Species: Botaurus lentiginosus
American Bittern
Species
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Encyclopedia of Puget Sound

EGGS: Eggs measure 49 by 37 mm and are elliptical, buff-brown to deep olive-brown, smooth, and slightly glossy (Harrison 1978).
Classification
Kingdom
Animalia
Phylum
Craniata
Class
Aves
Order
Ciconiiformes
Family
Ardeidae
Genus
Botaurus
NatureServe
Classification
Other Global Common Names
Avetoro Norteño - butor d'Amérique
Informal Taxonomy
Animals, Vertebrates - Birds - Wading Birds
Formal Taxonomy
Animalia - Craniata - Aves - Ciconiiformes - Ardeidae - Botaurus - May constitute a superspecies with B. PINNATUS (AOU 1998).
Ecology and Life History
EGGS: Eggs measure 49 by 37 mm and are elliptical, buff-brown to deep olive-brown, smooth, and slightly glossy (Harrison 1978).
Short General Description
A large wading bird (bittern).
Migration
true - true - true - These birds arrive at nesting areas in the northeastern U.S. in mid to late March, about a month before the more southerly wintering least bittern (Bent 1926), but peak numbers of birds may not arrive until mid-April (Palmer 1962). Arrives in the Great Lakes region primarily in April. Wanders considerably after breeding. Southward migration extends from September to October and November (Palmer 1962).
Non-migrant
true
Locally Migrant
true
Food Comments
Eats mainly fishes, crayfishes, amphibians, mice and shrews, insects, and other animals (Palmer 1962). Feeds young by regurgitation. Stealthy forager. The trunk is highly compressed to facilitate movement through dense vegetation. The repertoire of feeding behaviors is relatively small. Of 28 recognized heron foraging behaviors (Kushlan 1978), only four are used: standing in place, neck swaying (which may enable bitterns to overcome glare or permit a quicker strike by having muscles in movement when strike begins), walking slowly, and walking quickly. This is a solitary feeder that relies more on stealth than pursuit to capture prey. Its coloration, particularly its ventral stripes, provides camouflage in dense, vertical marsh vegetation, complements its inactive feeding repertoire, and permits solitary foraging (Kushlan 1978). Crypsis is thought to function mostly to reduce visibility to prey and competitors rather than to predators (Kushlan 1978). <br><br>The long, thick bill enables the taking of a variety of large and small prey (Kushlan 1978), a conclusion supported by analyses of stomach contents. Based on 160 specimens (133 with food remains) collected throughout North America, stomach contents included insects (23%, including many Odonates), frogs and salamanders (21%), fish (21%, including catfish, sunfish, yellow perch, suckers, killifishes, and sticklebacks), crayfish (19%), mice and shrews (10%), snakes (5%), and small quantities of crabs, spiders, and unidentified invertebrates (Cottam and Uhler 1945). Nine stomachs from Pennsylvania contained fish, frogs, crayfish, watersnakes, snails, beetles, and grasshoppers (Warren 1890). Have been observed intercepting dragonflies in midair (Dudones 1983). Garter snakes (THAMNOPHIS SIRTALIS) feeding on frogs at pond margins are occasionally eaten (Ingram 1941). A captive individual ate 23.9 g (dry weight) of food (mice) per day, and required 22 hours to digest a meal and eject a pellet (Rhoades and Duke 1975).
Reproduction Comments
Nesting occurs solitarily (non-colonially) on all-purpose territories that provide both feeding and nesting sites, but occasionally up to a few pairs nest in a small area (Harrison 1979). Polygyny is suspected to occur (Palmer 1962). Mating rituals are elaborate, and involve display of a tuft of white nuptial feathers located on the sides of the neck (see Baker 1980, Johnsgard 1980). BOTAURUS bitterns may undergo a change in iris color from yellow to orange during courtship (Wood 1986). <br><br>The nest consists of a platform of reeds, sedges, cattail, or other available emergent vegetation, and is lined with fine grasses. Nests are usually placed on the ground, in a tussock, a few inches above water, or are floating; are surrounded by water, and have dense, overhead cover (Bent 1926, Vesall 1940, Cogswell 1977, Harrison 1978, Terres 1980). Nests may also be built in grassy uplands (Vesall 1940, Duebbert and Lokemoen 1977). Nests are usually accessed by two, well-beaten pathways (Gabrielson 1914). <br><br>Egg-laying begins in late April or early May, about a month after the arrival at nesting areas, and continues until mid-June (Bent 1926). In the north-central U.S., nests may contain eggs from about early May to early July (Brewer et al. 1991). Clutch size ranges from two to seven eggs, usually three to five (Duebbert and Lokemoen 1977, Graber et al. 1978). Incubation, by the female only, begins with the first egg (Palmer 1962). Hatching occurs after 24-28 days (Burns 1915, Bent 1926, Vesall 1940), and chicks remain at or near the nest for two weeks (Gabrielson 1914, Vesall 1940, Harrison 1979, Terres 1980). Chicks are fed only by the female, and are given fish, frogs, snakes, crayfish, and mice (Gabrielson 1914, Byers 1951). Nests often become fouled with food debris (Vesall 1940). Post-fledging behavior of young is unreported. <br><br>Apparently single-brooded (Palmer 1962). In upland habitats in North and South Dakota, 57% of 72 nests hatched at least one egg (Duebbert and Lokemoen 1977). Little is known about sources of egg, chick or post-juvenile mortality, age at fledging or first breeding, or territory size. Age at fledging for the closely-related Eurasian bittern is 50-55 days (Cramp 1977). One banded American bittern lived at least eight years (Clapp et al. 1982). Probably undergoes extensive post-breeding dispersal, which has resulted in numerous sightings, mostly between September and December, at locations as distant as Iceland, Norway, and Great Britain (Cramp 1977). Information on molt is incomplete. Adults undergo a complete post-breeding molt from August to November, and possibly a pre-breeding renewal of body plumage (Palmer 1962, but see Bent 1926).
Ecology Comments
Basically solitary. Low population density. Too little is known of rates of predation on nests and adults to infer the importance of predation as a factor limiting populations. Similarly, only minimal information is available on the effects of parasites and disease. Wading birds are known to be susceptible Type C botulism (occasionally), avian cholera (infrequently), chlamydial infections (frequently), sarcocystis (rarely), and aspergillosis (infrequently) (Friend 1987). Known to harbor lice and flies (Peters 1936) and a number of species of nematodes (Boyd 1966).
Length
71
Weight
706
Conservation Status
NatureServe Global Status Rank
G4
Global Status Last Reviewed
1996-11-20
Global Status Last Changed
1996-11-20
Other Status
LC - Least concern
Distribution
Conservation Status Map
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Global Range
H - >2,500,000 square km (greater than 1,000,000 square miles) - H - BREEDING: southeastern Alaska and southern Mackenzie to Newfoundland, south to southern California, central Arizona (formerly), southern New Mexico, central Kansas, central Missouri, central and western Tennessee, western Kentucky, central Ohio, southern Pennsylvania, northeastern West Virginia, eastern Maryland, and eastern Virginia (rarely North Carolina); locally in Texas, Louisiana, Florida, and Mexico south to Puebla and the state of Mexico (AOU 1983). In the northeastern U.S., abundance declines sharply south of northern New England and New York (Gibbs and Melvin 1992). Range is large but highly discontinuous due to restricted habitat. NON-BREEDING: southwestern British Columbia, northern Nevada, northern Texas, Ohio Valley (rarely), and New York south to southern Mexico (rarely or formerly to Panama) and the West Indies (AOU 1983). Occurs in winter primarily near the coast; areas of relatively high density include southern Florida, San Joaquin Valley (California), eastern North Carolina (no longer common, H. LeGrand, pers. comm.), Okefenokee Swamp, southern Louisiana, and various national wildlife refuges elsewhere (Root 1988).
Global Range Code
H
Global Range Description
>2,500,000 square km (greater than 1,000,000 square miles)