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LatestPhoto
Spreading their wings out to dry ensures that the Pied Cormorant's feathers do not become waterlogged.
Photo: Chris Johnson

February 15, 2002
The Pied Cormorant
  Real Audio
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Log Transcript

This is Genevieve Johnson speaking to you from Western Australia. The Odyssey has anchored off the small coastal town of Geraldton overnight, seeking shelter from gale force winds and heavy seas. We are not alone out here, waking this morning to find the rocky harbor walls covered in Pied Cormorants.

This large black and white cormorant with a striking white face and brilliant yellow or orange facial skin, is Australia's most common cormorant. Some colonies number in the thousands and favor gathering on rocky outcrops or loafing on piers and buoys.

As we observe these birds, they appear to be incessantly preening themselves, then spreading their wings out to dry. Being an aquatic species, they are always tending to their plumage, constantly oiling their feathers with secretions or preen glands on their rumps. This ensures that their feathers do not dry out or become waterlogged.

LatestPhoto
A group of Pied Cormorants perching on rocks near the Odyssey.
Photo: Chris Johnson

Although the sea covers more than 70% of the earth's surface, seabirds comprise only 3.8% of the world's bird species. Many seabird species are extremely numerous and play a significant role in the ecology of the world's oceans.

There are more than 400 species of seabirds, though none are entirely aquatic as they must come to shore to lay their eggs, while all have specific adaptations to suit their water based lifestyles. Cormorants are masters at diving from the surface and pursuing prey at depth. Their comparatively wide bodies enhance stability underwater, while their legs are placed at the posterior end of the body, the best position for streamlining, steering and propulsion.

Some seabirds are aerial specialists, plunge diving at speed from the air, others use their wings as flippers enabling them to literally fly underwater. Cormorants hunt entirely by foot propulsion, during the backward - power stroke, the webbed feet are spread apart propelling the bird through the water, during the forward - recovery stroke, the webs are closed and the toes curled to decrease resistance.

Watching these cormorants closely, it is obvious that their mobility on land has been compromised by their aquatic adaptations. The flightless cormorants we encountered in the Galapagos Islands have lost their ability to fly entirely. Like all cormorant species, the back set position of the legs makes walking difficult, while perching with large webbed feet can be problematic. As a result, they often choose wide flat surfaces on which to stand.

LatestPhoto
Pied Cormorants.
Photo: Chris Johnson

Seabirds as a general rule lack the colourful plumage of their terrestrial cousins. Almost without exception, seabirds are black, white, brown or grey, with brighter colors being confined to the head. In the Pied cormorant, the plumage is most probably a reflection of its hunting method. It is known that fish react less to birds with white underparts. Therefore their light underside makes them less conspicuous to fish swimming beneath them.

Although relatively numerous, all seabirds, including the Pied cormorant are susceptible to a wide range of pollutants. This may include external contact with discarded fishing gear, plastic bags, oil spills, discharges from ships at sea or even introduced predators. Many birds are also vulnerable to ingesting objects that humans have discarded, while overfishing their food stocks can also pose a threat. It is important that we realize that the effects of our actions can be far reaching. Fortunately, growing awareness has meant many important seabird colonies are now protected.

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Log by Genevieve Johnson

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