The lesser black-backed gull (Larus fuscus) and the black-backed gull (Larus marinus) are two similar looking gull species that can be easily confused with one another. However, there are some key differences between these two seabirds in terms of appearance, behavior, habitat and distribution.
Appearance
While the lesser black-backed gull and black-backed gull do share some similar physical traits such as black upper wing plumage, there are some noticeable differences in their size and coloring:
- Size: The black-backed gull is significantly larger than the lesser black-backed gull. The black-backed gull has a body length of 25-28 inches compared to the lesser black-backed gull which is 21-25 inches long.
- Bill: The bill of the black-backed gull tends to be larger and thicker than that of the lesser black-backed gull.
- Leg color: The legs of adult lesser black-backed gulls are yellow while those of the black-backed gull are pink.
- Upperwing pattern: On the lesser black-backed gull, the black coloration on the upper wings only extends partially down the length of the wing. On the black-backed gull, the black extends all the way down the upper wing.
- Head coloring: Adult lesser black-backed gulls have a darker grey head and breast than black-backed gulls whose heads are more white.
In summary, the larger size, thicker bill, pink legs, more extensive black upperwing pattern, and paler head help distinguish the black-backed gull from the lesser black-backed gull which is smaller with a more delicate bill, yellow legs, less black on the wing, and a darker head.
Behavior
The behavior of these two gull species also differs in some ways:
- Feeding: Black-backed gulls are more predatory and will prey on large fish, other birds and even small mammals. Lesser black-backed gulls are more likely to feed on smaller fish, insects and human food waste.
- Vocalizations: The calls of the two species sound different. The black-backed gull has a deeper, throatier, laughing call compared to the higher pitched, mournful wailing calls of the lesser black-backed gull.
- Aggression: Black-backed gulls tend to be more aggressive especially around nesting colonies. Lesser black-backed gulls are less domineering.
- Migration: Lesser black-backed gulls migrate further distances to overwintering grounds than black-backed gulls which are more likely to stay nearer their breeding territories in winter.
So in summary, black-backed gulls exhibit more predatory feeding habits, a deeper call, greater aggression, and shorter migration distances compared to lesser black-backed gulls.
Habitat
The habitats where these gull species nest and feed also differ:
- Nesting: Black-backed gulls usually nest on rocky cliffs and isolated rocky islands. Lesser black-backed gulls nest more often on beaches, rooftops, and grassy islands.
- Feeling grounds: Black-backed gulls frequent more rocky intertidal areas and the open ocean. Lesser black-backed gulls can thrive in more urban and inland environments.
So black-backed gulls are more associated with rocky coastal areas for breeding and feeding while lesser black-backed gulls utilize a broader range of coastal, urban and inland habitats.
Distribution
The distributions of these two gull species differ as well:
- Black-backed gull: Occurs across Northern Europe, Iceland, Northern Asia and parts of Alaska. Widespread along the Atlantic coast of North America.
- Lesser black-backed gull: Breeds across parts of Northern and Central Europe. Also occurs in Iceland, parts of Western Asia. In North America, colonies occur locally on the Atlantic coast.
So while there is some overlap, black-backed gulls occupy a larger geographic breeding and wintering range spanning both the Pacific and Atlantic coasts. The lesser black-backed gull has a more restricted range concentrated in Europe and the Atlantic coast of North America.
Identification Tips
Here are some quick tips for distinguishing these two similar looking gull species in the field:
- Size – Black-backed is significantly larger
- Legs – Yellow on lesser black-backed, pink on black-backed
- Wing pattern – Black extends further on black-backed
- Head color – Darker grey on lesser black-backed
- Bill – Thicker on black-backed
- Behavior – Black-backed is more predatory and aggressive
- Call – Deeper laughing call on black-backed
- Range – Black-backed has larger global range
Using a combination of these visual cues, vocalizations and behavioral traits along with range can help properly differentiate between these two seemingly similar gulls.
Conclusion
In summary, while the lesser black-backed gull and black-backed gull share similarities in appearance, there are distinct differences in terms of their size, coloring, vocalizations, behavior, preferred habitats, and geographic ranges that allow them to be distinguished from one another. Being able to properly identify these species takes practice studying their nuances in the field or using resources like bird guides. But with attention to key identification criteria, the lesser black-backed gull and black-backed gull can be confidently told apart.
