Xantus’s Murrelets (Synthliboramphus hypoleucus) are small seabirds found in the California Current System in the Pacific Ocean. The Xantus’s Murrelet is the most southerly living of all the auk species. For more information, see our guide on invertebrates.
This is just as the night falls over remote islands of California, Mexico, and the Caribbean. The Xantus’s Murrelet, a small, sleek seabird that is mostly unknown by casual observers, is one of the coast’s greatest secrets.
The black-and white birds, which are among the smallest in the auk family, are also the most unusual. The birds spend almost their entire life at sea and only come ashore in the darkness to breed. The chicks can leave the nest only a few days after hatching, racing out into the ocean. These murrelets are the only seabirds that raise their young entirely in the ocean.
The Xantus Murrelet, named after John Xantus de Vesey, a 19th-century Hungarian naturalist who collected the first specimens of the species off the coasts of Baja California, is a fascinating mixture of mystery, adaptability, and resilience. It is a small fish, less than 10 inches in length and weighing around 6 ounces. However, it can withstand harsh conditions offshore and travel vast distances on the ocean with agility.
Explore the fascinating world of this rarely-seen bird. From its taxonomy to its breeding strategies, and its ongoing conservation challenges.
A Taxonomic Tale: One Name, Two Birds
For many years, the Xantus’s Murrelet (Synthliboramphus Hypoleucus) was considered a single bird. Detailed research in the last few decades revealed that we were mistaken about what was once considered a single bird. It is actually a pair of subspecies and possibly a separate species. Each has its own breeding range, genetic markers, and plumage features.
1. Guadalupe Murrelet (Synthliboramphus hypoleucus hypoleucus)
- Rage: Breeds in Baja California. Specifically, on the San Benito Islands.
- Identification is characterized by its distinctive white eye crescents — prominent markings above and beneath the eye giving it a spectacled appearance.
2. Scripps’s Murrelet
- Range: Found on the Channel Islands of southern California, including Santa Barbara Island, as well as the offshore Islands of Baja California.
- Identification: Does not have the distinctive eye crescents of the Guadalupe species. Has a more distinct white facial patterning.
Despite their visual and genetic differences, they overlap in some areas on the San Benito Islands. This has resulted in hybridization. Some taxonomists treat them as different species because of their differences.
A Wide Range of Remote and Vast Locations
The Xantus’s Murrelet, the most southern breeding member of the auk family, nests on a few islands scattered along the Pacific Coast of California and Mexico.
After the breeding season ends, these birds strong data-end=”3698″ data-start=”3676″>dispersed northward/strong>, riding the cool waters of the ‘California Current. These birds migrate northward after the breeding season is over, following the cool waters in the California Current. The birds have been seen as far north as British Columbia, but are usually far offshore and hard to spot on land.
The range of these murrelets is closely tied to the productivity of the ocean. They depend on the upwellings, which bring nutrient-rich waters to the surface and fuel the plankton that supports the fish population on which they feed. They are therefore most common in areas with oceanic conditions that encourage a large number of small schooling fish.
They are Compact, Contrastive, and Quick
The Xantus’s Murrelet, though often overlooked by other seabirds with more vibrant colors, is a stunning bird to see up close. It’s the smallest of all auks, measuring just 24-25 cm (under ten inches). The plumage is a classic example of countershading–black above and white below–a useful adaptation for avoiding predators both above and below in the open ocean.
- Hea: Small, rounded head with a sharp, thin black bill suited to catching slippery fish.
- Eyes: Dark and intense. Sometimes framed by crescents, in the Guadalupe Race.
- Body: A sleek and torpedo-shaped body for underwater pursuit.
- Flight: Direct and rapid with fast wingbeats. They sit low in water and take off with a fluttering flutter.
They share parts of their range with the Craveri’s Murrelet. The Craveri’s Murrelet has slightly longer wings and different facial markings.
Small Birds, Big Appetite: Feeding at Sea
The Xantus’s Murrelet, also known as the Pelagic Forager, finds its food away from shore. They wing-propelled divers and use their short, powerful wings to hunt down prey below the waves.
Their diet is primarily composed of: According to Cornell Lab of Ornithology, this species is well documented.
- Rockfish and especially juvenile Sebastes fish
- Sometimes, squid and other small invertebrates.
It is known that they feed on tuna and other predatory fish, which herd small schools of fish to the surface. The murrelets use the chaos to their advantage, diving into the water and picking out isolated fish. According to Audubon Society, this species is well documented.
Feeding occurs most often in the mornings and evenings. Foraging trips can be long, taking them many miles away from their breeding islands.
The Ocean is their Nursery
The breeding method of the Xantus Murrelet is almost unique in the bird kingdom. They nest in caves or small crevices. They nest in scattered colonies, which are usually loose.
- Nesting season: typically from February to June
- Two eggs per clutch is the limit.
- Incubation: Lasts approximately 30 Days
- Parental Care: Both parents share incubation duties
What is remarkable about them is what happens once the chicks have hatched. The downy chicks, who are already able to swim and walk, leave the nest within 24 to 48 hours and proceed straight to the ocean. They follow the calls from their parents.
The nighttime dash to the water from the nest is dangerous, but vital for survival. Once the chicks are in the water, the parents will lead them away from the island into offshore areas where they begin a new life as a fully marine family.
All feeding occurs at sea, a highly unusual behavior among seabirds. The seabirds feed only at sea, a behavior that is highly unusual and makes it difficult to study their life after nesting.
The Challenges of Studying the Shadowy Seabird
Xantus’s Murrelets are one of the most poorly understood members of the auks family. They nest in remote and often inaccessible places. They spend the majority of their life at sea. We know most about them from the brief times when they return to land for breeding.
It is not known how mothling pattern affects migration and population health. A female bird collected in late June on Isla Guadalupe was found to be molting its flight feathers. This rendered her unflightable. This indicates a post-breeding period of molt, which may expose birds to greater predation and limit their ability to escape changing conditions.
Threats to Conservation
IUCN has classified Xantus’s Murrelets as Vulnerable. This is mainly due to their restricted breeding range and low reproduction rate.
The following are the major threats:
- Introduced predators such as cats and rats on nesting islands
- Oil Spills can be found in the range of their foraging, contaminating their feathers and their food
- Light pollution can cause birds to be disoriented when returning at night to their nests
- Climate Change could change ocean currents, reducing prey availability.
- Bycatch during commercial fishing
Conservation measures have been implemented. Several nesting islands have now been protected, and invasive species eradication programs have been successful in restoring important breeding sites. Removals of cats and rats from Anacapa Island and the Santa Barbara Islands have significantly improved breeding success in recent years.
The species is still vulnerable because of its specialized lifestyle, and it’s important to continue monitoring.
Conclusion
The Xantus’s Murrelet is not the most well-known seabird, but it certainly is one of the most fascinating. It is small in size, but adaptable and powerful. It has carved a niche for itself in the most unpredictable and dynamic environments of the Pacific. Its nocturnal habits of nesting and its oceanic parenting style are a challenge to many of our preconceived notions about seabirds.
The story of the Xantus’s Murrelet, in a time where so much nature is threatened or fading away, is one of resiliency and survival. The Xantus’s Murrelet reminds us of the diversity in the world, which includes not only the bright, bold, and loud, but also those who are quiet and elusive, living between the sea and the sky and leaving a ripple.
