Ring-billed gulls (Larus delawarensis) are a common gull species found across North America. They are medium-sized gulls with distinctive markings that make them easy to identify. Here is an overview of the key physical characteristics, diet, habitat, breeding, and behavior of ring-billed gulls.
Physical Characteristics
Ring-billed gulls are around 17-20 inches in length with a wingspan of around 50 inches. Some of their key identifying features include:
- Adults have white heads, underparts, and tails.
- Their backs and wings are gray.
- They have yellow eyes with red eye rings.
- The bill is yellow with a distinctive black ring around it ( juveniles lack the ring).
- Their legs and feet are yellowish-green.
Ring-billed gulls take around 3 years to reach full adult plumage. Juveniles are mottled brown and gray. By their second year, they appear more white but still have some brown markings and a dark bill.
Diet
Ring-billed gulls are omnivorous and opportunistic feeders. Their diet includes:
- Aquatic prey – They feed on small fish, crabs, mollusks, and other marine invertebrates.
- Earthworms and insects.
- Rodents and other small mammals.
- Bird eggs and hatchlings.
- Grains, seeds, berries.
- Garbage and scraps from human sources.
They forage in a variety of habitats including shorelines, lakes, rivers, fields, parking lots, and landfills. They often swoop down to snatch food from the water or ground while in flight. They may also wade into shallow water to catch prey.
Habitat
Ring-billed gulls occupy a wide range of habitats across North America including:
- Coastlines – Beaches, mudflats, estuaries.
- Lakeshores
- Rivers
- Marshes and wetlands
- Fields and grasslands
- Urban areas – Landfills, parking lots, fast food outlets, rooftops.
They thrive around human activity and man-made habitats. Though migratory, many are year-round residents across much of their range. They winter along coasts, large lakes, and south to Mexico and the Caribbean.
Breeding
Ring-billed gulls breed in colonies numbering in the dozens to thousands of pairs. Nesting occurs near water – on islands, shorelines, and human structures like rooftops. Courtship begins in March, with nest-building in April or May. Nests are shallow scrapes lined with vegetation and debris. The female lays a clutch of 2-4 eggs. Incubation lasts around 4 weeks. The chicks hatch in May-July and fledge in 4-6 weeks. Both parents help build the nest, incubate the eggs, and feed the young. Ring-billed gulls reach sexual maturity and begin breeding around age 3.
Behavior
Ring-billed gulls exhibit the following behaviors and traits:
- They are social birds found in flocks outside of breeding season.
- They bathe frequently and can drink saltwater.
- They are vocal – their calls include a laughing “klee-uk” and buzzing “arr-reah”.
- They are aggressive and territorial during nesting.
- They may congregate in large numbers at food sources.
- They roost on beaches, waters, and structures at night.
- They soar, glide, dive, and paddle with their feet to move and forage.
Population and Conservation
Ring-billed gulls have a large population estimated at around 2.5 million birds. Their numbers increased substantially in the 20th century with the availability of landfills as a food source. However, declines in some areas have been noted since the 1970s. This may be due to factors including botulism outbreaks, PCB pollution, and competition from other gull species. Ring-billed gulls are not under threat as a species, but some localized populations may be vulnerable. Conservation measures include managing botulism at landfills and monitoring PCB levels in the environment.
| Key Fact | Description |
|---|---|
| Scientific Name | Larus delawarensis |
| Length | 17-20 in |
| Wingspan | Around 50 in |
| Weight | 1-1.5 lb |
| Plumage | White head, underparts, tail. Gray back and wings. Black ring around yellow bill. |
| Diet | Omnivorous – fish, invertebrates, worms, rodents, eggs, grain, garbage, scraps. |
| Habitat | Coastlines, lakes, rivers, wetlands, fields, urban areas. |
| Nesting | Colonies near water. Nest is shallow scrape lined with debris. |
| Clutch Size | 2-4 eggs |
| Conservation Status | Least Concern |
Conclusion
In summary, ring-billed gulls are adaptable, opportunistic gulls common across North America. They are identifiable by their medium size, white and gray plumage, yellow bill with black ring, and yellow eyes with red rings. They utilize a wide range of habitats and feed on diverse food sources, especially around human activity. Their populations are generally stable, though some localized declines have occurred. Ring-billed gulls provide important ecosystem services like scavenging and face threats from pollution and disease in some areas.
