Diving sea birds are seabirds that are specialized for plunge diving or diving underwater to catch prey. Some common examples of diving sea birds include penguins, puffins, gannets, cormorants, murres, auklets, and shearwaters. Diving seabirds have a number of adaptations for diving into the water and swimming underwater that distinguish them from other types of seabirds.
What are the key adaptations of diving seabirds?
Diving seabirds have evolved a number of morphological and physiological adaptations that enable them to effectively pursue prey underwater. Some key adaptations include:
- Streamlined body shape to reduce drag and allow efficient movement underwater
- Wings modified for propulsion underwater – wings are shorter, stouter, and have more area devoted to propulsion
- Webbed feet for swimming and steering underwater
- Legs set far back on the body to make them more efficient for swimming
- Dense plumage that is waterproofed by oils from the preen gland
- Ability to reduce buoyancy by compressing plumage and air spaces
- High myoglobin levels in muscles to store oxygen for long dives
- Slow heart rate and peripheral blood vessel constriction to conserve oxygen usage
- Salt excreting glands to remove excess salt from sea water they drink
- Nictitating membrane that covers the eye underwater
The combination of these adaptations allows diving seabirds to plunge into water, swim and steer efficiently underwater, withstand water pressure, see clearly underwater, stay warm, and hold their breath for an extended time while pursuing prey at depth.
What types of prey do diving seabirds eat?
Diving seabirds prey predominantly on fish, crustaceans, and cephalopods that they catch underwater. Some examples of prey consumed include:
- Small schooling fish like sardines, anchovies, and herring
- Squid
- Krill
- Shrimp
- Crabs
- Mussels
Diving seabirds may target prey at varying depths depending on the species. Penguins and auks can dive to depths of several hundred feet, whereas gannets and boobies may plunge dive to depths of only around 30 feet or less.
How do diving seabirds catch prey underwater?
Diving seabirds use a few different techniques to catch prey underwater:
- Pursuit diving – The bird swims underwater using its wings for propulsion, chasing down prey.
- Plunge diving – The bird plunges from the air into the water to ambush prey.
- Surface plunging/diving – The bird floats on the surface then submerges just its head/neck underwater to catch prey near the surface.
- Bottom diving – The bird dives all the way to the seafloor to look for benthic prey like crabs and mussels.
Penguins, cormorants, and auks primarily pursuit dive, using their wings to propel themselves after swift prey like fish and squid. Gannets, boobies and shearwaters plunge dive from a height to ambush prey from above.
How deep can diving seabirds dive?
Different species of diving seabirds can reach different maximum diving depths. Some examples include:
Species | Maximum Diving Depth |
---|---|
Emperor penguin | 1,850 feet |
Macaroni penguin | 400 feet |
Thick-billed murre | 660 feet |
Common murre | 300 feet |
Northern gannet | 100 feet |
Brown pelican | 20 feet |
In general, penguins tend to be the deepest divers, followed by auks like murres. Gannets and cormorants make moderately deep dives while boobies and pelicans stay relatively shallow. The deepest recorded dive for a bird was an emperor penguin diving to 1,850 feet!
How long can diving seabirds stay underwater?
Diving seabird species also vary in their maximum underwater dive durations. Some examples include:
Species | Maximum Dive Duration |
---|---|
Emperor penguin | 25 minutes |
Macaroni penguin | 8 minutes |
Thick-billed murre | 4.5 minutes |
Common murre | 3 minutes |
Northern gannet | 1 minute |
Brown pelican | 30 seconds |
Again, penguins can stay underwater the longest, often diving for 15-25 minutes at a time. Auks stay under for several minutes while pursuing fish. Gannets and cormorants have dive times of about 1 minute. Boobies and pelicans only make very brief dives of seconds to a minute.
How fast can diving seabirds swim underwater?
The swimming speeds of diving seabirds vary by species and depend on the type of propulsion they use. Some examples of underwater swimming speeds include:
- Emperor penguin – up to 9 mph
- Macaroni penguin – up to 7 mph
- Puffin – up to 5 mph
- Cormorant – up to 3 mph
- Booby/Gannet – up to 6 mph
Penguins and auks are the fastest underwater swimmers thanks to their wing propulsion. Cormorants swim slower with their feet for propulsion. Gannets and boobies reach higher speeds when plunge diving due to their aerial momentum carrying them underwater.
Where are diving seabirds found?
Diving seabirds occur widely in oceans and coastal regions around the world. Their distribution includes:
- Penguins – Southern hemisphere, including Antarctica, Australia, New Zealand, and South America
- Auks – Northern hemisphere, including arctic, north Pacific, and north Atlantic
- Cormorants – Widespread globally
- Gannets and Boobies – Tropical and temperate regions including South Pacific, South Africa, etc.
- Pelicans – Tropical and subtropical regions globally
In general, penguins and auks dominate the polar and subpolar regions. Cormorants, gannets, boobies and pelicans are more prevalent in tropical and temperate oceans globally.
Which diving seabird species dive the deepest?
The deepest diving seabird species include:
- Emperor penguin – can dive to 1,850 ft depth
- King penguin – can dive to 1,250 ft
- Macaroni penguin – can dive to 935 ft
- Thick-billed murre – can dive to 700 ft
- Chinstrap penguin – can dive to 660 ft
In general, larger penguin species dominate the deepest dives, with the emperor penguin holding the record amongst all birds with dives documented to nearly 1,900 feet deep. The largest auks like murres are also very deep divers, reaching 700 feet routinely.
Do male and female diving birds dive differently?
There can be some differences between male and female diving seabirds in their diving behavior:
- Males often make deeper, longer dives – In species like gannets and boobies, males dive deeper and stay underwater longer than females. This may reflect males being able to withstand the higher pressures and exertion better with their larger size.
- Females make more frequent, repetitive dives – Females seem to make more repetitive short dives, possibly so they can return faster to feed chicks at the nest. Males focus more on deep foraging dives.
- Diving patterns change with breeding stage – Both sexes adjust their diving activity based on whether they are incubating eggs or feeding chicks. They make shorter, shallower dives when breeding to return to the nest quicker.
So while both sexes are capable divers, they employ slightly different diving strategies that are influenced by factors like body size and reproductive duties.
How do diving seabirds reproduce?
Diving seabirds have adapted reproductive strategies for their marine environments. Key aspects include:
- Forming dense breeding colonies on coastal cliffs, offshore rocks, or islands
- Nesting in burrows, crevices, or rudimentary nests on the ground
- Laying 1-3 eggs depending on species
- Incubating eggs for 3-10 weeks before hatching
- Caring for semialtricial chicks that require extensive feeding for weeks to months
- Feeding chicks with energy rich regurgitated fish/crustacean meals
- Chicks fledging and heading to sea once they can fly and dive competently
The breeding habitats and long chick rearing of diving seabirds allows both parents to efficiently forage at sea and provision for the high energy demands of their chicks. The chicks grow rapidly to be ready to head to sea and start diving on their own.
How many different species of diving seabird are there?
There are around 62 recognized species of diving seabirds in four main families:
- Penguins – 18-20 species
- Auks – 22 species (murres, auklets, puffins, etc.)
- Cormorants and shags – ~40 species
- Gannets and boobies – 10 species
Additional diving seabird groups with only 1-2 species include the diving petrels, dippers, and skuas. Overall, diving seabirds represent a substantial and highly adapted subset of marine bird species.
Which species is the most abundant diving seabird?
Some of the most abundant diving seabird species worldwide include:
- Common murre – Estimated global population of 21-39 million
- Little auk – Estimated 18-40 million breeding pairs globally
- European shag – Estimated 1.5-2 million breeding pairs
- Rock shag – Estimated 2.5-5 million individuals
- Blue-footed booby – Hundreds of thousands of pairs globally
Overall, auks like murres and little auks are likely the most numerous diving seabirds. Among cormorants, shags like the European shag and rock shag have very large populations. For gannets and boobies, the blue-footed booby is one of the most common species.
Which diving seabird species are endangered or threatened?
Some diving seabird species that are endangered or threatened include:
- Penguins: Yellow-eyed penguin, Galapagos penguin, erect-crested penguin
- Cormorants: Spectacled cormorant, Red-faced cormorant
- Auks: Marbled murrelet, Craveri’s murrelet, Kittlitz’s murrelet
- Gannets/Boobies: Abbott’s booby, Chatham Island shag
Key threats to these species include: habitat loss, introduced predators, overfishing of prey sources, pollution and oil spills, disturbance of breeding colonies, and climate change impacts. Conservation efforts focus on protecting breeding habitats and marine food webs.
How are seabirds affected by pollution and marine plastics?
Seabirds, including diving seabirds, face a number of threats from pollution and plastic waste:
- Plastic entanglement – Birds get caught in floating plastic debris which can lead to drowning or severe injuries
- Plastic ingestion – Birds mistake plastic bits for food/prey and ingest them, damaging their digestive system
- Oil pollution – Oil spills coat birds’ plumage so they can’t fly/dive or regulate temperature
- Chemical pollution – Toxins get into the marine food web and are consumed by birds, causing illness or reproductive harm
It is estimated over 200 species of seabirds are impacted by marine plastics. Effects include reduced survival, body condition, and reproductive success. Cleaning up and preventing marine pollution is key to help protect seabird populations.
Conclusion
Diving seabirds represent a highly adapted and diverse group of marine birds occupying an important niche as underwater predators. While they face a number of conservation threats, their unique adaptations for plunge diving and swimming, from wing-propelled penguins to deep-diving auks, make them incredible examples of evolutionary specialization to marine habitats and resources.