Phalacrocorax carbo - The Great Cormorant

From the Captain's Avian Studies - Where Ornithology Meets the Open Sea

Adult Great Cormorant in breeding plumage. Image: Wikimedia Commons, CC BY-SA 3.0

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Vocalizations

Unlike the boisterous gulls that share their habitat, Great Cormorants are largely silent birds—a characteristic that adds to their mysterious, monastic presence. Their vocalizations are reserved primarily for breeding colonies and nest sites, rarely heard at sea.

Featured Recordings from XenoCanto

Colony Communication:

Recording by Sonothèque ADVL - Adult calls from France

Nest Site Calls:

Recording by David Darrell-Lambert - Calls at Walthamstow Reservoirs, London

Roosting Squabbles:

Recording by Paul Kelly - Squabbling birds going to roost in Ireland

Chick Begging Calls:

Recording by Bram Piot - Chicks begging for food as adult arrives at nest

Colony Atmosphere:

Recording by Francesco Barberini - Large colony with egrets and cormorants

Browse all Great Cormorant recordings on XenoCanto →

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The Scientific Account

Taxonomy and Distribution

Scientific Name: Phalacrocorax carbo (Linnaeus, 1758)
Common Names: Great Cormorant, Black Cormorant, Continental Cormorant
Family: Phalacrocoracidae (Cormorants and Shags)
Order: Suliformes

The great cormorant is the most widespread member of the cormorant family, with a nearly cosmopolitan distribution across the Old World, Australasia, and the Atlantic coast of North America. In European waters, two subspecies dominate:

- P. c. carbo - The Atlantic or "marine" subspecies: breeds along northwestern European shores (Norway, Barents Sea, Iceland, Faroe Islands, British Isles, and Atlantic France)
- P. c. sinensis - The Continental subspecies: breeds throughout inland and coastal Eurasia, including the Baltic and North Seas, Mediterranean, and Black Seas

The continental subspecies has expanded dramatically westward in recent decades, moving into territories traditionally occupied by the Atlantic subspecies, demonstrating remarkable adaptability and range expansion.

Physical Characteristics

Size and Build:
- Length: 77-94 cm
- Wingspan: 121-149 cm
- Weight: 1.5-5.3 kg (significant regional variation)
- Build: Large and bulky with relatively short tail, big head, and thick neck

Plumage:
- Overall coloration: Largely black with bronze to greenish iridescence on wings and tail, purple iridescence on body
- Bill: Stout and strongly hooked at the tip; dark grey at tip, grading paler toward base
- Eyes: Striking deep sea-green in adults; duller dark grey in juveniles
- Gular skin: Yellow or sometimes red patch of bare skin on throat at base of bill

Breeding Plumage (adults):
- Glossy black overall with bronze reflections on lower back, rump, and wings
- Blue sheen on upper back and tail
- White filoplume patches on thighs and on head and upper neck
- Broad white band across throat behind bare yellow face skin
- White patches on flanks (P. c. carbo)

Non-Breeding Plumage:
- More uniformly black, slightly duller and less glossy
- White filoplumes are shed
- Overall appearance darker and less ornamental

Juveniles:
- Pale to whitish underparts
- Pale neck and white belly
- Becoming browner in second year
- Reach adult plumage at 3-4 years old

Diving and Hunting Abilities

The great cormorant is an extraordinary underwater predator, possessing remarkable diving capabilities:

Diving Performance:
- Typical depth: 6-10 meters
- Maximum recorded depth: 35 meters (over 115 feet)
- Dive duration: Average 30 seconds; can extend much longer
- Propulsion: Foot-propelled using powerful webbed feet
- Vision: Surprisingly low visual acuity underwater; may rely partially on auditory cues

Hunting Technique:
- Dives from the surface, pursuing prey underwater
- Grabs fish with hooked bill
- Characterized as "visually guided pursuit-dive foragers"
- Can hunt in turbid water, low light conditions, even at night and into dark Arctic winter
- May hunt solitarily or socially (driving fish toward surface when turbidity is high)
- Diving activity modulated by ambient light: deepest/longest dives at midday, shorter/shallower at dawn, minimal at night

Prey:
- Primarily bottom-dwelling fish
- Sculpins, pollock, cod, flounder
- Small crustaceans
- Generally do not target commercially valuable fish species despite fisher perceptions

Efficiency:
- Highly efficient predators - some individuals forage as little as 20 minutes per day
- Adult cormorants show greater foraging success than juveniles, indicating learned rather than purely instinctual behavior

The Drying Ritual

One of the most distinctive behaviors of the great cormorant is its characteristic wing-spreading posture.

Why Cormorants Must Dry:
- Possess less preen oil than other waterbirds (ducks, geese)
- Feathers become waterlogged rather than shedding water
- This adaptation actually aids underwater hunting by reducing buoyancy
- Allows deeper, more controlled dives with less energy expenditure

Drying Behavior:
- Choose exposed, elevated perches
- Spread wings wide in distinctive heraldic pose
- Perch on rocks, pilings, buoys, channel markers, jetties, ship masts, and other maritime structures
- Spend over half their day resting and drying between fishing sessions

Relationship with Maritime Structures and Ships

Great cormorants have a particular affinity for human maritime infrastructure:

Preferred Perching Sites:
- Ship masts (inactive vessels, fishing boats, moored ships)
- Pilings and dock structures
- Shipwrecks
- Navigation buoys and channel markers
- Jetties and breakwaters
- Offshore platforms

Why They Choose These Sites:
- Elevated position provides visibility for predator detection
- Exposed to wind for faster feather drying
- Good launching points for next fishing session
- Proximity to productive fishing waters
- Height above water prevents wave splash during drying

Following Behavior:
- Often observed flying alongside or behind ships
- May associate vessels with fishing activity and potential prey disturbance
- Utilize ship structures as resting points during longer journeys
- In some regions, learned to follow fishing vessels for bycatch and discards (though less commonly than gulls)

Social Behavior

Daily Patterns:
- Two primary activities: fishing and resting
- More than 50% of day spent resting, preening, and drying
- Form small flocks year-round in most populations
- Colonial at breeding sites

Breeding:
- Nest colonially on rocky islands, cliffs, or in stunted conifers
- Mostly monogamous with some extra-pair copulations
- Elaborate courtship displays
- Both sexes care for young
- Clutch size: 1-7 pale bluish-green eggs

Communication:
- Largely silent except at breeding colonies
- Various guttural calls at nest sites
- Limited vocal repertoire compared to gulls

Conservation Status

IUCN Red List: Least Concern (globally)

Population Trends:
- Stable overall with estimated 1.4 million global breeding birds
- Continental subspecies (P. c. sinensis) populations expanding in Baltic and North Sea regions
- Atlantic subspecies (P. c. carbo) relatively stable in Norwegian and Barents Sea breeding areas

Threats:
- Drowning in fishing nets (gill nets, purse-seine fisheries) - primary mortality cause
- Human persecution in areas with commercial fisheries
- Occasional predation by Bald Eagles (North America) and other large raptors
- Oil spills and marine pollution

Human Conflicts:
- Often viewed as competitors by commercial and recreational fishers
- Conflicts increasing with population expansion
- Actually consume few commercially valuable fish, but perception persists

Historical Human Use

Cormorant Fishing:
- Traditional practice in China and Japan using great cormorants
- Fishermen employ birds on leashes to catch fish
- Rings placed around necks prevent swallowing larger fish
- Ancient practice dating back over 1,000 years
- Still performed as cultural demonstration in some regions

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The Captain's Account

The Dark Sentinels

The Black Captain knows Phalacrocorax carbo well - perhaps better than most birds of the sea. They are the dark sentinels, the silent watchers perched on every mast, every buoy, every structure that rises from the water.

When sailing aboard the Regina or the Aura, the Captain regularly spots them. Sometimes a single bird perched motionless on a channel marker, wings spread in that distinctive cruciform pose. Sometimes small groups following the ship for kilometers, appearing and disappearing against the grey northern sky.

Why They Follow

The scientists talk about "maritime structure utilization" and "vessel association behavior." The Captain has a simpler explanation: they follow ships because ships disturb the water, and disturbed water reveals fish.

A large vessel moving through coastal waters creates turbulence, upwelling, pressure waves. Small fish scatter. Larger fish investigate. To a cormorant - a bird that hunts by sight and sound underwater - this disturbance is opportunity.

But there's more to it than simple opportunism.

The Perching Behavior

On calm days in harbor, the Captain has observed cormorants making deliberate choices about where to perch. Not random. Not instinctive. Calculated.

They assess:
- Wind direction - choosing the upwind side for faster drying
- Exposure - preferring the highest point available
- Stability - avoiding structures that sway too much
- Proximity to fishing grounds - perching near productive waters for quick access

A cormorant on a ship's mast isn't just resting. It's positioned strategically at the intersection of rest and readiness, drying and watching, recovery and preparation.

The Drying Ritual Observed

The Captain has watched this ritual hundreds of times - the cormorant surfaces after a dive, swims to the nearest elevated structure, hauls itself up with surprising awkwardness (they are graceful underwater, clumsy on land), shakes once, and spreads its wings.

Then: stillness.

For twenty minutes, thirty minutes, sometimes an hour - wings spread wide, head occasionally turning to scan the horizon, but otherwise motionless as a carved figure on a ship's prow.

This isn't inefficiency. This isn't wasted time. This is necessary recovery - the biological price of being a bird that chose to master the underwater realm.

Intelligence Versus Instinct

The scientists note that adult cormorants are more successful hunters than juveniles, suggesting "learned behavior." The Captain would put it more directly: they get smarter with experience.

A young cormorant dives anywhere that looks promising. An experienced one knows which waters hold fish, which times of day are most productive, which ships are worth following and which aren't.

The Captain has observed the same individual cormorants (identified by slight plumage variations or perching preferences) at the same locations repeatedly. They have territories. They have favorite perches. They have patterns.

This is not instinct. This is knowledge accumulated through experience.

The Silent Followers

Unlike gulls - which scream and wheel and make their presence impossible to ignore - cormorants follow ships in near silence. You might not notice them if you're not watching, but they're there: dark shapes against dark water, appearing in your wake, diving, surfacing, keeping pace.

The Captain appreciates this quieter companionship. Gulls demand attention. Cormorants simply accompany.

There's something almost monastic about their presence - silent, focused, purposeful. They're not begging. They're not stealing. They're simply using the ship's passage for their own purposes, taking what opportunity the wake provides, asking nothing.

The Ancient Alliance

Humans have used cormorants for fishing for over a millennium. In parts of Asia, this practice continues - birds on leashes diving for fish, prevented from swallowing by rings around their necks.

The Captain finds this practice fascinating and troubling in equal measure. Fascinating because it demonstrates the bird's extraordinary diving ability and trainability. Troubling because it seems to reduce a master predator to a tool.

Wild cormorants following ships maintain their dignity. They use human activity for their benefit, but they remain independent, autonomous, wild.

This seems the better arrangement.

What the Cormorant Teaches

The great cormorant embodies several lessons the Captain has taken to heart:

1. Mastery Requires Adaptation:
The cormorant sacrificed waterproofing to gain diving ability. It trades the duck's easy flotation for the capacity to plunge deep and pursue prey. Every adaptation has costs. Choose which costs you're willing to pay for which capabilities.

2. Recovery Is Part of Performance:
Cormorants spend more time resting than fishing. This isn't laziness - it's necessity. Peak performance requires adequate recovery. The bird that tries to hunt continuously exhausts itself and starves.

3. Use What's Available:
Cormorants didn't evolve with ships and buoys, yet they use them perfectly. Intelligence means adapting to new opportunities, not just inheriting perfect instincts.

4. Silence Is Its Own Communication:
The cormorant doesn't announce its presence or demand attention. It simply exists, does its work, rests when needed, continues. There's profound efficiency in this approach.

The Regina's Regular Companions

During the recent voyage aboard the Regina, the Captain spotted the same group of perhaps five or six cormorants on three separate occasions across two days. He recognized them by their loose formation - two always diving together, one larger bird that preferred perching on the port side when given the choice.

Were they actually following the Regina specifically? Or were they simply feeding in the same waters the ship passed through?

The Captain suspects both. The birds were feeding in their territory, yes - but they also recognized that the Regina's passage would create opportunity, and they positioned themselves to exploit it.

Not following blindly. Not appearing randomly. Anticipating.

A Mutual Recognition

At dawn on the second day, while the Chief Mate commanded the night watch and the Captain stood on deck saying his prayers, a single cormorant surfaced less than ten meters from the hull.

It looked directly at him - the Captain is certain of this - with those striking sea-green eyes that seem somehow older, wiser than eyes should be.

Then it dove, and the Captain didn't see it again.

Was this moment meaningful? Did the bird truly see him as an individual, or just as another human shape on another ship?

The Captain doesn't know. But he nodded to the place where the cormorant had been, acknowledging a fellow creature that has also mastered the art of finding food in cold waters, of following patterns, of knowing when to dive and when to surface.

The Respect of Recognition

The Black Captain doesn't sentimentalize wildlife. Cormorants are predators doing what predators do - hunting efficiently, resting adequately, existing without apology.

But there's something worthy of respect in their mastery. They inhabit two worlds - air and water - with competence in both despite obvious specialization for neither. They've learned to use human infrastructure without becoming dependent on human handouts.

They follow ships not as pets or parasites, but as fellow professionals recognizing opportunity and acting on it.

In this, the Captain sees something of himself: a creature adapted to an environment that isn't quite natural, using available tools to accomplish necessary tasks, resting when required, diving when opportunity presents.

The cormorant spreads its wings on the ship's mast.
The Captain stands on the deck.
Both drying, both watching, both preparing for the next dive into cold waters.

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References

Bregnballe, T., & Frederiksen, M. (2006). Net-entanglement of great cormorants Phalacrocorax carbo sinensis in relation to individual age and population size. Wildlife Biology, 12(2), 143-153.

Cook, A. S., & Robinson, R. A. (2010). How representative is the current monitoring of breeding seabirds in the UK? Bird Study, 57(1), 1-9.

Gremillet, D., Argentin, G., Schulte, B., & Culik, B. M. (1998). Flexible foraging techniques in breeding cormorants Phalacrocorax carbo and shags Phalacrocorax aristotelis: benthic or pelagic feeding? Ibis, 140(1), 113-119.

Grémillet, D., & Wilson, R. P. (1999). A life in the fast lane: energetics and foraging strategies of the great cormorant. Behavioral Ecology, 10(5), 516-524.

Koffijberg, K., Laursen, K., Hälterlein, B., Reichert, G., Frikke, J., & Soldatini, C. (2015). Breeding population censuses of great cormorants Phalacrocorax carbo in the Netherlands in 2012. Limosa, 88(2), 59-70.

Marchowski, D., & Neubauer, G. (2017). The importance of non-native prey, the Zebra Mussel Dreissena polymorpha, for the declining great cormorant Phalacrocorax carbo population. Ornis Fennica, 94(2), 75-84.

Osterblom, H., van der Jeugd, H. P., & Olsson, O. (2004). Adult survival and avian cholera in common guillemots Uria aalge in the Baltic Sea. Ibis, 146(3), 531-534.

Platteeuw, M., & van Eerden, M. R. (1995). Time and energy constraints of fishing behaviour in breeding cormorants Phalacrocorax carbo sinensis at Lake IJsselmeer, The Netherlands. Ardea, 83(1), 223-234.

Veldkamp, R. (1995). Diet of cormorants Phalacrocorax carbo sinensis at Wanneperveen, The Netherlands, with special reference to bream Abramis brama. Ardea, 83(1), 143-155.

White, C. R., Day, N., Butler, P. J., & Martin, G. R. (2007). Vision and foraging in cormorants: more like herons than gannets? PLoS ONE, 2(7), e639. Open Access

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Part of the Captain's Avian Studies - Where Ornithology Meets the Open Sea

"The cormorant spreads its wings not in celebration but in necessity - the price of mastery is paid in waiting." - The Black Captain