A yellow-eyed penguin and chicks Yellow-eyed penguins are the least social of all penguins, being solitary breeders. They maintain the largest territory size of any penguin, sometimes up to 1 nest per hectare in forested areas.

Nests are made of sticks and coarse grass, built against a solid obstruction such as rock, tree trunk or flax plant. It must provide shelter from harsh weather and the heat of the sun. The long 28 week breeding season begins in mid-August when partnerships are formed or renewed, and nest sites selected.

Two eggs are laid in mid-September to mid-October. Eggs are green and change to white within 24 hours. Egg size is 75 mm x 54 mm.

Incubation period is 38 - 54 days (average 43 days), and is shared by both parents. The average hatching date on mainland New Zealand is the beginning of November.

From hatching until chicks are 6 weeks old (a period known as the 'Guard Phase'), one parent remains with the chicks while the other parent goes to sea to fish for food for the chicks. Chicks fledge from mid-February to mid-March.

Although juvenile yellow-eyed penguins are known to disperse northwards as far as Cook Strait during their first year at sea, adults are found at their breeding area throughout the year.

Approximately 50% of surviving juveniles return to breed at the place where they were hatched.