The emperor goose (Chen canagica) is a large goose species that breeds in Alaska and northeastern Siberia. Their diet consists primarily of plant material, supplemented with some animal matter. In this article, we will explore the details of the emperor goose’s diet and feeding habits.
Plant Foods
The majority of the emperor goose’s diet is made up of plant foods. They feed extensively on sedges, grasses, aquatic vegetation, berries, and agricultural crops.
One of their favorite plant foods is the rhizomes, roots, and tubers of sedges and grasses. They use their serrated bills to dig up these underground plant parts. Some of the sedges they commonly eat include cottongrass (Eriophorum), spike rush (Eleocharis), and bulrush (Scirpus).
The emperor goose also grazes extensively on grasses and herbs. Some grass species commonly eaten include bluejoint (Calamagrostis canadensis), northern reedgrass (Calamagrostis stricta), and tufted hairgrass (Deschampsia caespitosa). They supplement their grass diet with other herbaceous plants like horsetail (Equisetum arvense), mare’s tail (Hippuris vulgaris), and pondweed (Potamogeton).
In coastal salt marshes, emperor geese feed on glasswort (Salicornia), buckwheat (Polygonum), arrowgrass (Triglochin), and other succulent vegetation. They are one of the few species that can feed on glasswort, as most other waterfowl find it too salty.
Emperor geese also consume berries whenever they can find them. Some preferred berry species are crowberry (Empetrum nigrum), blueberry (Vaccinium uliginosum), and cloudberry (Rubus chamaemorus).
Being opportunistic feeders, emperor geese will also graze in agricultural fields, especially during migration and wintering. They may feed on waste corn, wheat, barley, and oats left behind after harvest.
Aquatic Vegetation
In addition to terrestrial vegetation, emperor geese consume aquatic plants from shallow lakes, ponds, streams, and intertidal zones. Some aquatic plants commonly eaten include:
- Pondweeds (Potamogeton species)
- Watermilfoil (Myriophyllum sibiricum)
- Mare’s tail (Hippuris vulgaris)
- Muskgrass (Chara species)
- Water crowfoot (Batrachium Species)
- Arrowhead (Sagittaria cuneata)
Their serrated bill allows them to grip and tear aquatic plants. They will often tip upside down with their head underwater to reach vegetation growing beneath the water surface.
Animal Foods
While emperor geese mostly eat plant material, they supplement their diet with some animal foods when available. These animal foods provide important proteins and nutrients.
Insects
Emperor geese eat insects opportunistically while grazing on land. Some insects commonly consumed include:
- Crane flies
- Mosquitoes
- Caddisflies
- Midges
- Grasshoppers
- Dragonflies
Insect egg masses and larvae are also eaten. Emperor geese will graze along shorelines eating insect larvae like midge larvae (chironomids) out of the mud.
Mollusks and Crustaceans
Emperor geese feed on small aquatic invertebrates like snails, shrimp, amphipods, and other crustaceans. These are obtained by foraging in shallow water and mudflats. Being non-filter feeders, they do not consume these animals in as large quantities as some ducks.
Fish
On occasion, emperor geese will prey on small fish, especially when nesting. Some fish commonly taken include sticklebacks, sculpins, lampreys, and smelts. Fish eggs are also opportunistically eaten when encountered.
Carrion
Emperor geese are somewhat opportunistic and will scavenge on carrion of fish, birds, and mammals when it is available. However, plant foods still make up the bulk of their diet.
Habitat and Feeding Behavior
Emperor geese inhabit a variety of habitats during the year which affects the types of foods they can access.
Coastal Habitats
Emperor geese breed in coastal wetlands and marshes in Alaska and Russia. Here they feed extensively on grasses, sedges, and aquatic vegetation in brackish intertidal areas. They also graze on adjacent mudflats and tidal flats, consuming algae, aquatic invertebrates, and some intertidal fish like sticklebacks.
Inland Lakes and Ponds
During molting and migration, emperor geese stop at inland lakes and ponds to build up energy reserves. They feed on pondweed, watermilfoil, and other aquatic plants by tipping upside down and stretching their neck underwater. Grass and sedge shoots are also grazed at the water’s edge.
Tundra
On the Arctic tundra, emperor geese walk and graze extensively during the summer months. They feed on cottongrass, sedges, berries, and insect larvae while on the tundra. Grubbing through the vegetation and soil with their bill, they extract energy-rich rhizomes and roots.
Agricultural Lands
Today, emperor geese frequent agricultural fields more than they did historically. During migration and winter, they now feed heavily on unharvested waste grains and crops, especially rice, corn, wheat and barley. This high-energy food allows them to continue migrating and reach wintering grounds in good condition.
Feeding Behavior
Emperor geese feed by walking slowly on land or wading in shallow water, all the while pecking and grazing. Their wide bill allows them to rip and consume large chunks of vegetation. They spend around 60-90% of each day feeding. Emperor geese are gregarious birds and feed in flocks, which allows them to locate productive feeding sites.
Diet by Season
The types of foods emperor geese eat shifts throughout the year as they migrate and inhabit different regions.
Spring
In late spring, emperor geese arrive back at breeding grounds in Alaska and Russia. At this time, they feed heavily on below-ground plant parts like rhizomes to rebuild energy reserves after migration. They also begin grazing on new shoots of sedges, grasses, and aquatic plants to prepare for nesting.
Summer
In summer, emperor geese rely more on foliose foods like grasses, sedges, and aquatic plants. They also consume more insects while breeding, including mosquito egg masses which are rich in protein. Grazing on protein-rich cottongrass spikes helps female geese obtain nutrients needed for egg production.
Fall
In early fall, emperor geese start to feed more heavily to accumulate fat reserves for the long migration south. At this time, they continue grazing on sedges, grasses, and berries. But they also start consuming more agricultural grains as crops become available.
Winter
On wintering grounds, the bulk of the emperor goose’s diet consists of agricultural waste grain and vegetation from managed wetlands and rice paddies. Corn, wheat, barley, oats, and rice all become major food sources during winter.
Role of Food in Migration
The availability of high quality food resources plays a major role in powering the emperor goose’s migration each year.
In fall, emperor geese build up fat reserves by gorging on energy-rich foods before migration. They select foods like agricultural grains, aquatic tubers, and stems that maximize fat deposition. During migration, emperor geese stop to rest and feed in locations with abundant food such as agricultural fields.
In spring, their migration north is timed with the flush of emergent aquatic plants and vegetation on the tundra. The surge of highly digestible protein and nutrients from new plant growth allows the geese to regain condition after expending energy during migration and winter. Timed access to nutritious food supplies is crucial for their migration and subsequent breeding.
Adaptations for Feeding
Emperor geese have several key adaptations that allow them to feed on their specialized diet:
- Serrated edges on the mandibles help grip and tear aquatic vegetation.
- Hardy digestive system allows them to feed extensively on fibrous plant material.
- Long neck enables them to reach aquatic vegetation under water.
- Webbed feet propel them in water and muddy substrates.
- Ankle joints allow feet to pivot forwards or backwards to maneuver in water and on land.
- Sharp vision aids in detection of plant food items and insects.
- Short toenails provide stability when walking on muddy or soft substrates.
Conclusion
In summary, the emperor goose consumes a wide variety of food items but relies predominantly on grazing and foraging on plant material. Sedges, grasses, aquatic vegetation, and agricultural grains make up the bulk of their diet. This is supplemented seasonally with protein-rich foods like insects, fish, and aquatic invertebrates. Their diverse diet and ability to utilize multiple habitats allows emperor geese to migrate vast distances and survive the extremes of the Arctic climate.
