Least bittern
Ixobrychus exilis
ITIS Species Code:   174846         NatureServ Element Code:   ABNGA02010
NatureServe Global Rank: 
NatureServe State (NC) Rank: 
Federal Status: 
NC State Status: 
Southern Blue Ridge:  18 Southern Piedmont:  n/a South Atl. Coastal Plain:  n/a
Land Unit

US Fish & Wildlife Service
US Forest Service
US National Park Service
US Department of Defense
NC State Parks
NC University System
NC Wildlife Res. Com.
NC Forest Service
NC Div. of Coastal Mgmt.
Local Governments
Non-Governmental Org.
Other Public Lands
Private Lands

GAP Status 1-2
All Protected Lands




% of Dist. on
Prot. Lands

42.5 %
1.0 %
19.4 %
14.5 %
3.1 %
0.4 %
11.1 %
0.1 %
3.0 %
4.3 %
4.3 %
0.2 %
< 0.1 %

70.8 %
% of Dist. on
All Lands

8.3 %
0.2 %
4.6 %
2.8 %
0.6 %
< 0.1 %
2.2 %
< 0.1 %
0.6 %
< 0.1 %
0.8 %
< 0.1 %
79.6 %

13.9 %
Occasional on the barrier islands (Fussell and Lyons 1990), fairly common locally along the coast, and rare at a few inland sites in the piedmont and mountains (Potter et al. 1980, Simpson 1992).

Nests solitarily or in loose colonies (Kaufman 1996) in fresh, brackish, or salt water habitats that provide dense vegetation, especially if scattered bushes or other woody growth, such as mangroves, is present (Ehrlich et al. 1988, Palmer 1962). May nest in association with Boat-tailed Grackles (Kaufman 1996).

Nest is placed near open water in dense vegetation 8 to 14 inches above shallow water (Palmer 1962), on the ground, or at a height of up to 8 feet in a low shrub (Ehrlich et al. 1988). Forages by climbing on reeds over shallow or deep water, rather than by wading (Kaufman 1996).


BREEDING: Tall emergent vegetation in marshes, primarily freshwater, less commonly in coastal brackish marshes and mangrove swamps. Prefers marshes with scattered bushes or other woody growth. In the northeastern U.S., breeds mainly in wetlands along lakes, rivers, and estuaries on the coastal plain; generally absent from the Appalachian highlands and mountainous parts of New York and northern New England (Gibbs and Melvin 1992). Readily uses artificial wetlands.

Habitats vary throughout North America, but nesting usually occurs among dense, tall growths of emergent vegetation (particularly cattail (TYPHA spp.), sedge (CAREX spp.), bulrush (SCIRPUS spp.), or common reed (PHRAGMITES AUSTRALIS)), interspersed with some woody vegetation and open, fresh water (Weller 1961, Palmer 1962, Kushlan 1973, Swift 1987, Frederick et al. 1990). Both fresh and brackish marshes are used (Palmer 1962, Swift 1987, Andrle and Carroll 1988). Occurrences have been associated particularly with cattail, vegetated edges along deep, open waters (Weller 1961), and nutrient-rich microhabitats (Kushlan 1973). Nests typically 0.15-0.75 m above water near open water (Terres 1980, Harrison 1979, Brewer et al. 1991), in water typically 10-50 cm deep. Spend nearly all the diurnal period in dense, grass-like vegetation; open habitats such as mats of emergent vegetation are rarely used (Frederick et al. 1990).

Weller and Spatcher (1965) found more nests at two Iowa marshes during years when ratios of emergent vegetative cover to open water were equal (the 'hemi-marsh' condition). More densely or sparsely vegetated wetlands contained fewer nests, and interspersion of water and cover may thus be an important characteristic of breeding habitats. In Wisconsin, were restricted to deep-water and shallow-water cattail habitats, apparently avoiding areas of dry cattail, river bulrush (SCIRPUS FLUVIATILIS), and sedge (Manci and Rusch 1988). Variably-sized wetlands were used in Maine, with dense, tall stands of cattail, which were often associated with relatively stable water regimes at managed impoundments and coves on lakes (Gibbs and Melvin 1990).

On moist-soil impoundments in Missouri, least bitterns were associated with waters up to 50 cm deep and rank, dense vegetative cover bordering open water (Fredrickson and Reid 1986). Were not associated with open, sparse, or short vegetative cover or muddy openings (Fredrickson and Reid 1986).

Among six tidal marshes along the Hudson River in New York, Swift (1987) reported that presence was related to the extent of tall bulrush-cattail cover and site elevation (i.e., depth of tidal flooding). Favored sites had tall, dense vegetation and low-lying, 'wetter' sites (peak water depths averaged 70 cm), perhaps because nests are usually placed over water or near open water (Weller 1961, Palmer 1962, Kushlan 1973, Aniskowicz 1981). In tidewater areas of Chesapeake Bay, Stewart and Robbins (1958) reported abundance in narrow-leaved cattail (TYPHA ANGUSTIFOLIA) marshes, common in other coarse marsh types and weak-stemmed brackish marsh types, but scarcity in salt marshes.

In the Florida Everglades, observed from airboats at densities (birds/km) of 0.13 in canals, 0.04 in open grasslands, and 0.37 along airboat trails (Frederick et al. 1990). Most individuals were seen in mixed sawgrass (CLADIUM JAMAICENCIS)/cattail (29% of birds), homogeneous sawgrass (23%), and homogeneous cattail (9%), and, within these vegetative associations, were seen twice as frequently in dense than sparse stands (Frederick et al. 1990). Open sloughs, rush prairies, mats of emergent vegetation, and burn areas were used infrequently (Frederick et al. 1990, but see Kushlan 1973). The strong association with cattail in northern regions (e.g., Weller 1961, Swift 1987, Manci and Rusch 1988, Gibbs and Melvin 1990) may occur because cattail is the most common tall plant growing in dense stands above deep water in most northern areas (Frederick et al. 1990). In South Carolina, nests frequently were associated with boat- tailed grackle colonies (Condor 95:139-144).

Sites where least bitterns were flushed during spring migration in Missouri (n = 61) had a mean water depth of 23 cm, vegetation height of 64 cm, and stem density of 287 stems/meter squared (Reid 1989), and were dominated by burreed (SPARGANIUM EURYCARPUM), water smartweed (POLYGONUM COCCINEUM), and cattail. Reid (1989) observed a shift in habitat use to taller (121 cm), sparser (165 stems/meter squared) stands in fall (n = 15 flush sites). Feeding platforms (n = 52) occurred over water averaging 29 cm in depth and among stands of emergent vegetation averaging 199 stems/meter squared.

NON-BREEDING: Overwintering birds occur in brackish and saline swamps and marshes (Palmer 1962, Hancock and Kushlan 1984), but little is known about wintering habitats.

Occupied Landcover Map Units:
Code NameDescription NC Natural Heritage Program Equivalent
3 Tidal Marsh Fresh and brackish tidal marshes, including cord grass, wild rice, sawgrass and needlerush alliances. Brackish Marsh, Interdune pond, Maritime wet grassland
124 Maritime Scrubs and Tidal Shrublands Coastal shrubs including wax-myrtle, swamp rose, alder, yaupon, and greenbriar. Maritime Shrubs, Salt Shrub
372 Interdune Herbaceous Wetlands Dune swales with permanently flooded to intermittently exposed hydrology. Species composition depends on salinity and can include cut grass, spike-rush, mosquito fern, and hornwort. Interdune Pond, Maritime Wet Grasslands
371 Maritime Grasslands Dune grass community consisting of sea oats and beach grasses. Dune grass, Maritime dry grassland
380 Coastal Plain Fresh Water Emergent Emergent vegetation in fresh water seepage bogs, ponds and riverbeds of the coastal plain. Includes alliances dominated by sedges, eelgrass, as well as cane found in unforested cane-brakes. Small Depression Pond, Sandhill Seep, Floodplain Pool, Unforested Floodplain Canebrake, Riverscour Prairies, Vernal Pools
173 Coastal Plain Riverbank Shrubs Shrub dominated riverbanks, commonly dominated by willows and/or alders. Sand and Mud Bar
238 Piedmont/Mountain Submerged Aquatic Vegetation Seasonally to permanently flooded areas with aquatic vegetation. Waterlily, pondweed, hydrilla smartweed are a few of the species that can occur. Piedmont/Mountain Semipermanent Impoundment (in part)
239 Piedmont/Mountain Emergent Vegetation Emergent vegetation of all wetland hydrologies. Sites would commonly support species such as tussock sedge, rushs, and cattail alliances. Rocky Bar and Shore (in part)
267 Riverbank Shrublands Riverside shrubs with temporarily flooded hydrologies. Found in the both the Mountains and Piedmont. Containing dominants such as smooth alder and a Carolina or black willows. Sand and Mud Bar
269 Floodplain Wet Shrublands Saturated shrublands of the Piedmont, includes buttonbush, swamp-loosestrife, decodon and alders. Piedmont/mountain Semipermanent Impoundment
205 Agricultural Pasture/Hay and Natural Herbaceous Farm fields used for pasture grass or hay production, as well as old fields dominated by native and exotic grasses. No equivalent
View Entire Landcover Legend
Additional Spatial Constraints:
Exclude all area outside of known range.
Exclude all land greater than 50 meters from an open water feature.
Exclude all land greater than 50 meters from wet vegetation.
Exclude areas of intensive human activity including moderately to highly developed landscapes.
Aniskowicz, B. T. 1981. Behavior of a male least bittern IXOBRYCHUS EXILIS after loss of mate. Wilson Bulletin 93:395-397.

Manci, K.M., and D.H. Rusch. 1988. Indices to distribution and abundance of some inconspicuous waterbirds at Horicon Marsh. Journal of Field Ornithology 59:67-75.

Gibbs, J. P., and S. M. Melvin. 1992. Least bittern, IXOBRYCHUS EXILIS. Pages 71-88 in K. J. Schneider and D. M. Pence, editors. Migratory nongame birds of management concern in the Northeast. U.S. Fish and Wildlife Service, Newton Corner, Massachusetts.

Ehrlich, P.R., D.S. Dobkin, and D. Wheye. 1992. Birds in jeopardy:the imperiled and extinct birds of the United States and Canada, including Hawaii and Puerto Rico. Stanford University Press, Stanford, California. 259 pp.

Evers, D. C. 1992. A guide to Michigan's endangered wildlife. Univ. Michigan Press, Ann Arbor. viii + 103 pp.

Herkert, J. R., editor. 1992. Endangered and threatened species of Illinois:status and distribution. Vol. 2:Animals. Illinois Endangered Species Protection Board. iv + 142 pp.

Simpson MB Jr. 1992. Birds of the Blue Ridge Mountains. Chapel Hill and London: University of North Carolina Press.

Fussell, J. III and M. Lyons. 1990. Birds of the Outer Banks [pamphlet]. Eastern National Parks and Monument Association Coastal Wildlife Refuge Society.

Swift, B. L. 1987. An analysis of avian breeding habitats in Hudson river tidal marshes. New York State Department of Environmental Conservation, Division of Fish and Wildlife, Delmar, New York. Unpublished report. 62 pp.

Hands, H.M., R.D. Drobney, and M.R. Ryan. 1989. Status of the least bittern in the northcentral United States. Missouri Coop. Fish Wildl. Res. Unit Rep. 13 pp.

Kaufman K. 1996. Lives of North American Birds. Boston, New York: Houghton Mifflin Company.

Palmer, R. S. (editor). 1962. Handbook of North American birds. Vol. 1. Loons through flamingos. Yale University Press, New Haven. 567 pp.

Weller, M. W., and C. S. Spatcher. 1965. Role of habitat in the distribution and abundance of marsh birds. Iowa State University Agricultural and Home Economics Experiment Station Special Report No. 43. Ames, Iowa. 31 pp.

Frederick, P. C., et al. 1990. Relative abundance and habitat preferences of least bitterns (IXOBRYCHUS EXILIS) in the Everglades. Florida Field Nat. 18:1-20.

Weller, M. W. 1961. Breeding biology of the least bittern. Wilson Bulletin. 73:11-35.

Payne, R. B., and C. J. Risley. 1976. Systematics and evolutionary relationships among the herons (Ardeidae). Univ. Michigan Mus. Zool., Misc. Publ. No. 150. 115 pp.

Cogswell, H.L. 1977. Water birds of California. Univ. California Press, Berkeley. 399 pp.

Harrison, H.H. 1979. A field guide to western birds' nests. Houghton Mifflin Company, Boston. 279 pp.

Potter, E. F., J. F. Parnell, and R. P. Teulings. 1980. Birds of the Carolinas. Univ. North Carolina Press, Chapel Hill. 408 pp.

Terres, J.K. 1980. The Audubon Society encyclopedia of North American birds. Alfred A. Knopf, New York.

Brown, M., and J.J. Dinsmore. 1986. Implications of marsh size and isolation for marsh bird management. Journal of Wildlife Management 50:392-397.

American Ornithologists' Union (AOU), Committee on Classification and Nomenclature. 1983. Check-list of North American Birds. Sixth Edition. American Ornithologists' Union, Allen Press, Inc., Lawrence, Kansas.

National Geographic Society (NGS). 1983. Field guide to the birds of North America. National Geographic Society, Washington, D.C.

Fredrickson, L.H., and F.A. Reid. 1986. Wetlands and riparian habitats:a nongame management overview. Pages 59-96 in J.B. Hale, L.B. Best, and R. L. Clawson, (eds.) Management of nongame wildlife in the Midwest:a developing art. Proc. Symp. 47th Midwest F

Andrle, R.F., and J.R. Carroll. 1988. The atlas of breeding birds in New York State. Cornell Univ., Ithaca, New York. 551 pp.

Ehrlich, P.R., D.S. Dobkin, and D. Wheye. 1988. The birder's handbook:a field guide to the natural history of North American birds. Simon and Shuster, Inc., New York. xxx + 785 pp.

Root, T. 1988. Atlas of wintering North American birds:An analysis of Christmas Bird Count data. University of Chicago Press. 336 pp.

Stiles, F.G., and A.F. Skutch. 1989. A guide to the birds of Costa Rica. Comstock Publ. Associates, Cornell University Press, Ithaca, New York. 511 pp.

Brewer, R., G.A. McPeek, and R.J. Adams, Jr. 1991. The Atlas of Breeding Birds of Michigan. Michigan State University Press, East Lansing, Michigan. xvii + 594 pp.

Kushlan, J. A. 1973. Least bittern nesting colonially. Auk 90:685-686.

10 March 2005
This data was compiled and/or developed by the North Carolina GAP Analysis Project.

For more information please contact them at:
NC-GAP Analysis Project
Dept. of Zoology, NCSU
Campus Box 7617
Raleigh, NC 27695-7617
(919) 513-2853