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Botaurus lentiginosusAmerican bittern

By Marie S. Harris

Geographic Range

During the breeding season, the American Bittern ranges from the Mid-United States to northern Canada. Its wintering range stretches from the south Atlantic coast across the Gulf coast and west to southern California.

Habitat

In the breeding range, the American Bittern inhabits areas of freshwater wetlands with tall emergent vegetation, shorelines, and vegetative fringes. The bird prefers beaver-created wetlands to those of glacial origin.

Physical Description

The American Bittern is a medium-sized heron with a stout body and a neck, short legs, and a white neck. The upperside of the bird is brown finely speckled with black. The undersides are heavily streaked with brown and white. There is a long black patch that extends from below the eye down the side of the neck.

  • Average mass
    600 g
    21.15 oz
    AnAge
  • Average basal metabolic rate
    2.7412 W
    AnAge

Reproduction

The American Bittern is considered monogamous; however, it is possibly polygynous under some circumstances. Pair formation occurs in early May when the female arrives at the nesting site. The female then chooses the nest site, which is usually in dense emergent vegetation over water that is 4-5 cm in depth. The nest is built by the female and is constructed of reeds, sedges, cattail, or other emergent vegetation. Egg laying is performed daily with one egg laid in the in the morning. Incubation begins before the full clutch is laid and lasts 24 to 28 days. Brooding and feeding duties are performed solely by the female. The hatchlings leave the nest after one to two weeks, but they receive supplemental feedings by the adults up to four weeks after hatching.

  • Average eggs per season
    4
    AnAge
  • Average time to hatching
    34 days
    AnAge

Lifespan/Longevity

Behavior

Little is known about migration patterns of the species. Northern populations that occupy areas where temperatures can reach below freezing are known to migrate. Southern populations occupying regions where temperatures are milder, however, appear to be non-migratory. Members of the species appear to be highly asocial, with minimal pair bonds between the sexes. Foraging is completely solitary.

Communication and Perception

Food Habits

The basic diet of the American Bittern includes insects, amphibians, crayfish, and small fish and mammals. When foraging, it relies mostly on stealth, waiting motionless for its prey to pass by. Its coloration adds to its ability to go undetected by prey. When its prey is in reach, the bird darts forward and seizes the prey in its bill. The prey is then killed by biting or shaking and is swallowed head first. Microhabitats for foraging include vegetation fringes and shorelines. Even-aged stands of older, dense or dry vegetation are avoided.

Economic Importance for Humans: Positive

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Economic Importance for Humans: Negative

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Conservation Status

The American Bittern population is undergoing a substantial decline due to loss and degredation of habitat. The species was listed as a Nongame Species of Management Concern by the United States Fish and Wildlife Service in 1982 and 1987. It is listed as a species of special concern in the state of Michigan. Eutrophication, siltation, chemical contamination, and human disturbance have significantly reduced habitat quality by damaging the food supply. Changes in wetland isolation and stabilized water regimes are also eroding habitat quality. Acid rain is also another significant threat to the species due to its damaging effects on wetlands.

Other Comments

Within the thick vegetation of its habitat, the American Bittern uses resounding calls to communicate. The eerie calls for which it known has won the species many nicknames: stake-driver, thunder-pumper, and mire-drum. The species remains relatively unstudied due to its secretive nature and inaccessible habitats.

Contributors

Marie S. Harris (author), University of Michigan-Ann Arbor.

Glossary

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.

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acoustic

uses sound to communicate

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.

chemical

uses smells or other chemicals to communicate

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.

forest

forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.

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).

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

rainforest

rainforests, both temperate and tropical, are dominated by trees often forming a closed canopy with little light reaching the ground. Epiphytes and climbing plants are also abundant. Precipitation is typically not limiting, but may be somewhat seasonal.

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

tactile

uses touch to communicate

visual

uses sight to communicate

References

Gibbs, J.P., et. al., The Birds of North America No.18. The Academy of Natural Sciences of Philadelphia, 1992.

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