The dusky seaside sparrow was a small songbird once abundant within a small range in Southern Florida. The birds mainly lived in the marshes of Merritt Island and could be distinguished from other seaside sparrows by their distinctive black-and-white plumage and unique song. Like all highly localized species, however, duskies proved extremely vulnerable to any kinds of unexpected changes. And, unfortunately, both Merritt Island and the birds were subject to an onslaught of change in the second half of the twentieth century.
This is an extinction story in two acts.
Act One: Mosquitos, NASA, and the remaking of an island
When the Soviet Union launched Sputnik into space in 1957, the U.S. quickly began scouting land for their inaugural space center. Merritt Island was ideally placed for a rocket launch site: coastal, temperate, accessible, relatively underdeveloped, and with close proximity to the equator.[1] At first, it might seem like the connection between the building of the Kennedy Space Center in the 1960s in the dusky’s critical habitat and the subspecies’ subsequent extinction demands little explanation. After all, the space industry has never been a friend to the environment: rocket launches routinely generate ecological devastation through their complex earthly and outer-space externalities.[2] However, when Apollo 11 lifted off from Merritt Island on July 11, 1969, the dusky had already been all but decimated. In fact, the bird was largely a collateral victim of a more mundane, on-the-ground battle between NASA and mosquitoes.
[Image description: A satellite image showing a slender coastal island just off the coast of the ocean.]
Florida has long figured mosquitoes as antagonists to economic growth. The state’s tropical climate is as attractive to vacationers as it is to insects—and the two don’t tend to mix well. At one of the first meetings of the Florida Anti-Mosquito Association in 1922, one attendee put the perceived battle between humans and mosquitoes bluntly: this was a war “which will in all probability end in the extermination of one side or the other.”[3] Such problems were particularly acute on Merritt Island. As a result of the sheer number of mosquitoes, the island had partially staved off large-scale settlement prior to the Space Race.[4] And indeed, when NASA began buying up parts of the land in 1960, they found the resident mosquitoes crippling, with upwards of 500 landings of mosquitoes per minute draining the blood and the spirit of workers and residents.[5]
In waging their self-described “war” against mosquitoes, NASA joined with local government and ecologists to reduce the insects’ presence on the island. Initial assaults involved systematic spraying of DDT and other toxic chemicals throughout the island’s marshlands.[6] Though this initially worked well throughout the 1960s, the mosquitos eventually became resistant to chemical assault, and more permanent control methods were sought. Most notably, “mosquito impoundments” were rolled out across the island, where large swaths of marshland were flooded and diked to remove the moist ground needed for saltmarsh mosquito females to lay their eggs. These impoundments were implemented on an almost unfathomable scale: by 1989, they covered 26,973 acres of the so-called “Merritt Island National Wildlife Sanctuary” surrounding the Kennedy Space Center.[7]
[Image description: Archival image of a distant person standing outside on a mound of land, overlooking a flooded landscape.]
As a result of these anti-mosquito measures, the ecology of Merritt Island was completely transformed, to the extreme detriment of the Dusky Seaside Sparrow and other “non- target” species. The impact of DDT on wildlife is well documented, and ecologists at the time estimated chemical spraying contributed to a 70% decline of the sparrow population on the Island.[8] Flooding and diking, though, all but eradicated suitable habitats for duskies, further reducing their populations and severely limiting any hope of their recovery.[9] In this transformed ecology, new predators were introduced, the dusky’s nesting material species drowned, and nesting sites were harder to come by. Combined with other pressures like highway construction and wildfires, the dusky had little room to breathe.
Act Two: Taxonomy, the Endangered Species Act, and the remaking of a sparrow
By 1980, the total remaking of Merritt Island had all but decimated the dusky. Only six of them remained in the wild—and to make matters worse, all were male.[10] However, there was some hope to be found for the future of the subspecies in captive crossbreeding efforts. Biologists captured the remaining duskies to breed them with Scott’s seaside sparrows, intending to “backcross” the resulting hybrid offspring with other of the “pure” duskies—and so on—to eventually reconstitute something almost genetically and morphologically identical to the dusky seaside sparrow. In 1980, three healthy dusky-Scott’s were hatched, one of which then mated with another Scott’s—proving these hybrid duskies could be fertile and thus potentially able to be backcrossed.[11]
However, these crossbreeding experiments proved highly contentious, particularly as environmental enforcement agencies struggled to interpret the new Endangered Species Act of 1973 (ESA). Though at first the Fish and Wildlife Agency declared that hybrid duskies—as offspring of an Endangered Species-—would be protected under the ESA, this decision was quickly reversed as a result of a more general policy that understood hybrids as a threat to “the gene pool or outcome of the endangered species.”[12] Dusky advocates considered such perspectives to be rooted in ideas of racial purity, and many argued that there was no scientific basis for resisting dusky crossbreeding.[13] Species—and especially subspecies—are not static or pregiven categories, and hybridization often occurs in the wild with little negative consequence.[14] The ESA, however, would not make room for such fluctuating environmental realities. As Law scholar Kevin D. Hill aptly wrote, “Presented with the choice of a 98.7% pure Dusky or none at all, the [U.S. Department of the Interior] Solicitor chose extinction. To save an abstraction of the species, the reality was allowed to die.”[15]
The anti-hybrid policy meant that the backcrossing programme could no longer receive federal funds, forcing dusky advocates to seek alternative sources. The birds found an unlikely ally in Florida’s Walt Disney World, who were looking for new attractions for their Discovery Island Zoological Park and, regardless of taxonomic squabbles, were excited about the publicity potentials of rescuing a local bird from extinction. And so, the last four remaining pure duskies were transported to Disney in 1983. After so much wasted time, however, the birds were past their biological prime. Ongoing crossbreeding efforts thus provided disappointing results, with hatchlings either not surviving or proving infertile.[16] Meanwhile, the original duskies continued to expirate, and the death of ‘Orange-band’ in June 1987 from old age marked the end of the ‘pure’ dusky line.
Though this date is often cited as the extinction of the dusky seaside sparrow, four hybrids remained in captivity at Disney (one of which was considered 87% genetically dusky).[17] However, without any of the original duskies, public interest waned, especially after an article argued that the dusky was not really any different from other subspecies of seaside sparrow, and thus was perhaps not “deserving” of special protection at all.[18] In June 1989, the hybrids were lost, likely killed by rats who entered the cage through holes in the aviary, with the remaining birds being released to their deaths.[19] The neglect of the hybrids’ enclosure was likely linked to a lack of funds and public interest: these not-quite offspring of a not-quite subspecies were, apparently, of little value. Though mosquito control pushed the birds to the edge, then, the dusky seaside sparrow ultimately became a victim of semantics-induced-neglect.
After the dusky
There is much to learn from the extinction story of the dusky seaside sparrow. Perhaps most of all, it offers a warning against environmental policy with single-species focus. First, the dusky was collateral in landscape-altering policies with a tunnel vision to reduce mosquitos. Then, the subspecies became a victim of their own protection: obsession with the purity of the dusky’s ecological line led to this line disappearing altogether. A more holistic system of environmental management that prioritized ecological wellbeing on a systematic, rather than species-based, level, would surely have produced less devastating outcomes. Following decades of advocacy, conservation policy today is generally less laser focused. However, the ESA still forces a priority of species-level conservation in the United States, and the law is still without an ecologically appropriate hybrid policy.[20]
Today, Walt Disney World is absent of both duskies and mosquitoes. Discovery Island was closed in 1999, and the crumbling animal enclosures—perhaps including the duskies’—have since been reclaimed by the wild. At Disney’s nearby theme park, however, there is a notable lack of nonhumans: though DDT is a technology of the past, Disney World still employs systematic strategies to deter mosquitos, such as waterways engineering and garlic spraying.
After the dusky, colonial-capitalism continues its attempts to eliminate, mitigate, and manage Floridian nature. As the state wrestles with the fate of having more at-risk species than almost any other, the story of the dusky seaside sparrow offers a warning of all that has been—and could be—lost.
[1] Mark J. Walters, A Shadow and a Song: The Struggle to Save an Endangered Species (Post Mills, VT: Chelsea Green Publishing Company, 1992).
[2] Hannah Hunter and Elizabeth Nelson, “Out of Place in Outer Space?: Exploring Orbital Debris through Geographical Imaginations,” Environment and Society 12, no. 1 (2021): 227–45.
[3] Quoted in Gordon M. Patterson, The Mosquito Wars: A History of Mosquito Control in Florida (Gainesville, FL: University Press of Florida, 2004), 33.
[4] Walters, A Shadow and a Song, 2.
[5] Patterson, Mosquito Wars, 40; Walters, A Shadow and a Song, 26-27.
[6] Walters, A Shadow and a Song, 26.
[7] Patterson, Mosquito Wars, 141.
[8] Rachel L. Carson, Silent Spring (Boston, MA: Mifflin, 1962); Trost, 1968, quoted in Paul W. Sykes, Jr, “Decline and disappearance of the Dusky Seaside Sparrow from Merrit Island, Florida,” American Birds, 34 no. 5 (1980): 733.
[9] Sykes, “Decline and disappearance,” 733.
[10] John C. Avise and William S. Nelson, “Molecular Genetic Relationships of the Extinct Dusky Seaside Sparrow,” Science 243, no. 4891 (1989): 646–48.
[11] Walters, A Shadow and a Song, 139.
[12] Alex Erwin, “Hybridizing Law: A Policy for Hybridization under the Endangered Species Act,” Environmental Law Reporter 47 (2017): 16.
[13] Walters, A Shadow and a Song, 157.
[14] Erwin, “Hybridizing Law”; Kevin D. Hill, “The Endangered Species Act: What Do We Mean by Species?,” Boston College Environmental Affairs Law Review 20 (1993): 239-256.
[15] Hill, “Endangered Species Act,” 261.
[16] Walters, A Shadow and a Song, 170, 172.
[17] Ibid., 193.
[18] Avise and Nelson, “Molecular Genetic Relationships.”
[19] Walters, A Shadow and a Song, 194.
[20] Erwin, “Hybridizing Law.”
*Cover image: Dusky seaside sparrow, Paul W. Sykes, date unknown.
[*Cover image description: A photograph of a small, black-and-white speckled bird with a patch of yellow on its face, sitting atop a tree branch.]
Edited by Genie Yoo, reviewed by Evelyn Ramiel.