sheet-like costume with a black-tipped crane-puppet head, with no exposed human anatomy visible to the chick, and with all handler vocalizations replaced by playback of recorded adult Whooping Crane calls. Lishman in 1995 hand-reared eight Sandhill Cranes in the costume protocol as the proof-of-concept population. The first captive-reared Whooping Crane cohort followed in subsequent years. The pilot of the lead ultralight, when leading a juvenile crane flight, wore the same crane costume in the cockpit. The intensive imprinting protocol — six months of daily costume contact across hatching, ground training, and flight training — was structurally similar in operational discipline to the extended training protocols developed across the broader history of human-animal working partnerships, though differently oriented in that the Whooping Crane chicks were being deliberately prevented from forming the human attachment that working-animal training has historically depended on.
The route Lishman built: Necedah to St. Marks
In 2000, Lishman conducted the major path-finding flight that established the Eastern Migratory Population (EMP) route — the approximately 1,200-mile southbound corridor that Operation Migration would subsequently use as the operational migration path. The northern terminus was the Necedah National Wildlife Refuge in Juneau County, Wisconsin, selected for its extensive wetland habitat, its remote location away from population centers, and its geographic separation from the AWBP’s central-flyway corridor. The southern terminus was the St. Marks National Wildlife Refuge on the Florida Panhandle Gulf Coast, with the Chassahowitzka National Wildlife Refuge on Florida’s west coast as a secondary wintering site. The complete route incorporated 23 layover stops at private airstrips, refuges, and farms across Wisconsin, Illinois, Indiana, Kentucky, Tennessee, Georgia, Alabama, and Florida, with each layover scheduled to provide rest, feeding opportunity, and weather buffering for the juvenile crane flight. The average migration covered 25 to 100 miles per day depending on weather, with the complete southbound migration requiring approximately 90 days of cumulative flight time across multi-day weather holds. Multi-day continuous flight of the kind some migratory bird species perform without ground rest — supported by unihemispheric sleep patterns documented across multiple long-distance avian migrators — was not a feature of the ultralight-led juvenile flights, which were structured as staged morning departures with afternoon ground rests at the layover network.
The first operational Whooping Crane migration departed Necedah on October 17, 2001, carrying seven juvenile cranes following two Cosmos Phase II ultralight aircraft piloted by Lishman, Duff, and the broader Operation Migration team. The migration reached Chassahowitzka National Wildlife Refuge in early December 2001, after 49 days of staged flight, with the seven juvenile cranes successfully completing their first southbound migration. The flight became, in the immediate aftermath of the September 11 terrorist attacks, the operationally most visible uplifting wildlife-conservation story in the American media cycle. John Christian of the U.S. Fish and Wildlife Service publicly described the project as “the wildlife equivalent of putting a man on the moon” — a quote that subsequently became the operational reputation Operation Migration carried for the next fifteen years.
The 2001-2015 operational era
Across the 2001 to 2015 operational period — fifteen migration seasons, with new cohorts of approximately seven to twenty juvenile cranes departing Necedah each fall and arriving in Florida by mid-winter — Operation Migration pilots and ground crew led 186 Whooping Cranes across cumulative migration distance of 17,457 miles. The juvenile cranes, after completing their first led migration, subsequently returned independently northward to Wisconsin each spring and continued the migration tradition into adulthood without further human guidance, as the cultural-transmission protocols underlying the project had predicted. The northbound return migration is, in operational terms, structurally more demanding than the human-led southbound flight — the cranes execute the route without aircraft assistance, navigating across approximately 1,200 miles in coordinated multi-bird formation flights that depend on the same neural-synchronization mechanisms documented across flocking birds. By 2006, the first wild-hatched chick of the EMP — a juvenile produced by two adult cranes that had themselves been led south by ultralight in earlier cohorts — fledged at Necedah, establishing that the population was reproductively viable. By 2010, the EMP had grown to approximately 100 adult cranes, achieving the 100-individual recovery threshold that the 2007 International Recovery Plan had specified, though the 25-breeding-pair threshold remained out of reach.
The reproductive bottleneck at Necedah became the dominant operational challenge for the project across the 2006-2015 window. The wetland habitat at Necedah, which had been selected for its habitat quality and remoteness, turned out to host an exceptionally aggressive population of black flies (genus Simulium) whose adult swarms — emerging in May and June, precisely during the Whooping Crane incubation period — drove nesting cranes off their eggs in repeated documented abandonment events. The black fly population had been an underappreciated variable in the original site selection. Across the 2006-2012 nesting seasons, repeated nest-abandonment events produced unsustainably low reproductive success, with hatchling production lagging well below the rate required to offset adult mortality. The project responded with a combination of egg-pulling-and-incubation protocols, supplemental captive rearing, and experimental nest-treatment interventions, but the underlying problem — that the EMP’s primary breeding refuge was, in spring, a black-fly-saturated habitat — remained a structural constraint on natural reproduction.
The 2007 International Recovery Plan’s recovery criteria — 100 individuals and 25 breeding pairs — drove the methodology evolution that subsequently dominated Operation Migration’s late-period operations. The original costume-rearing-and-ultralight-led method, while operationally successful at producing migrating juveniles, was producing cranes that, even when they survived to breeding age, exhibited reduced parental-rearing competence and reduced reproductive success compared to the parent-reared AWBP cranes. The hypothesis that emerged from the late-2000s evaluation was that costume-reared cranes were missing critical parent-bird behavioral inheritance — the small-scale interactions between adult and chick that are not adequately replicated by costume-clad human handlers, however carefully the costuming protocol is maintained.
The method transition: Ultralight-Led to Direct Autumn Release to Parent-Reared
Across the early 2010s, the Whooping Crane Eastern Partnership (WCEP) — the multi-agency consortium overseeing the EMP, which includes the U.S. Fish and Wildlife Service, the Wisconsin Department of Natural Resources, the International Crane Foundation, the Natural Resources Foundation of Wisconsin, the Patuxent Wildlife Research Center (which closed its Whooping Crane breeding operations in 2018), the Calgary Zoo, the Audubon Nature Institute, and Operation Migration — progressively shifted the project’s primary release methodology away from costume-reared, ultralight-led migration toward two alternative methods. Direct Autumn Release (DAR) involved releasing costume-reared juvenile cranes at Necedah in mid-autumn, near established adult cranes, with the juveniles expected to associate with the adults and follow them south on the established migration route without human aircraft involvement. Parent-Reared (PR) involved rearing captive Whooping Crane chicks under genuine adult Whooping Crane parents in the captive-breeding facilities, then releasing the parent-reared juveniles at Necedah in autumn, with the same expectation that they would associate with established adults and learn the route through wild observation.
The methodology transition was driven by both the cost structure of ultralight operations — Operation Migration’s annual operating budget across the late 2000s and early 2010s ran approximately $1.5 million in direct costs — and by the accumulating evidence that parent-reared cranes outperformed costume-reared cranes on multiple long-term metrics, particularly reproductive success at adulthood. The final ultralight-led migration departed Necedah in 2015, carrying the last cohort of costume-reared juvenile cranes south by aircraft. The U.S. Fish and Wildlife Service formally directed Operation Migration to wind down its ultralight operations after the 2015 season, and Operation Migration resigned from the Whooping Crane Eastern Partnership on August 17, 2018, citing operational and financial constraints. The organization formally dissolved at the end of 2018, twenty-four years after Lishman and Duff had founded it. Lishman, who had died in December 2017, did not live to see the dissolution of the organization he had built.
Cultural drift and the route the cranes have rebuilt
The EMP cranes that Operation Migration led south across the 2001-2015 window did not, across the subsequent decade, continue to use the original Necedah-to-St. Marks route the program had so carefully constructed. Across the 2010s and 2020s, the EMP has progressively exhibited short-stopping behavior — adult cranes that, instead of continuing south to the Florida Gulf Coast wintering grounds Operation Migration had originally taught, terminate their southbound migration in central Alabama or southern Indiana and overwinter in agricultural fields and wetlands at substantially higher latitudes than the original Florida wintering sites. As of the November 2025 status update issued by the International Crane Foundation, the EMP wintering distribution was: approximately 46 birds in Wisconsin, 6 in Indiana, 8 in Illinois, and 2 in Kentucky during the late-fall pre-migration tally, with the remaining birds distributed across Alabama, Tennessee, and the broader southern flyway. Florida wintering — the original program objective — has become a minority outcome. The cranes have modified the route in subsequent generations.
The short-stopping behavior is structurally consistent with broader patterns observed in bird migration ecology under contemporary climate change — warming winter temperatures at intermediate latitudes have reduced the thermoregulatory and feeding cost of overwintering at higher latitudes, and migratory birds across multiple species have responded by reducing migration distance. The Whooping Crane case is interpretively interesting because it demonstrates that culturally transmitted migration routes are not static cultural inheritances but are subject to modification by subsequent generations responding to environmental change. The cranes inherited a route from their human teachers. The cranes have, in the time since, edited the route. The cultural transmission is bidirectional — Operation Migration taught the cranes the original southbound corridor, and the cranes have taught their offspring a progressively shorter version of it, with the route modifications propagating through the population by the same collective-decision-making mechanisms documented in flocking and herding species.
The current 2025-2026 EMP status
As of the most recent November 2025 International Crane Foundation update, the Eastern Migratory Population consists of 72 individual cranes (41 females, 28 males, 3 unknown sex), of which 16 are wild-hatched (cranes produced by EMP adult pairs nesting in Wisconsin or adjacent states without captive-rearing intervention) and the remainder are captive-reared releases. The population growth has been substantially slower than the original recovery plan projected. The 2024 Thompson et al. paper “Whooping Crane Chick Survival in the Reintroduced Eastern Migratory Population,” published in Ecology and Evolution in April 2025, documented that EMP recruitment rates — wild-hatched chicks surviving to reproductive age — remain below mortality rates for the adult population, meaning that the population requires continued captive-rearing supplementation to maintain numbers. The 22-breeding-pair count remains below the 25-pair recovery threshold.
The three primary mortality causes for EMP cranes, in order of incidence, are: predation (approximately 54.1 percent of documented mortalities, primarily by coyotes, bobcats, and great horned owls), impact trauma (approximately 18.8 percent, primarily from power line collisions), and poaching (approximately 10.5 percent, from illegal shooting events typically targeting cranes mistaken for legal game species). The mortality cause distribution in the EMP differs notably from the parallel Louisiana Non-Migratory Population (LNMP) reintroduction that began in 2011 — the LNMP exhibits a different mortality profile with impact trauma at 37.1 percent and poaching at 22.6 percent, reflecting the different habitat and land-use context of the Louisiana wintering grounds versus the Wisconsin breeding habitat. The continued poaching mortality across both populations — despite the federal Endangered Species Act protections that have applied to the Whooping Crane since 1967 — has driven the development of conservation enforcement infrastructure parallel in operational logic to the field-deployed anti-poaching dog programs operating across African endangered-species range, though differently structured to the specific land-use context of the central and southern United States.
In early 2025, a wild Whooping Crane known by the field-research-team designation as “Ducky” died of Highly Pathogenic Avian Influenza (HPAI), becoming the first confirmed Whooping Crane mortality from the H5N1 avian influenza outbreak that has, across 2022-2025, caused mass mortality events across North American waterbird populations. The Ducky case raised significant concern within the broader avian-conservation community because the EMP population is small enough that even single-digit additional HPAI mortalities could materially compromise population recovery trajectories. The current monitoring posture across WCEP partners includes active HPAI surveillance, with all dead-bird recoveries tested for the H5N1 virus.
The 2025 nesting season produced one wild-hatched chick that fledged — W1-25 — the seventh successful wild-hatched fledgling produced by the EMP since the program’s inception. The September 2025 ICF update confirmed W1-25’s successful first flight and tracked the juvenile’s behavioral integration with adult EMP pairs in Wisconsin. The chick designation reflects the project’s standardized identification system: W (wild-hatched) plus sequential year-designation, with the 25 indicating 2025 hatching year.
The cultural-transmission frame and what Operation Migration actually demonstrated
The structural significance of the Operation Migration project for the broader study of animal culture and behavioral inheritance is the explicit operational demonstration that a culturally transmitted behavior can be reconstructed from outside the species, by a species capable of designing the transmission protocol, and can subsequently be modified by the receiving population in ways the original transmission protocol did not anticipate. The Whooping Crane did not have a migration to learn from in 2001. The AWBP’s central-flyway route was the only surviving inheritance, and the EMP was structurally separated from that population. The migration that the EMP cranes now execute — short-stopped in Alabama or Indiana rather than continued to Florida, with route modifications that have accumulated across multiple subsequent generations of wild-hatched adults — is a cultural product that began as a Lishman-and-Duff ultralight reconstruction and has, in twenty-five years of subsequent transmission, become the cranes’ own.
The cultural-inheritance comparison to the other documented animal culture systems — sweet-potato washing in Japanese macaques, song dialects in Bay Area sparrow populations, tool traditions in the Taï Forest chimpanzee community, signature whistles transmitted through bottlenose dolphin matrilines — is structurally interesting because the Operation Migration case is the only one in which the cultural transmission was explicitly designed and operated by an external species (humans), with the express purpose of substituting for a lost intra-species transmission lineage. The macaques, sparrows, chimpanzees, and dolphins all transmit their cultural inheritances within their own species. The EMP Whooping Cranes are now transmitting a culture that humans had to introduce because the cranes’ own transmission lineage had been broken at the 1941 bottleneck.
The implication for the broader theory of cultural transmission in non-human species is that cultural knowledge is, in operational terms, ecological infrastructure — equivalent in conservation significance to genetic diversity, habitat availability, and demographic viability. A species can be genetically intact, demographically viable, and habitat-secure and still be ecologically broken if its cultural transmission lineage has been disrupted. The Whooping Crane in 1941 was genetically reduced but not yet at irreversible inbreeding-collapse risk. Its habitat had been heavily reduced but was still operationally available at Aransas and Wood Buffalo. Its cultural-inheritance lineage, however — the migratory route, the breeding-site fidelity, the seasonal-timing transmission — had been reduced to a single thread, and the conservation work of the subsequent eighty years has been substantially focused on rebuilding cultural redundancy rather than just genetic and demographic numbers.
What the cranes show about how cultural knowledge is rebuilt
The 186 Whooping Cranes that Operation Migration led across 17,457 miles of cumulative ultralight migration between October 2001 and the final flight in 2015 did not, individually, represent a recovered species. They represented the operational instantiation of a cultural-transmission protocol that the conservation infrastructure had to design from biological first principles, test in real-world flight conditions, refine across multiple methodological generations, and ultimately retire when the data demonstrated that parent-reared and direct-autumn-release alternatives produced better long-term reproductive outcomes. Lishman’s contribution — the original 1988 goose flight, the 1993 first continental migration, the path-finding for the Wisconsin-to-Florida route, the costume-rearing-and-ultralight protocol that operated the project for fifteen years — was, in its essential structure, the construction of a substitute parental tradition that the species had lost and could not rebuild on its own. The Eastern Migratory Population’s current 72 cranes, scattered between Wisconsin breeding grounds and the Alabama-Indiana wintering grounds the cranes have themselves chosen, are the inheritors of that substitute tradition, and they are the only Whooping Cranes alive that know any migration route other than the AWBP’s central-flyway corridor.
The cranes that hatched in 2025, including W1-25 — the most recent wild-fledged EMP juvenile — will learn the migration route the same way Whooping Crane juveniles have always learned migration: by following the adults. The adults the 2025 juveniles will follow learned the route from earlier adults who learned it from earlier adults who learned it, ultimately, from the costume-rearing-and-ultralight protocol that Operation Migration operated through the early 2000s. The cultural lineage that humans constructed in 2001 has now been transmitted, with progressive modification, through approximately six successive crane generations. The route the 2025 juveniles will fly is no longer Lishman’s route. It is the route the cranes have, between them, taught each other across the intervening quarter century.
The five-foot-tall, seven-and-a-half-foot-wingspan, twenty-two-to-thirty-year-lifespan, whooping-call-carrying-across-the-prairie Whooping Crane is, on the available evidence from the AWBP at Aransas and the EMP across the eastern flyway, capable of executing a culturally transmitted long-distance migratory tradition across multiple generations with high fidelity to the inherited route — a behavioral capacity supported by an avian brain architecture that, per the comparative-cortices literature on bird and mammal cognition, achieves cognitive complexity through a pallial organization fundamentally different from the layered mammalian neocortex., with adaptive modification when environmental conditions favor short-stopping, with the same individual-recognition and pair-bond fidelity that characterizes the broader crane-family behavioral repertoire, and with no apparent need for further human teaching once the cultural lineage has been established. The 1941 bottleneck destroyed everything except the AWBP migration. The 2001-2015 ultralight project rebuilt a second migration. The cranes, between themselves, have done everything since. The behavior is cultural. The transmission is reliable. The original teachers — Bill Lishman, who died in 2017, and the Operation Migration ground crew that dissolved in 2018 — are no longer needed. The cranes are the carriers of the tradition now, and they will be the only carriers of it for as long as the species continues to exist.
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