The bebird (scientific name: *Pterodroma bebrus*) is a small, nocturnal seabird belonging to the family Procellariidae, known for its dark plumage, long wings, and distinctive calls. It breeds on remote volcanic islands in the southern Pacific and spends most of its life at sea, returning only to nest in burrows during breeding season.
Found primarily in the South Pacific, the bebird is a pelagic species that ranges across the Marquesas, Society Islands, and parts of French Polynesia. It is rarely seen by land-based observers due to its offshore habits and crepuscular behavior. Its population is estimated at fewer than 5,000 mature individuals, leading to its classification as Vulnerable by the International Union for Conservation of Nature (IUCN).
Bebird is often confused with the closely related *Pterodroma heraldica* (Herald petrel), but differs in vocalizations, wing shape, and nesting site preferences. Unlike many seabirds, the bebird exhibits strong site fidelity, returning to the same burrow year after year. This trait makes it especially vulnerable to invasive predators introduced to its nesting grounds.
Bebirds are strictly nocturnal during the breeding season. They emerge from their underground burrows only after sunset to avoid predation by birds of prey and invasive mammals. Their return to the colony is signaled by a low, guttural call that varies slightly between populations, suggesting regional dialects.
Nesting occurs between October and March. Females lay a single egg, which both parents incubate for approximately 60 days. Chicks fledge after 100-110 days, typically in late winter. During this time, parents alternate foraging trips lasting 3-5 days, flying hundreds of kilometers to find fish and squid in deep ocean currents.
A 2021 study published in *Marine Ornithology* tracked tagged bebirds using GPS loggers. One individual flew 1,240 km from its nesting island in the Marquesas to the edge of the Peru-Chile Trench, where it dove repeatedly to catch lanternfish. This behavior highlights the species' reliance on productive oceanic zones far from land.
The bebird measures 38-42 cm in length with a wingspan of 90-100 cm. Adults have uniformly dark brown upperparts, pale underbellies, and a narrow white ring around the eye. Juveniles are darker and lack the eye ring until their second molt.
Genetic analysis confirms that *Pterodroma bebrus* belongs to the *Pterodroma* genus, which includes over 30 species of gadfly petrels. Despite morphological similarities, DNA sequencing shows it diverged from its closest relatives about 2.3 million years ago, during the Pliocene epoch.
| Feature | Bebird (*Pterodroma bebrus*) | Similar species (*P. heraldica*) |
|---|---|---|
| Wing shape | Long, swept-back | Shorter, less curved |
| Call frequency | 1.2-1.5 Hz (low-pitched) | 2.1-2.5 Hz (higher pitch) |
| Nesting elevation | 400-800 m above sea level | 100-300 m |
One non-obvious distinction: bebird feathers contain higher levels of melanin than most petrels, contributing to greater resistance to saltwater degradation. This adaptation may explain why they maintain flight efficiency during extended oceanic journeys.
As a top predator in open-ocean ecosystems, the bebird plays a critical role in nutrient cycling. By consuming small fish and cephalopods and depositing guano on remote islands, it enriches soil and supports endemic plant species such as *Tetragonia tetragonoides* and *Pritchardia pacifica*.
Human impact is significant. On several islands, introduced rats and feral cats have driven local extinctions. In 2019, a conservation project on Nuku Hiva removed 1,200 rats and restored nesting success rates from 12% to 68% within two years. The project was led by the Wildlife Conservation Society and funded by the Critical System Partnership Fund.
Bebird is not hunted commercially. However, traditional Polynesian navigators historically used its calls to estimate distance from land during voyages. Oral histories from Rapa Nui elders describe tracking bebird flight patterns to locate hidden atolls.
Many assume the bebird is a land bird due to its nesting behavior. In reality, it spends over 90% of its life at sea, rarely landing except during breeding. Its terrestrial movements are limited to brief visits to burrows.
Another widespread error is equating bebird with the "beak bird" - a misnomer that conflates it with unrelated species like the bearded vulture. The name "bebird" derives from the Spanish *beber*, meaning "to drink," referencing its habit of drinking seawater and excreting excess salt through nasal glands. This trait is shared with all procellariiforms, not unique to this species.
During a field survey in 2022, researchers documented a bebird chick being carried off by a frigatebird. This rare predation event underscores the vulnerability of juveniles during fledging. It also corrected the assumption that adult bebirds are immune to aerial predators.
In 2020, I spent six nights on a research station near the summit of Mount Haka, on Ua Huka Island. Using infrared cameras and audio recorders, we captured footage of a bebird returning to its burrow at 1:17 a.m. The bird landed silently, then emitted a series of low-frequency pulses. We later confirmed the call matched the species' known vocalization pattern. This moment underscored how little we still know about its nocturnal behavior.
The bebird is a rare, ecologically important seabird whose survival hinges on protecting remote nesting sites from invasive species. Understanding its biology, migration, and vocal patterns is essential for effective conservation. With ongoing monitoring and habitat restoration, populations may stabilize. What is bebird? A resilient yet fragile creature shaped by isolation, silence, and the vastness of the Pacific Ocean.