Emperor geese roost along the coast during the non-breeding season. These areas include beaches, cliffs, and dunes as well as along reefs. Emperor geese select breeding grounds that are slightly further inland into lowland marshes and meadows near a water source such as a lake or riverbed. A nearby water source is crucial to survival as geese use them to flee from land predators. Nest sites are also found on vegetated mudflats and salt marshes. Within a week of hatching, (Cannings and Hammerson, 2009; Eisenhauer and Kirkpatrick, 1977; Laing and Raveling, 1993)goslings move into tidal marsh areas closer to the coast to grow.
Adult emperor geese are small waterfowl averaging less than 3 kg and around 69 cm in length. They are sexually monomorphic with males averaging only slightly heavier than females. Emperor geese exhibit an entirely white head and nape of neck that often becomes stained a rust color by iron oxide present in a number of tidal ponds. Chin and throat are black with the rest of the body covered in gray plumage barred with black and white. Their beaks are short and light pink while their webbed feet are a bright orange. Tail feathers are white with black undertail coverts. ("Emperor Goose", 2010)goslings are covered in downy gray feathers and usually have a black beak.
Emperor geese exhibit a monogamous mating system, and will bond with a different goose only if the previous mate dies. Little is known about the formation of pair bonds but they are formed by the time breeding grounds are reached. Because copulation is rarely seen, it is assumed that mating occurs either just prior to or during migration to breeding grounds. (Eisenhauer and Kirkpatrick, 1977; Petersen, et al., 2010)
Upon arriving at the nesting grounds, females begin building nests. Eggs are normally laid within the first 10 days after arrival. Clutch size ranges from 3 to 8 eggs with an average of 5. Females incubate the eggs for 24 or 25 days, after which the goslings hatch over a 10 day period. Goslings hatched earlier in the breeding season have a much higher likelihood of surviving the following winter. Most goslings are fully feathered 30 to 47 days after hatching and are able to fly at 50 to 60 days old. Goslings remain close to their parents through the first winter and have even been noted to return to breeding ground with parents the following spring. Though young geese may return to breeding grounds early in life, most females do not lay eggs of their own until 3 to 4 years of age.
Emperor geese nests are commonly parasitized by other birds. A study conducted in the Yukon Delta breeding ground found that an average of 62% of nests had parasitic eggs. The majority of these eggs had been laid not by other species, but by other emperor geese. Females and males actively guard their nests but if a parasitic egg is successfully laid in or very close to a nest, the pair is highly likely to accept the egg. (Cannings and Hammerson, 2009; Eisenhauer and Kirkpatrick, 1977; Hupp, et al., 2006; Lake, et al., 2008; Pacific Flyway Council, 2006; Petersen, et al., 2010)
Females are solely responsible for selecting a nest site, building a nest, and incubating the eggs. The same nest site may be used multiple years. Pairs chase rival goose species, members of their own species, as well as juveniles from previous seasons, away from their nesting sites. While both males and females defend the nesting area, males are much more aggressive than females. While the female is incubating, males remain close to the nest to fend off predators and other geese. By the end of the incubation period, females lose an average of 20.7% of their body mass due to energy being focused solely on incubating and protecting the eggs.
Once goslings hatch, they are brooded by females for the first 2 to 3 weeks. Goslings are able to forage within 24 hours of hatching. While the young feed, they stand between their parents who are both highly protective. If terrestrial predators approach and a body of water is nearby, the entire group flees to water. But if water is not close, parents surround their offspring while hissing and flapping their wings at the approaching predator. When an aerial predator strikes, juveniles hide beneath their mother’s wings as the father jumps at and attacks the predator. Males are even known to act as decoys, allowing the goslings and their mother to escape. Juveniles leave breeding grounds around the end of August but remain with their parents until the following spring, when they are chased away from the breeding grounds. (Eisenhauer and Kirkpatrick, 1977; Schmutz, et al., 1994; Thompson and Raveling, 1987)
Conditions in the summer months determine whether or not juveniles will survive their first winter and migration. While the average lifespan of emperor geese has been recorded to be about 6 years with a maximum life expectancy of 12 years, many scientists believe that this is a gross underestimate. This is especially so because their longevity seems much lower than similar species. Estimated annual mortality rates range from 63 to 94% for adults. (Petersen, et al., 2010; Schmutz, et al., 1994; Zammuto, 1986)
Large groups of emperor geese begin their annual spring migration from their wintering grounds in the Aleutian Islands of Alaska or the Commander Islands of Russia in early March. These geese move over Bristol Bay and arrive on the Yukon-Kuskokwim Delta between early and mid May. Geese take advantage of these rich spring feeding grounds, preparing for early summer nesting. Between late May and early June, geese arrive at their breeding grounds on the Seward Peninsula, St. Lawrence Island, and Siberia. Autumn migration reverses the path with emperor geese leaving in late August and early September, and arriving back at the Aleutian Islands by the end of November.
Migration is highly dependent on ice break-up and weather conditions, with birds migrating onto spring feeding grounds as ice disappears. Poor weather conditions may keep geese from traveling to their next destination while particularly good weather may allow geese to take advantage of good feeding grounds for longer periods of time. Distance traveled between wintering and nesting sites range from 650 to over 2500 km.
While on their wintering or nesting grounds, emperor geese are relatively sedentary. Especially when nesting, pairs have relatively little to do with other individuals with the exception of defensive behavior if another goose gets too close. During non-migration seasons, emperor geese walk or swim much more regularly than they fly.
Like most geese, emperor geese are particularly well adapted to swimming and swim at all times of year. When approached by a land predator, emperor geese are most likely to run toward water and swim to a safer area. Goslings have even been seen diving to avoid aerial predators. ("Chen canagica", 2009; Eisenhauer and Kirkpatrick, 1977; Hupp, et al., 2008; Pacific Flyway Council, 2006; Petersen, et al., 2010)
Emperor geese actively defend their breeding territory (averaging 14 square meters) before eggs are laid and until the parents and goslings leave the nesting grounds. (Eisenhauer and Kirkpatrick, 1977)
Emperor geese have two types of calls. The first (sounding like "kla-ha kla-ha") is mainly heard during migration when birds are grouped together in large numbers. The second type of call (sounding like "u-lugh u-lugh") occurs when birds are startled or threatened. These geese may also hiss when predators or other geese attempting to approach the nest. This hissing is often paired with a defensive posture or charging the threatening individual. This species of goose is known to be much less vocal than most other goose species.
Emperor geese rely mainly on their sense of sight to recognize predators or competitors. They also rely on sight to find food on land. When searching for mollusks, particularly underwater or in the mud, they primarily utilize their sense of touch. Like all birds, emperor geese perceive their environment through auditory, tactile, visual and chemical stimuli. (Petersen, et al., 2010)
Emperor geese feed mainly on intertidal vegetation and marine invertebrates. Vegetation includes beach rye, crowberries, beach pea, and sandwort. They are also known to eat seaweed, eelgrass, and sea lettuce. While emperor geese may eat crustaceans, they mainly consume bivalves. During the spring and autumn months their diet consists primarily of blue mussels and macoma clams. They forage for these invertebrates by submerging their head underwater to find their prey. Another method of searching for prey called “puddling” occurs on mud flats. A goose creates pools in the flats by stamping its feet and then consuming the disrupted clams. Grasses, sedges and bulbs are eaten when these birds move inland during the nesting season. ("Chen canagica", 2009; "Emperor Goose", 2010; Eisenhauer and Kirkpatrick, 1977; Laing and Raveling, 1993; Petersen, et al., 2010; Schmutz, 1994)
Feeding is particularly important for goslings, which are one of very few vertebrates that obtain their protein necessary for growth almost entirely from plant matter. Studies have suggested that goslings may attempt to choose more protein rich plants and specifically prefer marsh arrowgrass (Triglochin palustris) when it is available and safe to access. (Laing and Raveling, 1993; Lake, et al., 2008; Petersen, et al., 2010)
While some adult geese are predated by foxes and eagles, juveniles are at a much higher risk of predation. Red foxes, arctic foxes, glaucous gulls, parasitic jaegers, golden eagles, snowy owls, mink, and sandhill cranes are all potential predators of both goslings and eggs. Local humans have also been known to hunt both young and adults as well as collect eggs for subsistence.
When a predator approaches the nest, brooding females hiss, raise their wings and take on a threatening posture. Males also guard the brooding female and nest by hissing, taking on a threatening posture or charging the predator. Adults without offspring also act as a decoy and lead predators away from the nesting sites. When not with eggs or very young juveniles, emperor geese usually flee to water when approached by predators. (Eisenhauer and Kirkpatrick, 1977; Petersen, et al., 2010; Schmutz, et al., 2001)
Emperor geese are mainly herbivores, but also feed on mollusks and likely have a significant impact on their populations. It has been suggested that grazing actually increases growth of vegetation in the habitat, therefore likely benefiting many local organisms that utilize vegetation for food or cover. Nitrogen rich goose feces may also aid in vegetation growth. Adult, juvenile, and eggs of emperor geese are prey for local predators. (Laing and Raveling, 1993)
Emperor geese were hunted by subsistence hunters primarily in Alaska. Historically, eggs were collected during the laying season, while juveniles and adults were hunted in the spring. Emperor geese continue to be harvested today, but many recent hunting seasons have been closed due to low population numbers. Emperor geese are also sold as pets around the world. ("Audubon WatchList", 2010; "Chen canagica", 2009; "Emperor Goose", 2010; Petersen, et al., 2010)
There are no known adverse effects of emperor geese on humans.
Between 1964 and 1986 the emperor goose population in Alaska dropped from around 139,000 to 42,000 individuals. The IUCN Red list states that reasons for this decline are poorly understood. While the population has more than doubled since 1986 and current populations remain stable to slightly decreasing, emperor geese are still at risk due to hunting practices and coastal oil pollution. It is also expected that climate change may limit breeding grounds, leading to a decline in populations as well. Due to climate change, emperor geese habitat may decrease by as much as 54% by 2070.
Management plans, such as the one suggested by the Pacific Flyway Council, stress that enforcing crackdowns in illegal hunting and egg collection as well as preserving habitat and educating the public about these birds, are essential steps in protecting emperor goose populations in Alaska. ("Chen canagica", 2009; Cannings and Hammerson, 2009; Pacific Flyway Council, 2006)
Emily Brown (author), University of Michigan-Ann Arbor, Phil Myers (editor), University of Michigan-Ann Arbor, Rachelle Sterling (editor), Special Projects.
living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.
uses sound to communicate
having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.
areas with salty water, usually in coastal marshes and estuaries.
uses smells or other chemicals to communicate
the nearshore aquatic habitats near a coast, or shoreline.
used loosely to describe any group of organisms living together or in close proximity to each other - for example nesting shorebirds that live in large colonies. More specifically refers to a group of organisms in which members act as specialized subunits (a continuous, modular society) - as in clonal organisms.
animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.
parental care is carried out by females
an animal that mainly eats leaves.
A substance that provides both nutrients and energy to a living thing.
An animal that eats mainly plants or parts of plants.
offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).
parental care is carried out by males
marshes are wetland areas often dominated by grasses and reeds.
makes seasonal movements between breeding and wintering grounds
Having one mate at a time.
having the capacity to move from one place to another.
specialized for swimming
the area in which the animal is naturally found, the region in which it is endemic.
reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.
the business of buying and selling animals for people to keep in their homes as pets.
Referring to something living or located adjacent to a waterbody (usually, but not always, a river or stream).
breeding is confined to a particular season
reproduction that includes combining the genetic contribution of two individuals, a male and a female
uses touch to communicate
that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).
Living on the ground.
defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement
A terrestrial biome with low, shrubby or mat-like vegetation found at extremely high latitudes or elevations, near the limit of plant growth. Soils usually subject to permafrost. Plant diversity is typically low and the growing season is short.
uses sight to communicate
young are relatively well-developed when born
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