Birder’s Notebook: Brant––The “sea goose”

Recently I hunkered on the beach, watching a family of brant bobbing in the waves, tipping tails to the sky to pick strands of eel grass from the icy shallows along the shore of Norton Sound.

The long lines and vees of migratory geese that stream through the Bering Strait region in the fall are long gone. However, often a few brant stop off late in the season to refuel in the midst of their journey south. These stragglers can be seen feeding on their favorite meal of eel grass in the rapidly freezing waters of Safety Sound or slurping up bits of eel grass that wash into Norton Sound.

Brant are small, compact, shortnecked, dark geese with lacy, white necklaces. They are dubbed the “sea goose” because, unlike other geese, coastal habitats are their home throughout the year.

Brant breed throughout much of the coastal circumpolar north, and flights to and from their southern wintering areas are among the longest migrations made by waterfowl.

There are several subspecies of brant. The black brant is the subspecies that nests in Alaska and eastern Russia. In Alaska, the largest nesting colony is along the coast of the Yukon-Kuskokwim Delta, and smaller colonies are scattered along the northwest coast and the North Slope.

In spring thousands of black brant migrate through this region en route to their salt marsh breeding grounds on the North Slope. Some flocks fly over the peninsula and others follow the coastline, stopping to rest and feed in salty coastal lowlands. Their passage brings an additional valued subsistence resource to the region.

Brant migration peaks in the Bering Strait region during the last half of May, but the passage of nonbreeding subadults may continue through mid-July. Brant don’t breed until they are two or three-years-old, and these young geese make the long flight to the North Slope to molt their flight feathers. The rich, brackish coastal marshes and freshwater wetlands north of Teshekpuk Lake host the world’s largest molting concentrations of brant.

On the Seward Peninsula, brant are rare breeders in salt marsh habitats along the peninsula’s northwest coast. However, annual U.S. Fish and Wildlife Service waterfowl surveys in that area find few brant and biologists suspect that most birds seen there are en route to the North Slope to breed or molt.

Like other geese, brant usually form life-long pair bonds. Pairs typically form in the winter. Females have a strong tendency to return to their original nesting ground, and it is believed males follow their mates’ lead to her natal area. Thereafter the pair returns faithfully to their established nesting and wintering grounds.

Brant nest and rear their young in salt marshes, usually within five miles of the coast. The male vigorously guards the territory and nest while the female incubates. When she leaves the nest to feed, she covers the eggs with down that keeps the eggs warm for relatively long absences.

Interestingly, the eggs are laid over 30 hours apart, yet, they hatch almost simultaneously. The later eggs have a higher metabolic rate and require less time to develop than the first eggs.

Brant goslings are down-covered at hatch and can walk, swim, feed themselves and leave the nest in about a day. Like other geese, both parents care for the young, leading them to feeding areas where they find their own food. The parents, especially the male, are watchful and defensive as the young graze.

The goslings feed day and night and develop quickly. Young brant grow more rapidly and can fly at an earlier age than other geese. Their rapid growth rate is related to the high protein content of the new shoots of young grasses they graze on. As a result, goslings that hatch early in the season have more nutritious food and grow faster than later hatchlings.

Brant are almost entirely vegetarians. On the breeding grounds they graze on grasses and sedges in salt grass meadows, and supplement with pondweed and tundra berries later in the summer. Some aquatic insects, mollusks and worms are eaten incidentally.

In wintering areas, eel grass is the brant’s primary food, supplemented with other aquatic plants. Brant forage by wading or tipping up in the shallows or by walking on the shore or tidal flats.

Fall migration from the North Slope begins in mid to late summer after molting adults have regained flight and fledglings can fly. Brant parents accompany their young on their first migration and families stay together as a unit within big flocks.

The southward movement of brant past the Seward Peninsula peaks in mid-September. Most flocks pass by the end of September, but small numbers of brant may be seen in our coastal waters into early November. The Norton Sound wetlands are not much used by brant in the fall, but the northwest coast of the Seward Peninsula may be heavily used.

Izembek Lagoon at the tip of the Alaska Peninsula has vast beds of eel grass and is a major staging area in spring and fall for migrating brant. In fall, a large part of the black brant population spends over a month at Izembek feeding on eel grass to build up fat reserves for migration.

In late October or early November, large flocks leave on nonstop flights to Baja, Mexico. They fly at night, departing on the passage of a low-pressure system to provide tailwinds for about half their journey to Mexico.

Some black brant winter in coastal waters and bays from southwest coastal Alaska to California. Most brant from western North America and eastern Russia winter in Baja, but winter surveys show an increasing proportion is wintering in Alaska.

Breeding surveys indicate a decreasing number of breeders in the Yukon-Kuskokwim Delta and an increase on the North Slope. Overall, the long-term population trend is down, but the population is best characterized by dramatic fluctuations.

The variability is in part due to the brant’s very specific food requirements on both their breeding grounds and wintering areas. No other goose species is so reliant on a single type of plant for food as brant are on eel grass during the nonbreeding season. As a result of their specialized food requirements brant are more susceptible to starvation than are most other geese, and breeding success is highly variable.

GRIT FOR THE GIZZARD— After preening on the beach, a brant moved into the breaking waves at sunrise to slurp up some suspended sand. Like all waterfowl, brant need grit to help grind and digest food in the gizzard. When wave action doesn’t stir up sand, they will stomp their feet in pools of water to stir up grit and drink the slurry. Brant have a well-developed salt gland so they can drink salt water, but they often seek freshwater runoff along the coast.

LATE MIGRANTS— In November a flock of late migrating black brant stopped for a meal of their favorite food of eel grass in Safety Sound. The brant in the lower left is tipped up, feeding in typical brant fashion. Notice the differing amounts of white on the necks of the two brant on the right. A Canadian study found that brant tend to pair with birds with similar amounts of white in their necklaces.

SPRING MIGRATION— A small flock of brant stopped to rest and refuel at Safety Sound during spring migration. Thousands of brant pass through the region en route to their salt marsh breeding grounds on the North Slope.

* JUVENILE BRANT— A juvenile brant was feeding on bits of eel grass along the beach near the Nome breakwater. Notice the light-colored edges on the wing feathers that distinguish juveniles from adults.