Glaucous and Iceland gulls are two similar-looking gull species that occupy Arctic and subarctic regions. They can be challenging to differentiate, especially in winter when their plumage is mostly white. However, there are some key differences in size, structure, plumage, and behavior that birders can use to tell them apart. Understanding these differences allows for better identification and appreciation of these northern gulls.
How to Identify Glaucous and Iceland Gulls
Here is a quick overview of the main identification features of adult glaucous and Iceland gulls:
Glaucous Gull
- Larger and bulkier with a thicker neck
- Bill size massive, heavy and rounded
- Wingtips do not extend far beyond tail tip when at rest
- Legs pink
- White plumage clean and bright
- Slow, steady wingbeats
- Often solitary forager
Iceland Gull
- Smaller and more slender with a thinner neck
- Bill relatively short and tapered
- Wingtips extend clearly beyond tail tip when at rest
- Legs flesh-colored
- White plumage neat but not as bright as glaucous
- Buoyant flight style with quick, snappy wingbeats
- Gregarious, often found in flocks
These differences are explained in more detail below.
Size and Structure
The glaucous gull is a very large gull, similar in size to the great black-backed gull. The Iceland gull is medium-sized, noticeably smaller than the glaucous.
Species | Length | Wingspan |
---|---|---|
Glaucous Gull | 25-28 in | 55-67 in |
Iceland Gull | 20-24 in | 49-55 in |
The glaucous gull has a thick neck and large, bulky body, giving it a front-heavy appearance. The Iceland gull looks more slender and elongated. When seeing the birds side by side, the size difference is striking.
Bill Size and Shape
Bill size and shape are helpful clues for identification. The glaucous gull has a massive bill that is heavy and rounded. The bill of the Iceland gull looks petite in comparison. It tapers to a point, giving it a slender, more elegant look. The tapered bill of the Iceland gull can resemble a smaller herring gull bill.
Wingtips Relative to Tail
When the birds are at rest, look at the wingtips relative to the tail. On the glaucous gull, the wingtips do not extend far beyond the tail tip. But on the Iceland gull, the wingtips project clearly beyond the end of the tail, making the tail look shorter. This difference is more obvious on flying birds.
Plumage
Winter Plumage
In their white winter plumage, glaucous gulls appear very pale, even bleach white. Iceland gulls look snowy white but not quite as bright and clean as the glaucous. The Iceland gull’s wings and back may show some faint grayish mottling. However, at a distance or in poor light, the plumage difference can be difficult to discern.
Other Plumage Differences
First year birds offer some plumage clues. Juvenile glaucous gulls are whiter overall with neat, fine streaking. Young Iceland gulls are browner and more coarsely streaked below.
Adult Iceland gulls get a grayish hood in summer. Adult glaucous gulls show a pinkish flush on the neck and chest in breeding plumage. But these subtler breeding plumage differences are not always easy to notice in the field.
Legs and Eyes
Leg and eye color can be helpful for confirming an identification. Glaucous gulls have pink legs and eyes with a yellow orbital ring. Iceland gulls have greenish legs and eyes with a reddish orbital ring. However, lighting conditions can make leg and eye color tough to discern sometimes.
Behavior
Glaucous and Iceland gulls exhibit some general behavioral differences:
Flight Style
In flight, glaucous gulls have slow, heavy, and steady wingbeats. Iceland gulls seem more energetic and buoyant, beating their wings faster.
Foraging
When foraging, glaucous gulls are often solitary. Iceland gulls are more social, foraging in flocks more often. Iceland gulls may also feed in association with other gull species or waterfowl.
Vocalizations
The calls of Iceland and glaucous gulls sound similar – laughing, long calls and short barks or yelps. But Iceland gulls tend to sound higher pitched and more complex in their vocalizations. With practice an experienced birder can pick out this difference.
Where to Find Them
Understanding the range and habitat use of Iceland and glaucous gulls gives useful context for identification:
Glaucous Gull
- Circumpolar Arctic breeder, winters south to the Great Lakes and northeastern U.S.
- Coastal habitats, lakes, rivers, harbors
- Scavenges at landfills, sewage outflows
- Solitary wanderer
Iceland Gull
- Breeds in Greenland, winters from New England to Mid-Atlantic
- Coastal and inland lakes, rivers, fields
- Often found in plowed fields with other gulls
- Gregarious, flocks with other birds
Where their winter ranges overlap, habitat preferences and behavior may help confirm identification.
Similar Species
Other gull species may also be mistaken for Iceland or glaucous gulls. Here is how to differentiate them:
Thayer’s Gull
- Smaller with a thinner bill than Iceland gull
- Bill size and shape resemble herring gull
- Wingtips at rest fall between Iceland and glaucous
- Legs dusky pink
- Winter adult has bold dark eyes
Herring Gull
- Smaller with a thinner bill than Iceland gull
- Legs pink
- Adults have black wingtips with white spots
- Juveniles have black tail band
Slaty-backed Gull
- Similar size and structure to glaucous gull
- Legs are yellow to flesh-toned
- Adult has slaty gray back in summer
- Juvenile has dark tail band
Careful attention to multiple field marks is needed to distinguish between these potentially confusing species.
Hybrids
Hybrid gulls occur where the ranges of Iceland and glaucous gulls overlap. This includes areas of southern Greenland, Newfoundland, and the northeastern U.S. Hybrids show intermediate characteristics between the parent species which can make identification challenging. Potential hybrids are best identified by the presence of multiple field marks from each parent species. Consult an expert if you suspect a hybrid gull.
Conclusion
Telling apart Iceland and glaucous gulls requires a knowledge of size, structure, plumage, and behavioral differences. With practice, birders can learn to recognize the more slender Iceland gull with its smaller bill, longer wingtips, and buoyant flight from the larger, bulkier glaucous gull. Paying attention to range, habitat, flocking behavior and vocalizations provides additional identification clues. While similar, these northern gulls show consistent differences that allow for accurate identification with some diligent study.