Brant Life History

Habitat

Habitat Marshes

In lower latitudes of the Arctic, Brant nest in colonies at marshy edges with sedges and other emergent vegetation. Farther north, colonies are smaller and some pairs are solitary, nesting on islands, deltas, and river valleys. After nesting, Brant move to staging sites in the Arctic to molt, places that have sedge- and grass-rich plains for foraging next to shorelines that provide escape from predators. Most migrating and wintering Brant in eastern North America use coastal waters, especially lagoon systems behind barrier beaches, where eelgrass, sedges, and algae are plentiful. These habitats are found chiefly from southern New England to North Carolina. In western North America, wintering Black Brant use similar habitats, foraging in sheltered bays and estuaries from British Columbia to Baja California, Mexico; here too, eelgrass beds are key features of the habitats. When not feeding, Brant roost on mudflats, barrier islands, and sand spits near their foraging areas.

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Food

Food Plants

Brant are vegetarian in diet. In breeding and molting areas, they graze on plants including hairgrass, alkaligrass, marestail, dupontia, saxifrage, sedge, pondweed, and arrowgrass, along with various mosses. During migration and in wintering areas, Brant on both coasts rely extensively on eelgrass and large green algae, grazing when exposed by the tides or by tipping up in shallow water like a dabbling duck. With the extensive losses of eelgrass beds in the East, some Brant now feed heavily on grasses in cultivated and developed areas. Spring flocks also feed on new shoots of saltmarsh cordgrass in the lower portions of marsh. In the West, wigeongrass, surfgrass, marsh arrowgrass, and pickleweed are also favored foods. Like other geese, Brant ingest grit to help process the food in their gizzards.

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Nesting

Nest Placement

Nest Ground

Nests on the ground, usually not far from water and typically near grassy areas for feeding.

Nest Description

Females push away a few inches of soil with their feet and form a depression using their bodies. As egg-laying begins, they add grass, willow leaves, and their own down feathers to the basin to complete the nest. Nests average 18 inches across; the egg cup averages 12 inches across and 2 inches deep.

Nesting Facts

Clutch Size:3-5 eggs
Number of Broods:1 brood
Egg Length:2.8-2.9 in (7.06-7.29 cm)
Egg Width:1.9-1.9 in (4.72-4.74 cm)
Incubation Period:23-24 days
Nestling Period:1 day
Egg Description:

Buffy, creamy white, or pale olive.

Condition at Hatching:

Fully covered with down and ready to walk, swim, and feed within a day.

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Behavior

Behavior Ground Forager

Brant pairs are socially monogamous, pairing for life. However, most females also mate with males other than their partner during the egg-laying period. Pairs form in the birds’ second year, probably on the wintering grounds, and males probably follow females back to their natal areas. Pairs are territorial, even in colonies, and are aggressive toward others of their species. Most populations of Brant move toward molting areas as a family, though only the adults molt flight feathers at this time. They also, like most geese, migrate to wintering areas as families, even remaining together as family units within much larger flocks. In wintering areas, adults often defend a foraging space around their young. Although Brant appear placid and peaceable, their flocks have clear hierarchies: pairs with young dominate pairs without young, which in turn dominate unpaired birds. Their threat displays are much like those of Canada Geese, with lowered head, open bill, and sometimes open wings. Conflicts sometimes escalate into chases.

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Conservation

Conservation Restricted Range

Brant nesting areas are north of the region surveyed by the North American Breeding Bird Survey, meaning population trends are uncertain. Their numbers appear to have declined since the 1970s. Partners In Flight estimates the global breeding population of Brant (all subspecies and types) at about 220,000 individuals, rates the species a 14 out of 20 on its Continental Concern Score, and includes it on their Yellow Watch List for species with restricted ranges. According to the North American Waterfowl Management Plan, the total population size within North America from 2002­–2011 averaged 315,200. (Note that this number includes all individuals, whereas the global number cited above counts only breeding individuals). These populations are below target levels set by waterfowl biologists. Among numerous challenges, the most serious is probably the loss of wintering habitat as a result of climate change and sea level rise. Rising ocean levels will also cover coastal feeding areas (grazing grounds) used during the nesting season. Waterfowl hunting is carefully monitored by the U.S. Fish and Wildlife Service; recent estimates indicate roughly 30,000 Brant are hunted each year in the United States. In the Arctic, some native communities collect Brant eggs for subsistence and hunt flightless molting birds during "drives." The rapid growth of petroleum development on the nesting grounds is also likely to harm Brant populations. As a wetland-dependent species, habitat loss and water quality issues occur throughout the range of this species.

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Credits

Bellrose, F. C. (1976). Ducks, Geese and Swans of North America. Second edition. Stackpole Books, Harrisburg, PA, USA.

Lewis, T. L., D. H. Ward, James S. Sedinger, Austin Reed and D. V. Derksen. (2013). Brant (Branta bernicla), version 2.0. In The Birds of North America (P. G. Rodewald, editor). Cornell Lab of Ornithology, Ithaca, New York, USA.

North American Waterfowl Management Plan Committee. (2012). North American Waterfowl Management Plan 2012: People conserving waterfowl and wetlands. Washington: Canadian Wildlife Service, U.S. Fish and Wildlife Service, Secretaria de Medio Ambiente y Recursos Naturales.

Partners in Flight (2017). Avian Conservation Assessment Database. 2017.

Raftovich, R.V., K.K. Fleming, S.C. Chandler, and C.M. Cain. 2019. Migratory bird hunting activity and harvest during the 2017–18 and 2018-19 hunting seasons. U.S. Fish and Wildlife Service, Laurel, Maryland, USA.

Sibley, D. A. (2014). The Sibley Guide to Birds, second edition. Alfred A. Knopf, New York, NY, USA.

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