Ross's geese () are an arctic species in summer months and patchily distributed in the United States and Mexico in winter, non-breeding months.
The summer breeding range is in the Canadian Arctic, including the coast of Nunavut, Manitoba, and Ontario in Canada. About 95% of the breeding population of Ross's geese inhabit the Queen Maud Gulf Migratory Bird Sanctuary. Additional birds breed along the western and southern coasts of the Hudson Bay. Also, Ross's geese are found in the south end of Southampton Island and north of Foxe Peninsula.
In fall and spring, Ross's geese migrate latitudinally from Canada along narrow corridors through Montana, Idaho, Nevada, and Oregon. This group overwinters in north and central California (including Los Angeles and San Francisco), a disjunct area in southern California, and Baja California.
In recent decades, a number of non-breeding Ross's geese have been migrating through central Canada and central plains states of the United States, including North and South Dakota, Nebraska, Kansas, and Oklahoma. During the winter, these non-breeding areas include New Mexico, Texas, Oklahoma, Arkansas, Missouri. This wintering range extends southward into Mexico. Specifically, non-breeding geese inhabit the southern half of New Mexico, the gulf coast and the northern panhandle of Texas. In Mexico, Ross's geese are found in the Sierra Madre Mountains east of the state of Chihuahua, and from the US/Mexico border southward to Durango, Mexico.
The breeding grounds for Ross's geese are found in the Arctic tundra. Ross's geese spend time in and around freshwater lakes or ponds, grasslands, wetlands, and sometimes rocky areas. Wetlands in the Queen Maud Gulf Migratory Sanctuary cover a substantial portion of suitable habitat, and breeding sites are located in floodplains of the McConnell River and on small islands in lakes and ponds. The substrate of these breeding areas is dominated by moss, lichens, and scarce grasses and other herbaceous vegetation.
Nesting in large groups (reportedly between 3 to 64 nests/1000 m^2), these geese select nests in sparse shrubby areas, on sandy-grassy areas, moss beds, and rocky or gravel areas. Apart from islands, areas sheltered from the wind also were selected.
During the spring migration, the nonbreeding range were found in habitats such as grain fields and wet meadows in California.
In nonbreeding wintering areas, these geese foraged daily in farmlands and wetlands. They roosted nightly in the wetlands or else along reservoirs.
BirdLife International (2016) lists their elevation range of 1200m to 2500m. However, most of their breeding grounds lie at elevations from 300 to 600 m (Queen Maud Gulf Migratory Bird Sanctuary). Elevation has otherwise not been reported. (BirdLife International, 2016; Hanson and Jones, 1974; Jónsson, et al., 2020)
Ross's geese are white, with a black tip at the end of their wings (tips of their primaries). Rarely, these geese can express a blue morph, in which their heads are white but their bodies are primarily dark "blue" or brownish-black. Their beak is stubby, high at base and triangular shape with a rounded tip. The legs of Ross's geese are red and they have webbed feet. Ross's geese have a short neck, and their bill is short relative to the head size (as compared to other geese).
Female adult Ross's geese are commonly smaller than male adults. The total length of male Ross's geese measures between 59-64 cm (average 62 cm), while females ranged from 57-62 cm (average 58.7 cm). Males average 1484 grams while females weighs 1340 grams. The average wingspan is between 113-116 cm long.
Eggs are reported to weigh 94 g. At this time of egg-laying, a 1400-g female may expend 99 kcal/day (BMR). At hatching, these geese are precocial and downy. Within two weeks post-hatching, young Ross's geese come in two distinct colors groupings: gray (which includes light and dark gray, and even white) or yellow (light and dark yellow, or even blackish-yellow). Hatchlings in the same clutch are more likely to all be the same color morph, but even this occurs only about 60% of the time). Gray is more common of the two morphs, but there are no trends across sexes. The precocial hatchlings' bill will be a darker color compared to an adult's bill. Weight at hatching is 64-66 grams, with a body length of ca. 15 cm.
As the hatchlings grow as juveniles, their plumage comes to resemble that of an adult. However, they secondary tips are black instead of white, like the adults. (Alisauskas and Ankney, 1992; Cooke and Ryder, 1971; Jónsson, et al., 2020)
Ross's geese form long-term pair bonds, also known as perennial monogamy. Occasionally, males will try to form other polygynous bonds with several females. Typically, the long-term pairs form in the winter or during the spring migration. The attempt to form other bonds most of the time fails, due to the other female's response. To attract females, males will walk towards the females with their neck feathers pushed out and then they will make a high-pitched call. The female Ross's geese will avoid the male geese or make a loud vocalization to resist the extra-pair copulation. The copulatory actions occur by one male mounting one female wile grasping her nape with his bill. The female is submerged for four seconds, but the act lasts around 15 seconds. Once the male gets off the female's back, the male swims beside the female. (Anderson and Titman, 1992; Calvert, et al., 2019; Jonsson and Afton, 2008)
Ross's geese breed yearly and seasonally in their arctic breeding grounds. Perennial pairs of Ross's geese build the nest on tundra vegetation (on moss, short grass, gravel) along a waterway or on small islands in the waterbody. Females will construct a large and insulated nest using twigs, grasses or mosses. The breeding season is from May to July, and these birds breed colonially. Nests typically are interspersed with those of lesser snow geese (Anser caerulescens).
Alisauskas and Ankney (1992) stated that a 1400-g female can lay an average of 0.77 eggs/day, and egg mass was reported as 94 g. Females lay between two to six eggs in a brood, typically four. Bluhm (1992) found that nest success is closely tied to snowmelt and ambient temperature. The longer the snow remains, the later the breeding season starts. Later breeding season equates to fewer geese attempting to nest and smaller clutch sizes.
Females expend a significant amount of energy during breeding season, as they reduce their feeding efforts. They reportedly feed rarely while laying eggs and rarely leave the nest during the short incubation time.
The color of the eggs is white and can stain during incubation. The average egg length can go up to 8 cm and the width up to 5 cm. The female will incubate for about 21-22 days and hatching will occur in June-mid-July. After hatching, the young can leave the nest within hours and can swim and feed. The young can gather their own food. Full fledging occurs between 40-45 days. Time of independence will depend on time of fledging. Although independent, the young will remain within the family unit for about 1 year. Time to sexual maturity for both sexes is 2 to 3 years. (Alisauskas and Ankney, 1992; Anderson and Titman, 1992; Bluhm, 1992; Calvert, et al., 2019; Jónsson, et al., 2020; Krapu and Reinecke, 1992)
Before hatching, perennial pairs of Ross's geese select the site, but only the females will incubate. The males will assist by protecting the territory or will guard the eggs when the females take a break to feed (which is only for short periods of time).
The hatchlings are precocial and able to feed themselves and swim 24 h after hatching. However, even after hatching, both parents will tend to and protect the young. Male will take the major role for protecting the young after nest departure. The young will remain with adults until the next spring, about 1 year. (Anderson and Titman, 1992; Calvert, et al., 2019; Jonsson and Afton, 2008; Krapu and Reinecke, 1992)
Based on banding data, Ross's geese can live at least 22.5 years in the wild. This individual was shot, suggesting a longer natural lifespan. Indeed, of the 6 oldest geese on record (aged 17 to 21.5), 5 of the 6 were hunted, rather than being found dead.
Young geese have high mortality rates, and 18.8% of the eggs laid survive until age 3 when they are deemed breeding adults. Once they reach adulthood, survivorship is higher, with ca. 84% of males and 47% of females living from year to year.
Expected lifespan for those reaching adulthood is 5.8 yr. Survivorship for adults goes hand-to-hand with the increase/decrease of population and increase/decrease of the harvest of Ross's geese. Juvenile survivorship does not depend on the increase of harvest.
Ross's geese are diurnal, feeding and roosting during daylight hours. These geese can swim, walk, run, fly. Their flight is considered strong, and they average 4.1 wingbeats per second on their breeding grounds. They are thought to be more maneuverable in the air than other goose species. These geese can make a variety of vocalizations, including soft cackling noises, as well as honking grunts, moans, and yelps.
Ross's geese live colonially in the breeding season. They typically are non-aggressive and will only attack if they feel threatened. If Ross's geese attack, they will race towards the intruder, making a hissing sound. Both sexes can squawk. Ross's geese can attack by biting and wing-slapping the intruder.
Migration begins in October where they leave their Canadian nesting grounds. Ross's geese will migrate southwards to California, Texas, and Mexico. They live in mixed flocks with other goose species in the nonbreeding months. Ross's geese return to the Canadian nesting grounds in April-May in preparation for breeding season.
Typically, males spend their time alone on breeding grounds while they are drinking or feeding. While females are incubating the eggs, the males will guard their territory. Young stay with parents for up to 1 year. After spring migration, Ross's geese do not maintain family units. (Graves, 2020; Jónsson, et al., 2020)
Pairs of Ross's geese will establish a nest-site territory where eggs will be maintained until hatching. The nest-site territory must be free of snow. Anderson and Titman (1992) estimated their territory to be 10 square meters during the breeding season, but it may range between 6 - 15 square meters. They do not defend a territory outside of the breeding season. (Anderson and Titman, 1992; Jónsson, et al., 2020)
Ross's geese of both sexes produce a wide variety of vocalizations. Most noises are some variety of high-pitched honk or squawk. They grunt or moan when defending their territory. They can also make hissing sounds if an intruder threatens them or attacks. In winter months or other times when non-territorial, they can emit a "kowk" noise when agitated. In flight, they can make a "keek" sound that is high-pitched.
Sex-specific noises include a yelp call by males trying to bond with a female, and a "kuk" sound by females when trying to gather their young.
Nonvocal sounds may accompany these vocalizations. For example, these geese can raise their neck feathers and even vibrate them when they are threatened or acting territorial. They can also point their neck upwards or diagonally to make themselves look more threatening.
Therefore, acoustics and vision is important for intra- and interspecific communication. They use tactile efforts when mating, raising young, and foraging for grains. They can probe soft substrates with their bills and find suitable food items. (Jónsson, et al., 2020; Raveling, 1978)
Ross's geese are herbivores, feeding by grazing and grubbing. Ross's geese will primarily feed on grasses, sedges, roots, seeds, bryophytes, and waste grain. During the breeding time in the summer, they will mainly eat roots and sedges.
When nesting, females forage less often while egg-laying, and rarely while incubating. Gloutney et al. (2001) examined female feeding habits during the breeding season, and quantified activity. They found that females did forage more before and during egg-laying efforts, spending 25-50% of daylight hours foraging. In comparison, typically less than 10% of their time was spent foraging while incubating eggs. In this study, females mostly foraged on bryophytes, chickweed (Stellaria) and a variety of sedges (Carex). Ross's geese also consume eggshells from previous years. The discarded eggshells serve as a necessary source of calcium.
In the winter, they will feed on domestic or agricultural grains. They have been know to feed on corn (Zea maize) crops. (Fox, et al., 2016; Gloutney, et al., 2001; Jónsson, et al., 2020; Krapu and Reinecke, 1992)
Predation can occur at the egg and hatchling stages. The most common predators of the eggs and gosling are parasitic jaegers (Stercorarius parasiticus), glaucous gulls (Larus hyperboreus), long-tailed jaegers (Stercorarius longicaudus), and herring gulls (Larus argentatus). Predators of both eggs and adult geese include arctic foxes (Vulpes lagopus), gray wolves (Canis lupus), wolverines (Gulo gulo), and grizzly bears (Ursus arctos).
To avoid an attack during incubation, female Ross's geese will vocalize, hiss, and assume a prone position with their neck on the ground and legs under the body. Adult male Ross's geese may also vocalize and maintain threatening poses to protect their nest.
On the wintering grounds, Graves (2020) reported an incident in Arkansas in March 2019, in which a bald eagle (Haliaeetus leucocephalus) pursued a Ross's goose, steered it towards the water, killed it and swam/towed it back to shore to consume it. Additional winter predators include golden eagles (Aquila chrysaetos) and red-tailed hawks (Buteo jamaicensis). (Graves, 2020; Jónsson, et al., 2020; Wobeser, et al., 1979)
The Ross's geese are granivores, consuming roots, seeds, and mosses. Multiple birds, including jaegers and gulls, feed on the eggs and hatchings. Large mammals (foxes, wolves, bears) prey on the adults.
Endoparasites commonly found in Ross's geese are nematodes, trematodes, and cestodes. Nematodes include Amidostomum anseris, Heterakis dispar, Trichostrongylus tenuis, and Epomidiostomum crami. Trematodes include Notocotylus attenuam, Echinostoma revolutum, and Zygocotyle lunatum. Cestodes infecting the intestines include those in the genus Hymenolepis.
Ross's geese are equally affected by ectoparasites or commonly known as fleas Ceratophllus vagabundus. The adult fleas are found in nests due to blood covered on the egg surface. Bird lice (Ornithobius goniopleurus) also have been reported in these geese. (Arnold, 2005; Fedynich, et al., 2009; Jónsson, et al., 2020)
Ross's geese are a target for market hunting, providing ecotourism funds in California. The bag limits varied over the years in California, but up to eight kills per day were allowed in 1994. Hunting is legal in Canada and in the United States. (Government of Canada, 2015; Jónsson, et al., 2020)
Chlamydiosis can be transferred from Ross's geese to humans. The way this disease spreads is by bird droppings or tissues that enters the human body through inhalation. The infected birds do not have to exhibit symptoms to spread the disease to humans.
Avian cholera caused by the bacterium Pasteurella multocida is also found in Ross's geese. This can be passed along humans via direct contact or airborne inhalation. (Samuel, et al., 2005; Wobeser and J. Brand, 1982)
The IUCN Red List states that Ross's geese are a species of "Least Concern." Ross's geese are protected under the US Migratory Bird Act that controls the hunt, capture, and kill of all birds that migrate in North America. They hold no special status on the US Federal list, CITES, and the State of Michigan list.
A threat to Ross's geese includes climate change, specifically, severe weather. As reproductive success for these birds is tied to timing of snowmelt, this threat could become a problem in the future. The severity of this threat is still unknown. Diseases such as avian cholera (Pasteurella multocida) can be transferred from bird-to-bird. This is common because these bird live colonially during the breeding season and overwinter in large multispecies flocks. This disease can lead to mortality in young and adults. Birds consuming fragments of lead and iron shot has been noted on wintering grounds.
Despite these threats, Ross's geese are on the rise. They were recognized as rare in the early 1900s, with only 25,000-30,000 birds overwintering in California. In the US, hunting of these geese was banned in 1931; Canada soon followed with a hunting ban. Since the 1960s, their numbers have steadily increased. By the 1980s and 1990s, bag limits of 2-4 geese/day were reinstated in California. Since 2014, they have been listed by Canada as overabundant. Nearly 2 million birds are believed to exist today.
Previous conservation efforts included the establishment and protection of breeding habitats in Queen Maud Gulf Migratory Bird Sanctuary, as well as wetlands conservation efforts in California. Currently, most conservation measures mostly fall in line with hunting bag limits. Because of their overabundance in Canada, Canada has assumed liberal bag limits to keep numbers in check. Manitoba, Canada allows a bag limit of 50 geese/day. In the US, Ross's geese are protected under the Migratory Bird Act. Daily bag limits vary by location; in Indiana, 20 light-feathered geese (snow [Anser caerulescens] and Ross's geese) are allowed per day. Virginia allows 25/day for the same geese group. (BirdLife International, 2016; Government of Canada, 2015; Indiana Department of Natural Resources, 2021; Jónsson, et al., 2020; Virginia Department of Wildlife Resources, 2021)
Jannet Ortiz (author), Radford University, Karen Powers (editor), Radford University, Victoria Raulerson (editor), Radford University, Christopher Wozniak (editor), Radford University, Genevieve Barnett (editor), Colorado State University.
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
living in landscapes dominated by human agriculture.
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.
an animal which directly causes disease in humans. For example, diseases caused by infection of filarial nematodes (elephantiasis and river blindness).
uses smells or other chemicals to communicate
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
union of egg and spermatozoan
an animal that mainly eats leaves.
A substance that provides both nutrients and energy to a living thing.
mainly lives in water that is not salty.
an animal that mainly eats seeds
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 regions of the earth that surround the north and south poles, from the north pole to 60 degrees north and from the south pole to 60 degrees south.
having more than one female as a mate at one time
breeding is confined to a particular season
reproduction that includes combining the genetic contribution of two individuals, a male and a female
a wetland area that may be permanently or intermittently covered in water, often dominated by woody vegetation.
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. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.
A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.
A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.
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.
movements of a hard surface that are produced by animals as signals to others
uses sight to communicate
young are relatively well-developed when born
Alisauskas, R., C. Ankney. 1992. The cost of egg laying and its relationship to nutrient reserves in waterfowl. Pp. 30-61 in B Batt, ed. The Ecology and Management of Breeding Waterfowl. Minneapolis, MN: University of Minnesota Press.
Allen, J. 1876. Anser rossii in Oregon. Bulletin of the Nauttall Ornithological Club, 1/2: 52.
Anderson, M., R. Titman. 1992. Spacing patterns. Pp. 251-289 in B Batt, ed. The Ecology and Management of Breeding Waterfowl. Minneapolis, MN: University of Minnesota Press.
Arnold, D. 2005. Review of the genus Ornithobius (Phthiraptera: Ischnocera: Philopteridae), with descriptions of two new species. Journal of the Kansas Entomological Society, 78/2: 158-166.
BirdLife International, 2016. "Anser rossii" (On-line). The IUCN Red List of Threatened Species 2016: e.T22679909A92834499. Accessed November 27, 2021 at https://dx.doi.org/10.2305/IUCN.UK.2016-3.RLTS.T22679909A92834499.en.
Bluhm, C. 1992. Environmental and endocrine control of waterfowl reproduction. Pp. 323-364 in B Batt, ed. The Ecology and Management of Breeding Waterfowl. Minneapolis, MN: University of Minnesota Press.
Blumstein, D., A. Moller. 2008. Is sociality associated with high longevity in North American birds?. Biology Letters, 4/2: 146-148.
Calvert, A., R. Alisauskas, D. Kellett. 2019. Fitness heterogeneity in adult snow and Ross's geese: Survival is higher in females with brood patches. The Auk, 136/3: 1-16.
Cooke, F., J. Ryder. 1971. The genetics of polymorphism in the Ross' goose (Anser rossii). Evolution, 25/3: 483-490.
Fedynich, A., R. Finger, B. Ballard, J. Garvon, M. Mayfield. 2009. Helminths of Ross' and greater white-fronted geese wintering in south Texas, U.S.A. Comparative Parasitology, 72: 33-38.
Fowler, D., E. Webb, M. Vritiska. 2020. Condition bias of decoy-harvested light geese during the conservation order. Journal of Wildlife Management, 84/1: 33-44.
Fox, A., J. Leafloor, T. Balsby, K. Dickson, M. Johnson, C. Nicolai, J. Reneerkens. 2016. Non-breeding cackling, Ross's and snow geese on Baffin Island show no loss of body mass during wing moult. Ibis, 158/4: 876-880.
Gloutney, M., R. Alisauskas, A. Afton, . Slattery. 2001. Foraging time and dietary intake by breeding Ross’s and lesser snow geese. Oecologia, 127: 78–86.
Government of Canada, 2015. "Status of Birds in Canada 2019" (On-line). Ross's goose (Anser rossii). Accessed November 28, 2021 at https://wildlife-species.canada.ca/bird-status/oiseau-bird-eng.aspx?sY=2019&sL=e&sM=a&sB=ROGO.
Graves, G. 2020. Bald eagle swims to shore with Ross's goose. Journal of Raptor Research, 54/1: 84-85.
Hanson, H., R. Jones. 1974. An inferred sex differential in copper metabolism in Ross's geese (Anser rossii): Biogeochemical and physiological considerations. Arctic, 27/2: 111-120.
Henshaw, H. 1879. Occurrence of Ross's goose (Anser rossii) on the Pacific coast and inland. Bulletin of the Nuttall Ornithological Club, 4/2: 126.
Indiana Department of Natural Resources, 2021. "Light goose conservation order permits" (On-line). Accessed November 28, 2021 at https://www.in.gov/dnr/fish-and-wildlife/hunting-and-trapping/waterfowl-and-migratory-game-birds/migratory-gamebird-seasons-and-regulations/light-goose-conservation-order-permits/.
Jonsson, J., A. Afton. 2008. Lesser snow geese and Ross's geese form mixed flocks during winter but differ in family maintenance and social status. Wilson Journal of Ornithology, 120/4: 725-731.
Jónsson, J., J. Ryder, R. Alisauskas. 2020. "Ross's Goose (Anser rossi), version 1.0. In Birds of the World (A.F. Poole, Editor)." (On-line). Cornell Lab of Ornithology, Ithaca, NY, USA. Accessed November 02, 2021 at https://birdsoftheworld.org/bow/species/rosgoo/cur/introduction.
Krapu, G., K. Reinecke. 1992. Feeding ecology and nutrition. Pp. 1-29 in B Batt, ed. The Ecology and Management of Breeding Waterfowl. Minneapolis, MN: University of Minnesota Press.
Massey, E., L. Carlson, D. Osborne. 2020. Temporal trends in body condition of Arctic geese wintering in the Mississippi Alluvial Valley. Journal of Fish and Wildlife Management, 11/1: 11-21.
Raveling, D. 1978. The timing of egg laying by northern geese. The Auk, 95/2: 294-303.
Ross, M., R. Alisauskas, D. Douglas, D. Kellett, K. Drake. 2018. Density-dependent and phenological mismatch effects on growth and survival in lesser snow and Ross's goslings. Avian Biology, 49/12: 1-16.
Samuel, M., D. Shadduck, D. Goldberg, W. Johnson. 2005. Avian cholera in waterfowl: The role of lesser snow and Ross's geese as carriers of avian cholera in the Playa Lakes region. Journal of Wildlife Diseases, 41/1: 48–57.
USGS Bird Banding Laboratory, 2021. "Longevity Records Of North American Birds. Version 2021.1" (On-line). Accessed November 28, 2021 at https://www.pwrc.usgs.gov/bbl/longevity/longevity_main.cfm.
Virginia Department of Wildlife Resources, 2021. "Migratory gamebirds" (On-line). Accessed November 28, 2021 at https://dwr.virginia.gov/hunting/regulations/migratory-gamebirds/.
Wilson, S., R. Alisauskas, D. Kellett. 2016. Factors influencing emigration of Ross's and snow geese from an Arctic breeding area. Journal of Wildlife Management, 80/1: 117-126.
Wobeser, G., D. Hunter, B. Wright, D. Nieman, R. Isbister. 1979. Avian cholera in waterfowl in Saskatchewan, spring 1977. Journal of Wildlife Diseases, 15/1: 19-24.
Wobeser, G., C. J. Brand. 1982. Chlamydiosis in 2 biologists investigating disease occurrences in wild waterfowl. Wildlife Society Bulletin, 10/2: 170-172.