Cormorants are pretty common and easy to see. So it’s easy to get used to them and forget just how incredible they actually are. Here are some fascinating facts to celebrate these “sea crows”.
The name cormorant is thought to be a shortened version of corvus marinus – “marine raven” or “sea crow”. This is also reflected in their family name, Phalacrocoracidae, which means “bald raven”. They were likely called ravens in historic times because of the black colour. The bald part presumably comes from the bare skin at the base of the bill, or from the white plumes that the Eurasian Great Cormorant, Phalacrocorax carbo, develops in breeding plumage.
There are 40 cormorant species worldwide. The smallest is the Little Cormorant Microcarbo niger, which lives in India and SE Asia and may weigh as little as 360 g (as much as a big pigeon). The largest is the Flightless Cormorant Nannopterum harrisi. These strange cormorants have tiny wings and are restricted to two islands in the Galapagos. Because they are not limited by having to fly, they can weigh up to 4 kg!
But one species eclipsed even these giants: the Spectacled or Pallas’s CormorantUrile perspicillatus. These birds were thought to have weighed 3.5 – 6.8 kg and one bird was reported “big enough to feed three starving men”. The bird was first documented in 1741 but became extinct around 1850 due to hunting. It lived in the icy Bering Sea.
Cormorants are foot-propelled divers. This means that they use their feet and not their wings to swim underwater. As such, all four their toes are connected by webs. Clearly this works for them: they can reach speeds of up to 4 metres per second – faster than an Olympic swimmer!
In order to sink and swim more effectively, cormorants’ feathers are more wettable than other birds’ plumage. They further increase their weight by swallow stones – like a scuba diver would wear a weight belt.
Why do cormorants spend so much time sitting around with their wings held open? Well, the downside to having plumage that becomes drenched is that lowers your body temperature considerably. In cold seas cormorants can only hunt in bouts of a few minutes before they have to warm up again.
This also means that they have to stay near the shore where they can perch on rocks, shipwrecks or trees to dry out. But there are three species that can rest while floating on the water. This allows them to travel much further out to sea, usually in long lines (called skeins). These three specialists are the Guanay Cormorant, Leucocarbo bougainvillii, which lives in the cold waters off South America’ west coast; the Socotra Cormorant, Phalacrocorax nigrogularis of the Arabian Sea; and our very own Cape CormorantPhalacrocorax capensis.
What do cormorants get up to under the water? I’ve been privileged enough to snorkel alongside a Little Black Cormorant, Phalacrocorax sulcirostris, in Australia and watch it hunting. They sneak around, ambush fish around corners, stick their necks into hiding places and dart out to pursue fish at incredible speeds. They grab fish with their hooked bills – unlike darters, which spear fish with their sharp bills.
Small prey is swallowed directly underwater. But bigger prey is brought to the surface to be swallowed. This can be a lengthy process. The first step is to reposition the prey so that it is swallowed head first, to avoid fish bones sticking in the throat. The birds repeatedly toss the fish into the air and catch it until the angle is perfect. Some time after eating, cormorants regurgitate a pellet of crushed fish bones.
You can tell how deep a cormorant is diving down to by watching it carefully. If it is hunting in shallower water, it simply slips below the surface. But if it is planning a deep dive it makes a half-jump and enters the water at a near vertical angle. Cormorants fitted with miniature video cameras have been documented diving 80 metres down to the sea floor. Most dives are much shallower though; for example, Crowned Cormorants Microcarbo coronoatus, usually dives less than 5 m deep.
Cormorants have a unique little bone at the back of their skulls called an occipital style. This provides a place for the massive jaw muscles to anchor, and helps the cormorant snap its bill closed at a terrific speed.
Cormorants incubate their eggs with their feet!
The diet of a cormorant is dominated by fish, but they will also eat molluscs, crustaceans and cephalopods like squid and octopus and even water snakes. The Bank Cormorant, Phalarcrocorax neglectus, specialised in catching Rock Lobsters along our West Coast.
People have developed a special relationship with cormorants in some parts of the world. In some Asian countries, particularly China and Japan, cormorants help fishermen with their catch. The birds are tied to long strings and swim around under flaming lamps which attract fish at night. A ring is placed around the bird’s neck, which only allows it to swallow small fish. Big fish are brought back to the fishermen. Archeological finds have shown that this practice used to occur in Egypt, Peru, Korea and India too.
The Pokémon Cramorant is based on these birds.
ABOVE: A small colony of Cape Cormorants nesting on a moored ship.
ABOVE: A White-breasted Cormorant. Check out its powerful, hooked bill that is used to grab fish at amazing speeds under the water.