The Kirtland’s Warbler, a federally listed endangered species, is one of the world’s rarest birds. Their numbers dwindled to less than 167 singing males just 20 years ago! Their only consistent breeding grounds are in the 6000 sq. mile Au Sable River drainage area in Michigan’s Lower Peninsula. This area is unique in many ways most of which due to the soil composition which is sandy. Defined as Grayling Sand, it is the only suitable soil that Jack Pines flourish in.
These birds are sometimes referred to as the “bird of fire” because they nest only in young Jack Pine forests of 40+ acres which require intense heat to open the cone and release seeds. Kirtland’s numbers plummeted when there were fewer fires causing their desired nesting areas to decline substantially. They will only nest on the ground in large areas of young Jack Pine forest that are between five and 20 feet tall, preferably with extremely high densities of trees. The low branches on the young trees protect the nest from predators. When the trees reach about 15 years of age the branches at the bottom begin to die, leaving the nests exposed. Kirtland’s find these trees undesirable for nesting.
Jack Pine (typical age/height for nesting)
In addition to the decline in habitat, Brown-headed Cowbirds have posed an additional threat to successful nesting. The Kirtland’s Warbler is extremely susceptible to nest parasitizing by Cowbirds which lay their eggs in “host” nests forcing the parents to feed young which are not their’s. Thanks to human intervention, Cowbird numbers are being managed and far less nests are being parisitized by Cowbirds.
A Protected Species
This bird was first discovered in 1851 by noted Ohio naturalist Dr. Jared P. Kirtland when it was collected near Cleveland. In 1879 it was discovered to winter on the Bahama Islands in areas that contain low scrub. But the nesting range was not discovered until sometime around 1900 when some trout fishermen heard an unfamiliar bird singing in the Jack Pine barrens along the Au Sable River. Norman A. Wood, then University of Michigan curator of birds, is credited for finding and identifying the first nest in Michigan in 1903.
Male Kirtland’s warblers arrive back in Michigan from the Bahamas between May 3 and May 20, a few days ahead of the females. The males establish and defend territories and then court the females when they arrive. As the female builds a nest of leaves and grass, lined with mosses or deer hair, the male begins to bring her food. This duty continues through laying and the incubation process, with which the males rarely help. Four to five cream white eggs speckled and blotched with brown are laid in late May, followed by an incubation of 13-16 days. Both parents feed the chicks, which grow quickly and have left the nest within nine days, staying in the undergrowth and lowest branches of the trees. Within five weeks, the parents have ceased feeding their young.
The efforts of the US Fish and Wildlife and various other organizations have helped significantly. Numbers of singing males are over 2,000 in recent counts and Kirtland’s Warblers have been documented as nesting in various counties in Wisconsin, Minnesota and the latest being Canada.
Nesting Map by County
The US Fish and Wildlife Service offers tours departing from Grayling, MI and Mio, MI during mid-May through the end of June and is probably your best chance at seeing this rare and endangered bird. The said chance at seeing a Kirtland’s Warbler on one of these tours is greater than 90%.
Fish and Wildlife Tour