What does it look like?
Indian ring-neck parrots are 38-42cm, typically with a green body. Colour variations are available due to selective breeding/mutation. Colours other than green usually cost more to buy. The neck is encircled by a red band (males) or indistinct emerald band (females). Males also have a black bib from underside of the beak down to the neck band, and may have a bluish tinge on the back of the head. Sub-adult males are difficult to distinguish from females. Males become sexually mature and develop the neck ring at 2-3 years old. Life-span in captivity is approximately 20 years (in some cases up to 34 years). It is gregarious and feeds and breeds in groups.
Broad climatic tolerance from cool and wet to hot and dry. Naturalised in at least 35 countries. Probability of occurrence declines with increasing number of frost days per annum, and reproductive success is greater in warmer climates (for example, Mediterranean) than in cooler climates (for example, United Kingdom). However, these birds are well established in London and elsewhere in the Southern UK, therefore are unlikely to be limited by cold in Auckland.
Why is it a problem?
Gregarious foraging, enabling domination of food sources. High levels of inter-specific aggression. Relatively early breeding season overseas resulting in pre-emptive cavity occupancy, followed by aggressive and often successful defence of cavities against other species, and some reports of eviction of other species from cavities. Therefore, potential to competitively exclude other cavity nesting species from the nest habitat. Appear to defend only the nest cavity rather than the entire tree, therefore may have lesser impact on non-cavity nesting species. More likely to be aggressive with smaller body-mass bird species. Aggressively attack potential nest predators such as rats, often successful, sometimes resulting in death of the predator.
Clutch size ranges from 1-7 eggs. Number of eggs per clutch may be influenced by cavity type. Populations in some regions produce two clutches per year, others only one. New Zealand breeders indicate two broods per year are unlikely here. Nestlings fledge at around 7 weeks of age. Rapid rate of population increase documented in overseas invasions (for example, average annual population increases of around 15-30% in the UK, 22% in Netherlands). Although abundance may increase rapidly, geographic range expansion may be slower (0.4 km/y in UK). Establishment of breeding populations overseas is positively correlated with human populations, that is, there are greater numbers where people live.