Gulls are seabirds that belong to the family Laridae. They are found across most of the world, typically in coastal regions or around inland waterways. Gulls go through several distinct plumages as they mature from chick to adult. Identifying the age and plumage stage of gulls is an important skill for birders and ornithologists. This allows them to better understand gull behavior, migration patterns, and population dynamics.
There are several key factors to look for when identifying immature gulls:
Plumage
The plumage of immature gulls differs markedly from adults. Chicks hatch covered in down feathers. As they grow, they molt into juvenile plumage which lacks the crisp, clean appearance of adult feathers. Immature gulls have feather tracts that are brownish-gray rather than bright white. Their wingtips lack the bold black-and-white pattern seen in adults. The head, neck and underparts are often mottled or streaked.
Bill Color
Adult gulls have brightly colored bills that can range from yellow to red to greenish, depending on species. Immature gulls tend to have dusky black or brownish bills, which become paler as they near adulthood. Pay attention to bill color when identifying young gulls.
Eye Color
Adult gulls have bright white “headlights”, with iris colors from yellow to dark reddish-brown. Immature gulls have dark brown or blackish eyes. The eyes lighten gradually before reaching adult coloration.
Plumage Stages
Gulls molt and replace their feathers gradually over years. Young gulls go through several distinct plumage stages:
Chick Down
Gull chicks hatch covered in fluffy down. Down is thick and soft for insulation. Chick down is usually light brown, tan or gray above with some white patches.
Juvenile Plumage
The chick’s first set of contour feathers creates the juvenile plumage stage. Juveniles have buffy-brown coloration with little patterning. The bill is blackish, the eyes are dark brown. Birds in their first year are considered juveniles.
First Winter Plumage
In early fall, juveniles molt partially into first winter plumage. This incorporates some grayish-brown feathers. First winter birds have a mix of new grayish and worn brownish feathers.
First Summer Plumage
By spring, first winter birds molt again into first summer plumage. This has extensive gray feathering with brown mottling especially on the head, neck and underparts. The eyes and bill remain dark.
Second Winter Plumage
In fall of their second year, the gulls molt again into second winter plumage. This features whiter feathers on the head, body and tail. The back becomes lighter gray.
Second Summer Plumage
Second winter birds molt again into second summer plumage in spring. Now they display considerable white on the head, underparts and tail. The wings have bold black markings. The eyes and bill are lighter.
Third Winter Plumage
In fall of their third year, gulls enter their third winter plumage stage. They increasingly resemble adults, with white head, underparts and tail. Back and wings are light gray. Eyes and bill are nearing adult coloration.
Third Summer Plumage
By spring of their third year, the gulls complete the immature phase with third summer plumage. This is nearly identical to definitive adult plumage in pattern, though some feathers retain brownish marks. The bill may still be a bit darker than adult coloring.
Definitive Adult Plumage
By fall of their fourth year, gulls complete the molt to definitive adult plumage. This is the bright, crisp pattern they will retain for life during future molting cycles. Adult gulls have white heads, tails and underparts with gray upperparts and black wingtips. The eyes and bill take on full adult coloration.
Differences Among Gull Species
While all gulls follow the same basic molting sequence, there are some key differences among species to pay attention to when identifying immature birds:
Herring Gull
- Juvenile birds have brown plumage all over.
- By first winter, paler gray feathers emerge on the back and wings.
- Tail becomes whiter by second winter.
- Only gull with pink legs.
Ring-billed Gull
- Juvenile plumage is brown overall with some white mottling on head.
- First winter birds have gray back, brown wings.
- Bold white tail base by second winter.
- Yellow bill with black ring.
California Gull
- Juveniles have solid brown coloration.
- First winter birds develop gray back and upper wing feathers.
- Head starts to show white streaking by second winter.
- Greenish-yellow bill and legs.
Franklin’s Gull
- Juveniles have brown plumage overall, may show some white streaking.
- First winter birds develop gray back and shoulder feathers.
- Underparts become increasingly white by second winter.
- Dark reddish bill and legs.
Bonaparte’s Gull
- Juvenile body is dark sooty brown all over.
- First winter birds have a gray back, brown wings and tail.
- Head and underparts become mostly white by second winter.
- Black bill and legs.
Identifying Immature Gulls In Flight
When seen in flight, identifying immature gulls can be especially tricky. However, there are some helpful clues:
Flight Style
Immature gulls may appear less steady and graceful in flight than adults. Their wingbeats can seem hurried or uneven.
Wingtips
Check for dark wingtips versus the bold black-and-white pattern of adults. Immatures have less contrast on the wings.
Undersides
On juveniles and first-winters, look for brownish undersides and underwings versus the clean white of adults.
Tail Pattern
A solid brown tail indicates a juvenile. Mottled brown-and-white suggests a first or second-winter bird. Clean white tails occur on adults.
Flock Behavior
Mixed flocks may include both immature and adult birds. Immatures tend to remain on the edges or periphery of flocks.
Tricky Identifications
Some immature gulls can resemble other species. Here are tips for telling them apart:
Immature Herring Gull vs. Ring-billed Gull
- Check legs – pink on Herring, yellow on Ring-billed.
- Herring larger with heavier bill.
- Ring-billed shows whiter tail base earlier.
Immature California Gull vs. Ring-billed Gull
- California larger with longer wings and legs.
- Ring-billed has more white in the tail.
- California bill becomes orange-yellow.
Immature Bonaparte’s Gull vs. Black-headed Gull
- Bonaparte’s smaller with faster wingbeats.
- Black-headed has brown hood into first winter.
- Bonaparte’s black bill versus red bill of Black-headed.
Geographic Range
The range and habitats utilized by immature gulls varies by species:
Species | Key Range as Immatures | Habitats |
---|---|---|
Herring Gull | Coastal regions of northern North America | Beaches, harbors, tidal flats |
Ring-billed Gull | Widely distributed across North America | Lakes, rivers, agricultural land |
California Gull | Western North America | Coastlines, lakes, marshes |
Franklin’s Gull | Central North American prairies | Prairie wetlands, lakes |
Bonaparte’s Gull | Breeds in Canada and Alaska | Coastal in winter, inland lakes in summer |
Paying attention to location and habitat can provide helpful clues when identifying immature gulls by species. For example, an all-brown juvenile gull along the ocean shoreline is very likely a Herring Gull.
Behavioral Differences
Immature and adult gulls occupy different ecological niches and exhibit some differing behaviors:
Diet
Immatures are less accomplished foragers than adults. They rely more on terrestrial prey and less on marine food sources. You may see immatures scavenging in parking lots or agricultural fields.
Social Dominance
Adult gulls are dominant over immatures in competition for food and other resources. Immatures may wait on the outskirts to avoid aggression from adults.
Roosting and Loafing
Immatures tend to roost and loaf in separate groups from adult gulls. They also utilize different areas, with immatures favoring more peripheral or sheltered spots.
Migration
Younger gulls often winter further south than adult birds. Some remain in wintering grounds longer into spring before migrating back north to breeding areas.
Vocalizations
The harsh cries of adult gulls are well-known. Immatures make softer, shorter calls less frequently as they develop adult vocal structures.
Conclusion
Identifying immature gulls by species can be a challenge even for experienced birders due to their complex molting cycles. Focus on plumage patterns, bill and eye color, flight style and geographic location to accurately age and identify young gulls. With practice, you’ll become adept at spotting subtle differences and decoding the many phases of gull maturity.