There are some 36 species of shag worldwide. Twelve of these are found in New Zealand, of which eight are endemic (found nowhere else). In many countries, shags are called cormorants. The name shag is thought to refer to the shaggy crest some species have on their heads. Four species of shag are found at ZEALANDIA: the kawau pū (black shag), kāruhiruhi (pied shag), kawau tūī (little black shag) and kawau paka (little shag). These four species all belong to the genus Phalacrocorax, the black footed shags, which are found mainly in freshwater or coastal seawater. The black shag is found worldwide, but those in Australia, New Guinea, and New Zealand are classified as their own subspecies.
Shags are swift underwater swimmers, with a sharp hooked beak to help them catch fish and small crustaceans. After a bout of fishing, shags must spend a lot of time perched with their wings spread out, preening and drying their feathers. This is because their feathers are not waterproof, making it easier for them to dive and stay underwater, but it also means the birds quickly get waterlogged and cold and must dry off afterwards.
As the english name suggests, this large shag is black with brownish wings. Feathers can appear slightly iridescent in strong sunlight, showing that the feathers are browner in the centre and black along the edges, giving the bird a distinct scaled look. They have a small white patch on the cheeks and throat and skin around the eyes and bill is yellow which darkens to an orange/red during breeding season. Also in breeding season mature birds develop a white thigh patch, and a small black crest (or shag!) on the nape and upper neck. Immature birds underparts mottled with white.
Black shags were once shot and killed in large numbers by fishermen who saw them as competitors for commercial fish species and a menace to young trout. Between 1890 and 1940, the New Zealand Acclimatisation Societies paid a bounty for each shag killed and many black shag colonies were exterminated. It was only as recently as 1986 that shags were partially protected after research showed that they take very few trout, preferring eels and slower swimming perch. Perch, like trout, are an introduced species, and are now considered a pest because of the detrimental impact they have on water quality and native invertebrates and fish species. There are perch in the lower lake at Zealandia, which is possibly one of the reasons the shags like it here so much!
The black shag was first recorded roosting in ZEALANDIA in 1995, on macrocarpas that are now lying the lower lake near the pontoon. Until recently only a few roosted here, and not all year round as they left to nest elsewhere, but since 2009 several pairs have nested here successfully and numbers of roosting birds have increased but they are still outnumbered by the other shag species in the sanctuary.