The tubenoses, also known as the Procellariiformes, are an order of seabirds characterized by their tubular nostril openings. This order includes some of the most widespread and well-known seabird families, including albatrosses, petrels, shearwaters, storm petrels, and diving petrels.
Tubenoses play an important role in marine ecosystems worldwide. They are found across all the world’s oceans and seas, with the exception of the inland and coastal seas. There are over 100 species of tubenoses, ranging in size from the giant petrels that have a wingspan of over 2 meters, to the storm petrels that are only 15-20 cm long.
The tubular nostrils that give this order its name are a key adaptation for their way of life. The tubes on their beak help channel air to their olfactory nerves, giving them an excellent sense of smell. This allows them to detect very small concentrations of odor molecules either in the air or dissolved in water. This powerful sense of smell helps tubenoses find food across vast distances in the open ocean.
Unique Adaptations
In addition to their tubular nostrils, tubenoses have evolved a number of other adaptations that aid their marine lifestyles:
- Their bodies are streamlined for efficient flying and swimming. They have narrow, aerodynamic bodies and long, narrow wings.
- They are able to drink seawater and have special glands that filter and excrete the excess salt.
- They have waterproof feathers to keep their skin dry even after diving into water.
- They have webbed feet for paddling and steering underwater.
- Their legs are set far back on their bodies to provide better propulsion in water.
These adaptations allow tubenoses to travel huge distances over open oceans in search of patchily distributed food. Most species are aerial specialists, using their efficient flight to range widely. However, some groups like the diving petrels are wing-propelled pursuit-divers, using their wings to propel themselves underwater.
Feeding Habits
Most tubenoses are carnivorous or omnivorous. Their diets generally consist of fish, squid, crustaceans, and other marine invertebrates. Some larger species like giant petrels are opportunistic scavengers. Tubenoses use their keen sense of smell to locate prey patches in the open ocean.
Feeding strategies vary across the different families:
- Albatrosses, petrels, and shearwaters are aerial hunters. They seize prey while swimming at the ocean surface.
- Fulmars feed by dipping down to the water surface while in flight.
- Diving petrels and some storm petrels dive underwater to chase mobile prey.
- Prions have bills edged with lamellae that help filter small prey from seawater.
Many species also readily scavenge on dead animal matter, fishery discards, and garbage. Foraging trips can last for days or weeks, covering thousands of kilometers.
Breeding and Nesting
One of the most intriguing aspects of tubenoses is their breeding habits. They nest in colonies on remote islands, cliffs, or mounds. This helps provide protection from land predators.
They exhibit some unusual nesting strategies adapted to the marine environment:
- There is no nest construction. The single egg is incubated on bare ground, in a burrow, or under the parent’s body.
- Parents may leave the nest for days or weeks to find food, returning only briefly to relieve their mate.
- Chicks are semi-precocial. They have thick down and are able to wander from the nest site.
- Parents find their own chick among the colony by voice and scent recognition.
These adaptations allow tubenoses to reproduce despite their need to travel immense distances to find patchy food resources. However, their reliance on sparse, isolated nest sites makes them vulnerable to introduced predators and human disturbance.
Distribution and Migration
Tubenoses have a global distribution, occurring across all the world’s oceans. Different species occupy overlapping ranges throughout tropical, temperate, and polar marine environments. When not breeding, they wander the open seas and rarely approach land.
Many species embark on lengthy seasonal migrations that take them between breeding and feeding areas. Their migrations may span hemispheres, crossing the equator in order to follow food resources and take advantage of seasonal winds and currents. Some examples include:
- Sooty shearwaters breeding in New Zealand and migrating north to the Arctic waters
- Northern fulmars and shearwaters that migrate south from Arctic regions in the winter
- Wilson’s storm petrels that migrate from Antarctic to Arctic waters between breeding seasons
These marathon migrations demonstrate the incredible flying abilities of tubenoses. Many species travel more than 50,000 km annually during their migratory cycles.
Ecological Role
As highly mobile predators, tubenoses help regulate prey populations and transport nutrients between marine ecosystems. Breeding colonies enrich surrounding areas with guano. Tubenoses are also important indicator species due to their sensitivity to environmental changes. Some key ecological roles include:
- Predator-prey interactions: Tubenoses exert top-down pressure on marine food webs as predators of fish, squid, zooplankton, and other species.
- Nutrient transport: Their migrations redistribute nutrients (e.g. nitrogen, iron) across latitudes from productive to nutrient-poor regions.
- Guano fertilization: Deposits of guano (feces) at colonies can fertilize terrestrial and aquatic habitats.
- Ecosystem indicators: Population changes reflect the health of their prey populations and marine habitats.
However, some tubenoses populations have crashed due to human activities. Many species are threatened by fisheries bycatch, introduced predators, habitat destruction, and pollution.
Evolutionary History
The Procellariiformes evolved early within a group of ancestral seabirds that also gave rise to penguins, loons, and grebes. The earliest tubenose fossils date to the Oligocene epoch around 35 million years ago.
Several evolutionary processes led to their distinct adaptations:
- The shift to pelagic habitats selected for aerial agility, waterproofing, and a keen sense of smell to find patchy food.
- Long-distance migrations evolved to link productive high-latitude feeding areas with tropical nesting grounds.
- Reduced parental care was necessitated by travelling immense distances to find food.
- Predator-free islands provided safe nesting habitat that further enabled their wide-ranging lifestyle.
This combination of traits allowed tubenoses to colonize the world’s oceans more comprehensively than any other group of birds. They now comprise over 75 extant species occupying every marine habitat.
Taxonomy and Classification
The taxonomy of tubenoses has been revised extensively based on anatomy, DNA analysis, and foraging ecology. They are currently grouped into four families:
- Albatrosses (Diomedeidae) – 14 species
- Petrels and Shearwaters (Procellariidae) – 75 species
- Storm Petrels (Hydrobatidae) – 21 species
- Diving Petrels (Pelecanoididae) – 4 species
There are approximately 114 species divided among 33 genera. The albatrosses are sometimes split into their own order (Diomediformes) due to distinct traits. However, DNA evidence confirms their close relationship with other tubenoses.
Classification within the families is based on size, bill shape, foraging methods, and other anatomical traits adapted to ecological niches. For example, the storm petrels are divided into several genera based on foot and leg morphology related to feeding style (pattering on water vs. diving).
Behavioral Ecology
The behavioral ecology of tubenoses provides insights into their adaptations for locating food and navigating over huge ocean distances:
- Foraging strategies – They use area-restricted search patterns to find and concentrate effort within prey patches. Some species also follow dimethyl sulfide scent cues to find feeding flocks.
- Navigation – They orient using the sun, stars, geomagnetic fields, and possibly scent maps to navigate across thousands of kilometers.
- Information sharing – Recruitment to food resources is aided by social interactions at breeding colonies and aggregations at sea.
Additionally, tubenoses exhibit complex breeding systems and social behaviors. Many species have dual foraging strategies with sexual segregation based on divergent diets or provisioning roles between sexes. Mate fidelity, site fidelity, and coloniality provide benefits but also influence population genetics and disease transmission.
Threats and Conservation
Many tubenose populations are in decline worldwide due to human activities. The primary threats they face include:
- Fisheries bycatch – Tubenoses get caught on longlines, gillnets, and in trawls. Hundreds of thousands drown annually.
- Invasive predators – Rats, cats, and other predators introduced to breeding islands prey on eggs and chicks.
- Habitat degradation – Breeding colonies are impacted by development, pollution, and climate change.
- Plastic pollution – Plastics are ingested or entangle birds, resulting in starvation or drowning.
Around 28 species are classified as threatened on the IUCN Red List. Conservation efforts focus on reducing bycatch, eradicating invasive predators, protecting colonies, and preserving habitat. Public education and international agreements on longline fishing also help protect populations.
Conclusion
In summary, the tubenoses are a highly successful order of seabirds adapted to life across the world’s oceans. Their tubular nostrils provide an excellent sense of smell to locate prey. Additional adaptations allow them to travel vast distances in search of patchily distributed foods. While formidable flyers, many species also swim proficiently and dive underwater. Tubenoses play vital roles as predators, scavengers, and nutrient transporters in marine food webs. However, many populations now face substantial threats from human activities. Ongoing conservation efforts aim to protect these unique and ecologically important seabirds.