Botaurus lentiginosus - (Rackett, 1813)
American Bittern
Other English Common Names: American bittern
Taxonomic Status: Accepted
Related ITIS Name(s): Botaurus lentiginosus (Rackett, 1813) (TSN 174856)
French Common Names: butor d'Amérique
Spanish Common Names: Avetoro Norteño
Unique Identifier: ELEMENT_GLOBAL.2.103409
Element Code: ABNGA01020
Informal Taxonomy: Animals, Vertebrates - Birds - Wading Birds
Image 7514

© Larry Master

Kingdom Phylum Class Order Family Genus
Animalia Craniata Aves Pelecaniformes Ardeidae Botaurus
Genus Size: B - Very small genus (2-5 species)
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Concept Reference
Concept Reference: American Ornithologists' Union (AOU). 1998. Check-list of North American birds. Seventh edition. American Ornithologists' Union, Washington, D.C. [as modified by subsequent supplements and corrections published in The Auk]. Also available online:
Concept Reference Code: B98AOU01NAUS
Name Used in Concept Reference: Botaurus lentiginosus
Taxonomic Comments: May constitute a superspecies with B. pinnatus (AOU 1998).
Conservation Status

NatureServe Status

Global Status: G5
Global Status Last Reviewed: 06Apr2016
Global Status Last Changed: 06Apr2016
Ranking Methodology Used: Ranked by inspection
Rounded Global Status: G5 - Secure
Reasons: Widespread distribution but populations are declining; threat of habitat destruction.
Nation: United States
National Status: N4B,N4N (05Jan1997)
Nation: Canada
National Status: N5B,N3N,N5M (25Jan2018)

U.S. & Canada State/Province Status
Due to latency between updates made in state, provincial or other NatureServe Network databases and when they appear on NatureServe Explorer, for state or provincial information you may wish to contact the data steward in your jurisdiction to obtain the most current data. Please refer to our Distribution Data Sources to find contact information for your jurisdiction.
United States Alabama (S3N), Alaska (S3B), Arizona (S1S2), Arkansas (S2N), California (S3S4), Colorado (S3S4B), Connecticut (S1B), Delaware (S1B), District of Columbia (S1S2B,S2N), Florida (S3N), Georgia (S3?), Idaho (S1B), Illinois (S1S2), Indiana (S2B), Iowa (S2B), Kansas (S1B), Kentucky (SHB), Louisiana (S4N), Maine (S4B), Maryland (S1B), Massachusetts (S2B), Michigan (S3), Minnesota (S4B), Mississippi (S1N), Missouri (S1), Montana (S3B), Nebraska (S4), Nevada (S3B), New Hampshire (S3B), New Jersey (S1B,S3N), New Mexico (S3B,S3N), New York (S4), North Carolina (S1B,S3N), North Dakota (SNRB), Ohio (S2), Oklahoma (S1S3), Oregon (S4), Pennsylvania (S1B), Rhode Island (S1B,S1N), South Carolina (SNRN), South Dakota (S4B), Tennessee (S1), Texas (S3), Utah (S3S4B,S3N), Vermont (S3B), Virginia (S1B,S2N), Washington (S4B,S3N), West Virginia (S1B,S1N), Wisconsin (S2S3B), Wyoming (S3B)
Canada Alberta (S3S4B), British Columbia (S3B,SNRN), Labrador (S3B,SUM), Manitoba (S4B), New Brunswick (S4B,S4S5M), Newfoundland Island (S4B,SUM), Northwest Territories (S3B), Nova Scotia (S3S4B), Nunavut (S3B,S3M), Ontario (S4B), Prince Edward Island (S4B), Quebec (S4), Saskatchewan (S5B)

Other Statuses

IUCN Red List Category: LC - Least concern

NatureServe Global Conservation Status Factors

Range Extent: >2,500,000 square km (greater than 1,000,000 square miles)
Range Extent Comments: 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).

Area of Occupancy: >12,500 4-km2 grid cells
Area of Occupancy Comments: The species is estimated to occupy almost 3.5 million square kilometers (Birdline International, 2014).

Number of Occurrences: 81 to >300
Number of Occurrences Comments: Estimate provided by NatureServe (2014).

Population Size: 10,000 - 1,000,000 individuals
Population Size Comments: National Audubon Society (2014) estimates three million in 2003-04 but NatureServe (20140 estimtes between 10,000 and one million.

Number of Occurrences with Good Viability/Integrity: Some to many (13-125)
Viability/Integrity Comments: Lowther, et. al. (2009) suggest that this species may be a relict over much of the U.S., with this species being much more abundant than in the U.S.

Overall Threat Impact Comments: Threatened by loss and degradation of wetlands due to drainage, filling, conversion to agriculture or recreational use, siltation, and pollution. The most serious factor limiting populations is availability of wetland habitat. The entire life cycle is dependent on wetlands, yet over half the original wetlands in the conterminous U.S. have been destroyed (Tiner 1984). The most serious losses have occurred among palustrine emergent wetlands, of which about 4.75 million acres (1.92 million ha) were lost between the mid-1950s and mid-1970s (Tiner 1984). Inland, freshwater wetlands, the most important nesting and wintering areas, are among the most threatened habitats (Tiner 1984). Larger wetlands (greater than 10 ha) may support large portions of regional nesting populations, and loss of these wetlands can be critical to populations in many areas. Small wetlands (less than five ha) may serve as important alternate feeding sites and as "stepping stones" during movements between larger wetlands, but receive no legal protection in most states. Habitat quality also may be limiting. Eutrophication, siltation, chemical contamination, and human disturbance may seriously reduce habitat quality, even at large protected wetlands. Eutrophication, caused by inflow of nitrates and phosphates from urban and agricultural areas, in combination with silting and turbidity, has damaged the aquatic fauna that serve as prey for endangered Eurasian bitterns in Great Britain (Day and Wilson 1978). Marshland invasion by purple loosestrife (LYTHRUM SALICARIA) and phragmites (PHRAGMITES AUSTRALIS) may substantially alter waterbird habitats in the northeastern U.S., but effects on bitterns have not been assessed. Acid deposition is a potential threat given the dependence on wetland habitats vulnerable to acidification, the high proportion of amphibians in their diet (Cottam and Uhler 1945), and the large numbers of bitterns and large proportion of the breeding range in regions receiving rainfall of reduced pH (the northeastern U.S. and central and eastern Canada). Amphibians are typically vulnerable to strong reductions in water pH (Freda 1985), and the Eurasian bittern avoids waters with pH less than 4.5 (Cramp 1977), probably because such waters lack amphibian and fish prey. However, American bitterns usually occupy habitats with substantial growths of emergent vegetation, even in more northerly parts of their range (DesGranges and Houde 1989; Gibbs et al., in press.). Such areas typically are of circumneutral pH and are chemically buffered against strong shifts in acidity. Little is known about the effects of contaminants. However, heavy metals, PCBs, and organochlorines have been found in tissues of a number of heron species (Fleming et al. 1983), despite bans on use of some of these chemicals (i.e., organochlorines) since the 1970s. Agricultural chemicals may have significant, indirect effects by entering wetlands via runoff from upland areas and reducing prey populations. Many of this bird's prey, including aquatic insects, crayfish, and amphibians, are vulnerable to agricultural pesticides. Wading birds are known to be moderately susceptible to oil toxicosis. A nematode parasite, EUSTRONGILIDES, contracted from small fish, can devastate wading bird populations, and thrives in waters polluted with nutrients and silt; bittern populations at wetlands and impoundments receiving stormwater and runoff from residential and agricultural areas may be particularly vulnerable to epizootics of Eustrongylidosis (P. Frederick, pers. comm.). Illegal shooting incidental to upland gamebird or waterfowl hunting has an unknown impact populations. Records maintained by the Massachusetts Division of Fisheries and Wildlife indicate that at least three bitterns were shot and killed on or adjacent to wildlife management areas in that state during pheasant hunting seasons between 1986-90 (B. Blodget and W. Easte, pers. comms.). Historically, hunting may have been a greater source of mortality than it is today. Audubon (1840) reported that American bitterns were "common" in markets of New Orleans in the early 1800s. Several of this bird's common names, such as Indian Hen and Meadow Hen, may reflect its popularity as food for native Americans and colonists. In Europe, illegal hunting has a significant impact on Eurasian bittern populations and has led to declines and prevented population recovery in many areas (Day 1981). Human disturbance in or along the margins of wetlands has unknown impacts on reproduction, feeding ecology, and site fidelity. In Great Britain, recreational boaters are thought to limit the availability of undisturbed feeding sites for Eurasian bitterns at protected wetlands (Bibby 1981). Draining, filling and disturbance of wetlands and environmental contamination (especially by chlorinated hydrocarbons) are suspected as causes of decline in Connecticut (Zeranski and Baptist 1990).

Short-term Trend: Increase of >10%
Short-term Trend Comments: This trend is based on BBS data (Sauer, 2014) from 2002 to 2012, when there was an estimated 3.13% annualized increase in population size. However, this has NOT been the trend overall (See long-term trend).

Long-term Trend: Decline of 30-70%
Long-term Trend Comments: Long-term data not available rangewide. However, habitat trends suggest that substantial declines have probably occurred. The entire life cycle is dependent on wetlands, yet over half the original wetlands in the conterminous U.S. have been destroyed (Tiner 1984). Breeding Bird Survey (BBS) data (1966-1987) indicate a decline in the north-central U.S. (Hands et al. 1989, Brewer et al. 1991) and possibly in New England (USFWS 1987), due mainly to loss and degradation of wetlands. BBS data suggest a 2.4% annual decline in U.S. populations between 1966 and 1989, but no significant trends were evident for populations in the eastern U.S. or Canada; other sources suggest that declines have occurred in portions of New York and in southern New England, Pennsylvania, New Jersey, and Delaware (Gibbs and Melvin 1992). National Audubon Society (2014) estimates a 59% decline from 1966 through 2006) Sauer, et. al. (2014) estimate an 0.89% decline over the last 46 years, which equates to a 33% decline over the time period.

Intrinsic Vulnerability: Moderately vulnerable
Intrinsic Vulnerability Comments: Many large expanses of shallow wetlands that this bird requires has been lost or degraded (National Audubon Society, 2014).

Environmental Specificity: Narrow. Specialist or community with key requirements common.
Environmental Specificity Comments: Large, healthy freshwater marshes are essential for this species (National Audubon Society, 2014).

Other NatureServe Conservation Status Information

Inventory Needs: Continuing inventory of this bird species is needed because it may be declining significantly throughout its range (National Audubon Society, 2014).

Protection Needs: Preservation of wetland habitats, particularly large (greater than 10 ha), shallow wetlands with dense growths of robust emergents, is the most urgent protection need. Protect habitat through land purchases and easements.

Global Range: (>2,500,000 square km (greater than 1,000,000 square miles)) 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).

U.S. States and Canadian Provinces

Due to latency between updates made in state, provincial or other NatureServe Network databases and when they appear on NatureServe Explorer, for state or provincial information you may wish to contact the data steward in your jurisdiction to obtain the most current data. Please refer to our Distribution Data Sources to find contact information for your jurisdiction.
Color legend for Distribution Map
NOTE: The maps for birds represent the breeding status by state and province. In some jurisdictions, the subnational statuses for common species have not been assessed and the status is shown as not-assessed (SNR). In some jurisdictions, the subnational status refers to the status as a non-breeder; these errors will be corrected in future versions of these maps. A species is not shown in a jurisdiction if it is not known to breed in the jurisdiction or if it occurs only accidentally or casually in the jurisdiction. Thus, the species may occur in a jurisdiction as a seasonal non-breeding resident or as a migratory transient but this will not be indicated on these maps. See other maps on this web site that depict the Western Hemisphere ranges of these species at all seasons of the year.
Endemism: occurs (regularly, as a native taxon) in multiple nations

U.S. & Canada State/Province Distribution
United States AK, AL, AR, AZ, CA, CO, CT, DC, DE, FL, GA, IA, ID, IL, IN, KS, KY, LA, MA, MD, ME, MI, MN, MO, MS, MT, NC, ND, NE, NH, NJ, NM, NV, NY, OH, OK, OR, PA, RI, SC, SD, TN, TX, UT, VA, VT, WA, WI, WV, WY
Canada AB, BC, LB, MB, NB, NF, NS, NT, NU, ON, PE, QC, SK

Range Map
Note: Range depicted for New World only. The scale of the maps may cause narrow coastal ranges or ranges on small islands not to appear. Not all vagrant or small disjunct occurrences are depicted. For migratory birds, some individuals occur outside of the passage migrant range depicted. For information on how to obtain shapefiles of species ranges see our Species Mapping pages at

Range Map Compilers: NatureServe, 2002; WILDSPACETM 2002

U.S. Distribution by County Help
State County Name (FIPS Code)
CT Fairfield (09001), Hartford (09003), Litchfield (09005), Middlesex (09007), New London (09011)*, Tolland (09013), Windham (09015)
DE Kent (10001), Sussex (10005)
GA Lowndes (13185)
IA Dickinson (19059), Hancock (19081)*, Osceola (19143), Winnebago (19189)*
ID Ada (16001), Bear Lake (16007), Bingham (16011), Blaine (16013), Boise (16015), Bonner (16017), Bonneville (16019), Boundary (16021), Camas (16025), Canyon (16027), Caribou (16029), Custer (16037), Elmore (16039), Franklin (16041), Fremont (16043), Gem (16045), Gooding (16047), Jefferson (16051), Kootenai (16055), Lemhi (16059), Owyhee (16073), Payette (16075), Shoshone (16079), Twin Falls (16083), Valley (16085)
IL Brown (17009), Cass (17017), Cook (17031), DuPage (17043), Fulton (17057), Grundy (17063)*, Jasper (17079), Lake (17097), Mchenry (17111), Monroe (17133), Perry (17145), Shelby (17173)
IN Delaware (18035)*, Elkhart (18039), Fayette (18041), Fulton (18049), Gibson (18051), Greene (18055), Jay (18075), Kosciusko (18085)*, La Porte (18091), Lagrange (18087)*, Lake (18089), Madison (18095)*, Marion (18097)*, Marshall (18099), Montgomery (18107), Newton (18111), Parke (18121), Porter (18127), St. Joseph (18141), Starke (18149)*, Steuben (18151)*, Sullivan (18153), Tippecanoe (18157), Vermillion (18165), Vigo (18167), Warrick (18173)
KS Barton (20009), Douglas (20045), Stafford (20185)
KY Hopkins (21107)*, Jefferson (21111)*, McLean (21149)*, Muhlenberg (21177)*, Oldham (21185)*, Trigg (21221)*
MA Barnstable (25001), Berkshire (25003), Bristol (25005), Dukes (25007)*, Essex (25009), Franklin (25011), Hampden (25013), Hampshire (25015), Middlesex (25017), Nantucket (25019)*, Norfolk (25021)*, Plymouth (25023), Worcester (25027)
MD Anne Arundel (24003)*, Baltimore County (24005), Charles (24017), Dorchester (24019), Montgomery (24031)*, Prince Georges (24033)*, Somerset (24039), Talbot (24041), Wicomico (24045)
MI Alger (26003), Arenac (26011), Baraga (26013), Bay (26017), Charlevoix (26029), Cheboygan (26031), Chippewa (26033), Delta (26041), Gratiot (26057), Houghton (26061), Huron (26063), Iosco (26069), Jackson (26075), Kalamazoo (26077)*, Kalkaska (26079), Livingston (26093)*, Mackinac (26097), Macomb (26099), Manistee (26101), Marquette (26103), Mason (26105), Saginaw (26145), St. Clair (26147), Tuscola (26157), Washtenaw (26161)*, Wexford (26165)
MN Aitkin (27001), Anoka (27003), Becker (27005), Beltrami (27007), Big Stone (27011), Carlton (27017), Carver (27019), Cass (27021), Chippewa (27023), Chisago (27025), Clay (27027), Clearwater (27029), Cook (27031), Cottonwood (27033), Crow Wing (27035), Grant (27051), Hennepin (27053), Isanti (27059), Itasca (27061), Jackson (27063), Kanabec (27065), Kandiyohi (27067), Kittson (27069), Koochiching (27071), Lac Qui Parle (27073), Lake (27075), Lake of the Woods (27077), Mahnomen (27087), Marshall (27089), Mille Lacs (27095), Morrison (27097), Norman (27107), Otter Tail (27111), Pennington (27113), Pine (27115), Polk (27119), Pope (27121), Red Lake (27125), Renville (27129), Roseau (27135), Sherburne (27141), St. Louis (27137), Stevens (27149), Swift (27151), Wabasha (27157), Wadena (27159), Wilkin (27167), Yellow Medicine (27173)
MO Andrew (29003), Carroll (29033), Chariton (29041), Gentry (29075), Holt (29087), Jasper (29097), Lafayette (29107), Lincoln (29113), Linn (29115), Macon (29121), Pike (29163), Platte (29165), Ray (29177), Saline (29195), Scott (29201), St. Charles (29183), St. Louis (29189), Stoddard (29207), Wayne (29223)
MS Hancock (28045), Jackson (28059)
MT Blaine (30005), Carter (30011), Cascade (30013), Chouteau (30015), Fergus (30027), Flathead (30029), Glacier (30035), Golden Valley (30037), Lake (30047), Missoula (30063), Phillips (30071), Powell (30077), Ravalli (30081), Roosevelt (30085), Sanders (30089), Sheridan (30091), Teton (30099), Valley (30105), Yellowstone (30111)
NC Beaufort (37013), Carteret (37031), Hyde (37095), Pamlico (37137)
NE Arthur (31005), Box Butte (31013), Brown (31017), Cherry (31031), Fillmore (31059), Garden (31069), Garfield (31071), Grant (31075), Holt (31089), Kearney (31099), Knox (31107), Lancaster (31109), Lincoln (31111), McPherson (31117), Morrill (31123), Phelps (31137), Rock (31149), Sheridan (31161)
NH Coos (33007), Hillsborough (33011), Merrimack (33013), Sullivan (33019)
NJ Atlantic (34001), Bergen (34003), Burlington (34005), Cape May (34009), Cumberland (34011), Gloucester (34015), Hudson (34017), Monmouth (34025), Morris (34027), Ocean (34029), Passaic (34031), Salem (34033), Somerset (34035), Sussex (34037), Warren (34041)
OH Columbiana (39029), Hamilton (39061), Holmes (39075)*, Lucas (39095), Marion (39101), Ottawa (39123), Portage (39133), Summit (39153), Wayne (39169)*
OK Tillman (40141)
PA Adams (42001)*, Berks (42011)*, Butler (42019)*, Centre (42027)*, Chester (42029)*, Clearfield (42033)*, Clinton (42035)*, Crawford (42039), Erie (42049)*, Jefferson (42065)*, Lancaster (42071)*, Lawrence (42073)*, Luzerne (42079), Mercer (42085), Monroe (42089)*, Northumberland (42097), Philadelphia (42101), Potter (42105), Sullivan (42113), Tioga (42117), Wayne (42127)*
RI Providence (44007)*, Washington (44009)
TN Grundy (47061)*, Montgomery (47125)
VA Fairfax (51059)
WI Adams (55001), Ashland (55003), Barron (55005), Bayfield (55007), Brown (55009), Burnett (55013), Columbia (55021), Dane (55025), Dodge (55027), Door (55029), Douglas (55031), Florence (55037), Fond Du Lac (55039), Green Lake (55047), Iron (55051), Jackson (55053), Juneau (55057), Kenosha (55059), Langlade (55067), Manitowoc (55071), Marathon (55073), Marinette (55075), Marquette (55077), Monroe (55081), Oconto (55083), Oneida (55085), Outagamie (55087), Pepin (55091), Polk (55095), Portage (55097), Price (55099), Racine (55101), Rusk (55107), Sauk (55111), Sawyer (55113), Shawano (55115), St. Croix (55109), Taylor (55119), Vilas (55125), Washburn (55129), Waupaca (55135), Winnebago (55139), Wood (55141)
WY Albany (56001), Big Horn (56003), Campbell (56005), Carbon (56007), Crook (56011), Fremont (56013), Goshen (56015), Hot Springs (56017), Lincoln (56023), Natrona (56025), Park (56029), Sheridan (56033), Sublette (56035), Sweetwater (56037), Teton (56039), Uinta (56041)
* Extirpated/possibly extirpated
U.S. Distribution by Watershed Help
Watershed Region Help Watershed Name (Watershed Code)
01 Merrimack (01070002)+, Contoocook (01070003)+, Nashua (01070004)+, Concord (01070005)+, Merrimack (01070006)+, Upper Connecticut (01080101)+, West (01080107)+, Middle Connecticut (01080201)+, Miller (01080202)+, Deerfield (01080203)+, Chicopee (01080204)+, Lower Connecticut (01080205)+, Westfield (01080206)+, Farmington (01080207)+, Charles (01090001)+, Cape Cod (01090002)+, Blackstone (01090003)+*, Narragansett (01090004)+, Pawcatuck-Wood (01090005)+, Quinebaug (01100001)+, Shetucket (01100002)+, Thames (01100003)+*, Housatonic (01100005)+, Saugatuck (01100006)+
02 Rondout (02020007)+, Hackensack-Passaic (02030103)+, Raritan (02030105)+, Long Island Sound (02030203)+*, Middle Delaware-Mongaup-Brodhead (02040104)+, Middle Delaware-Musconetcong (02040105)+, Lehigh (02040106)+*, Crosswicks-Neshaminy (02040201)+, Lower Delaware (02040202)+, Schuylkill (02040203)+*, Brandywine-Christina (02040205)+*, Cohansey-Maurice (02040206)+, Broadkill-Smyrna (02040207)+, Mullica-Toms (02040301)+, Great Egg Harbor (02040302)+, Upper Susquehanna-Tunkhannock (02050106)+, Upper Susquehanna-Lackawanna (02050107)+, Bald Eagle (02050204)+*, Pine (02050205)+, Lower West Branch Susquehanna (02050206)+, Lower Susquehanna (02050306)+*, Gunpowder-Patapsco (02060003)+, Choptank (02060005)+, Patuxent (02060006)+*, Middle Potomac-Catoctin (02070008)+*, Monocacy (02070009)+*, Middle Potomac-Anacostia-Occoquan (02070010)+, Lower Potomac (02070011)+, Western Lower Delmarva (02080109)+, Eastern Lower Delmarva (02080110)+
03 Pamlico (03020104)+, Pamlico Sound (03020105)+, Lower Neuse (03020204)+, Alapaha (03110202)+, Pascagoula (03170006)+, Mississippi Coastal (03170009)+, Lower Pearl. Mississippi (03180004)+
04 Baptism-Brule (04010101)+, Beaver-Lester (04010102)+, St. Louis (04010201)+, Cloquet (04010202)+, Beartrap-Nemadji (04010301)+, Bad-Montreal (04010302)+, Keweenaw Peninsula (04020103)+, Sturgeon (04020104)+, Betsy-Chocolay (04020201)+, Tahquamenon (04020202)+, Waiska (04020203)+, Manitowoc-Sheboygan (04030101)+, Door-Kewaunee (04030102)+, Duck-Pensaukee (04030103)+, Oconto (04030104)+, Peshtigo (04030105)+, Menominee (04030108)+, Escanaba (04030110)+, Tacoosh-Whitefish (04030111)+, Fishdam-Sturgeon (04030112)+, Upper Fox (04030201)+, Wolf (04030202)+, Lake Winnebago (04030203)+, Little Calumet-Galien (04040001)+, Pike-Root (04040002)+, St. Joseph (04050001)+, Kalamazoo (04050003)+*, Upper Grand (04050004)+, Maple (04050005)+, Pere Marquette-White (04060101)+, Manistee (04060103)+, Betsie-Platte (04060104)+, Manistique (04060106)+, Lake Michigan (04060200)+, St. Marys (04070001)+, Carp-Pine (04070002)+, Lone Lake-Ocqueoc (04070003)+, Au Gres-Rifle (04080101)+, Kawkawlin-Pine (04080102)+, Pigeon-Wiscoggin (04080103)+, Shiawassee (04080203)+, Saginaw (04080206)+, Lake Huron (04080300)+, St. Clair (04090001)+, Lake St. Clair (04090002)+, Clinton (04090003)+, Huron (04090005)+*, Cedar-Portage (04100010)+, Cuyahoga (04110002)+, Ashtabula-Chagrin (04110003)+*, Chautauqua-Conneaut (04120101)+*, Lake Erie (04120200)+*
05 Upper Allegheny (05010001)+, Middle Allegheny-Tionesta (05010003)+*, French (05010004)+, Middle Allegheny-Redbank (05010006)+*, Upper Ohio (05030101)+, Shenango (05030102)+, Connoquenessing (05030105)+, Walhonding (05040003)+*, Upper Scioto (05060001)+, Whitewater (05080003)+, Lower Green (05110005)+*, Pond (05110006)+*, Upper Wabash (05120101)+, Tippecanoe (05120106)+, Middle Wabash-Little Vermilion (05120108)+, Sugar (05120110)+, Middle Wabash-Busseron (05120111)+, Embarras (05120112)+, Little Wabash (05120114)+, Upper White (05120201)+*, Lower White (05120202)+, Lower Cumberland (05130205)+*, Red (05130206)+, Silver-Little Kentucky (05140101)+*, Highland-Pigeon (05140202)+, Tradewater (05140205)+*
06 Upper Elk (06030003)+*
07 Mississippi Headwaters (07010101)+, Leech Lake (07010102)+, Prairie-Willow (07010103)+, Elk-Nokasippi (07010104)+, Pine (07010105)+, Crow Wing (07010106)+, Long Prairie (07010108)+, Platte-Spunk (07010201)+, Sauk (07010202)+, Clearwater-Elk (07010203)+, Crow (07010204)+, South Fork Crow (07010205)+, Twin Cities (07010206)+, Rum (07010207)+, Upper Minnesota (07020001)+, Pomme De Terre (07020002)+, Lac Qui Parle (07020003)+, Hawk-Yellow Medicine (07020004)+, Chippewa (07020005)+, Middle Minnesota (07020007)+, Cottonwood (07020008)+, Lower Minnesota (07020012)+, Upper St. Croix (07030001)+, Namekagon (07030002)+, Kettle (07030003)+, Snake (07030004)+, Lower St. Croix (07030005)+, Buffalo-Whitewater (07040003)+, Black (07040007)+, Upper Chippewa (07050001)+, Flambeau (07050002)+, South Fork Flambeau (07050003)+, Lower Chippewa (07050005)+, Red Cedar (07050007)+, Upper Wisconsin (07070001)+, Lake Dubay (07070002)+, Castle Rock (07070003)+, Lower Wisconsin (07070005)+, Winnebago (07080203)+*, Upper Rock (07090001)+, Crawfish (07090002)+, Kishwaukee (07090006)+, Des Moines Headwaters (07100001)+, The Sny (07110004)+, Salt (07110007)+, Peruque-Piasa (07110009)+, Kankakee (07120001)+, Iroquois (07120002)+, Chicago (07120003)+, Des Plaines (07120004)+, Upper Illinois (07120005)+*, Upper Fox (07120006)+, Lower Fox (07120007)+, Lower Illinois-Lake Chautauqua (07130003)+, Lower Illinois (07130011)+, Cahokia-Joachim (07140101)+, Big Muddy (07140106)+, Upper Kaskaskia (07140201)+
08 New Madrid-St. Johns (08020201)+, Upper St. Francis (08020202)+, Lower St. Francis (08020203)+
09 Bois De Sioux (09020101)+, Mustinka (09020102)+, Otter Tail (09020103)+, Upper Red (09020104)+, Buffalo (09020106)+, Eastern Wild Rice (09020108)+, Sandhill-Wilson (09020301)+, Red Lakes (09020302)+, Red Lake (09020303)+, Thief (09020304)+, Clearwater (09020305)+, Grand Marais-Red (09020306)+, Snake (09020309)+, Two Rivers (09020312)+, Roseau (09020314)+, Rainy Headwaters (09030001)+, Vermilion (09030002)+, Rainy Lake (09030003)+, Little Fork (09030005)+, Big Fork (09030006)+, Rapid (09030007)+, Lower Rainy (09030008)+, Lake of the Woods (09030009)+
10 Madison (10020007)+, Upper Missouri-Dearborn (10030102)+, Two Medicine (10030201)+, Teton (10030205)+, Judith (10040103)+, Upper Musselshell (10040201)+, Middle Milk (10050004)+, Peoples (10050009)+, Whitewater (10050011)+, Beaver (10050014)+, Porcupine (10050016)+, Big Muddy (10060006)+, Brush Lake closed basin (10060007)+, Yellowstone Headwaters (10070001)+, Clarks Fork Yellowstone (10070006)+, Upper Yellowstone-Pompeys Pillar (10070007)+, Popo Agie (10080003)+, Lower Wind (10080005)+, Upper Bighorn (10080007)+, Nowood (10080008)+, Big Horn Lake (10080010)+, Dry (10080011)+, North Fork Shoshone (10080012)+, South Fork Shoshone (10080013)+, Shoshone (10080014)+, Upper Tongue (10090101)+, Clear (10090206)+*, Little Powder (10090208)+, Boxelder (10110202)+, Upper Belle Fourche (10120201)+, Little White (10140203)+, Upper Niobrara (10150003)+, Middle Niobrara (10150004)+, Lower Niobrara (10150007)+, Lewis and Clark Lake (10170101)+, Upper North Platte (10180002)+, Pathfinder-Seminoe Reservoirs (10180003)+, Sweetwater (10180006)+, Middle North Platte-Casper (10180007)+, Middle North Platte-Scotts Bluff (10180009)+, Upper Laramie (10180010)+, Horse (10180012)+, Lower North Platte (10180014)+, Middle Platte-Buffalo (10200101)+, Salt (10200203)+, Upper Middle Loup (10210001)+, Dismal (10210002)+, Upper North Loup (10210006)+, Calamus (10210008)+, Cedar (10210010)+, Upper Elkhorn (10220001)+, Little Sioux (10230003)+, Tarkio-Wolf (10240005)+, Nodaway (10240010)+, Independence-Sugar (10240011)+, Middle Republican (10250016)+, Lower Kansas (10270104)+, Turkey (10270204)+, Upper Little Blue (10270206)+, Upper Grand (10280101)+, Lower Grand (10280103)+, Little Chariton (10280203)+, Lower Missouri-Crooked (10300101)+, Lower Missouri (10300200)+
11 Rattlesnake (11030009)+, Cow (11030011)+, Spring (11070207)+, West Cache (11130203)+
14 Upper Green (14040101)+, New Fork (14040102)+, Upper Green-Slate (14040103)+, Big Sandy (14040104)+, Bitter (14040105)+, Upper Green-Flaming Gorge Reservoir (14040106)+, Blacks Fork (14040107)+, Muddy (14040108)+, Great Divide closed basin (14040200)+, Little Snake (14050003)+, Muddy (14050004)+
16 Upper Bear (16010101)+, Central Bear (16010102)+, Bear Lake (16010201)+, Middle Bear (16010202)+
17 Lower Kootenai (17010104)+, Blackfoot (17010203)+, Bitterroot (17010205)+, Flathead Lake (17010208)+, Swan (17010211)+, Lower Flathead (17010212)+, Pend Oreille Lake (17010214)+, South Fork Coeur D'alene (17010302)+, Upper Spokane (17010305)+, Snake headwaters (17040101)+, Greys-Hobock (17040103)+, Salt (17040105)+, Idaho Falls (17040201)+, Upper Henrys (17040202)+, Lower Henrys (17040203)+, Teton (17040204)+, Willow (17040205)+, American Falls (17040206)+, Lake Walcott (17040209)+, Upper Snake-Rock (17040212)+, Beaver-Camas (17040214)+, Birch (17040216)+, Big Lost (17040218)+, Camas (17040220)+, Little Wood (17040221)+, Bruneau (17050102)+, Boise-Mores (17050112)+, South Fork Boise (17050113)+, Lower Boise (17050114)+, Middle Snake-Payette (17050115)+, Payette (17050122)+, North Fork Payette (17050123)+, Upper Salmon (17060201)+
CC CC-37 (CC-37)+*
+ Natural heritage record(s) exist for this watershed
* Extirpated/possibly extirpated
Ecology & Life History
Basic Description: A large wading bird (bittern).
General Description: A stocky wading bird with a straight pointed bill, relatively short neck and legs, and somewhat pointed wings; darker flight feathers; bill dull yellow with a dusky tip on the upper mandible; legs and feet are greenish yellow; breeding feathering includes generally inconspicuous white ruffs on the shoulders and two small green patches on the back; wing span 107 cm (NGS 1983). Terrestrial locomotion is slow and stealthy; flight is rapid and usually low.

MORPHOLOGY AND PLUMAGES: A brown, medium-sized heron, 60-85 cm long, with a stout body and neck and relatively short legs (Palmer 1962, Cramp 1977, Hancock and Kushlan 1984). Adult plumage is all brown above (finely flecked with black) and heavily streaked with brown and white below. The crown is rusty- brown. An elongated, black patch extends from below the eye down the side of the neck, a characteristic unique among herons (Hancock and Kushlan 1984). The throat is white. Sexes are similar, except that the male is slightly larger (Palmer 1962). Juveniles differ only in lacking black neck patches, which are obtained in the first winter. Plumage does not change seasonally. In flight, seem hurried, ungraceful, and stiff. When disturbed, they often freeze in an upright, concealing posture, with head and bill upturned.

VOCALIZATIONS: During the breeding season, males repeat from two to 10 times a distinctive, far-carrying call, rendered as "pump-er-lunk" by Palmer (1962), and which is often preceded by a series of clicking and gulping sounds. A detailed, anatomical description of how they vocalize, through inflation of the esophagus, was provided by Chapin (1922). They rely on their resounding calls to communicate among the dense, visually restricting emergent vegetation that dominates nesting habitats. Low frequency sounds, such as their "booming," attenuate less rapidly and are audible at greater distances in dense marsh vegetation than high frequency sounds (Cosens and Falls 1984). When flushed from a marsh, they often emit a hoarse "kok-kok-kok" or nasal "haink" (Palmer 1962).

EGGS: Eggs measure 49 by 37 mm and are elliptical, buff-brown to deep olive-brown, smooth, and slightly glossy (Harrison 1978).

Diagnostic Characteristics: Differs from night-herons in the following ways: wings are pointed rather than rounded, flight feathers are much darker than back (vs. no contrast), upperparts lack white spotting, and bill is more slender. Much larger than the least bittern (average length 71 cm vs. 33 cm). Differs from similar juvenile green heron in being larger (length 71 cm vs. 46 cm) and in having flight feathers of wings obviously darker than the middle of the back.
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).

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).

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.

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).
Non-Migrant: Y
Locally Migrant: Y
Long Distance Migrant: Y
Mobility and Migration Comments: 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).
Estuarine Habitat(s): Herbaceous wetland
Palustrine Habitat(s): HERBACEOUS WETLAND, Riparian
Habitat Comments: BREEDING: Primarily large freshwater and (less often) brackish marshes, including lake and pond edges where cattails, sedges, or bulrushes are plentiful and marshes where there are patches of open water and aquatic-bed vegetation. Occurs also in other areas with dense herbaceous cover, such as shrubby marshes, bogs, wet meadows, and, rarely, hayfields (Brewer et al. 1991). Readily uses wetlands created by impoundments. Wetlands of 2.5 ha or more may support nesting; smaller wetlands may serve as alternate foraging sites (Gibbs and Melvin 1992). See Hanowski and Niemi (1990) for a quantitative study of habitat in Minnesota.

Nests primarily in inland freshwater wetlands, sometimes in tidal marshes or in sparsely vegetated wetlands or dry grassy uplands. Breeding occurs primarily in wetlands with tall emergent vegetation. Sparsely vegetated wetlands and dry grassy uplands are sometimes used, as are tidal marshes in some areas (Stewart and Robbins 1958, Swift 1987). In comparison to the sympatric least bittern (IXOBRYCHUS EXILIS), uses a wider variety of wetland cover types, less densely vegetated sites, shallower water depths, and primarily freshwater habitats.

Wetlands used in Maine were dominated by emergent and aquatic-bed (floating-leaved and submergent) vegetation, had a high diversity of vegetative life forms, and a high degree of cover/water interspersion (Gibbs et al. in press; Gibbs and Melvin 1990). Portions of wetlands used were dominated by sedges (CAREX spp.), broad-leaved cattail (TYPHA LATIFOLIA), and ericaceous shrubs. In a study of Quebec lakes, lakes with patches of floating-leaved plants, emergent growth along shorelines, and abundant amphibian populations were preferred (DesGranges and Houde 1989).

At Horicon Marsh in Wisconsin, responded to tape-recorded calls only from shallow water cattail and dry cattail habitats and seemed to avoid deepwater cattails (Manci and Rusch 1988). At moist soil impoundments in Missouri, associated with water depths of less than 10 cm and vegetative cover characterized as "rank, dense, or sparse." Habitat use was not associated with "open" or "short" vegetative cover or water of depths of greater than 10 cm (Fredrickson and Reid 1986). In Minnesota, seven breeding territories had a mean water depth of 10 cm, vegetation height of 1.3 m, and density of sedge and grass stems of 117 stems/m squared (Hanowski and Niemi 1986).

NON-BREEDING: Migrant bitterns were flushed at 25 sites during spring in Missouri with mean water depth of 26 cm, vegetation height of 63 cm, and stem density of 157 stems/m squared. Characteristics of 35 flush sites in fall were similar, except that vegetation was taller (118 cm) (Reid 1989). In areas where temperatures stay above freezing and waters remain open, especially in coastal regions where the ocean moderates climate (Root 1988). Wintering habitat is much like breeding habitat, and overwintering populations are heavily dependent on managed wetland areas, such as those occurring at wildlife refuges (Root 1988). Occasionally occurs in habitats that are more open than the usual ones. Overwintering occasionally takes place in brackish coastal marshes (Hancock and Kushlan 1984).

Adult Food Habits: Carnivore, Invertivore, Piscivore
Immature Food Habits: Carnivore, Invertivore, Piscivore
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).

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).

Adult Phenology: Crepuscular, Nocturnal
Immature Phenology: Crepuscular, Nocturnal
Phenology Comments: More active when light intensity is low (Palmer 1962).
Length: 71 centimeters
Weight: 706 grams
Economic Attributes Not yet assessed
Management Summary
Stewardship Overview: Breeds and overwinters in freshwater wetlands with emergent vegetation and shallow water. Widely distributed across the Northeast, but little is known about population size, although trends appear to be stable. Loss and degradation of wetlands is the most serious threat. Frequents artificial impoundments at managed wildlife areas during the breeding and wintering seasons, thereby providing a good opportunity to manage habitat specifically for this bird. Slow drawdowns can be used to create foraging areas and to encourage dense stands of emergent vegetation. Standardized surveys should be conducted across the region to determine abundance and more accurate population trends of this as well as other secretive wetland birds. Point-counts using tape-recorded vocalizations could be used to survey wetlands across the region.
Restoration Potential: Because of extensive post-breeding dispersal (Cramp 1977), bitterns are able to colonize new habitats and persist as small, isolated populations. For example, the Eurasian bittern recolonized Great Britain in the 1940s, where it was extirpated in the 1870s, and now persists in six small populations (50 pairs total) located distantly from one another (Bibby 1981, Day 1981). Readily uses artificial wetlands created by impoundments at waterfowl refuges (Andrle and Carroll 1988, Gibbs et al. in press), a trait that could facilitate restoration of populations in regions where natural, inland freshwater wetlands have been destroyed (Connecticut, Rhode Island, central New York, New Jersey, and Maryland) or were scarce originally (central Pennsylvania and West Virginia). Also seems adaptable to a wide range of wetland habitats, ranging from margins of boreal lakes in Quebec (DesGranges and Houde 1989) to dense cattail marshes in New York (Andrle and Carroll 1988), and can thrive at wetlands of many types as long as suitable prey and adequate cover are available (Gibbs et al. in press). Information is too scarce, however, on the structure and potential growth rates of populations to speculate about the recovery potential.
Preserve Selection & Design Considerations: Wetland area is a consideration for preserve design because both occurrence (Brown and Dinsmore 1986) and abundance (Gibbs et al. in press, Gibbs and Melvin 1990) are greater on larger than smaller wetlands. Wetlands of 2.5 ha or more may support nesting; smaller wetlands may serve as alternate foraging sites (Gibbs and Melvin 1992). In Maine, inhabited wetlands from less than one to greater than 25 ha in size, but were more abundant in larger than smaller wetlands, and preferred impoundments and beaver-created wetlands to wetlands of glacial origin (Gibbs et al. in press, Gibbs and Melvin 1990). Eaton (1914) suggested that there were occurrences in New York at marshes of less than four ha. In Iowa, Brown and Dinsmore (1986) observed individuals only on wetlands of greater than 11 ha and suggested that occurrences at wetlands was possibly area-dependent. A minimum area of 2.5-5 ha is therefore suggested as being sufficient to support nesting activity (see Eaton 1910, Brown and Dinsmore 1986, Gibbs et al. in press). Smaller wetlands adjacent to large wetlands used for nesting may serve as important, alternate foraging sites for these birds, which are seen regularly flying between wetlands during the nesting season in Maine (J. Gibbs, pers. obs.). Vegetative features of wetland preserves should include a high diversity of vegetative life forms and an abundance of emergent vegetation well-interspersed with patches of open water and aquatic-bed vegetation. Water levels should be less than 10 cm deep (Fredrickson and Reid 1986). Retaining dense, woody riparian vegetation may provide a visual barrier that reduces human disturbance of nesting bitterns and also buffers a wetland ecosystem against upland runoff that may contain silt, pesticides, and other contaminants (Gibbs and Melvin 1992).
Management Requirements: Wetlands used for breeding need to be protected from chemical contamination, siltation, eutrophication, and other forms of pollution that harm these birds or their food supplies. Day and Wilson (1978) emphasized that merely preserving habitats for endangered populations of Eurasian bitterns is not adequate to ensure their longterm viability; management of vegetation and monitoring water quality at protected areas also is required.

Vegetative features of preferred habitats represent a particular stage of wetland succession. Wetland managers therefore need to periodically reverse vegetative succession while maintaining suitable habitats nearby to serve as alternate nesting areas during wetland manipulations. The concentration of both nesting and overwintering populations at protected and managed wetlands such as state and national wildlife refuges (Andrle and Carroll 1988, Root 1988) emphasizes the need to develop and implement beneficial habitat management procedures. Minor alterations of existing management schemes could greatly improve nesting habitat. Where littoral vegetation is scarce, moist soil plant management (Fredrickson and Taylor 1982) provides a cost effective method involving water-level manipulation to reestablish and promote growth of dense stands of emergent vegetation.

Complete drawdowns should be avoided so that populations of small fish, amphibians, and dragonfly larvae, which make up a large part of the diet, are conserved for the following season. Slow, rather than rapid, drawdowns emulate natural water recession patterns, concentrate foods, and help prevent oxygen depletion (Fredrickson and Reid 1986). Drawdowns can be used to create favorable water levels (less than 10 cm deep, Fredrickson and Reid 1986) for foraging. Liming and fertilizing dikes and adjacent fields can increase productivity and raise the pH of many nutrient-poor, acidic wetlands in the northeastern region (Jorde et al. 1989). Control of infestations of purple loosestrife and phragmites may improve habitats in many northeastern states.

Monitoring Requirements: Encountered too infrequently on Breeding Bird Surveys to assess population trends in most states. Use localized habitats that usually occur away from roads, and the seasonal peak of vocal activity (April-May) tends to occur earlier than when Breeding Bird Survey routes are run. Broadcast of tape-recorded calls can increase detectibility by eliciting responses from these rarely seen birds (Manci and Rusch 1988, Gibbs and Melvin 1989, Kibbe 1989). Broadcast surveys can be coordinated with surveys of other marshbirds (Swift 1987, Manci and Rusch 1988, Gibbs and Melvin 1989), many of which also are of management concern (e.g., Pied-billed Grebe [PODILYMBUS PODICEPS], Least Bittern, and Black Tern [CHLIDONIAS NIGER]). Surveys initially should be conducted annually (for two to three years) at many sites to provide baseline data on population distributions and abundance in a given region. Repeated surveys (e.g., once every three to five years) can then assess population trends. Surveys should be conducted during the peak of the breeding season. Standardization of survey methodology and coordination of state and regional surveys is necessary for results to be comparable between years and among areas, and might best be accomplished by having a single agency or organization responsible for coordinating survey efforts.
Management Research Needs: Develop standardized methodologies for population monitoring in the northeastern U.S.

Conduct surveys to determine abundance and distribution in the northeastern U.S.

Monitor trends in populations and habitat availability in the northeastern U.S.

Conduct a detailed, autecological study that examines basic features of the breeding biology of the species, including diet, home range, mating systems, ability to renest, sources and rates of mortality in adults, juveniles, nestlings, and eggs, and juvenile dispersal patterns and philopatry. This information could be gathered through radio-telemetry and banding studies.

Evaluate habitat requirements, including the vegetative characteristics, water quality, and minimum area of wetlands used by nesting, migrant, and overwintering birds. Also, evaluate effects of riparian zone management on wetland use.

Identify migration routes, major stopover sites, and major overwintering areas.

Examine the effects of contaminants, parasites, diseases, predation, water pollution, acid rain, human disturbance, and severe weather on populations.

Develop wetland management strategies that benefit nesting and migrant birds. Because the distribution of nesting birds is closely tied to protected wetlands at state and national wildlife refuges in many parts of the Northeast, assess the long-term viability of these sites as core-breeding areas for regional populations.

Monitor contaminant levels in adults and eggs in industrialized and agricultural regions of the northeastern U.S.

Evaluate the effects of marsh invasion by phragmites and purple loosestrife.

Biological Research Needs: Much is still unknown about this bird's biology and behavior (National Audubon Society, 2014). Little is known about the possible effects of contaminants on this species (Lowther, et. al. 2009).
Population/Occurrence Delineation
Use Class: Breeding
Minimum Criteria for an Occurrence: Evidence of breeding (including historical); and potential recurring breeding at a given location, minimally a reliable observation of one or more breeding pairs in appropriate habitat. Be cautious about creating EOs for observations that may represent single breeding events outside the normal breeding distribution.
Separation Barriers: None.
Separation Distance for Unsuitable Habitat: 10 km
Separation Distance for Suitable Habitat: 10 km
Separation Justification: Separation distance is not intended to delineate demographically independent populations or metapopulations (such units likely would be quite large) but rather serves to circumscribe breeding occurrences that are of practical size for conservation/management use.

Male and female home ranges in Minnesota averaged 415 ha and 337 ha, respectively (Brininger 1996). In another Minnesota study, the average male home range size was 127 ha (n=20, Azure 1998). Average size of the core use area (defined as the area of the home range in which bitterns were located 50% of the time) was 25 ha.

Inferred Minimum Extent of Habitat Use (when actual extent is unknown): .5 km
Inferred Minimum Extent Justification: Based on an average core home range of 25 hectares (Azure 1998). Include only the nesting marsh within the boundaries of the Inferred Extent polygon.
Date: 26Apr2004
Author: Cannings, S., and G. Hammerson

Use Class: Nonbreeding
Minimum Criteria for an Occurrence: Evidence of recurring presence of concentrations of wintering birds (including historical), and potential recurring presence at a given location. Normally only areas where concentrations greater than 10 birds occur regularly for at least 20 days per year would be deemed EOs. Be cautious about creating EOs for observations that may represent single events.
Separation Barriers: None.
Separation Distance for Unsuitable Habitat: 10 km
Separation Distance for Suitable Habitat: 10 km
Separation Justification: Separation distance arbitrary.
Inferred Minimum Extent of Habitat Use (when actual extent is unknown): .5 km
Inferred Minimum Extent Justification: Based on an average core home range in summer of 25 hectares (Azure 1998)
Date: 26Apr2004
Author: Cannings, S., and G. Hammerson
Population/Occurrence Viability
U.S. Invasive Species Impact Rank (I-Rank) Not yet assessed
NatureServe Conservation Status Factors Edition Date: 26Feb2014
NatureServe Conservation Status Factors Author: Hammerson, G., and D.W. Mehlman
Management Information Edition Date: 31Dec1992
Management Information Edition Author: GIBBS, J.P., AND S.M. MELVIN; REVISIONS BY D.W. MEHLMAN
Management Information Acknowledgments: Parts of this abstract were originally published by the U.S. Fish and Wildlife Service in Schneider and Pence (1992). Funding for the preparation of the original document was made possible by the U.S. Fish and Wildlife Service, Newton Corner, MA. Critical review of an earlier draft of this report was provided by P. Novak. The authors are grateful to library staff of the Smithsonian Institution, the Patuxent Wildlife Research Center (U.S. Fish and Wildlife Service), and the Peabody Museum at Yale University for bibliographic assistance. J. Longcore and D. McAuley facilitated a bibliographic computer search and provided other logistical support. The Maine Department of Inland Fishing and Wildlife provided office space and computer access during the preparation of this report. K.E. and H.C. Gibbs provided much indirect support to J.P.G.
Element Ecology & Life History Edition Date: 20Dec1994
Element Ecology & Life History Author(s): HAMMERSON, G., AND D.W. MEHLMAN

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