The California gull (Larus californicus) is a medium-sized gull species that breeds primarily in the interior of western North America. Like most gulls, California gulls go through multiple plumage cycles from the time they hatch to when they reach maturity. The first cycle refers to the plumage and appearance of California gulls in their first year after hatching.
California gulls typically hatch in May or June. The hatchlings are covered in down and rely on their parents for food and protection. Within a few weeks, they grow their juvenile plumage which they will keep until their first winter. This initial juvenile plumage represents the first cycle for the California gull.
Appearance
The first cycle California gull has a distinctive juvenile plumage that is quite different from the adult appearance. Some key features include:
– Brown mottled upperparts. The wings and back are covered in brown feathers with darker spotting and barring. This provides camouflage for the young birds.
– Black tail with clean white tip. The tail has a broad black band and a bright white tip.
– Black bill. The bill is completely black. Adults have a yellow bill with a red spot.
– Pink legs and feet. The legs are a fleshy pink color which gradually transitions to yellow as the bird ages.
– Dark eye. Juveniles have a dark brown iris while adults have a pale yellow iris.
– Variable head streaking. Some individuals have heavy dark streaks and markings on the head while others have a pale head with minimal markings.
– No hood. First cycle gulls lack the dark hood that adults acquire.
– Gray underparts. The breast and belly are a mottled grayish color. Adults have clean white underparts.
Overall, first cycle California gulls have a scaly, speckled appearance courtesy of the brown mottled feathers. The pink legs, dark eye, and lack of a hood help identify them as juveniles. The black and white tail with clean white tip is a useful identifier.
Timing of First Cycle
California gulls fledge and leave the nesting colony around four weeks after hatching. At this point, they have their full juvenile plumage. This first plumage cycle lasts through their first winter.
The juvenile plumage is molted starting around January or February of their first year. This molt leads to the second cycle plumage – immature plumage. So the first cycle lasts approximately 6-8 months from hatching to their first true molt.
The exact timing of molts and plumage cycles can vary by a few weeks depending on hatching date, food availability, and environmental conditions. But in general, the first juvenile plumage lasts from mid-summer when hatched until late winter of the first year.
Behavior
The behavior of first cycle California gulls also differs from the adult birds in a few key ways:
– Dependence on parents – For the first few months after leaving the nest, juveniles remain close to their parents and continue to beg for food. The parents continue to provide some feedings.
– Fishing skills – Young gulls have less fishing experience and may have lower success rates than adults when plunging into water to catch prey. They improve over time.
– Foraging habits – First cycle gulls stay around breeding colonies longer, feeding on scraps and leftovers. Older birds disperse more.
– Sociality – Juveniles tend to stay in small groups with other first-year birds. Adult gulls are more likely to be solitary or in pairs.
– Migration – Young gulls may migrate later in fall or winter than adults. Their first migrations are exploratory.
– Vocalizations – The calls of first cycle gulls are raspy begging screams. Adult gulls have a fuller more complex vocabulary of calls.
The initial dependency on parents, poorer feeding skills, and group foraging behavior of first cycle California gulls all reflect their young age and inexperience. Their behavior matures along with their plumage.
Range
The geographic range of first cycle California gulls generally matches the breeding range of the species along the west coast of North America.
Key areas include:
– Interior western North America – breeding sites scattered across prairie lakes and rivers from Canada south to Utah and Colorado. Most first cycle gulls remain around breeding areas.
– West coast – smaller numbers breed along the Pacific coast and juveniles remain near coastal nesting sites.
– Inland lakes – foraging at lakes and rivers across the interior west.
– Garbage dumps – congregations at landfills where waste provides food.
– Wintering grounds – as winter approaches, they move to ice-free lakes, coastal areas, and south into Mexico.
While a few juveniles may wander widely or cross large distances, most first cycle California gulls remain relatively close to where they were hatched during their first few months of life. They start to expand their range by mid-winter.
Diet
The diet of juvenile California gulls includes:
– Fish – especially smaller species like sticklebacks, minnows, and Killifish.
– Crustaceans – shrimp, aquatic insects, crabs.
– Insects – flies, grasshoppers, caterpillars.
– Earthworms and other invertebrates.
– Bird eggs and hatchlings – especially from other colonial waterbirds.
– Carrion – remains of fish, animals, garbage.
– Rodents and small mammals.
– Grains and berries.
– Scraps from human sources – landfills, fishing docks, parks.
| Food type | Percentage |
|---|---|
| Fish | 35% |
| Insects | 25% |
| Crustaceans | 15% |
| Other invertebrates | 10% |
| Carrion | 5% |
| Eggs/hatchlings | 5% |
| Grains/berries | 3% |
| Garbage/scraps | 2% |
Their diet consists of a wide mix of aquatic invertebrates, terrestrial insects, fish, plant matter, carrion, and human food sources. The ability to exploit diverse foods from lakes, rivers, landfills, and agricultural areas is key to their survival through the first year.
Foraging
First cycle California gulls forage through various techniques:
– Surface plunging – swooping down to grab insects, fish, or invertebrates from the water surface.
– Dipping – swimming and dipping head underwater to catch prey.
– Scavenging – feeding on carrion from lake shores and beaches.
– Begging – soliciting food from parents and other gulls.
– Digging – using bill to probe soil and dig for invertebrates.
– Gleaning – picking insects and worms off the ground or vegetation.
– Wading – walking through shallow water mixing prey items.
Their foraging improves throughout the first year as they gain experience and become more successful at catching fish and other prey. Foraging efficiency helps ensure they get adequate nutrition to survive their first winter.
Threats and Mortality
First cycle California gulls face a number of threats:
– Starvation – difficulty foraging can lead to starvation, especially in winter.
– Predators – eggs and chicks susceptible to coyotes, foxes, raccoons. Juveniles to peregrine falcons, eagles.
– Disease – avian cholera outbreaks in nesting colonies can kill many young gulls.
– Severe weather – late spring storms can kill nestlings.
– Pollution – ingestion of toxins from oil spills, lead, pesticides.
– Human activity – entanglement in fishing gear, hit by cars, eating sharp items.
– Lack of suitable habitat – drying of wetlands, human disturbance of nesting colonies.
| Mortality Factor | Percentage |
|---|---|
| Starvation | 35% |
| Predation | 25% |
| Disease | 15% |
| Severe weather | 10% |
| Pollution | 5% |
| Human activity | 5% |
| Habitat loss | 5% |
Starvation and predation account for the majority of first year mortality. Their survival relies heavily on the availability of abundant, high quality food sources. Parents continue to protect and provision them for several months post-fledging.
Mortality rates are estimated to be 40-60% in the first year. Lifespan increases to 7-15 years for gulls that survive this initial vulnerable period.
Conservation
California gulls are listed as Least Concern on the IUCN Red List. They have a large population and breeding range. However, a number of conservation measures can help support first cycle gulls:
– Protect breeding colonies – limit human disturbance and predator access.
– Monitor contaminant levels – reduce sources of lead, oil, pesticides.
– Wetland restoration – reverse loss of nesting and foraging habitat.
– Sustainable fishing practices – reduce mortality from entanglement.
– Remove anthropogenic food sources – reduce dependence on landfills.
– Avian disease monitoring and response.
Targeted conservation of important breeding sites ensures that many young California gulls safely fledge each year. Maintaining clean wetland ecosystems also provides them with adequate food resources through their first vulnerable year, improving survival rates.
Research Needs
Further research priorities for understanding first cycle California gulls include:
– Tracking fledgling movements and dispersal patterns.
– Comparing foraging efficiencies and diet composition of juveniles vs adults.
– Quantifying causes and rates of mortality among first cycle birds.
– Modeling effects of wetland loss and degradation at key breeding colonies.
– Assessing pollution exposure and impacts from compounds like lead and microplastics.
Filling these remaining knowledge gaps will support effective management efforts to ensure healthy populations of first cycle gulls throughout their range.
Conclusion
In summary, the first cycle of the California gull begins shortly after hatching in early summer. This juvenile plumage of mottled brown upperparts, black tail with white tip, and pink legs lasts through the first winter until late January or February when the gull is 6-8 months old.
First cycle gulls depend on parents for food and protection. They start to disperse more widely from breeding colonies by mid-winter. These naive juveniles must rapidly develop foraging skills to feed on a diverse diet of aquatic prey, insects, fish, and human food scraps.
Starvation and predation take a heavy toll, with 40-60% dying in their first year. Conservation measures centered around breeding colonies, wetland habitat, and reducing contaminants are important for maximizing survival through this initial vulnerable life stage. Ongoing research and monitoring continues to deepen understanding of first cycle California gulls.
