Geographic Range
The Kirland's Warbler breeds in northern central Michigan, in an area that is about 100 miles long and 60 miles wide. It is also a neotropical migrant, spending the winter in the Bahamas.
- Biogeographic Regions
- nearctic
- neotropical
Habitat
The Kirtland's warbler nests in groves of young Jack pines (Pinus banksiana) ranging in height from 5 to 18 feet. They also seek out areas with ground cover composed of blueberries, bearberry, or sweetfern. These warblers also require a very specific soil type, the Grayling Sands, which is important because they nest on the ground and their nests would be flooded if rain water did not drain away quickly. For this reason, nearly 90% of these birds breed in the drainage area of a single stream.
Their winter habitat in the the Bahamas consists of low scrub. During the night they retreat to higher shrubs to roost.
- Terrestrial Biomes
- savanna or grassland
- forest
Physical Description
- Other Physical Features
- endothermic
- bilateral symmetry
Reproduction
Nests are constructed in late May, followed by the laying of eggs in late May to mid-June. The number of eggs per clutch ranges from 3 to 6. In the rare event that a pair has a second clutch, fewer eggs will be laid than in the first. The female incubates the eggs for approximately 14 days before hatching occurs. During the incubation period, defense and care of the nest are predominantly the responsibilty of the female; however, the male will bring food to her. After the eggs hatch, both parents tend to the needs of the altricial young. The young gain weight rapidly during the first five days after hatching, doubling their weight every two days. During the last three days in the nest, their growth rate decreases and their energy is directed towards providing their own body warmth, plumage development,and heightened physical activity. The young leave the nest 9-10 days after hatching. During the fledging period, the brood is divided in half, each parent taking care of select offspring. The post juvenile molt occurs approximately one month after fledging.
- Key Reproductive Features
- iteroparous
- gonochoric/gonochoristic/dioecious (sexes separate)
- sexual
- oviparous
Lifespan/Longevity
Behavior
Males are the first to arrive at the nesting grounds in the spring, and they begin singing immediately. Females soon follow with late arriving males. Each male usually returns to the territory that he occupied the previous year; however, this true of females. Males aggressively defend their territories against other males, but territories are usually in close proximity to those of neighboring males, indicating a tendency towards loose colonialism.
- Key Behaviors
- flies
- motile
Communication and Perception
Food Habits
This species feeds primarily on insects; however, it is known to sample an array of other food materials including pine needles, grasses, and bluberries. Food is gathered by gleaning and flycatching on the wing.
Economic Importance for Humans: Positive
Negligible
Economic Importance for Humans: Negative
The warbler's endangered species status has affected the ability of private landowners to develop property containing warbler habitat.
Conservation Status
The Kirtland's Warbler has been the focus of much attention over the last 25 years because of its rarity and need for a very specific habitat. Natural forest fires were the original providers of such habitat, but the advance of white settlers resulted in the clearing of much of Michigan's natural forests. At first, the warbler benefited from such clearing; however, so did the Brown-Headed Cowbird (Molothrus ater). The Cowbird had a major impact on the warbler as a nest parasite. Cowbirds lay their eggs in the nests of other birds and leave the rearing of their young to these hosts. Cowbird young usually develop much faster than the young of the host species and are thus able to out-compete the hosts' young for food resources. Many of the hosts' young die as a result. Recognition of the effects of this phenomena on the Kirtland's Warbler in the early 1970's lead to a program of killing Cowbirds in the warbler's range. This program, coupled with the management of breeding grounds by way of controlled burns, has significantly aided the warbler. However, the Kirtland's Warbler seems to be faced with other problems that effect it during migration or during its time in the Bahamas. As a result, the breeding population in Michigan has not changed significantly recently from spring to spring.
Additional Links
Contributors
Ethan Kane (author), University of Michigan-Ann Arbor.
- Nearctic
-
living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.
- native range
-
the area in which the animal is naturally found, the region in which it is endemic.
- Neotropical
-
living in the southern part of the New World. In other words, Central and South America.
- native range
-
the area in which the animal is naturally found, the region in which it is endemic.
- tropical savanna and grassland
-
A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.
- savanna
-
A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.
- temperate grassland
-
A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.
- forest
-
forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.
- motile
-
having the capacity to move from one place to another.
- endothermic
-
animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.
- bilateral symmetry
-
having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.
- iteroparous
-
offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).
- sexual
-
reproduction that includes combining the genetic contribution of two individuals, a male and a female
- oviparous
-
reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.
- visual
-
uses sight to communicate
- tactile
-
uses touch to communicate
- acoustic
-
uses sound to communicate
- chemical
-
uses smells or other chemicals to communicate
References
Harrison, Hal H. 1984. Wood Warbler's World. Simon and Schuster, New York. pp. 172-178.
Mayfield, Harold. 1960. The Kirland's warbler. Cranbrook Institute of Science, Bloomfield Hills, MI. pp. 18, 19, 44, 45, 53, 54, 80, 84, 87, 89, 91, 100, 106, 107, 110, 123, 124.
Peterson, Roger Tory. 1980. A Field Guide to the Birds East of the Rockies. Houghton Mifflin, Boston. pp. 234-235.
Schreiber, Rudolf L., Anthony W. Diamond, Roger Tory Peterson, and Walter Cronkite. 1989.
Save the Birds. Houghton Mifflin, Boston. pp. 190- 191.
Mayfield, H. F. 1992. Kirtland's Warbler (Dendroica kirtlandi). Birds of North America, 19:1-16.