Swallow-tailed Gull

The Swallow-tailed Gull is easily identifiable due to its forked tail and striking plumage. Adults showcase a blend of white and gray, with the latter covering their back and wings. The head is distinctly black, adorned with a red eye ring that intensifies during the breeding season. Juveniles differ with mottled gray and brown plumage, lacking the adults' prominent eye ring. While both genders appear similar, males tend to be slightly larger and may exhibit a more vibrant red around the eyes during courtship. In flight, the Swallow-tailed Gull's forked tail and long, slender wings create a distinctive silhouette that sets it apart from other gulls. When perched, this gull stands with an elegant posture, often with its tail slightly fanned. The Swallow-tailed Gull is unlikely to be confused with other species due to its unique features, but birders should note its similarities to the Laughing Gull during non-breeding seasons, particularly when the latter exhibits a dark head.

The Swallow-tailed Gull primarily feeds on squid and small fish, such as sardines, which rise to the ocean surface during nighttime. This gull's nocturnal foraging is facilitated by excellent night vision, allowing it to exploit food resources unavailable to diurnal predators. Seasonal diet changes are minimal, though the availability of prey may influence their foraging locations. Swallow-tailed Gulls employ a technique of hovering above the water before plunging to capture prey. They typically feed alone or in small groups, taking advantage of the cover of darkness to avoid competition. The size of prey can vary, but they generally target individuals small enough to be swallowed whole.

Swallow-tailed Gulls are social birds, often nesting in colonies that provide safety in numbers. During the breeding season, they display territorial behavior, with males defending their nesting sites against intruders. Courtship involves elaborate displays, including head bobbing and mutual preening, which strengthen pair bonds. Flocking behavior is common outside the breeding season, with groups gathering at preferred roosting sites. These gulls have adapted to a nocturnal lifestyle, with peak activity occurring after sunset. In response to predators, they employ alarm calls and group defense strategies to protect their nests. Daily routines revolve around feeding, resting, and caring for young during the breeding season.

Swallow-tailed Gulls build their nests on rocky ledges or cliff faces, using materials such as small stones, coral, and seaweed. These nest sites provide protection from ground predators and harsh weather. The clutch typically consists of one egg, occasionally two, though the second egg is often non-viable. Incubation lasts about 35 days, with both parents sharing responsibilities. Upon hatching, chicks remain in the nest for approximately 60 days before fledging. Parental care extends beyond fledging, as adults continue to feed and protect their young. Swallow-tailed Gulls generally produce one brood per year, aligning their reproductive cycle with periods of food abundance.

The Swallow-tailed Gull produces a range of vocalizations, with a primary song consisting of rhythmic, low-pitched calls that resemble a soft, rolling chuckle. These calls serve as contact notes between mates or within the colony. Alarm calls are sharper and more repetitive, often used to alert others of potential threats. During the dawn chorus, a blend of calls fills the air, establishing territory and reinforcing social bonds. The gull's vocal repertoire, although less varied than some songbirds, plays a crucial role in communication and coordination within the colony.

• 1The Swallow-tailed Gull is the only fully nocturnal gull species in the world, feeding primarily at night.
• 2The gull's bright red eye ring is an adaptation that enhances its visibility to mates during courtship rituals.
• 3Swallow-tailed Gulls have specialized night vision, allowing them to hunt squid and fish in near darkness.
• 4Their nests are often found on steep cliffs, providing both protection from predators and a vantage point for hunting.
• 5The Swallow-tailed Gull's distribution is mainly limited to the Galápagos Islands, a testament to its specialized niche.
• 6These gulls can travel considerable distances at sea, sometimes venturing over 100 kilometers from their nesting sites.
• 7Unlike most gull species, Swallow-tailed Gulls are not scavengers and rely entirely on live prey for sustenance.

The Swallow-tailed Gull is classified as Least Concern by the IUCN, with a stable population trend. Despite its restricted range, the species benefits from the protected status of the Galápagos Islands. Primary threats include climate change, which could affect ocean currents and prey availability. Conservation efforts focus on habitat preservation and monitoring population health. Historically, the population has remained relatively stable, thanks in part to the limited human impact on its breeding grounds. Continued protection of its marine environment is essential for the long-term survival of this unique gull.