Portrait of the Dabchick

Forest and Bird, Issue 298, 1 November 2000, Page 24

Portrait of the Dabchick

GEOFF MOON

documents the life cycle of a threatened wetland bird.

‘he New Zealand dabchick is already extinct in the South Island, and clas- ~ sified as ‘threatened’ in its North Island habitat. It is the only grebe peculiar to New Zealand, though Australian species visit, and the South Island has a small population of the magnificent Australasian crested grebe. These grebes are collectively known as Podicipedidae for a strange physical feature: the name means ‘rump foot and refers to the fact that their feet are positioned well back on the body. The feet are lobe-webbed, which describes the flat web bordering each toe — a feature of all grebe species. Grebes can't walk on land, so their lifestyle is entirely aquatic. The lobed feet provide very efficient propulsion when a dabchick swims submerged in pursuit of aquatic insects and small fish, its main diet. The New Zealand dabchick, or weweia is reasonably common on the Rotorua lakes, the western border of Lake Taupo, and the dune lakes of the west coast. They also inhabit lakes and farm dams further south, especially in Wairarapa. The birds can be seen flying low over the water during the day, particularly during courtship displays. It seems the bird flies

strongly only at night, however, when migrating to different stretches of water. Nesting extends over many months of the year, with nests being found from July through to March. Favoured nesting sites are usually composed of water weeds anchored to raupo or trailing willow branches. They may also be found under overhanging clumps of sedge, under boatsheds and even in a suspended tyre hanging from a wharf. Nests are constructed of water weed and dead raupo stems. In most cases the nests are floating, as they sit on fallen raupo or low-lying branches. Material has to be constantly added as the weight.of the nest begins to sink it. The usual clutch consists of two or three white eggs, which soon become stained due to the birds’ habit of covering the eggs with weed, when vacating the nest. Some books state that the New Zealand dabchick is the only grebe which does not cover its eggs (eg Reader’s Digest Complete Book of New Zealand Birds). This is untrue, and may only be the case when a nest has been discovered by an observer and the bird has vacated the nest, having not had time to cover the eggs before leaving. Both sexes take turns at incubating over 20-24 days. The incubating birds make a submerged approach, surfacing close to the nest. This accounts for the girdle of chickweed adhering to the incubating bird;’s body, shown in some of these pictures. The chicks hatch at daily intervals, with the first-hatched chick finding its way to the parent’s back. The family leaves the nest after the last egg has hatched, and each parent takes its turn to carry the chicks while the other parent dives for food. The family group stays together, but the chicks disperse when another nest is built. — GEOFF MOON has been photographing and recording the lives of New Zealand birds for nearly 50 years. He is the author of many books.

The Other Grebes

The Australasian crested grebe (at right) is unmistakeable -a large bird found as a related subspecies in many parts of the world, including Europe, Africa and parts of Asia. In New Zealand it is restricted to South Island lakes, generally in the high country, or lakes in lowland Westland. The population of this threatened native bird is estimated to be 200-300, and fears are held for its future. Birdwatchers are more likely to confuse the New Zealand dabchick with one of two Australian species sometimes found here. The Australasian little grebe (below) has established a tiny breeding population in Northland in the past 20 years or so, and has also been reported from the South Island. It is smaller than the dabchick and has a yellow patch of skin at the base of its bill. The hoary-headed grebe is a rare vagrant from Australia. other grebe species are reported in New Zealand. | |