Identification of Domestic Graylag & Swan Geese and Their Hybrids

Both Graylag Goose (Anser anser) and Swan Goose (A. cygnoides) have a long history of domestication and hybridization with each other. The extensive hybridization of these two domestic geese often makes it impossible to determine for certain if a given individual is truly "pure." However, visual field marks can help one to determine an individual's identity to a degree that's frequently "accurate enough" for citizen science if not perfectly accurate in some cases. Below I will discuss some helpful features for identifying these species and their hybrids. Everything discussed below is referring to the domestic forms of both Graylag and Swan Goose rather than their wild-type counterparts.

Plumage

Although many domestic geese are mostly or totally white, I think it's important to first discuss some basic plumage characteristics of these two species when they are "normally" colored.

Graylags will often be grayish brown with a mostly monotone neck that is usually darker than much of the body. The neck feathers typically have more "ruffles" than Swan Geese. The ruffles appear more textured and look like lines in the neck feathers.

Swan Geese have more of a two-toned neck, with a richer brown "mane" running along the entire back of the head and neck. Swan Geese also tend to have a smoother neck than Graylag, without the aforementioned "ruffles."

Hybrids of the two species are variable, but show a mix of the characteristics from both species. Oftentimes they have a "mane" similar to pure Swan Goose, but more faded and less distinct. They will also often show more neck "ruffles" than pure Swan Goose.

Bill

The bill is possibly the most helpful feature for identifying these species. Graylags have bright orange or occasionally pinkish bills. Swan Geese without any white in their plumage seem to almost always show black bills, while Swan Geese with more white can show partially/completely orange bills.

Swan Goose bills are often proportionally larger compared to their heads, with a large "knob" at the base of their upper mandible. Graylag Goose bills are often smaller proportionally and don't have a knob at the base. If a goose looks otherwise like a Graylag, but has any kind of knob on the bill, it can be assumed that it's a hybrid. If a goose looks otherwise like a Swan Goose, but has a reduced knob, it's often safe to assume it's a hybrid.

Structure

Graylags are often more compact while Swan Geese are often more lanky, the latter having longer necks in relation to body size. The heads of Swan Geese tend to look longer than that of Graylags.

Hybrids with Canada Goose

Graylag x Canada Goose hybrids have a fairly consistent appearance when not completely white, only really resembling Greater White-fronted x Canada Goose hybrids.

Note the darker and often broader cheek patch, brighter orbital, orangey bill, browner head and neck, and duller plumage when compared to pure Canada Goose.
When this hybrid lacks its plumage features, however, it becomes more of a challenge to ID.

Graylag x Canadas tend to have smaller, thinner bills than pure Graylags. Their overall proportions, especially those of the body and neck, are often more thin and dainty than Graylags. Their proportions more closely resemble that of Canada Goose.

Swan x Canada Goose hybrids are similar to Graylag x Canadas but with longer heads, and typically a knob at the base of the upper mandible. They also typically have black bills and lankier proportions.

Both Graylag and Swan Geese tend to have a more or less straight vertical border between the bill and the feathers. The images on the left are about the most variability one will see in this trait (bottom left is a wild-type Graylag Goose but this feature remains consistent). Canada Geese have a more pushed in shape to the base of the bill, which translates to hybrids. Hybrids tend to be intermediate in this characteristic. If an all white goose has a thinner bill with a similar pushed-in shape to its base, it's a hybrid.

I don't recall coming across photos of any completely white Swan x Canada Geese, but oftentimes they will have large solid chunks (or thick "bars") of white on their underparts.

The above individual is likely the product of all three species. It is probably something along the lines of (Swan x Graylag Goose) x Canada Goose. Note present but limited bill knob, mostly orange bill, and intermediate proportions.

As I mentioned above, it's important to keep in mind that not all individuals are identifiable. Many are best left at Graylag/Swan Goose or Graylag/Swan x Canada Goose. Both Graylag and Swan Goose hybridize with other species than those mentioned here, but the ones I discussed are the most common, and are frequently an identification challenge. Thank you @that_bug_guy for the input on this guide.

Below are some examples of the variability of Graylag x Swan Goose hybrids.

In summary:

• Graylag Goose - Uniform gray, distinct neck ruffles, orange bill, no knob, often heavy-set
• Swan Goose - Cream with contrasting "mane," no neck ruffles, large knob, often slim
• Graylag x Swan Goose - Intermediate; faded "mane," two-toned bill, reduced knob and neck ruffles

Posted on February 2, 2024 12:10 AM by liliumtbn