Story: Introduced land birds
Page 9 – Starlings and mynahs
For farmers, the common starling (Sturnus vulgaris) has been a useful introduction. It helps control unwanted insects, including ticks on cattle and sheep, and crop pests such as caterpillars and grasshoppers. Some farmers encourage starlings to prey on grass grubs by placing nest boxes around fields.
However, starlings damage grapes and other fruit crops, and compete with tūī and bellbirds for the nectar of flax, rātā and other native plants.
The common starling is from Europe, North Africa and western Asia.
Around 1,000 birds were introduced to New Zealand from the 1860s to the 1880s. Starlings are found throughout mainland New Zealand, except in densely forested or mountainous country. They have spread to the Chatham, subantarctic, Kermadec island groups, and further afield to other Pacific islands.
In the breeding season, both males and females have a glossy purple- or green-black head and breast, and yellow bill – pink at the base in females, blue in males. Their wings and underbodies have yellow-buff speckles, which, in winter, also extend over the breast and head. They are about 21 centimetres long and weigh 85 grams.
Starling nests are untidy heaps of grass in holes in trees or buildings, or at the base of clumps of vegetation. Females lay four or five pale blue eggs, and about half lay a second clutch later in the season. Life expectancy is around three years, but the oldest recorded was 14.
Outside the breeding season, starlings gather each night in sheltered communal roosts, where predators are scarce. Specific trees may be used – for example, in central Wellington large numbers used to roost in a single pōhutukawa tree on The Terrace. On the Kapiti Coast starlings congregate at dusk on pest-free Mana Island. At dawn they disperse, travelling dozens of kilometres to feed. Some roosting flocks number a million birds.
The mynah (Acridotheres tristis) is native to Central Asia, from India to Afghanistan, and has been introduced around the Pacific. Although the same family as starlings, mynahs are larger, measuring about 24 centimetres long and weighing 125 grams.
The body is brown, with white wing patches and a glossy black head. The mynah has yellow legs, a yellow bill, and a tapered patch of yellow skin extending from the bill past its eye.
Mynahs were introduced in the 1870s, mainly in the South Island, to control insect pests. They had died out there by 1890, but were common around Wellington, East Cape, and from Whanganui to Waikato. They progressively expanded northwards, reaching Auckland around 1947, and have become very abundant in Northland. Meanwhile, they disappeared from the Wellington region.
Habitat and feeding
Mynahs are not found in dense forest, but are common in farmland, urban gardens and on roadsides. They feed on invertebrates (including worms, snails and caterpillars), fruit, scraps and road kill, as well as lizards, eggs and chicks.
Mynahs are aggressive birds with a shrill, raucous call. Because they damage fruit crops and threaten native birds, they are considered a pest in areas such as Northland.
In the breeding season, mynahs have heated territorial fights. They nest mainly in holes in trees, cliffs or buildings, and sometimes remove other birds in order to use their nest holes. Females lay three to four eggs and do most of the incubating. At night males gather at communal roosts.
For the rest of the year mynahs congregate in large roosting colonies. They live for up to 12 years.