The life-cycle of the kea can be divided up into 4 general periods;
- Incubation to fledging (0-4 months)
- Juvenile (1st year)
- Sub-adult (4 months – 2 years)
- Adult (3-4 years+)
Incubation – Fledging (0-4 months)
Key attributes:Reproductive/development period.
Keas nest on the ground in naturally formed cavities, usually within upland beech and lowland podocarp forest. Breeding occurs in most years, but only about half of all adult females breed in any given year. Breeding occurs as early as July through until January. The female lays a clutch of 3-5 eggs which she incubates for approximately 1 month. The female cares for the eggs and nestlings in the cavity, whilst the male forages for the whole family.
Because of the long period associated with rearing chicks (approximately four months from start of incubation to chicks fledging) it is uncommon for kea to rear more than one brood in a season. However, if the eggs fail to hatch or are damaged, or if the chicks die or are removed, pairs will generally re-nest almost immediately. This has been observed in both the wild and captive situations (Pullar, 1996; Barrett, pers. comm. DoC, 2009).
Kea are most vulnerable during this lifestage due to predation of chicks and females on nests by introduced predators; in particular stoats.
Juvenile Period (1st year)
Key attributes – Dispersal from natal area, flocking; social/learning period.
Kea are a highly gregarious species which in the wild, form large flocks with non-linear hierarchies. Studies by Jackson (1960) in Arthur’s Pass observed large groups of around 20 first year birds during the summer period. These large flocks were then seen to disperse into groups of 2 -6 in autumn. Movement of all groups was seasonally and food related with those birds that moved to higher altitudes (1,219m – 2,133m) in the warmer months observed foraging for food and retreating back to the shelter of beech forests (up to 1219m) during autumn and winter.
Studies by Clarke (1970), of kea population, movements and foods in Nelson Lakes National Park, also showed very definite changes in group composition and location related to different times of the year. During August – September it was observed that kea formed flocks of 6 -8 birds which dispersed in October – December into smaller groups of 2 – 3. In January and February large flocks of up to 13 individuals again formed.
Kea in their first year are vulnerable to many threats due to their extreme neophilia (love of all things novel).
Sub- adult (2nd – 3rd year)
Key attributes – Flocking; social/learning period.
Kea in their 2nd and 3rd years continue flocking in a mixed group learning about their environment and social structure.
Adult (3rd-4th years +)
Key attributes: Forming pairs and developing territories.
Once adults reach breeding age (3-4 years) they tend to leave the main flock and pair up for breeding (Jackson, 1963; Jackson, 1960). Pairs are generally considered monogamous, although there have been accounts of males pairing with more than one female (Jackson, 1963). Mating behaviour begins in midwinter around June. Egg laying begins in July and peaks in October, but can extend right through into January (Jackson, 1962; Jackson, 1960).
Kea are long lived and slowly reproducing, making their populations particularly sensitive to changes in adult survival rates, and also to changes in reproductive and juvenile survival rates.