Swans and geese both belong to the family Anatidae and subfamily Anserinae; however, swans belong more specifically to the genus Cygnus, while geese are split into the 3 genera Branta, Anser, and Chen. There are a great many species of geese, with hybridization being common and making it more difficult to classify them (hence belonging to 3 genera), while there are only 7 species of swan worldwide.
It may come as no surprise that swans and geese evolved together, along with ducks, for tens of millions of years. According to meticulous and detailed molecular analysis of extant organisms as well as fossils, the two branched off from ducks approximately 30 million years ago, during the Oligocene prehistoric era.
Geese and swans developed separate branches from one another approximately 12 million years ago, toward the end of the Miocene period. The majority of goose species split off and evolved only within the last 2 to 4 million years, likely in response to global cooling events that altered many ecosystems worldwide.
Swan & Goose Appearance & Size Differences
Overall, swans are larger the geese. The exception to this can sometimes be found in Bewick’s swans and tundra swans, which max out around 14 or 15 pounds, and the Canada goose, which can exceed the former and sometimes weigh over 20 pounds. There is some variation, of course, amongst swan species and goose species, particularly as hybridization occurs. For example, cackling geese have many subspecies and can range from 3 pounds to being as large as a Canada goose. As a general rule of thumb, though, swans are typically larger in terms of weight, body length, and wingspan than geese.
Geese also tend to have shorter, thicker necks than swans, and with the exception of Canada geese they often lack the signature curve often associated with swans. However, mute swans are typically the only ones to have this curve, with tundra swans and whooper swans occasionally possessing it as well.
Usually, the only goose species that is sometimes mistaken as a juvenile swan is the snow goose, as it looks similar to tundra and trumpeter swans with its white plumage. Snow geese are easily distinguished by their black wing tips (which no swan species possess), and very stout and thick bills that are a vibrant pink-orange color (tundra and trumpeter swans have longer, thinner bills that are mostly or entirely black). They are also about half the size of either of these swans, weighing in at a maximum of 6 pounds as adults, with a much shorter and thicker neck.
Swan & Goose Diet Requirement Differences
Swans and geese, having evolved to fill similar ecological niches, feed on much the same things. The majority of their diets are composed of vegetation – aquatic vegetation like pondweed, duckweed, algae, and tubers as well as berries and grasses in the summer and leftover crops like wheat, corn, and potatoes in the winter. Both types of birds will occasionally eat invertebrates like mollusks, insect larvae, snails, and worms as well as small fish and frogs if vegetation is scarce. The only real difference is that geese browse more on land than in water, while swans browse more in water than on land.
The exact nutrient requirements of geese and swans is a bit difficult to nail down, as the majority of resources are from breeding farms rather than studies conducted on wild birds. However, whether large or small, these birds require remarkably little protein – geese seem to do well with protein levels somewhere between 5 and 15%, while swans should not consume more than 5 to 8% protein as adults. Too much protein can result in angel wing and fatty liver lipidosis in waterfowl, as their livers are not made to process much protein and will become overworked.
The vast majority of their diet should come from fibrous, nutrient packed vegetation and grains. Exact levels will not be discusses here, as, like mentioned above, primary resources on this topic come from poultry farms and breeders rather than scientific studies conducted on wild birds. The issue with this is that farms and breeders often put a greater focus on growing larger birds faster, rather than actual health and a longer lifespan, and as such nutrient levels are often skewed. For example, many commercial waterfowl feeds have 20% or more protein in them – some have as much as 40%!
With this in mind, avoid feeding waterfowl pellet feeds, particularly ones advertising high protein. Focus instead on not feeding them at all (wild geese and swans are very resourceful, and more than capable of finding their own food), or if they’re domesticated feed them fresh vegetables, native aquatic plants like duckweed, small amounts of berries like blackberries, and grains like wheat and rye.
Swan & Goose Behavioural Differences
Swan and goose behavior are quite similar. Both typically mate for life, but will find a new mate if the other dies or they “divorce,” the latter of which usually only occurs in the event of offspring death. Most geese and swans return to the same location that they were born year after year, but it’s not unheard of for them to establish new territories, either due to being driven out by competitors, lack of resources, or simply by accident (sometimes during migration they can become confused by storms or altered magnetic fields and light wavelength, thus winding up in a different location).
Geese are, overall, quite social birds. Even during the breeding season when tensions are high, they can often be found in large groups of other geese, ducks, and sometimes swans. This benefits them, as a larger group means that predators are less of a threat.
Swans, however, are typically less social. They can be found in flocks with other waterfowl during the winter, but in general prefer to just stick with their mate and young. Even mated pairs can be found living separately, as they enjoy their independence. Predators are less of a concern due to their large size and more aggressive nature, and so sticking in flocks is less of a priority for them.
Swan & Goose Breeding Differences
Breeding behavior varies among species, but on average, geese begin mating around the age of 2 or 3 years, while most swans don’t mate until they’re 4 or 5 years of age (some as early as 2). Due to their monogamous nature, swans and geese raise young with both the father and mother present, each helping to provide food and protection. While swans only raise young as a mated pair, some goose species, such as the Canada goose, have been known to sometimes engage in group-rearing, in which goslings are raised together by several families. This is presumably to ensure greater chances of gosling survival.
Geese tend to be more docile overall than swans, but they can still be quite aggressive! The most aggressive goose species, perhaps surprisingly to those familiar with the honk and charge of an irate Canada goose, is the brant goose. The brant goose spends nearly 40% of its time engaged in aggressive behaviors during the breeding season. The black-necked swan is the most aggressive swan species, according to many ornithologists and bird hobbyists alike. Aggression amongst both bird types occurs most often during the breeding season, and when feeding.
Difference Between Swan & Goose Habitats
Swans and geese inhabit similar areas, however swans are more often found in cold climates (with the exception of the Australian black swan and South America’s black-necked swan), while geese are found in a greater variety of climates and regions.
Overall, swans are found almost exclusively in water, particularly when foraging for food. Their long necks are well-adapted for dipping far under the water to reach aquatic vegetation and the occasional mollusk or insect larvae, while their large bodies and comparatively thin legs make walking on land difficult. Geese are more likely to be seen foraging on land, such as in lawns, grasslands, and farm fields where they can find ample roots, leaves, and seeds to eat, but pretty evenly split their time between water and land.
Swan & Goose Population Differences
For the most part, geese are much more common than swans, with many species having booming populations due to widespread human agriculture. Swans have been experiencing a downward trend due to habitat degradation and loss (remember, they are much less able to be on land than geese are, and rely heavily on water).
Worldwide, there are an estimated 10,000 black-necked swans; somewhere around 200,000 tundra swans; 63,000 trumpeter swans; Bewick’s swan numbers are unknown but have been declining since 1990 from around 20,000 individuals; 500,000 black swans; 180,000 whooper swans; and 500,000 mute swans in their native range, with somewhere around 30,000 invasive mute swans in the US. A 2019 study found that among all 7 swan species (the Coscoroba swan is not a true swan), there are fewer than 2 million individuals worldwide.
Compare this to geese (we won’t list all of the species, as there are too many): there are over 5 million Canada geese; over 15 million snow geese; nearly 2 million Ross’s geese; over 2 million greater white-fronted geese; and approximately 850,000 bean geese. Overall, geese are increasing in number due to their ability to exist both aquatically and terrestrially, thus making them more adaptable.
However, there are a few goose species that are endangered with declining numbers, due primarily to being specialized species adapted to specific areas & conditions – the red-breasted goose, heavily poached in Romania to protect farm crops; the lesser white-fronted goose, due largely to their small size and resulting lessened ability to fight for resources as ecosystems become smaller and more degraded; and the Hawaiian goose, which as its name suggests is found only on the islands of Hawaii, many of which are experiencing increased development.
Swan and Goose Natural Predators
Swans have very few natural predators due to their large size and assertiveness. Coyotes, wolves, raccoons, and foxes sometimes prey on cygnets and eggs. On rare occasions, coyotes and wolves may kill adult swans, as well.
Geese have a few more predators, owing to their smaller size. The adults can be preyed on by coyotes, wolves, and large raptors like the hefty golden eagle and great horned owl. Goslings are eaten by the aforementioned, as well as by raccoons, foxes, bigger corvids like ravens and crows, and occasionally opportunistic bears.
The greatest threat that both swans and geese face is people. Both types of birds are often hunted or illegally poached for their feathers and meat, or to protect crops and gardens. In the case of Canada geese and mute swans, both of which have rapidly rising numbers, well-managed and responsible hunting programs can help keep their populations from exploding out of control.
In addition, our continued overpopulation and ever-expanding development have led to habitat loss, degradation, and fragmentation. As a very mobile (and often environmentally naïve) species, we also spread invasive plant and animal species that outcompete the native ones – this is why we so often stress in our articles to only obtain plant and animal species that are native and legal in your area.
