Of the four species of black-footed shag (Phalacrocorax genus) living in New Zealand, the best known and most widespread is the black shag or kawau (Phalacrocorax carbo novaehollandiae). This subspecies, found in Australia and New Guinea as well as New Zealand, belongs to a species which is also found extensively elsewhere – in Europe, Asia, Africa and North America – where it is known as the great cormorant. In some parts of the world, such as China and Japan, it has been trained to capture fish for humans; a ring around the neck prevents the bird swallowing its catch.
The black shag is found both on the coast and in fresh water inland. It feeds on fish, crustaceans and other invertebrates. Black shags are fairly common in New Zealand, with a population estimated at 5,000–10,000 individuals. They nest mostly in trees but occasionally on rock ledges, laying two to five blue-green eggs from June to October. The young fledge at about seven weeks. They are thought to live for up to 20 years.
‘The shag menace’
The black shag has a reputation among fishermen for robbing them of trout. As a result, between 1890 and 1940, acclimatisation societies put a price on them and many shag colonies were destroyed. In his 1945 publication The shag menace, angler H. G. Williams demanded a wholesale destruction of the black shag in order to ‘make the Dominion’s waters worthy of the claim to be the anglers’ Paradise.’ 1
Anglers the world over share this view of the black shag’s appetite for sport fish, and in Denmark and other countries, hunters are allowed to shoot them. But in New Zealand, after studies showed that shags have little impact on fish stocks, the black shag was partially protected in 1986. A landowner can still kill them if they damage commercial property, for example, on fish farms.
Crew on the Tangaroa, a government research vessel, observed unusual behaviour by immature black shags on a cross-Tasman trip in 1978. Some of the shags followed the ship, and came on board at night, sleeping among the anchor gear. Sometimes during the day they would perch in the rigging. It appeared that having only recently learned to fly, they were at times exhausted, and grateful for the nearby roost.
Conspicuously dressed with greenish-black plumage and a dazzling white front, the pied shag (Phalacrocorax varius) typically breeds in pōhutukawa or pine trees overhanging the sea. They are primarily coastal, preferring warm sheltered sites such as harbours, and feeding on fish and eels. They are found in coastal areas throughout most of New Zealand. Despite feeding only in coastal waters, some nest on freshwater lakes. In terms of population size, breeding, fledging and lifespan, the pied shag is similar to the closely related black shag.
Little black shags
Found in other parts of Australasia, the little black shag (Phalacrocorax sulcirostris) was first reported in New Zealand in 1840 and since then has expanded to most of the North Island. It is only occasionally seen in the South Island, with the first breeding there recorded in 2008. It likes to feed in packs; scores or even hundreds of the birds herd and trap small fish against a barrier in a frenzy of feeding. Adapted to both freshwater and coastal environments, its main foods are fish, including bullies and whitebait, and freshwater crayfish. It is fully protected.
There are between 1,000 and 5,000 breeding pairs. Like the other black-footed shags, little black shags lay two to five blue-green eggs, but breed later, in November–December. The life span is around nine years.
The little shag is known to Māori as kawaupaka. The species Phalacrocorax melanoleucos is found in Australia and other parts of the east Pacific; the subspecies Phalacrocorax melanoleucos brevirostris is found throughout New Zealand, where it is protected. There are between 5,000 and 10,000 breeding pairs.
The little shag comes in a variety of plumages: some juveniles are all black, whereas adults are black on the back with various white front markings – sometimes just at the throat, or covering the whole front, or a mix of the two. It is equally at home in fresh or salt water, and eats fish (including smelt and bullies), freshwater crayfish and sometimes frogs and tadpoles. It tends to feed close to shore in shallow waters.
Little shags live for up to six years. They live in large colonies of about 200 nests, laying two to five pale blue-green eggs between August and February. Nests are usually built in large trees.