There’s a historical marker located on I-75 in Michigan just north of the 251 exit, commemorating “The Return of Kirtland’s Warbler.” Kirtland’s warbler is perhaps the most remarkable conservation success story in Michigan and a testament to the power of the Endangered Species Act.
This year was the 47th Kirtland’s warbler census. Census volunteering is all about bird identification by ear. Hiking designated transects with a biologist trained in navigation, you ‘bushwack’ your way through dense jack-pine habitat on a plotted course, stopping at designated points to listen and plot singing males from all directions and covering about two kilometers each morning.
Although hearing many, I saw just one Kirtland’s warbler in the two mornings I volunteered on the 2017 census in the Huron National Forest near Oscoda, Michigan. I stood about ten to twelve feet from the singing male that appeared, just as I’ve read, quite unafraid. I imagine I could have easily walked right up to him, but I instinctively respected his space, for I was the visitor in his territory. In the next few minutes I was immersed in this visual and auditory moment, his vibrant sunflower yellow chest, rich grey-blue wings, and confident song.
It was a surreal moment connecting with the purity of nature, a gift that words cannot really describe. He was captivating.
It’s been fifty years since Kirtland’s was listed on the U.S. Fish and Wildlife Service’s endangered species list in 1967, when this iconic warbler was close to extinction. Now the population has grown to more than two thousand nesting pairs. Birders from over the world travel to Michigan’s northeastern lower peninsula in May and June each year for a chance to see it.
Why does the Kirtland’s warbler story inspire us so? Although the future looked bleak for Kirtland’s back in 1974 with a low count of 167 males, many dedicated, vigilant supporters—and fifty years of federal protections as an endangered species—have brought it back to a healthy population. People from diverse backgrounds—biologists, birders, concerned citizens all sharing an enthusiastic and determined bond—drew attention to Kirtland’s declining population, and this persistence saved it.
By the 1950’s, experts had good reason to believe the small population was in trouble, and two theories that had been evolving—cowbird parasitism and loss of jack pine habitat—were causing the decline. As early as 1923 ornithologist Nathan Leopold observed cowbird parasitism, and later studies in the 1960’s showed up to seventy-eight percent of Kirtland’s warbler eggs in cowbird-parasitized nests did not produce warbler fledglings. At the same time, Kirtland’s was losing jack pine nesting habitat as more development was moving into Michigan’s northeastern lower peninsula.
Kirtland’s builds a ground nest nestled underneath younger jack pines (about five to twenty years old) because the low-lying branches provide protection from predators and weather. When the jack pine reaches about twenty the lower branches thin out and the trees no longer offer viable nesting protection, and the warblers reject them. The jack pine is a tree designed to burn easily and needs fire to release its seeds. The natural fire ecology of this ecosystem, which had occurred naturally for thousands of years and had provided a steady supply of young jack pines, was rapidly changing. The successive jack pine forest habitat was quickly disappearing.
In 1951, advocate Harold Mayfield and Michigan Audubon organized the first official Kirtland’s warbler census. As William Rapai explains in his book, The Kirtland’s Warbler: The Story of a Bird’s Fight Against Extinction and the People Who Saved It, since Kirtland’s nesting grounds were limited to a well-defined geographic area and the singing males are quite easy to count (their song is distinctive, and they sing often in their territories) a census was feasible. “Mayfield’s idea was groundbreaking because no one had ever attempted a complete census of a single bird species before.”
They counted 432 males in the 1951 census and 502 in 1961. But the third census in 1971 confirmed a crisis—Kirtland’s males were down to a low of 201.
A greater environmental awareness had been arising in the 1960’s. Rachel Carson’s Silent Spring drew attention to the dire effects of chemical pesticides and DDT on wildlife, particularly the loss of birds—eagles and peregrine falcons were disappearing. Congress responded by passing the first federal protections for endangered species in 1966, the Endangered Species Preservation Act; and in 1967 the U.S. Fish and Wildlife Service chose Kirtland’s warbler as one of thirty-four birds for their list of endangered species shared with thirty-nine mammals, reptiles, amphibians, and fish.
In “The Class of 1967, 50 years later,” Ben Ikenson writes “[Kirtland’s warbler] was one of the first species with a formal recovery team and recovery plan” with a shared goal to prevent extinction and facilitate recovery. When the Endangered Species Act passed in 1973 protections for wildlife were further strengthened. Reflecting on the climate of political collaboration at that time, The Endangered Species Coalition writes, “The Endangered Species Act was a landmark conservation law that passed with overwhelming bipartisan support: 92-0 in the Senate, and 394-4 in the House.”
Kirtland’s is a conservation-reliant species, meaning humans will always need to intervene to create jack pine habitat and control cowbirds, and it now faces a new threat. Climate change brings new challenges for many migratory birds since successful nesting is meticulously linked to insect hatching and food availability, and this timing is altered with erratic weather and temperatures. In the Bahamas, Kirtland’s wintering grounds, climate change could cause a loss of shoreline resulting in a push for increased development on the interior of the islands—the warbler’s winter home.
Saving a species is a work in continual process. Because of the collaboration of many determined, insightful advocates and the protection of the Endangered Species Act, Kirtland’s warbler has a strong population today. Fifty years’ of protections has made the difference.