Many species of birds spend most of their lives at sea, only coming to land periodically to breed and raise their young. Of these seabirds, the one that likely spends the least amount of time on land is the Audubon’s shearwater.
Key Facts About Audubon’s Shearwater
- Scientific name: Puffinus lherminieri
- Range: Tropical and subtropical oceans worldwide
- Size: 25-30 cm long with a 65-75 cm wingspan
- Diet: Squid, fish, crustaceans
- Lifespan: Up to 22 years in the wild
The Audubon’s shearwater is a medium-sized seabird in the Procellariidae family. It gets its name from the American naturalist and painter John James Audubon, who first described the species in the 1800s. This long-winged seabird spends most of its life traversing the open ocean, only returning to islands and coastal cliffs to breed.
Breeding and Nesting
Audubon’s shearwaters return to land for a few months each year to nest and raise their young. Their breeding colonies are located on islands and sea cliffs across the tropical Atlantic, Pacific, and Indian Oceans. When they arrive at their nesting sites in the spring, the male birds will stake out breeding territories in burrows or crevices. Once females arrive, they will choose a mate and form a monogamous pair bond.
The timing of breeding varies based on location, but egg laying usually occurs from May to July. The female lays a single white egg each season. Both parents take turns incubating the egg for around 50 days before it hatches. Once the chick hatches, the parents take turns feeding it regurgitated fish and squid. The chick remains in the burrow, where the parents continue to care for it until it fledges at around 3 months old.
Nest Attendance
Throughout the breeding season, Audubon’s shearwaters spend the minimum time possible on land. They only visit the colony at night to incubate eggs, brood chicks, and provision their young. Their nest attendance patterns can be summarized as follows:
- Incubating parents exchange incubation duties every 1-10 nights
- Parents visit nest around 60 times total during 65 day incubation period
- Each nest visit lasts less than 24 hours
- Parents continue short, nocturnal nest visits to feed chick until fledging
This means the adult shearwaters likely spend less than 100 total days on land each year. The rest of their lives are spent roaming the oceans and only coming to shore under the cover of darkness to breed.
At-Sea Lifestyle
When not breeding, Audubon’s shearwaters are highly pelagic – meaning they spend all their time far out at sea, only returning to coastal land areas to nest. They are powerful fliers that are well-adapted for an aquatic lifestyle:
- Their long, narrow wings allow them to fly efficiently for hundreds of miles without landing.
- They have webbed feet for paddling on the ocean surface.
- Their plumage has a water-resistant coating.
- They have salt glands to excrete excess salt from drinking seawater.
- They can dive underwater to catch prey.
While at sea, Audubon’s shearwaters travel widely to forage. They often associate with tuna, dolphins, and whale pods to feed on the fish and krill these mammals push to the surface. At night, they rest floating on the surface of the water.
Migration
Audubon’s shearwaters undergo long annual migrations between their breeding and nonbreeding areas. Northern hemisphere birds migrate down to the South Atlantic and South Pacific after breeding. Southern hemisphere breeders migrate northwards to spend the nonbreeding season foraging in the North Atlantic and North Pacific. These extended journeys allow the birds to take advantage of the most productive waters year-round.
Threats and Conservation
Like many seabird species, Audubon’s shearwaters face a number of threats on land and at sea. Their breeding colonies are vulnerable to introduced predators like rats and feral cats. At sea, they are at risk from commercial fishing, pollution, plastic ingestion, and climate change impacts. Conservation efforts are ongoing to protect remaining colonies and reduce mortality risks at sea.
Protective Measures
- Predator control and eradication on breeding islands
- Monitoring and protection of nesting habitats
- Fishing gear modifications to reduce bycatch
- Plastic and marine pollution mitigation
- Climate change adaptation strategies for nesting sites
With proactive conservation, Audubon’s shearwaters can continue their unique lifestyle of only utilizing land for the essential purpose of raising their chicks each year.
Conclusion
In summary, Audubon’s shearwater is a highly pelagic seabird that only comes to land for a brief nesting period each year. Its specialized adaptations allow it to spend the rest of its life roaming the open ocean in search of food. Careful management of its breeding colonies and at-sea threats will help ensure this marine species continues its vital connectivity between land and sea into the future.
