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The scientific name for black brant, or the Pacific brent goose, is Branta bernicla nigricans. In addition to having the shortest tail of any type of goose, the black brant is small enough that the uninitiated may mistake the bird for a duck. Black brants' habitats range from Alaska and the Canadian Arctic to Baja California. Bird populations are affected by hunting and increasing pressure on habitats because of the growth of human populations. Foxes have also had a negative impact on bird population as foxes like to dine on black brant eggs.
Black brant geese are small birds in relation to other geese. These birds are roughly 24 inches (60 cm) long and can weigh up to 63.5 ounces (1800 g). The birds have largely black-brown upper bodies and are gray underneath with white tails. There are white rings around their necks.
Pacific brent geese rely almost entirely on eelgrass for nutrition. Eelgrass, or Zostera, is a saltwater plant that prefers shallow depths that are muddy or sandy. Although there is freshwater eelgrass, called Vallisneria, black brant geese only eat the saltwater varieties.
In fact, black brant geese rarely stray from the ocean. Over the years, these birds have adapted to their habitats by developing the ability to drink saltwater. Although when given a choice, Pacific brent geese will drink fresh water, these birds have a salt gland that enables them to consume salty water.
Black brant geese mate for life and return to the same nesting area every year. Females lay up to seven eggs in a shallow hole in the ground layered with moss and seaweed. A few days after hatching, the chicks will begin to look for food.
Most geese form straight lines or V-shapes when migrating. Unlike other geese, brant blacks, which migrate up to three thousand miles every year, do not fly in formation. Pacific brent geese fly in groups, which are called blizzards or knots, without patterns.
In addition to pressures from human beings and foxes, populations of black brant geese are affected by the availability of food sources. For example, during the 1930s, the wasting disease destroyed a significant amount of eelgrass in both North America and Europe. This not only caused a drop in bird population, the wasting disease and death of eelgrass affected the availability of local crabs, lobsters, and fish. As eelgrass recovered, the number of black brants increased.