(DRAFT) - Taxonomy
Species EAGLE, BALD
Species Id ESIS109001
Date 14 MAR 96
TAXONOMY
NAME - EAGLE, BALD
OTHER COMMON NAMES - EAGLE, BALD;EAGLE, AMERICAN;EAGLE, FISH;EAGLE, GRAY;EAGLE, MOTTLED;EAGLE, SEA;EAGLE, WASHINGTON'S;EAGLE, WHITE-HEADED;EAGLE and WHITE-TAILED;AGUILA CALUA
ELEMENT CODE -
CATEGORY - Birds
PHYLUM AND SUBPHYLUM - CHORDATA,
CLASS AND SUBCLASS - AVES,
ORDER AND SUBORDER - FALCONIFORMES,
FAMILY AND SUBFAMILY - ACCIPITRIDAE,
GENUS AND SUBGENUS - HALIAEETUS,
SPECIES AND SSP - LEUCOCEPHALUS,
SCIENTIFIC NAME - HALIAEETUS LEUCOCEPHALUS
AUTHORITY -
TAXONOMY REFERENCES -
COMMENTS ON TAXONOMY -
Bald Eagle
Haliaeetus leucocephalus (Linnaeus, 1766)
KINGDOM: Animal GROUP: Bird
PHYLUM: Chordata CLASS: Aves
ORDER: Falconiformes FAMILY: Accipitridae
Species Description. In the adult plumage, the head, neck, tail,
and upper and lower tail coverts are white. The remainder of the
plumage is dark brown. The bill, cere, iris, and feet are yellow,
and the distal 1/2 to 2/3 of the tarsus is bare in all plumages.
The juvenal and subadult plumages are mainly brown, including the
head and tail. White or buff mottling is extensive on some
individuals, particularly in the underwing coverts, tail, and abdomen.
The bill and cere of the immature are dark brown or gray, the iris is
brown, and the feet are yellow. The adult plumage is attained in 4 to
5 years (03,04,05,10,13).
Bald eagles from natal or breeding areas at northern latitudes
average larger than those from southern latitudes. Size variation
appears to be clinal, however, size differences were used as the basis
for subspecific division (09). Average measurements of northern and
southern bald eagles follow: Northern population...male wing=589 cm,
Taxonomy - 1 (DRAFT) - Taxonomy
Species EAGLE, BALD
Species Id ESIS109001
Date 14 MAR 96
female wing=640 cm; male tail=310 cm, female tail=339 cm; male
weight=4,000 g, female weight=6,3000 g. Southern population...male
wing=529 cm, female wing=577 cm; male tail=249 cm, female tail=271 cm;
(weights unavailable) (03).
Synonomy. Synonomy at the generic, species, and subspecies
levels has been reviewed in detail by Friedmann (36). Some of the
more common or important synonyms follow: Falco leucocephalus
Linnaeus, 1776; Aquila leucocephala Vieillot, 1807; Vultur
leucocephalus Temminck, 1807; Falco washingtoniensis Audubon, 1827;
Haliaetus leucocephalus Lesson, 1831; and Haliaetos leucocephalus
Bonaparte, 1838. Two subspecies of Haliaeetus leucocephalus are
currently recognized in North America; H.l. alascanus (Alaska and
Canada) and H.l. leucocephalus (Southern U.S.) (102).
Taxonomic Questions. Taxonomic debates involving the bald eagle
focus on the validity of subspecific distinctions and the proper
subspecies name for the northern race. The bald eagle was described
by Linnaeus in 1766 based on Catesby's "Bald Eagle" from Carolina
(i.e., South Carolina) (36). Audubon subsequently collected a very
large eagle near Henderson, Kentucky (07,09), which he concluded was a
distinct species from the bald eagle. Audubon gave this bird the name
Falco washingtoniensis (occasionally changed to washingtonii under the
principal of first reviser) (07). This bird was later thought to be
a wintering immature bald eagle, and the name washingtoniensis was
subsequently buried in the synonomy of Haliaeetus leucocephalus.
In 1897, Townsend determined that northwestern and southern bald
eagles differed in size, and he assigned the larger northern birds to
the new subspecies Haliaeetus leucocephalus alascanus (43). Bangs
(09) subsequently pointed out that Audubon's washingtoniensis and
Townsend's alascanus appear to both be northern populations of
Haliaeetus leucocephalus. He further implied that unless there were
sufficient differences found between northwestern (alascanus) and
northeastern (washingtoniensis) populations, the former should be
considered a synonym of the latter. Mengel (07) disagreed with this
conclusion, as he felt it unclear whether the bird being described
was actually a bald eagle. As such, Mengel (07) recommended that the
name alascanus be applied to the northern race of Haliaeetus
leucocephalus. The A.O.U. in 1957 (11) used the name alascanus for
the northern subspecies, whereas Stresemann and Amadon in 1979 (44)
used washingtoniensis.
The debate over the proper name of the northern race is probably
moot. Since size variation is apparently clinal, there is an
increasing tendency to disregard the subspecific taxonomy. The
offical listing classification of the bald eagle in 50 CFR 17.11 does
not include trinomials (01).
A variety of vernacular names have been used for this species,
including American eagle, gray eagle, sea eagle, white-headed eagle,
white-tailed eagle, fish eagle, Washington,s eagle, mottled eagle
(01,02,03,04,05,08,09,13), and Aguila calua (Spanish-Mexico).
Type Localities and Locations of Type Specimens. The type
species of the genus Haliaeetus is the white-tailed eagle, H.
albicilla. The type locality of Haliaeetus leucocephalus is South
Carolina. The species was described by Linnaeus based on a
description by Catesby (1729, Nat. Hist. Carolina, part 1, pl. 1).
Taxonomy - 2 (DRAFT) - Taxonomy
Species EAGLE, BALD
Species Id ESIS109001
Date 14 MAR 96
The type of H.l. washingtoniensis was collected near Henderson,
Kentucky by J.J. Audubon, and served as the basis for Audubon's
painting of "The Bird of Washington" (1827, Birds of America, pl. 11).
The location of the specimen is not known (07). The type of H.l.
alascanus was collected at Unalaska, Aleutian Islands, 22 May 1895, by
C.H. Townsend. The specimen, a male, is housed in the U.S. National
Museum (USNM 151567) (43).
Taxonomy - 3 (DRAFT) - Status
Species EAGLE, BALD
Species Id ESIS109001
Date 14 MAR 96
STATUS
Coded Status
E: Federal Endangered
T: Federal Threatened
Federal Migratory
E: Federal Endangered
T: Federal Threatened
Federal Migratory
Alabama; Federal Endangered
Alabama; State Listed
Alabama; Unofficially Listed
Arkansas; Federal Endangered
Arkansas; State Recognized
Florida; Federal Endangered
Florida; Officially Listed
Georgia; Federal Endangered
Georgia; State Listed
Kentucky; Federal Endangered
Kentucky; State Recognized
Louisiana; Federally Endangered
Louisiana; State Recognized
Maryland; Federal Endangered
Maryland; State Recognized
Status - 1 (DRAFT) - Status
Species EAGLE, BALD
Species Id ESIS109001
Date 14 MAR 96
Coded Status
Mississippi; Federal Endangered
Mississippi; State Listed
North Carolina; Federal Endangered
North Carolina; State Listed
South Carolina; Federal Endangered
South Carolina; State Listed
Tennessee; Federal Endangered
Tennessee; State Listed
Virginia; Federal Endangered
Virginia; State Listed
West Virginia; Federal Endangered
West Virginia; State Recognized
Status - 2 (DRAFT) - Status
Species EAGLE, BALD
Species Id ESIS109001
Date 14 MAR 96
Coded Status
West Virginia; Unofficially Listed
E: Federal Endangered
T: Federal Threatened
Federal Migratory
Non-consumptive recreational
Ceremonial/Cultural
COMMENTS ON STATUS -
U.S. STATUSES AND LAWS:
The bald eagle (Haliaeetus leucocephalus) has been designated an
Endangered species in the conterminous United States except in the
States of Washington, Oregon, Minnesota, Wisconsin, and Michigan
where the bald eagle has been designated a Threatened species pursuant
to the Endangered Species Act of 1973 (50 CFR 17.11; P.L. 93-205,
87 Stat. 884; 16 U.S.C. 1531-1540), as amended. Critical Habitat has
not been designated for this species.
Special rules concerning "take" of individuals from the
States where eagles are designated as Threatened can be found in
50 CFR 17.41(a). Rules concerning eagle permits can be found in
50 CFR 22.
This species is also protected by the Lacey Act of 1900
(P.L. 97-79; 16 U.S.C. 3371 et seq.), the Migratory Bird Treaty Act of
1918 (50 CFR 10.13; 16 U.S.C. 703-711 et seq.), and the Bald Eagle Act
of 1940 (16 U.S.C. 668-668d; 54 Stat. 250), as amended.
RESPONSIBLE FEDERAL AGENCIES:
USFWS -Responsible for the management/recovery, listing, and
law enforcement/protection of this species.
BIA, BLM, BR, DOD, DOE, NPS, & USFS:
-Responsible for the law enforcement/protection of this
species with applicable State and Federal laws on
public lands under their control. Also responsible
for management/recovery on public lands under agency
control.
All Federal agencies have responsibility to ensure that any
action authorized, funded, or carried out by that agency is not likely
to jeopardize the continued existence of the species or result in the
destruction or adverse modification of Critical Habitat (50 CFR 402),
Status - 3 (DRAFT) - Status
Species EAGLE, BALD
Species Id ESIS109001
Date 14 MAR 96
and to utilize their authorities to carry out programs for the
conservation of the species.
STATE STATUSES AND LAWS:
DESIGNATED STATUS: Endangered.
STATE/ADMINISTRATIVE AGENCY/STATE STATUTES:
(AL) Dept. of Conserv. and Nat. Resourc./Reg. 87-GF-7/Nongame;
(CA) Fish and Game Comm./ CA Fish and Game Code, Sec. 2052;
(CT) Dept. of Environ. Protection/ CT General Stat. Annot., Sec.
26-40d and 26-40e;
(GA) Game and Fish Div./ Rules and Regs. of the State of GA, Sec.
391-4-13-.09, Jan. 11, 1981;
(ID) Dept. of Fish and Game/ Idaho Code, Sec. 36-103;
(IL) Dept. of Conserv./ 17 Ill. Admin. Code 1010.30, Feb. 1982;
(IA) Div. of Fish and Game/ IA Admin. Code 290-19.1, Sept. 1977;
(KS) Fish and Game Comm./ KS Admin. Regs. 23-17-1, May 1980;
(MA) Div. of Fisheries and Wildl./ MA Gen. Laws Annot. 131, Sec.
26A;
(MS) Dept. of Wildl. Conserv./ MS Pub. Notice No. 2156, Eff.
Sept. 1, 1981;
(NE) Game and Parks Comm./ NE Admin. Rules and Regs., Vol. 13,
6-(4) 1984, Rev. Stat. of NE, Sec. 37-430 to 438;
(NV) NV Dept. of Wildl./ NV Admin. Code, Sec. 503.015 to 503.080,
Dec. 21, 1981;
(NH) Fish and Game Dept./ NH Code of Admin. Rules Fis. 1001.01,
1001.02, Eff. Apr. 28, 1980;
(NJ) Dept. of Environ. Protection/ Div. of Fish, Game and Wildl.,
NJ Admin. Code 7:25-11.2, Eff. Mar. 29, 1979;
(NY) Dept. of Environ. Conserv./ 6 NY Code, Rules and Regs.
182.5, Apr. 30, 1983;
(NC) Wildl. Res. Comm./ 15 NC Admin. Code 10 I .0003, Eff. July
28, 1979;
(OH) Dept. of Nat. Res., Div. of Wildl./ OH Admin. Code
1501:31-23-01, Eff. July 11, 1980;
(PA) Game Comm./ 58 PA Code Sec. 147.1, 147.21, Mar. 1983;
(SC) Wildl. and Marine Res. Dept./ SC Regs. 123-150;
(SD) Dept. of Game, Fish and Parks/ Admin. Rules of SD 41:10:02,
Eff. Mar. 16, 1978;
(TN) Wildl. Res. Ag./ TN Wildl. Procedures No. 75-15, as amended,
Dec. 8, 1978;
(TX) Parks and Wildl. Dept./ 31 TX Admin. Code Sec. 57.133
(127.30.09.003), July 1977;
(VT) Fish and Game Dept./ VT Regs. Annot. 13-79.1, July 1, 1975;
(VA) Comm. of Game and Inland Fisheries/ Code of VA Sec. 29-230
to 29-237;
(WI) Dept. of Nat. Res./ NR 27.03 WI Admin. Code, Eff. Oct.,
1981;
(WY) Game and Fish Dept./ WY Stat. Annot., Sec. 23-1-302.
DESIGNATED STATUS: Threatened.
STATE/ADMINISTRATIVE AGENCY/STATE STATUTES:
(CO) Div. of Wildl./ CO Rev. Stat., Sec. 33-8-103(4);
Status - 4 (DRAFT) - Status
Species EAGLE, BALD
Species Id ESIS109001
Date 14 MAR 96
(FL) Game and Freshwater Fish Comm./ Rule 39-27.03 FL Admin.
Code, July 1983;
(MI) Dept. of Nat. Res./ MI Compiled Laws Annot., Sec. 299.221 to
299.230, MI Admin. Code 299.1021 to .1028, Feb. 1983;
(MN) Dept. of Nat. Res./ MN Code of Ag. Rules, Sec. 1.5600 to
1.5601, Eff. Dec. 1, 1983;
(NM) Dept. of Game and Fish/ NM Regulation No. 624, Eff. July 22,
1983.
DESIGNATED STATUS: Recognized Endangered.
STATE/ADMINISTRATIVE AGENCY/STATE STATUTES:
(AZ) Game and Fish Dept./ AZ Rev. Stat., Sec. 17-101;
(AR) Game and Fish Comm./ AK Stat., Sec. 47-101, 47-117, 47-118,
and 47-119;
(DE) Dept. of Nat. Res. and Environ. Control/ 7 DE Code Annot.,
Sec. 601;
(IN) Div. of Fish and Wildl./ IN Stat. Annot., Sec. 14-2-8.5-1,
310 Indiana Admin. Code 3-3-6;
(KY) Dept. of Fish and Wildl. Res./ KY Rev. Stat. 150.183, 301 KY
Admin. Reg. 3:061;
(LA) Wildl. and Fisheries Comm./ LA Stat. Annot. 56:1901 to
56:1907;
(ME) Dept. of Inland Fisheries and Wildl./ ME Rev. Stat. Annot.,
Sec. 7001, 7751-7756;
(MD) Dept. of Nat. Res./ MD Nat. Res. Code Annot., Sec. 4-2A-01
to 4-2A-09, 10-2A-01 to 10-2A-09, Code MD Regs. 08.03.01.43,
Supp. 4;
(MO) Dept. of Conserv./ MO Rev. Stat. 252.240, 3 Wildl. Code of
MO 10-4.111, Eff. Jan. 1, 1983;
(MT) Dept. of Fish, Wildl., and Parks/ MT Code Annot. 87-5-101 to
112, MT Admin. Register 12.5.201;
(ND) Game and Fish Dept./ ND Century Code 20.1-10-02 and
20.1-02-05;
(OK) Dept. of Wildl. Conserv./ 29 OK Stat. Annot., Sec. 2-109,
2-135, 7-501, 7-502, 7-504, and 7-602;
(RI) Dept. of Environ. Mngmt./ Gen. Laws of RI Sec. 20-37-1 to
20-37-5;
(UT) Dept. of Nat. Res./ UT Code Annot. 23-13-2 to 23-13-4;
(WV) Dept. of Nat. Res./ WV Code, Sec. 20-7-7(1), WV Code, Sec.
20-1-1;
DESIGNATED STATUS: Recognized Threatened.
STATE/ADMINISTRATIVE AGENCY/STATE STATUTES:
(OR) Dept. of Fish and Wildl./ OR Rev. Stat. 498.026;
(WA) Dept. of Game/ WA Admin. Code 232-12-014, June 1, 1981.
STATE: Alabama, West Virginia
UNOFFICIAL LIST: (AL) Endangered; 1) Endangered and Threatened
Plants and Animals of Alabama. AL Mus. of Nat.
Hist., Bull. No. 2, 1976, Univ. of Alabama;
2) Vertebrate Animals of Alabama in Need of
Special Attention. AL Agri. Exp. Sta., Auburn
Univ., April 1986.
Status - 5 (DRAFT) - Status
Species EAGLE, BALD
Species Id ESIS109001
Date 14 MAR 96
(WV) Endangered; Special Animal List, Wildl.
Res. Div., WV Dept. of Nat. Res.
INTERNATIONAL STATUSES, TREATIES, AND AGREEMENTS:
The bald eagle (Haliaeetus leucocephalus) is listed in Appendix I
of CITES. The white-tailed eagle (Haliaeetus albicilla), a synonym
for the bald eagle, is listed as Vulnerable in the IUCN Red Data Book,
1979. The southern bald eagle (Haliaeetus leucocephalus
leucocephalus) is listed as Endangered in the IUCN Red Data Book,
1979, and as rare by the U.S. in the Western Hemisphere Conv. Annex,
1967.
The bald eagle in Canada, examined by the Comm. on the Status of
Endangered Wildl. in Canada (April 1985) was judged not in any "risk"
category. Raptors are not included under Canada's Migratory Bird
Convention Act. Most Provinces and Territories have Fish and Wildlife
Acts and most protect raptors. Provincial Endangered Species lists
are maintained by Ontario (Endangered Species Act, Chapter 138, Rev.
Stat. of Ontario, 1980) and New Brunswick (Chapter E-9.1, Reg. 82-248,
Endangered Species Act). The eagle is listed as Endangered on these
lists.
The bald eagle is on that listed by Mexico in "Especies de Fauna
en Peligro de Extincion en Mexico."
ECONOMIC STATUSES:
The bald eagle is the National Symbol of the United States; an
indicator of certain environmental pollutants; has a high aesthetic
value to many people; and preys on some species taken by humans
for food and recreation and occasionally on domesticated species. The
bald eagle both historically and presently has religious ceremonial
and cultural use by North American Indians. The Indians use feathers,
claws, bones, and beaks for these ceremonial/cultural purposes.
67/03/11:32 FR 04001/ - Listed as Endangered
73/04/25:38 FR 10208/10234 - Migratory Bird Treaty Act
74/01/04:39 FR 01158/01185 - Bald and Golden Eagles Protection Act
75/05/16:40 FR 21499/21500 - Critical Habitat-Notice of Intent
76/07/12:41 FR 28525/28527 - Proposed Modification of Endang. Status
77/02/22:42 FR 10462/10468 - CITES Implementation
78/02/14:43 FR 06230/06233 - Determ. of Certain Pop. to be Threatened
78/03/06:43 FR 09167/09172 - Survey of Native Spp. Protected by CITES
78/05/03:43 FR 21338/21339 - Status of Native Spp. Protected by CITES
80/05/20:45 FR 33768/33781 - CITES Report for 1978
83/01/12:48 FR 01325/01332 - Prop.; Raptor Exempt.-Fed. Falcon. Stand.
83/07/08:48 FR 31600/31610 - Final Rule; Rapt. Ex. Fed. Falcon. Stand.
83/12/08:48 FR 55100/55102 - Five Year Review
84/09/14:49 FR 36290/36293 - Propos. Conserv. Measures; re: Lead Pois.
85/07/22:50 FR 29900/29901 - Five Year Review
Status - 6 HABITAT ASSOCIATIONS
HABITAT - TERRESTRIAL
TERRESTRIAL
INLAND AQUATIC
COASTAL
SOCIETY OF AMERICAN FORESTRY TYPES
SAF TYPE STAGE CLOSURE
mature tree
Old Growth
White spruce balsam fir mature tree
White spruce balsam fir Old Growth
Longleaf Pine mature tree
Longleaf Pine Old Growth
Loblolly Pine-Shortleaf Pine mature tree
Loblolly Pine-Shortleaf Pine Old Growth
Shortleaf Pine-Oak mature tree
Shortleaf Pine-Oak Old Growth
mature tree
Old Growth
mature tree
Old Growth
mature tree
Old Growth
mature tree
Old Growth
Aspen-paper birch mature tree
Aspen-paper birch Old Growth
Douglas-fir-western hemlock mature tree
Douglas-fir-western hemlock Old Growth
Interior Ponderosa Pine mature tree
Interior Ponderosa Pine Old Growth
Western white pine mature tree
Western white pine Old Growth
mature tree
Old Growth
Sitka spruce-western hemlock mature tree
Sitka spruce-western hemlock Old Growth
Western larch mature tree
Western larch Old Growth
Lodgepole pine mature tree
Lodgepole pine Old Growth
Redwood mature tree
Redwood Old Growth
mature tree
Old Growth
mature tree
Old Growth
White spruce-birch mature tree
White spruce-birch Old Growth
LAND USE -
Residential
Herbaceous Rangeland
Shrub and Brush Rangeland
Mixed Rangeland
Deciduous Forest Land
Evergreen Forest Land
Habitat Associations - 1 LAND USE -
Mixed Forest Land
Streams and Canals
Lakes
Reservoirs
Bays and Estuaries
Forested Wetland
Nonforested Wetland
Beaches
Mixed Barren Land
Tundra Land: Shrub Brush
Tundra Land: Mixed
NATIONAL WETLAND INVENTORY CODES
NWI NWICLS NWIMOD NWISPEC
Riverine, intermittent UB4
Riverine, intermittent UB3
Riverine, intermittent UB2
Riverine, intermittent UB1
Riverine, intermittent SB4
Riverine, intermittent SB3
Riverine, intermittent SB2
Riverine, intermittent SB1
Riverine, intermittent RS2
Riverine, intermittent RS1
Riverine, intermittent RB1
Riverine, intermittent OW0
Riverine, intermittent FL6
Riverine, intermittent FL5
Riverine, intermittent FL4
Riverine, intermittent FL3
Riverine, intermittent FL2
Riverine, intermittent FL1
Riverine, intermittent BB2
Riverine, intermittent BB1
Riverine, intermittent AB5
Riverine, intermittent AB4
Riverine, intermittent AB3
Riverine, intermittent AB2
Riverine, intermittent AB1
Riverine, upper perennial UB4
Riverine, upper perennial UB3
Riverine, upper perennial UB2
Riverine, upper perennial UB1
Riverine, upper perennial SB4
Riverine, upper perennial SB3
Riverine, upper perennial SB2
Riverine, upper perennial SB1
Riverine, upper perennial RS2
Riverine, upper perennial RS1
Riverine, upper perennial RB2
Riverine, upper perennial RB1
Riverine, upper perennial OW0
Riverine, upper perennial FL6
Riverine, upper perennial FL5
Riverine, upper perennial FL4
Riverine, upper perennial FL3
Riverine, upper perennial FL2
Habitat Associations - 2
NWI NWICLS NWIMOD NWISPEC
Riverine, upper perennial FL1
Riverine, upper perennial BB2
Riverine, upper perennial BB1
Riverine, upper perennial AB5
Riverine, upper perennial AB4
Riverine, upper perennial AB3
Riverine, upper perennial AB2
Riverine, upper perennial AB1
Riverine, lower perennial UB4
Riverine, lower perennial UB3
Riverine, lower perennial UB2
Riverine, lower perennial UB1
Riverine, lower perennial SB4
Riverine, lower perennial SB3
Riverine, lower perennial SB2
Riverine, lower perennial SB1
Riverine, lower perennial RS2
Riverine, lower perennial RS1
Riverine, lower perennial RB2
Riverine, lower perennial RB1
Riverine, lower perennial OW0
Riverine, lower perennial FL6
Riverine, lower perennial FL5
Riverine, lower perennial FL4
Riverine, lower perennial FL3
Riverine, lower perennial FL2
Riverine, lower perennial FL1
Riverine, lower perennial EM4
Riverine, lower perennial EM3
Riverine, lower perennial EM2
Riverine, lower perennial BB2
Riverine, lower perennial BB1
Riverine, lower perennial AB5
Riverine, lower perennial AB4
Riverine, lower perennial AB3
Riverine, lower perennial AB2
Riverine, lower perennial AB1
Riverine, tidal UB4
Riverine, tidal UB3
Riverine, tidal UB2
Riverine, tidal UB1
Riverine, tidal SB4
Riverine, tidal SB3
Riverine, tidal SB2
Riverine, tidal SB1
Riverine, tidal RS2
Riverine, tidal RS1
Riverine, tidal RB2
Riverine, tidal RB1
Riverine, tidal OW0
Riverine, tidal FL6
Riverine, tidal FL5
Riverine, tidal FL4
Riverine, tidal FL3
Riverine, tidal FL2
Riverine, tidal FL1
Riverine, tidal EM4
Riverine, tidal EM3
Riverine, tidal EM2
Habitat Associations - 3
NWI NWICLS NWIMOD NWISPEC
Riverine, tidal BB2
Riverine, tidal BB1
Riverine, tidal AB5
Riverine, tidal AB4
Riverine, tidal AB3
Riverine, tidal AB2
Riverine, tidal AB1
Lacustrine, littoral UB4
Lacustrine, littoral UB3
Lacustrine, littoral UB2
Lacustrine, littoral UB1
Lacustrine, littoral RS2
Lacustrine, littoral RS1
Lacustrine, littoral RB2
Lacustrine, littoral RB1
Lacustrine, littoral OW0
Lacustrine, littoral FL6
Lacustrine, littoral FL5
Lacustrine, littoral FL4
Lacustrine, littoral FL3
Lacustrine, littoral FL2
Lacustrine, littoral FL1
Lacustrine, littoral EM4
Lacustrine, littoral EM3
Lacustrine, littoral EM2
Lacustrine, littoral BB2
Lacustrine, littoral BB1
Lacustrine, littoral AB5
Lacustrine, littoral AB4
Lacustrine, littoral AB3
Lacustrine, littoral AB2
Lacustrine, littoral AB1
Lacustrine, limnetic UB4
Lacustrine, limnetic UB3
Lacustrine, limnetic UB2
Lacustrine, limnetic UB1
Lacustrine, limnetic RB2
Lacustrine, limnetic RB1
Lacustrine, limnetic OW0
Lacustrine, limnetic AB5
Lacustrine, limnetic AB4
Lacustrine, limnetic AB3
Lacustrine, limnetic AB2
Lacustrine, limnetic AB1
Palustrine UB4
Palustrine UB3
Palustrine UB2
Palustrine UB1
Palustrine SS7
Palustrine SS6
Palustrine SS4
Palustrine SS3
Palustrine SS2
Palustrine SS1
Palustrine RB2
Palustrine RB1
Palustrine OW0
Palustrine ML2
Palustrine ML1
Habitat Associations - 4
NWI NWICLS NWIMOD NWISPEC
Palustrine FO7
Palustrine FO6
Palustrine FO5
Palustrine FO4
Palustrine FO3
Palustrine FO2
Palustrine FO1
Palustrine FL6
Palustrine FL5
Palustrine FL4
Palustrine FL3
Palustrine FL2
Palustrine FL1
Palustrine EM6
Palustrine EM5
Palustrine EM4
Palustrine EM3
Palustrine EM2
Palustrine EM1
Palustrine AB5
Palustrine AB4
Palustrine AB3
Palustrine AB2
Palustrine AB1
Estuarine, intertidal SS7
Estuarine, intertidal SS6
Estuarine, intertidal SS5
Estuarine, intertidal SS4
Estuarine, intertidal SS3
Estuarine, intertidal SS1
Estuarine, intertidal SB3
Estuarine, intertidal SB2
Estuarine, intertidal SB1
Estuarine, intertidal RS3
Estuarine, intertidal RS2
Estuarine, intertidal RS1
Estuarine, intertidal FO7
Estuarine, intertidal FO6
Estuarine, intertidal FO5
Estuarine, intertidal FO4
Estuarine, intertidal FO3
Estuarine, intertidal FO1
Estuarine, intertidal FL4
Estuarine, intertidal FL3
Estuarine, intertidal FL2
Estuarine, intertidal FL1
Estuarine, intertidal EM4
Estuarine, intertidal EM3
Estuarine, intertidal EM2
Estuarine, intertidal EM1
Estuarine, intertidal BB2
Estuarine, intertidal BB1
Estuarine, intertidal AB
Estuarine, subtidal OW0
Marine, intertidal RS3
Marine, intertidal RS2
Marine, intertidal RS1
Marine, intertidal FL6
Marine, intertidal FL3
Habitat Associations - 5
NWI NWICLS NWIMOD NWISPEC
Marine, intertidal FL2
Marine, intertidal FL1
Marine, intertidal BB2
Marine, intertidal BB1
COMMENTS ON HABITAT ASSOCIATIONS -
Bald eagle nest site selection varies widely from deciduous,
coniferous, and mixed forest stands in the east and midwest,
coniferous forests in the northwest, mangrove swamps in Florida,
cliffs in Alaska and Arizona, to ground nests on islands along the
Pacific coast (17,33,35,38,41). A common feature of bald eagle nest
sites throughout North America is their close proximity to water
(17,35,38,41). The majority of nest sites are within 1/2 mile of a
body of water such as coastal shorelines, bays, rivers, lakes, farm
ponds, dammed up rivers (i.e., beaver dams, log jams, etc.). Nests
are rarely located more than 2 miles from water (03,17,33,34,38,42,
45).
Bald eagles primarily nest in dominant or codominant trees
located along ecotones. Nests are often near a break in the forest
such as a burn, clearcut, field edge (including agricultural fields),
or water (17,35,40,42). Nest trees are usually characterized by open
branching and stout limbs. There is usually a clear flight path into
at least one side of the nest and an unobstructed view of water (17,
40,42). Nest sites are found in communities with moderate to low open
crown cover (33,38). Among other materials, cornstalks have been
known to have been used for nest linings (80,86,87).
In the eastern United States, pines are often preferred nest
trees. Eastern white pine (Pinus strobus) is the preferred nest tree
in Maine, although spruce (Picea spp.) is also frequently used. In
Minnesota, eastern white pine is preferred, with red pine (Pinus
resinosa) and quaking aspen (Populus tremuloides) ranking second
(35,38,45). In the Pacific northwest, Douglas fir (Pseudotsuga
menziesii) is the preferred nest tree. In the Chesapeake Bay region,
loblolly pine (Pinus taeda) is preferred, but oaks (Quercus spp.),
hickories (Carya spp.), and other hardwoods are also used (71). Near
Lake Erie, nest trees include sycamore (Platanus occidentalis) and
shellbark hickory (Carva ovata). Although preference for deciduous or
coniferous sites may occur locally, the factors involved in choosing
a nest site may depend more on tree and forest structure than on
species (38,41,42).
Bald eagle wintering areas possess many of the same
characteristics as nest sites. Wintering areas are usually located
near open water on rivers, lakes, reservoirs, and bays where fish and
waterfowl are abundant, or in areas with little or no water (i.e.,
rangelands, barren land, tundra, suburban areas, etc.) where other
prey species (e.g., rabbit, rodents, deer, carrion) are abundant
(17,37,47). Roost sites are an important component of wintering
areas. The perch trees in the roost are often the largest trees
within a stand (standing snags and utility poles have also been used),
with stout lower horizontal branches for easy access (17,37,47).
These sites provide a warmer microclimate than the surrounding area,
and are isolated from human activity (17,72). Roost sites may be used
at night by one to greater than one hundred bald eagles, as well as
during the day, especially during inclement weather (17).
Perch trees used during the day possess the same characteristics
as roost trees but are located closer to foraging areas, usually along
shorelines or other open areas. Perch tree preference varies widely
with geographic location and is strongly influenced by food
availability (17,37,45,46,47). Trees surrounding perches and roosts
Habitat Associations - 6 also provide a visual and physical buffer from human disturbance.
Lish and Lewis (85) documented abandonment of a roost site in Oklahoma
when timber harvesting and home building occurred in close proximity.
Bald eagle habitat occurs primarily in undeveloped areas with
little human activity (33,38). Major threats to bald eagle habitat
include poorly planned timber harvesting, outdoor recreation, and
development along shorelines (34,38,40,42,45,46). Habitat alteration
has also created bald eagle habitat in some cases. Nesting habitat
has been created by timber harvesting that provides openings in
formerly continuous forested areas, and winter habitat has been
created by reservoir construction (42).
Some tolerance for human activity has been documented in bald
eagles [e.g., low levels of recreational activity, vehicle traffic
near feeding areas (39,45,47), some habitat alteration, and road use
near active nests (42)]. Bald eagles are more tolerant of human
activity at feeding sites than nesting or roosting sites, and are more
tolerant during winter than during the nesting season (45,47).
Habitat Associations - 7 (DRAFT) - Food Habits
Species EAGLE, BALD
Species Id ESIS109001
Date 14 MAR 96
FOOD HABITS
TROPHIC LEVEL -
CARNIVORE
Food Habits - 1 (DRAFT) - Environment Associations
Species EAGLE, BALD
Species Id ESIS109001
Date 14 MAR 96
ENVIRONMENTAL ASSOCIATIONS
Environment Associations - 1 (DRAFT) - Life History
Species EAGLE, BALD
Species Id ESIS109001
Date 14 MAR 96
LIFE HISTORY
FOOD HABITS:
The bald eagle (Haliaeetus leucocephalus) is an opportunistic
predator that feeds primarily on fish but also takes a variety of
birds, mammals, and turtles (both live and as carrion) when fish are
less abundant or these other species are readily available (17,50,53,
54,55). Fish comprised 90.1 percent of all prey found at 6 nest sites
in Minnesota, birds 7.9 percent, mammals 1.3 percent, and
invertebrates 0.6 percent (56). In the Chesapeake Bay region in 1984,
fish accounted for 39 percent of occurrences of prey items collected
at nest sites, birds 35 percent, mammals 14 percent, and turtles 12
percent (71). In a study based mainly on stomach analysis, 18.8
percent of bald eagle food items were birds, 4.5 percent were mammals,
and 74.7 percent were lower vertebrates, primarily fish (50).
In Maine, researchers found that prey taken by bald eagles in the
nesting season varied between coastal and interior nest sites; fish
comprised 77 percent of food collected at inland sites, and avian
prey comprised 76 percent at coastal and offshore sites (73). A
similar opportunistic feeding strategy was found for bald eagles in
Alaska. In the Aleutian Islands, birds (primarily seabirds) comprised
61 percent to 81 percent of food remains at nests. In southeastern
Alaska, however, 2 studies documented 66 percent and 78 percent fish
in the bald eagles diet.
Fish. The percent of fish in the bald eagles diet varies with
geographic location, season, and relative abundance. Fish species
most commonly identified as bald eagle prey are catfish (Ictalurus
spp.), carp (Cyprinus carpio), gizzard shad (Dorosoma cepedianum),
salmon (Oncorhynchos spp.), and sucker (Catostomus spp., Moxostoma
spp.) (17,53,55,56,71,73). In Maine, 18 fish species were identified
as prey at nest sites during a five year period (1976 to 1980) (73).
In 1984, a minimum of 8 fish species were identified at bald eagle
nest sites in the Chesapeake Bay region (71). In the midwest during
winter, gizzard shad may be the most important prey species as eagles
feed on annual winter shad die-offs. Spawned-out salmon are an
important winter food source for bald eagles in the Pacific northwest
and Alaska (53).
Birds. Avian prey species are more important in the bald eagles
diet during winter when fish are less available due ice formation on
reservoirs, lakes, rivers, and bays. Bald eagles will capture
live, healthy birds but probably feed more on weakened, dying, or
dead birds, especially waterfowl (17,53,54,73,74).
A wide variety of bird species occur as bald eagle prey (53,54,
73,74,75). For the period 1977 to 1981, 45 species of birds were
identified as prey at nest sites in the Chesapeake Bay region.
Waterfowl were the most common avian prey [primarily mallards (Anas
platyrhynchos) and common goldeneyes (Bucephala clangula)], but
shorebirds and landbirds were also found (74). In a study in Maine,
36 species of birds were identified as prey, with black ducks (Anas
rubripes) and herring gulls (Larus argentatus) the most common (73).
Colonial nesting birds and seabirds have been identified as primary
prey on offshore islands and in coastal areas of the Atlantic and
Pacific (73,75).
Life History - 1 (DRAFT) - Life History
Species EAGLE, BALD
Species Id ESIS109001
Date 14 MAR 96
Mammals. A variety of mammals have also been identified as bald
eagle prey, although mammals are less important than fish and birds.
Mammals are taken as live prey or carrion in all seasons but become
more important during the winter months (17,53,54,73,74,75). Six
mammal species were identified as prey at bald eagle nest sites in the
Chesapeake Bay region in 1984. Muskrat (Ondatra zibethica) and
eastern cottontail (Sylvilagus floridanus) were the most common (71).
In Maine, muskrats and snowshoe hares (Lepus americanus) were the most
common mammal species collected at nest sites (73). In the Aleutian
Islands, Aleutian ground squirrels (Citellus parryi ablusus) were the
most common mammal prey item found at nests (75).
Mammals, primarily taken as carrion, have been identified as
important food items for wintering bald eagles. Deer (Odocoileus
spp.) and black-tailed jackrabbits (Lepus californicus) are the most
frequently mentioned mammal prey species for wintering bald eagles
(53,54,55,73).
Other Prey. Invertebrates comprise a very minor part of the
bald eagles diet (50,55,56,73,75). Reptiles also represent a small
portion of the food items of bald eagles, althouth several turtle
species have been identified as locally important in the eastern
portion of the bald eagles range (52,55). During the five year period
1977 to 1981, turtle shells were collected from 25 percent of the
successful bald eagle nests visited in the Chesapeake Bay region (52).
Stinkpot (Sternotherus odoratus) and norther diamondback terrapin
(Malachemys terrapin terrapin) made up the bulk of these turtle prey
remains (71).
HOME RANGE/TERRITORY:
Territorial behavior, both inter- and intraspecific, has been
observed in bald eagles on nesting territories. (Here territory is
defined as the area around the nest actively defended by one of both
of the resident breeding pair against intruding members of the same
species) (59,63,64,76,79). Bald eagles exhibit very little
territorial behavior on roosting and foraging areas at times other
than the breeding season, although aggressive interactions are common
(57,58,60,61,65).
Nesting Territory Size and Behavior. Territorial defense by
nesting bald eagles has been observed during studies on the Chippewa
National Forest. Nesting pairs were observed driving off both adult
and subadult bald eagles that ventured into their nesting territories,
both before egg laying and during incubation (59). Mattson (63)
described similar territorial defense by a nesting pair of bald eagles
in Michigan, however, Sherrod et al. (76) observed little
intraspecific aggression by nesting bald eagles on Amchitka Island,
Alaska.
Interspecific aggression by nesting bald eagles has been observed
less frequently. Territorial aggression toward ospreys was observed
in the Florida Keys where bald eagles and ospreys nested in close
proximity (78). Mattson (63), however, observed no territorial
aggression toward ospreys by a pair of nesting bald eagles in
Michigan, although ospreys were seen in the eagles nesting territory.
A few incidental observations of aggressive behavior toward other
bird species have also been documented (63).
Life History - 2 (DRAFT) - Life History
Species EAGLE, BALD
Species Id ESIS109001
Date 14 MAR 96
Territorial defense against human intrusion at nest sites has
been described by several researchers (59,76,79). The most common
response to human intrusion into the nesting territory is for the
adult(s) to flush from the nest (or a nearby perch) and circle
overhead calling intermittently. If the intruder remains in the area,
the adults would often soar up to a great height, leave the area, or
perch at a distant tree until the intruder leaves the territory (59,
79).
Sherrod et al. (76) described much more aggressive behavior by
nesting bald eagles on Amchitka Island. Most eagle pairs stooped at,
and in some cases struck, the researchers as they approached the nest
site (76). Unlike tree nesting populations, Amchitka Island is
treeless tundra, and eagles nest on the ground, which may contribute
to their aggressive behavior (76).
Several factors make it difficult to arrive at a definitive size
estimate for bald eagle nesting territories. These factors include
differences in habitat characteristics, nesting densities, population
levels, presence of human activity between various breeding areas, as
well as the differences in techniques used by researchers to estimate
territory size.
On Karluk Lake, Alaska, 14 nesting territories averaged 57 acres
in size and ranged from 28 to 112 acres determined by measuring the
distance between the nests and perch trees (64). In Michigan, nest
territory size for 1 nest was estimated to be 383 acres, determined by
the location of observed territorial defense by the breeding adults
(63). In southern Alaska an average territory size, with a radius of
about 1-1/2 mile, was estimated by measuring the straight line
distance between nests (81). In Florida, nesting territories were
estimated to have a radius of about 1/2 mile from the nest tree,
however, it is not clear what method was used to determine the
territory size. In two localities, three active nests were located
within 1,000 feet of each other (80).
Seasonal Home Range and Behavior. Bald eagles are known to use
communal roost sites and to congregate at foraging areas in winter
and summer (57,58,60,61,65). Intraspecific aggression is common at
these foraging areas where individual eagles have been observed
attempting to steal or displace other eagles from food items (60,61,
65). Bald eagles also attempt to displace other eagles and defend
preferred perch sites at night roosts and foraging areas (58,61,65).
Bald eagles exhibit little interspecific aggressive behavior
toward other birds at roosts and foraging sites. One of the few
exceptions is occassional aggression toward other species (e.g.,
American crow, Corvus brachyrhynchos) competing for food items (60).
Bald eagles are less aggressive toward humans outside of the breeding
seasons and tend to avoid human activity in roosting and foraging
locations (39).
Home range sizes for 14 radio-tagged bald eagles wintering in
Missouri varied from 48.2 square km (11,930 square acres) in 1976 to
18.5 square km (4,544 square acres) in 1978. The difference in
average home range size was attributed to greater prey availability in
1978 (77).
Radio telemetry was also used to determine the home range size
for 10 adult bald eagles wintering in the San Luis Valley, Colorado.
Life History - 3 (DRAFT) - Life History
Species EAGLE, BALD
Species Id ESIS109001
Date 14 MAR 96
Mean minimum home range size was 310.7 square km (76,800 square
acres). Home ranges of mated adults were significantly smaller than
those of unmated birds. Home ranges commonly overlapped but no eagles
were observed attempting to exclude other eagles from their ranges
(57).
PERIODICITY:
Bald eagles are diurnally active. In a study on the northern
Chesapeake Bay, eagles equipped with radio transmitters left night
roosts for foraging sites on an average of one hour after sunrise
(range: 30 minutes before to 280 minutes after sunrise) (82). These
same birds returned to night roosts an average of 40 minutes before
sunset (range: 115 minutes before to 15 minutes after). Bald eagles
tended to remain in roosts later in the morning and returned earlier
in the evening during inclement weather (e.g., rain, snow, or fog)
(82).
MIGRATION PATTERNS:
Bald eagles from the northern interior parts and the southernmost
parts of the species' range are migratory. Northern birds begin
moving south as open water freezes in autumn (usually in October)
(47). These birds apparently travel southward until concentrations of
food are located. Generally, immatures move further south than adults
(48). Northward movements often occur during thaws, and northward
migration begins in February or March (47,57).
Band recovery data show that many bald eagles wintering in the
interior of the United States are from breeding and natal areas in
Saskatchewan, Northwest Territories, Alberta, and Manitoba (62). Many
of these birds winter along the Missouri River and its tributaries
from Montana to Missouri, or in Wyoming or Colorado. Others migrate
through western Montana and western Idaho and winter in the basins
of Utah, California, and Oregon. Bald eagles from the eastern
interior of Canada and the Great Lakes region winter along the
Mississippi River and its tributaries (60,62).
Bald eagles from southeastern parts of the species range move
northward at the close of the breeding season during summer (June to
August) (83). These birds spend the summer in the region from the
Chesapeake Bay north and west to southern Canada and the Great Lakes,
and apparently return south in September (83).
Harmata (57) radio tracked 4 bald eagles from their wintering
grounds, in the San Luis Valley of Colorado, northward during spring
migration. One eagle was tracked to its eventual nest site in
northeast Saskatchewan, which was reached 15 days after its departure
from the wintering grounds. Migration speed averaged 50 km/hour, and
average daily flights were about 180 km. Migratory flights occurred
mainly on days with incomplete cloud cover and light morning winds,
between 1000 hours and 1800 hours. Prominent physiographic features
(e.g., mountain ridges, canyons, and rivers) apparently aided in
orientation (57).
COVER/SHELTER REQUIREMENTS:
Vegetative and topographic cover is important to bald eagles as a
shield from disturbance and as protection from adverse weather. The
Life History - 4 (DRAFT) - Life History
Species EAGLE, BALD
Species Id ESIS109001
Date 14 MAR 96
sheltering effects of cover are important at nests (33), winter
perches (84), and winter roosts (83).
Habitat use by bald eagles in winter is strongly affected by wind
speed and temperature. Under adverse weather conditions, particularly
high winds, bald eagles use perches and night roosts in low areas
where adjacent trees or hillsides provide a windbreak. In South
Dakota, bald eagles sought sheltered perches when temperatures dropped
below 0 degrees Celsius and/or when winds exceeded 20 km/hour (84).
The trees selected for perch and roost sites were taller than
surrounding trees, had more open canopies, and had stouter branches
(83,84); however, at many roosts the surrounding forest is often
relatively dense (82). Perch sites usually face open water on at
least one side (83), and roosts are usually close to foraging areas.
Trees surrounding perches and roosts also provide a visual and
physical buffer from human disturbance. Lish and Lewis (85)
documented abandonment of a roost site in Oklahoma when timber
harvesting and home building occurred in close proximity.
REPRODUCTIVE SITE REQUIREMENTS:
Bald eagles nest almost exclusively in live trees, although
coastal and desert populations in western North America frequently
nest on cliffs or on the ground (17,76). Habitat characteristics of
bald eagle nest sites, including nest tree species, are discussed in
the Habitat Association narrative (field N-Habitat). The average
height of nest trees has been estimated for several breeding areas.
Average nest tree height in the Chesapeake Bay region was 27 meters
(88), 26 meters in Florida (42), and 39 meters in southeastern Alaska
(81). Nest trees typically have stout limbs and open canopies that
provide a clear flight path into at least one side of the nest (40,
42).
The nest structure is usually placed just below the crown of the
tree (usually in the top 1/3), in a central crotch adjacent to the
trunk (42,80,86,87). Foliage above the nest offers some protection
from the sun and inclement weather (64). Average nest height has
been estimated at 23 meters in the Chesapeake Bay region (88), 22
meters in Florida (42), and 32 meters in southeastern Alaska (81).
The typical nest is constructed of large sticks with softer
materials, such as dead weeds, cornstalks, grasses, and sod, added as
nest lining (80,86,87). Ground nesting bald eagles on Amchitka
Island, Alaska construct nests of grasses, moss, kelp, and in some
cases driftwood (76). A slight depression, or egg cup, is formed in
the nest lining about 10 cm in depth and 36 cm in diameter (64). The
depth of the nest averages about 100 cm, and the width across the top
averages 150 cm (64,88). In most cases the nest is shaped like an
inverted cone or bowl. Most are wide at the top and narrow at the
base (86). Some nests are reused in subsequent years, and reach a
great size and weight as new nest material is added (80). One of the
largest nests ever recorded measured 2.9 meters wide and 6.1 meters
deep (80). A nest blown out of a tree in Maryland weighed 1,274
pounds (87).
REPRODUCTIVE CHARACTERISTICS:
Bald eagles reach sexual maturity at 4 to 6 years of age. Four
Life History - 5 (DRAFT) - Life History
Species EAGLE, BALD
Species Id ESIS109001
Date 14 MAR 96
years is the youngest confirmed age at which bald eagles have
successfuly raised yound in the wild. However, these birds were
released as fledglings as part of a reintroduction program (96).
Little is known of the average age of first breeding of wild-reared
eagles. The maximum age of breeding in the wild is also not known,
although captive bald eagles have laid eggs for up to 15 years (100).
An adult male eagle (minimum age 21) was recaptured in 1981 in Alaska
and was paired with a adult female. Both were actively nesting (101).
Bald eagles are monogamous and are believed to mate for life. If a
mate is lost a new pair bond is formed, often in the same breeding
season (100).
The breeding season consists of courtship, nest building,
incubation, raising nestlings, and providing food to the juveniles for
up to eight weeks after fledging (59,89). The breeding season varies
with latitude. Courtship and nest building begins in September and
October in Florida (80) but not before March and April in Alaska (64).
The timing of breeding activity can also vary within a breeding
population. In several breeding populations the date of egg laying
varies as much as five to seven weeks between pairs (45,80).
A single clutch of one to three eggs is laid per breeding season
and incubation lasts 34 to 38 days. Eggs are laid one to three days
apart (59,67). Bald eagles have been known to lay a second clutch
if the first is lost early during the incubation period (66,68).
Incubation is shared by both male and female but the difference in
time spent incubating by each sex has not been determined (59).
Hatching success has been estimated to be 75 percent (69). The young
fledge from 9 to 14 weeks (59,89). Nest success has been estimated
to be 60 percent with an average of one young fledged per occupied
nest (17,69).
PARENTAL CARE:
Bald eagle adults display nest territory defense from the start
of nest building to the period following fledging. This behavior
varies from calling in response to disturbance, to actively defending
the nest site and driving off intruders (59).
Young bald eagles are altricial. After the first day of hatching
the young eaglet immediately begins to accept food brought by the
parents. This process is continually repeated by the adults in an
apparent response to the "begging" calls of the young eaglets (59,89).
The young are continually brooded by both adults in the period
following hatching. The amount of time spent brooding decreases as a
function of the age of the young, and ceases at approximately six
weeks after hatching. At least one adult remains in the vicinity of
the nest at all times in the early posthatching period, possibly to
protect the young from predators, to brood in case of inclement
weather, or to provide shade. Because the young are confined to the
nest during this period, parental care continues until fledging (59).
The exact time of fledging appears to be variable (perhaps
influenced by weather or food availability) but generally occurs from
9 to 14 weeks after hatching. A majority of young fledge between
the 10th and 12th week (59,89).
During the 6 to 8 week period following fledging the young remain
at the nest or in the immediate vicinity. Parents continue to bring
Life History - 6 (DRAFT) - Life History
Species EAGLE, BALD
Species Id ESIS109001
Date 14 MAR 96
food to the young and remain defensive of the nest territory, but this
activity gradually decreases over time (89).
POPULATION BIOLOGY:
Bald eagles are long-lived birds with relatively low reproductive
potential, a strategy common to most large birds of prey (99).
Although much information is available on natility rates, little data
exist on age-specific survival rates, mortality rates, rates of
population change, sex ratio, or longevity (98). Estimates of age
ratio (immatures/adults) are available from surveys of wintering bald
eagles, but these estimates are subject to various biases (48).
Grier (98) used hypothetical but realistic estimates for natality
and mortality parameters in bald eagle population models, and found
differences in productivity in determining population size.
Accordingly, management programs for bald eagles should stress
survival-enhancing activities in addition to those that increase
productivity.
Available information suggests most bald eagle populations,
particularly those in the lower 48 states, are increasing. This
evidence includes an estimated ten percent increase in the ratio of
immatures to adults in the wintering population in the lower 48 states
from the early 1960s to the early 1980s (21), a 6.1 percent increase
in known numbers of occupied breeding areas in the lower 48 states
from 1982 to 1985 (97), and an 8.3 to 24.8 percent increase in
numbers of autumn migrants in the eastern United States between the
early 1970s and 1985 (97). The above rates are biased to an unknown
degree because of differences in survey methods and coverage between
time periods.
SPECIES INTERRELATIONSHIPS:
Bald eagle interrelationships with other species generally fall
into two categories, territoriality and kleptoparasitism (pirating or
stealing food from another individual).
The most widely occurring interrelationship is that between bald
eagles and ospreys (Pandion haliaetus). In general, bald eagles and
ospreys are toleratnt of each other. Nevertheless, in several studies
different types of behavior have been described, for example:
1) Eagles attacking ospreys carrying fish, 2) eagles driving off
osprey from foraging areas, 3) eagles displaying territorial defense
toward ospreys, 4) ospreys displaying territorial defense toward
eagles, and 5) ospreys harassing perched eagles (78,90,91). This
interspecific competition has been reported to negatively affect
nesting success 978).
Other species with which bald eagles interrelate (mainly through
kleptoparasitism) are American crows (Corvus brachyrhynchos) (65,92),
common mergansers (Mergus merganser) (65,93) great black-gulls (Larus
marinus), common ravens (Corvus corax) (92), and northern harriers
(Circus cyaneus) (93). Bald eagles also observe the feeding behavior
of several of these species to key in on possible food sources (65,
92). In general, bald eagles do not show territorial aggression
toward these species (65).
OTHER LIFE HISTORY DESCRIPTORS:
Life History - 7 (DRAFT) - Life History
Species EAGLE, BALD
Species Id ESIS109001
Date 14 MAR 96
No additional information concerning other life history
descriptors is available.
Life History - 8 (DRAFT) - Management Practices
Species EAGLE, BALD
Species Id ESIS109001
Date 14 MAR 96
MANAGEMENT PRACTICES
RESULT MANAGEMENT PRACTICE
Beneficial Controlling/Restricting Air Space Usage
Beneficial Controlling/Restricting Boating Activities
Beneficial Controlling/Restricting Off-Road Vehicles
Beneficial Restricting/regulating human disturbance of populations
Beneficial Developing/maintaining/protecting wetlands
Beneficial Controlling water levels
Beneficial Controlling/Restricting Mining
Beneficial Controlling/Restricting Road Maintainance Actions
Beneficial Maintaining undisturbed/undeveloped areas
Beneficial Restricting/regulating human use of habitats
Beneficial Land Acquisition
Beneficial Water Right Acquisition
Beneficial Controlling pollution [thermal, chemical, physical]
Beneficial Controlling/Restricting Pesticide Use
Beneficial Controlling/Restricting Herbicide Use
Beneficial Controlling/Restricting Agricultural Practice
Beneficial Creating Artificial Habitat/Nesting Structure
Beneficial Reforestation
Beneficial Restricting Timber Harvest
Beneficial Maintaining Later Stages of Succession
Beneficial Stocking captive-reared wild-strain animals
Beneficial Transplanting wild animals
Beneficial Transplanting Wild Eggs/Wild Seeds
Beneficial Supplemental Feeding
Beneficial Disease Control Measures
Beneficial Rehabilitating Individuals
Beneficial Restricting Poaching
Adverse Harassment/Vandalism/Indiscriminate Killing
Existing Harassment/Vandalism/Indiscriminate Killing
Adverse Commercial Exploitation
Existing Commercial Exploitation
Adverse Sport Hunting/Fishing
Existing Sport Hunting/Fishing
Adverse Off Road Vehicles
Existing Off Road Vehicles
Adverse Boating
Existing Boating
Adverse Hiking/Camping
Existing Hiking/Camping
Adverse Food Supply Reduction
Existing Food Supply Reduction
Adverse Surface Mines
Existing Surface Mines
Adverse Rural Residential/Industrial Areas
Existing Rural Residential/Industrial Areas
Adverse Recreational development
Existing Recreational development
Adverse Transmission Lines/Towers
Existing Transmission Lines/Towers
Management Practices - 1 (DRAFT) - Management Practices
Species EAGLE, BALD
Species Id ESIS109001
Date 14 MAR 96
RESULT MANAGEMENT PRACTICE
Adverse Soil compaction by heavy equipment in mine areas
Existing Soil compaction by heavy equipment in mine areas
Adverse Siltation
Existing Siltation
Adverse Dissolved Oxygen Reduction
Existing Dissolved Oxygen Reduction
Adverse Draining wetlands, marshes, ponds, lakes
Existing Draining wetlands, marshes, ponds, lakes
Adverse Reservoirs
Existing Reservoirs
Adverse Dredging
Existing Dredging
Adverse Developing/maintaining stream bank vegetation
Existing Developing/maintaining stream bank vegetation
Adverse Shoreline modification/development
Existing Shoreline modification/development
Adverse Applying pesticides
Existing Applying pesticides
Adverse Environmental Contamination/Pollution
Existing Environmental Contamination/Pollution
Adverse Predator control
Existing Predator control
Adverse Grazing
Existing Grazing
Adverse Forest Alteration
Existing Forest Alteration
Adverse Harvesting
Existing Harvesting
COMMENTS ON MANAGEMENT PRACTICES -
The major factor leading to the decline and subsequent listing
of the bald eagle as an endangered species was disrupted reproduction
resulting from contamination by organochlorine pesticides. A drastic
decline in bald eagle populations in the eastern United States
followed the introduction of dichlorodiphenyltrichloroethane (DDT)
as an insecticide in 1947. As bald eagles accumulated DDT residues by
eating contaminated fish and waterfowl, decreases in eggshell
thickness were detected. Subsequent research has shown that DDT and
its metabolites interrupt the calcium metabolization process essential
to eggshell formation in birds by inhibiting the production of the
enzyme carbonic anhydrase. Declines in eggshell thickness were
associated with diminished hatching success (23), and productivity of
affected bald eagle populations dropped (17,22). The use of DDT was
suspended in the United States in 1972, and by the late 1970s,
eggshell thickness and hatching success showed signs of increasing in
several breeding populations (17,22).
Other chlorinated hydrocarbons that may have been involved in
bald eagle population declines are dieldrin and endrin (17,26,29).
The effects of these chemicals are less certain, but both are thought
to primarily affect raptors by direct mortality (17,26,29).
Management Practices - 2 (DRAFT) - Management Practices
Species EAGLE, BALD
Species Id ESIS109001
Date 14 MAR 96
Additionally, lethal levels of polychlorinated biphenyls (PCBs) and
lead have been reported in necropsied bald eagles; the extent to which
either of these contaminants may have contributed to population
declines is unknown (14,17,22,24,25,28).
Currently, the four leading causes of death in bald eagles,
based upon necropsises of carcasses submitted for analysis since the
early 1960s, are shooting, electrocution, impact injuries, and lead
poisoning (32). It should be noted that this sample is heavily
weighted toward the former three mortality factors, as carcasses of
eagles killed directly by humans or human structures are more likely
to be recovered than carcasses of eagles that die from slow poisoning
(usually as a result of animal damage control programs or the indirect
consumption of poisioned carrion) or natural causes. Additionally,
there are signs that the effects of some of these mortality factors
are decreasing. In the early 1960s, shooting accounted for 60 percent
of bald eagle deaths, but by the late 1970s, only 18 percent of eagles
necropsied had been shot (17). Take of eagles can be attributed to
their commercial value to taxidermists and the American Indian.
Electrocution by powerlines was a major mortality factor in Colorado,
Idaho, Neveda, Utah, and Wyoming (27) until the early 1970s, when
utility companies began implementing powerline modifications that
have reduced eagle deaths considerably (27).
Lead poisoning of bald eagles occurs primarily when wintering
eagles feed upon waterfowl that have ingested lead shot (20,32).
The number of bald eagles that have been diagnosed as having died of
secondary lead poisioning has increased dramatically since 1979,
but this may reflect increased intrest in the problem rather than
actual trends in the numbers of eagles poisoned. The U.S. Fish and
Wildlife Service has reviewed available information waterfowl in order
to designate steel shot zones in areas where lead poisoning of bald
eagles is likely to occur (32). Therefore sport hunting has had a
documented indirect affect on the bald eagle.
Another class of threats facing the bald eagle are those related
to habitat loss and disturbance. Most biologists agree that habitat
loss is the greatest threat to the bald eagle and many other birds of
prey (70). Habitat loss results from the physical alteration of
habitat as well as from human disturbance associated with development
or recreation (i.e., hiking, camping, boating, and ORV use).
Activities that can and have negatively impacted bald eagles include
logging, mining (with associated heavy equipment), recreational
activities, overgrazing (particularly in riparian habitats), road
construction, wetland filling, and industrial development (17,21,26).
These activities, as well as suburban and vacation home developments,
are particularly damaging when they occur in shoreline habitats.
Development (including reservoirs...depending on the circumstances)
and resource recovery activities that produce increased siltation and
industrial pollution can cause dissolved oxygen reductions in aquatic
habitats, reductions in bald eagle fish prey populations (i.e., food
supply reduction) followed by reductions in the number of eagles (24).
Not all developments in floodplain habitats are detrimental to bald
eagles, as some reservoirs and dams have created new wintering habitat
that produce dependable food supplies (17).
Management Practices - 3 (DRAFT) - References
Species EAGLE, BALD
Species Id ESIS109001
Date 14 MAR 96
References
***** REFERENCES FOR ALL NARRATIVES EXCEPT N-OCCURRENCE *****
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22 Grier, J.W. 1982. Ban on DDT and subsequent recovery of
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24 National Audubon Society. 1973. The endangered bald eagle.
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27 Worthington, V., ed. 1976. Power line electrocution-hazards made
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28 Wiemeyer, S.N., B.M. Mulhern, F.J. Ligas, R.J. Hensel, J.E.
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29 Cromartie, E., W.L. Reichel, L.N. Locke, A.A. Belisle, T.E. Kaiser,
T.G. Lamont, B.M. Mulhern, R.M. Prouty, and D.M. Swineford. 1975.
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30 Jacobson, E., J.W. Carpenter, and M. Novilla. 1977. Suspected
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31 U.S. Department of the Interior. 1977. Man-made disease kills two
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32 Feierabend, J.S. 1985. The Eyas Forum. Eyas 8(2):2-4.
33 Andrew, J.M. and J.A. Mosher. 1982. Bald eagle nest site
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34 Haywood, D.D. and R.D. Ohmart. 1983. Preliminary report on
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35 Mathisen, J.E. 1983. Nest site selection by bald eagles on the
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36 Friedmann, H. 1950. The birds of North and Middle America. U.S.
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38 Gerrard, J.M., P. Gerrard, W.J. Maher, and D.W.A. Whitfield. 1975.
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References - 2 (DRAFT) - References
Species EAGLE, BALD
Species Id ESIS109001
Date 14 MAR 96
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Date 14 MAR 96
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Date 14 MAR 96
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Date 14 MAR 96
119 Herron, G.B. 1985. Nongame/Wildl. Depredation Specialist, NV
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