WAT E R F O W L M A N A G E M E N T H A N D B O O K

13.1.15. Life History

and Habitat Needs of
the Black Brant

Dirk V. Derksen and David H. Ward

U.S. Fish and Wildlife Service Species Profile—Black Brant
Alaska Fish and Wildlife Research Center
1011 East Tudor Road Scientific name: Branta bernicla nigricans
Anchorage, AK 99503 Weight* in pounds (grams):
Adults—male 3.6 (1,802), female 3.3 (1,648)
Immatures—male 3.4 (1,710), female 2.9
The black brant is a sea goose that depends on (1,456)
coastal habitats from high arctic nesting sites in Age at first breeding: 2−4 years
Canada, Alaska, and Russia to wintering areas in Clutch size: 3.3−3.5, range 1−7
the Pacific coastal states, the Baja California Incubation period: 24 days
peninsula, and mainland Mexico estuaries. Age at fledging: 45−50 days
Population estimates are based on aerial surveys in Nest sites: Grass−sedge tundra communities
Mexico, California, Oregon, and Washington during on islands or peninsulas in large, shallow
mid-winter. Despite much annual variability in ponds along low coastal floodplains to 5
estimates, a plot of the counts from 1964 to 1992 miles inland
reveals a significant downward trend in the winter Food habits: Predominantly herbivorous,
populations (Fig. 1). Three of four major colonies on except for small amounts of fish eggs,
the Yukon−Kuskokwim (Y−K) delta declined an crustaceans, and mollusks
average of 60% during the first half of the 1980’s.
*October weights at Izembek Lagoon, Alaska
This is significant because about 79% of the world
population of the black brant nest in these colonies
(Table). Because few other breeding colonies have
been consistently monitored, we have little Mexico, industrial and recreational development in
understanding of their dynamics. several estuaries may further limit winter habitats.
Spring subsistence harvest in western Alaska Wildlife conservation agencies in Canada, Mexico,
coupled with fox predation on reduced Y−K delta Russia, and the United States recently cooperated
populations, has limited the recovery of key nesting to examine population dynamics and factors that
colonies. Degradation and loss of important staging limit recovery of the black brant. This examination
and winter estuarine habitats from commercial and revealed important discoveries for management.
recreational development and disturbance are This leaflet is a summary of these findings. More
largely responsible for population reductions in complete information on the life history of the black
British Columbia and the Pacific coastal states. In brant is in Bellrose (1980) and Palmer (1976).

Fish and Wildlife Leaflet 13.1.15. • 1993 1

 Table. Number of nests and percent of total nests in
colonies throughout the population of the black
brant.
Number Percent
Location and colony of nests of total

Alaska
Yukon−Kuskokwim Delta
Kigigak Island 1,050
Baird Inlet 10,122
Tutakoke River 6,591
Kokechik Bay 5,874
Small colonies 4,163
Subtotal 27,800 78.9
Seward Peninsula−Chukchi Sea
Fig. 1. Status of the black brant based on midwinter aerial Arctic Lagoon 50
surveys with the calculated regression line indicated. Nugnugaluktuk River 100
Kasegaluk Lagoon 50
Subtotal 200 0.6
North Slope Coastal Plain
Distribution Meade River Delta 50
Teshekpuk Lake 200
Colville River 400
The black brant nests from Prince Patrick and
Prudhoe Bay 500
Melville islands in the western Canadian high
Subtotal 1,150 3.3
arctic and the Beaufort Sea islands to the coastal
plain of Canada and Alaska. Small colonies occur Russia
on the north side of the Chukotka Peninsula in Wrangel Island 100
Ayon Island 50
Russia and on Wrangel Island. The largest Anadyr Basin 170
concentration of nesting brants is on the delta of
Subtotal 320 0.9
the Yukon and Kuskokwim rivers in western Alaska
(Table; Fig. 2). Canada
In the arctic, molting areas support as many as Low Arctic
32,000 birds near Teshekpuk Lake on Alaska’s Liverpool Bay 300
Banks Island 2,250
coastal plain and 4,000 birds on Wrangel Island Victoria Island 1,200
(Fig. 2). Brants also molt in large but uncounted
Subtotal 3,750 10.6
flocks on the Y−K delta.
A major shift in the winter distribution of the High Arctic
Prince Patrick Island 500
black brant occurred during the 1950’s and 1960’s. Melville Island 1,500
The species traditionally wintered on the Pacific
Subtotal 2,000 5.7
coast from Puget Sound south to Baja California.
In 1958, black brants were discovered using Total 35,220
lagoons on the Mexican mainland bordering the
Gulf of California. Concomitantly, the number of
wintering birds in California declined drastically
migrating from Izembek Lagoon to more southerly
from a 10-year (1949−1958) mean of 42,000 to a
habitats is not clear.
mean of 6,800 between 1959 and 1968. In two years
since 1968, no brants have wintered in California.
Since 1965, in excess of 80% of the black brants
counted during winter surveys in Mexico, Spring Migration and Breeding
California, Oregon, and Washington were observed
in Mexico. From 1981 to 1988, an average of 4,400 Spring migration occurs during a 4-month
brants wintered in the Izembek Lagoon area of the period (Fig. 3) starting in mid-February when the
Alaska Peninsula. Whether these wintering brants birds begin northward movement from winter
are from specific breeding colonies or their areas to staging habitats in California, Oregon,
physiological condition prevents them from Washington, and British Columbia. Eelgrass and

2 Fish and Wildlife Leaflet 13.1.15. • 1993

Fig. 2. Distribution of major black brant colonies and number of nesting pairs.

Fig. 3. The chronology of important life

history events in the annual cycle of the
black brant (irrespective of sex).

Fish and Wildlife Leaflet 13.1.15. • 1993 3

sea lettuce and other marine algae are important from many different nesting colonies during the
in the diet of migrants at these staging habitats; annual wing molt. At the Teshekpuk Lake molting
they also feed on roe of Pacific herring, on area, there are more males (57.2%) than females
crustaceans, and on mollusks. By late April, brants and more After Second Year (76.6%) than Second
reach Izembek Lagoon, Alaska, where they may Year birds. Failed breeding birds are 61.7% and
spend from 2 to 4 weeks feeding on eelgrass before non-breeding birds are 38.3% of the molting
emigration to nesting areas. population.
The birds establish bonds during the winter Molt is a nutritionally demanding process in
and arrive at breeding areas as pairs. They attain many species of birds, including the black brant.
maximum numbers on the Y−K delta in late May During the molt at Teshekpuk Lake, adult females
and in arctic and western Canada by mid-June. lose more carcass mass, lipid, and protein than
Preferred nest sites are on peninsulas or islets in adult males and subadults. Males lose an average
large wetland complexes, some of which are
122 g and females 141 g of lipid during the molt
subject to tidal action. Most brants first breed
process. For brants to complete the molt and regain
when they are 3 years of age; fewer than 50% nest
the necessary lipid reserves for migration,
at age 2.
Brants lay from one to seven eggs and an managers must insure minimal disturbance in
average clutch of 3.5 eggs at Y−K delta colonies and molting areas. Feeding is the predominant
3.8 eggs at Colville River delta colonies in northern behavior (52% of all activities) of molting brants
Alaska. The mean incubation period is 24 days. throughout the 24-h cycle. Protein-rich tufted
The arctic fox is the most important predator of hairgrass and sedges are the most important
eggs and goslings on the Y−K delta colonies. plants in the diet of molting brants at Teshekpuk
Control measures to eliminate foxes enhanced Lake.
nesting success and significantly increased nesting Adults with fledged young follow traditional
brants at the Tutakoke River colony on the Y−K routes from breeding areas to fall migration
delta. Glaucous gulls and parasitic jaegers also staging sites along the Siberian, Beaufort,
take eggs and goslings. Chukchi, and Bering seas (Fig. 2). The single most
Adults with broods move from colony sites to critical fall staging habitat is near the tip of the
rearing habitats along tidal flats. Broods Alaska Peninsula at Izembek Lagoon. Nearly the
sometimes congregate in large creches. Creeping entire world population of the black brant spends
alkali grass and Hoppner sedge are the most as long as 9 weeks there feeding on the extensive
important plants in the diet of adults and beds of eelgrass. Eelgrass is as much as 99% of
developing young. Adults with broods begin to molt their diet during this period. In the Izembek
their flight feathers in the second week of July, and Lagoon complex, brants from high arctic colonies
most can fly by the second week of August. Young (e.g., Prince Patrick and Melville islands) are
fledge in 45−50 days, and most birds are capable of spatially segregated from birds that nest in
flight by mid-August (Fig. 3). Brants remain in western colonies (Mackenzie and Y−K deltas). This
family groups throughout the brood-rearing period.
behavior allows assessment of productivity and
age ratios of two distinct breeding stocks.
Managers can establish appropriate harvest
Postbreeding Dispersal and Fall regulations and management for each stock.
Disturbance of staging brants is of concern
Migration because it could reduce foraging time and increase
energetic costs and thus lower fat deposition,
Brants that lose their clutches or do not nest
undertake a molt migration, usually in late June, which may compromise successful migration to
to secluded areas in the high arctic. They distant winter habitats. At Izembek Lagoon,
congregate in large numbers on molting areas for aircraft flights were the most frequent (0.57
a month or more (Fig. 3) until new flight feathers events/h) type of anthropogenic disturbance. Bald
are grown. Important molting areas have been eagles caused 0.25 disturbances/h. All
discovered on Alaska’s north slope and Wrangel disturbances occurred at 1.07/h. A predictive model
Island (Fig. 2). These areas, dominated by large shows that if brants were exposed to 45−50 daily
freshwater lakes and ocean estuaries, provide disturbances by aircraft, they would not gain any
essential habitat for tens of thousands of brants weight at Izembek Lagoon.

4 Fish and Wildlife Leaflet 13.1.15. • 1993

 In late October or early November, brants from vessel and aircraft traffic, that may displace
depart Izembek Lagoon during low pressure birds from traditional foraging areas.
systems that generate the favorable southerly The quality and quantity of important marine
winds for transoceanic migration. When food plants such as eelgrass, widgeongrass, and sea
meteorological conditions are appropriate, nearly lettuce must be maintained. Threats to these
all brants leave Izembek Lagoon within about 12 h, resources include increasing pollution, dredging,
usually at night. and other industrial and recreational development
in estuaries in British Columbia, the Pacific coastal
states, Baja California, and mainland Mexico.
Winter Ecology Habitats in Alaska, Russia, and northern
Canada are presently relatively secure, but
Black brants arrive in winter habitats in Baja petroleum and related development should be
California within 60−95 h of departure from monitored and strategies developed for the
Izembek Lagoon. They metabolize nearly one-third protection of colonies, molting areas, and staging
of their body mass during the 2,600 nautical mile sites that are not managed for waterfowl. Methods
flight across the Pacific Ocean to San Quintin Bay, to protect habitats include acquisitions, land
Baja California, Mexico. exchanges, easements, and cooperative
Most brants from the Y−K delta, low arctic management agreements.
Canada, and Russia winter in estuaries on the
Baja California peninsula and mainland Mexico.
Birds that nest in high arctic colonies in Canada
winter in the Puget Sound area. Suggested Reading
Black brants forage most (58−87%) of the day
on marine plants to replace fat reserves expended Anthony, R. M., P. L. Flint, and J. S. Sedinger. 1991. Arctic
fox removal improves nest success of black brant.
during migration. Eelgrass is the primary food in
Wildlife Society Bulletin 19:176−184.
San Quintin Bay. Farther south on the Baja
Bellrose, F. C., editor. 1980. Ducks, geese, and swans of
California peninsula at San Ignacio Lagoon, North America. 3rd ed. Stackpole Books, Harrisburg,
Scammons Lagoon, and Magdalena Bay, brants Penn. 540 pp.
feed on eelgrass and widgeongrass. Dau, C. P. 1992. The fall migration of Pacific Flyway
At San Quintin Bay, disturbances by hunters, brant Branta bernicla in relation to climatic
aircraft, vessels, and avian predators occurred at conditions. Wildfowl 43: In press.
an average rate of 1.21/h. Boat traffic caused 65% Derksen, D. V., W. D. Eldridge, and M. W. Weller. 1982.
and hunters caused 23% of all disturbances. The Habitat ecology of Pacific black brant and other
level of disturbance is greater in this bay than in geese moulting near Teshekpuk Lake, Alaska.
molting, staging (see above), and other winter Wildfowl 33:39−57.
habitats. Disturbance during winter is of special Kramer, G. W., L. R. Rauen, and S. W. Harris. 1979.
Populations, hunting mortality and habitat use of
concern because it could harm the physiological
black brant at San Quintin Bay, Baja California,
condition of prenesting brants and thus lower
Mexico. Pages 242−254 in R. L. Jarvis and J. C.
reproductive success. Bartonek, editors. Management and biology of
Pacific Flyway geese: a symposium. Oregon State
University Book Stores, Inc., Corvallis.
Management Mickelson, P. G. 1975. Breeding biology of cackling geese
and associated species on the Yukon−Kuskokwim
Effective management must focus on Delta, Alaska. Wildlife Monographs 45. 35 pp.
conservation of the terrestrial and marine habitats Palmer, R. S., editor. 1976. Handbook of North American
on which black brants depend during nesting, birds. Vol. 2. Waterfowl. Yale University Press, New
staging, and wintering. Some of these areas are Haven, Conn. 521 pp.
Reed, A., R. A. Stehn, and D. H. Ward. 1989. Autumn use
protected as state and federal refuges, but many
of Izembek Lagoon, Alaska, by brant from different
critical habitats remain outside conservation units. breeding areas. Journal of Wildlife Management
Even some habitats that are inside refuge 53:720−725.
boundaries are not free from activities that may Smith, R. H. and G. H. Jensen. 1970. Black brant on the
affect brants. Management of refuges and other mainland coast of Mexico. Transactions of the North
key habitats should include monitoring and, if American Wildlife and Natural Resources
necessary, regulation of disturbances, especially Conference 35:227−241.

Fish and Wildlife Leaflet 13.1.15. • 1993 5

Spencer, D. L., U. C. Nelson, and W. A. Elkins. 1951. Ward, D. H., and R. A. Stehn. 1989. Response of brant
America’s greatest goose-brant nesting area. and other geese to aircraft disturbance at Izembek
Transactions of the North American Wildlife Lagoon, Alaska. U.S. Fish and Wildlife Service
Conference 16:290−295. Report, Anchorage, Alaska. 193 pp.

Appendix. Common and Scientific Names of the Plants and

Animals Named in the Text.
Plants
Hoppner sedge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Carex subspathacea
Sedges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Carex spp.
Tufted hairgrass . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Deschampsia caespitosa
Creeping alkali grass . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Puccinellia phraganodes
Widgeongrass . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ruppia maritima
Sea lettuce . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ulva lactuca
Eelgrass . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Zostera marina

Birds
Black brant . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Branta bernicla nigricans
Bald eagle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Haliaeetus leucocephalus
Glaucous gull . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Larus hyperboreus
Parasitic jaeger . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Stercorarius parasiticus

Mammals
Arctic fox . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Alopex lagopus

Fish
Pacific herring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Clupea harengus

Note: Use of trade names does not imply U.S. Government endorsement of commercial products.

UNITED STATES DEPARTMENT OF THE INTERIOR

FISH AND WILDLIFE SERVICE
Fish and Wildlife Leaflet 13
Washington, D.C. • 1993