Swoose: The Swan-Goose Hybrid

A Swoose—a swan and a goose hybrid—may sound like the stuff of fiction, but it has been a documented reality. Very few written records or photographs exist of this swan goose hybrid, as most birders have relatively little interest in wildfowl hybrids. News of the Swoose became widely recognized within the public domain in 2010 despite observations occurring as early as 2004 in Dorset, England. Read on to learn more about the Swoose and the evidence we have so far.

What is a Hybrid Bird?

Before delving deeper into the Swoose, it is worth understanding what makes a hybrid bird. Hybrid birds occur when two individuals of distinctly different species come together to mate. In the case of the Swoose, this is a swan and a goose which produces a swan goose hybrid offspring. Hybrid birds' viability – or capacity to survive, thrive, and reproduce – varies greatly, and many hybrid birds are sterile. A swoose hatchling, for example, is thought to rarely live past the fledging stage.

Natural distinctions between species – song, color, markings, behavior etc. – tend to keep most birds mingling with their kind. However, a hybrid bird will pop up now and then, providing that genetics isn't always a strict barrier to mating possibilities.

About 10% of the world's avian species are known to have hybridized with other species. But why? There isn't a clear answer. Since most hybrids are pairings between two closely related species, the explanation might be mistaken identity. Other cases could result from interspecific parasitism, during which a bird lays some of its eggs in the nest of another species. The resulting offspring then imprint onto their hosts and may grow up preferring them as partners.

The Dorset Swoose

Observations of the Swoose have been recorded as early as 2004. On the River Froome in Dorset, birders witness a mute swan mating with a domestic goose to produce a single swoose. Members of the Radipole Ringing Group observed the pairing. Despite indications that Swoose rarely survives past the fledgling stage, this individual continued to survive years later.

It wasn't until 2010 when photographs online sparked birder interest once again around the Swoose. These images seemed to confirm the Dorset Swoose was alive and thriving. Observers collected feathers from the Swoose preening site and from its parents to send for genetic analysis. This would confirm that this individual was indeed a Swoose. Tragically the feather samples were lost before scientists could conduct research.

The Dorset Swoose is usually observed in the company of a mute swan and young cygnets, though it is unknown whether they are related.

Swoose: How Many Recorded Instances Are There?

There are very few documented records of Sweese and even fewer validated photographs. Many photos or discussions claiming to be about the Swoose are actually of goose hybrids (usually domestic goose x Canada Goose). Here are those that we do know of:

  • In 1928, John C Phillips published a research paper in The Auk highlighting a hybrid between a male black swan and a female Canada goose.
  • In 2001 a Dutch Aviculture website posted a photo of two hybrids between a mute swan and a white domestic goose.
  • In 2001 Christopher Randler published an article on the "Field Identification of Hybrid Wildfowl – Geese", which contained a photo of a hybrid between a mute swan and a domestic goose, taken in Switzerland in January 1997.
  • In 2002 Eric & Barry Gillham's "Hybrid Ducks: The 5th Contribution to an Inventor" contains two photographs of swan x goose hybrids. One photo is of a Coscoroba swan and a domestic goose; the other is a Coscoroba swan and a Hawaiian goose.

How Do You Identify a Swoose?

You may now be wondering what the defining characteristics are for identifying a Swoose. These goose swan hybrids have been sighted in a range of feather colorations. As our understanding of the Swoose—and hybrid birds more broadly—is ever evolving, there is no definitive list, but there are a few tell-tale signs.

Swan-goose hybrids are rarer than intra-swan hybrids, such as a mute swan x black swan combination, so it's essential to eliminate that possibility.  

Here are defining features of a swan x goose hybrid (termed "swoose"):

  • Legs and feet are pale
  • Primaries are not white where they would be on swan species
  • Yellow-orange color on the bill
  • Raised knob at the bill base
  • Dark plumage

It's important to note that a pair of adult birds accompanying a young bird may not be its biological parents. In some species, including swans and geese, parental birds may adopt youngsters that have lost their biological parents, or another bird may have laid an egg within their nest. Other circumstances may be the mother mating with another bird than its usual partner or replacing her partner since mating. 

Top Tips to Identify a Hybrid Bird

  • We Are Family: Hybrids are most often recognized by physical features passed down from their parents. With that in mind, pick out field marks that remind you of a similar-looking bird. Are they common in your area? Do they share similar features that make it likely for them to hybridize? Geese and swans inhabit the same habitat and have similar features, hence the feasibility of a Swoose.
  • Listen: It takes a very experienced birder, sometimes with the help of technical equipment, to discern the subtle differences in bird calls, but on some occasions, the hybrid birds' voice will be distinctly different.
  • Study Your Local Hybrids: Online forums make it easy to exchange information and sightings with other birders. They are also often the first place where observers will share any photos. Many field guides will also cover the most commonly encountered hybrids for you to look out for. 
  • Take Photos: Often, the features required to identify a hybrid bird can be difficult to confirm in the field, especially as the individual is likely to move around a lot or fly out of sight. Getting images of these tricksters can be helpful for more detailed study and for soliciting the opinions of other birders online.