| Rangewide Distribution: Southern
& south central Canada; northern to north central & eastern United
States Abundance: Fairly common but declining in northeastern United States & New England Breeding Habitat: Marshes & wet meadows with emergent vegetation Nest: Sticks, grass & sedge on dry ground or over water; separate exit & entrance Eggs: 4-5 buff-brown or olive-buff Incubation: 28-29 days Fledging: Unknown number of days |
American Bitterns once nested fairly commonly in all marshes
of the state (Widmann 1907). Currently Missouri lists them as
an Endangered species. They are generally restricted to undisturbed
wetlands of greater than eight hectares supporting dense stands
of cattails and other tall, emergent vegetation interspersed with
patches of open water (Gibbs et al. 1992). They are extremely
secretive except when establishing breeding territories. Territorial
vocalizations include distinct pumping sounds that carry great
distances over the marsh. Nests are usually platforms of dead
plant material placed over shallow water and well-hidden among
dense vegetation (Harrison 1975).
Code Frequency
The reported rarity of American Bitterns as a summer resident (Robbins and Easterla 1992) was supported by the findings of the Atlas Project. In only six blocks was the species recorded in habitat appropriate for breeding. Because of the difficulty in surveying marshes and detecting breeding evidence, it may be they bred in all six blocks. In one, at the Ted Shanks Conservation Area, breeding was confirmed in 1986 by the observation of a nest with Eggs:.
Distribution
Because of the extreme rarity of this species as a breeder, locations discovered during the Atlas Project provide little information on distribution or abundance. Gibbs et al. (1992) suggested that only the northern third of Missouri constitutes potential breeding range for this species. Early in the century, the American Bittern bred commonly throughout the state (Widmann 1907).
Phenology
Most evidence of breeding was obtained in June, however, a territorial individual was recorded on July 27. Terres (1987) reported egg dates that ranged from April through July and, according to Ehrlich et al. (1988), American Bitterns can rear two broods per season.
Breeding Evidence
Reported in 6 (<1%) of 1,207 blocks
| Blocks | % of Blocks | ||
|---|---|---|---|
| Confirmed | 1 | 16.7% | |
| Probable | 1 | 16.7% | |
| Possible | 4 | 66.6% | |
