Acridotheres tristis(Photo: KW Bridges, University of Hawai'i)
Taxonomic name: Acridotheres tristis (Linnaeus, 1766)
Synonyms: Acridotheres tristas, Acridotheres tristas (Linnaeus, 1766)
Common names: common myna (English), Hirtenmaina (German), Indian myna (English), Indian mynah (English), Martin triste (French), mynah (English)
Life form: bird
Mynas are native to India, but have been introduced all over the world, mainly for their being able to reduce the insect population in agricultural areas. However, they reduce biodiversity by competing for nesting hollows, destroying chicks and eggs and evicting small mammals.
Description
The Myna is a medium sized chocolate-brown bird with a black head and neck, about 25 cm tall, with a black head and neck, a yellow beak, eye patch, feet and legs. White wing patches are obvious when the birds are flying. Mynas are distinctive because, unlike most other birds, they walk rather than hop. In the breeding season, they are strongly territorial and neighbouring pairs often fight furiously. However, in autumn and winter they often feed in flocks of 5-20 birds. These flocks can travel 10+ km between their roosting and feeding sites each day. Except for incubating females, mynas spend the night at cornmunal roosts, some of which are of 1000+ birds. Territorial birds normally have a bout of intense calling for 5-15 minutes when they arrive in their territories in the early morning. Males call more often than the females, and pairs sometimes duet. The territorial call is a rowdy medley of notes, raucous, gurgling, chattering, even bell-like, in rapid sequence. Adults with young utter a harsh "squark" and the call of flying young is a persistent "chi-chi-chi". At their communal roosts mynas maintain a noisy chattering, even well after nightfall and before dawn. In Hawke's Bay, New Zealand, some mynas (identified through colour-bands) were found to have lived over 12 years.
Occurs in:
agricultural areas, urban areas
Habitat description
Mynas are tropical birds. Their spread is limited to places that are warm enough and have enough food for them, to not need to leave their nests for too long whilst incubating eggs. If they do and it is cold, the eggs will chill and fail. In New Zealand, they seemed to find it too cold around Nelson and their southern populations declined except for some individuals that were found permanently based in piggery sheds where it was warm enough and there were sufficient sources of food that they thrived (P. R. Wilson pers. comm.) Favoured roosts are in isolated stands of tall trees. In Singapore, mynas are commonly found roosting in large clumps or long rows of tall trees with dense canopies, often of similar height and species (Hails 1985, Yap et al. 2002).
General impacts
In New Zealand mynas prey on the eggs and nestlings of feral pigeons, Silver and Southern Black-backed or Kelp Gulls, and on those of the small native and introduced passerines (Thomson 1922, Oliver 1955, Wodzicki 1965).
Mynas inflict damage to grape and other fruit crops. (Heather and Robertson 1997) like apricots, apples, pears, strawberries and gooseberries.In Singapore, there are no significant impacts of common mynas on other species of birds (Hails 1985, Kang 1989). However, they are perceived as a nuisance because of their habit of roosting communally at night near human habitation (Hails 1985).
Geographical range
Native range: Natural breeding range from Afghanistan east through India and Sri Lanka to Bangladesh.
Known introduced range: Mynas through natural range extension or introductions in the 1900s have reached much of Southeast Asia. They have been widely introduced around the world, and are established in South Africa, Australia, New Zealand, Solomon Islands, New Caledonia, Fiji, Western Samoa, Cook Islands, Hawaii.
They have also been reported on La R??union (Philippe Clergeau., pers.comm., 2005).
Invasion pathways to new locations
Acclimatisation Societies: Introduced to New Zealand by Acclimatisation Societies and private individuals
Taken to botanical garden/zoo: In Israel all escaped from one private facility of exotic birds in the center of the Tel Aviv public park.
Local dispersal methods
Escape from confinement
Self-propelled (local): escaped mynas breed in the wild.
Management information
Long term management practices include habitat modification, resource limitation and public education.
Preventative measures: The Bureau of Rural Sciences, Australia, recently developed a risk assessment model ( Bomford, 2003) which has been endorsed by the National Vertebrate Pests Committee and may be used as the basis for future exotic species import applications.To assign an exotic species to a threat category, three risk scores are calculated: the risk that (1) an escaped or released individual would harm people, (2) escaped or released individuals would establish a wild free-living population (3) the species would be a pest if a wild population did establish. These three risk scores are then used to assign the exotic species to one of four threat categories: extreme, serious, moderate or low.
Acridotheres tristis has been assigned an Extreme threat catergory for Australia. These animals should not be allowed to enter, nor be kept in any State or Territory. (Special consideration may be given to scientific institutions on a case by case basis.) Any species that has not been assessed previously should be considered to be in the Extreme Threat Category and should be treated accordingly, until a risk assessment is conducted.
Nutrition
Diet is a mix of invertebrates and fruits, scraps found at rubbish tips, on roads, and from places where stock and poultry are fed. They also eat chicks, eggs and lizards. The main invertebrates eaten include beetle larvae and adults, bugs, caterpillars, worms, flies, snails and spiders, mainly taken from the ground and especially along roads, where many insects are killed by cars. They also feed by pecking prey from the surface in short pasture and grain stubble.
Reproduction
Pairs stay together year after year and keep the same territory in successive years. The nest is a cup of dry grass, twigs and leaves, usually in a hole of a tree, cliff, building or other structure, but sometimes they will nest in a thick tangle of vegetation. In New Zealand laying is from mid-October to early March, mostly in November and January. Each pair usually raises two broods a year. Mynas lay 1-6 (average 4) greenish-blue eggs in the early morning. Incubation starts with the laying of the last egg, and is mainly by the female during the day, but by the female alone at night, for 13-14 days. Both parents feed the nestlings during the 20-32 (average 25) day fledging period and for upto 3 weeks after leaving the nest. Juveniles form small flocks when they become independent. Many young form pairs when nine months old, but only a few females attempt to breed in their first year.
Source: ISSG Global Invasive Species Database (http://www.issg.org/database) |
