The Blue penguin breeds along the entire coastline of New Zealand, the Chatham Islands, and southern Australia. Blue penguins have also been reported from Chile (where they are known as Pingüino pequeño or Pingüino azul and South Africa, but it is unclear whether these birds were vagrants. Rough estimates (as new colonies continue to be discovered) of the world population are around 350,000-600,000 animals. The species is not considered endangered, except for the White-Flippered subspecies found only on Banks Peninsula and nearby Motunau Island in New Zealand. Blue penguins breed underground in burrows or natural holes, although they will make use of any man-made cavity. Near human habitation it is not uncommon to find them nesting under buildings, stacks of timber or even railway tracks. Artificial nest boxes are readily adopted.
Blue penguins in New Zealand have rather variable breeding seasons. The core egg-laying period for most of New Zealand is September to November, and only one clutch is laid. In good food years, blue penguins in Otago will egg-lay from May to February, with many pairs raising two clutches of chicks.Usually two eggs are laid and are incubated for 36 days, with both parents sharing the incubation and feeding duties. The chicks are guarded by one parent for the first 2-3 weeks, after which both parents must go to sea to keep up the supply of fish. Chick growth is rapid, with adult weight (1000g) being achieved in 4-5 weeks. Chicks usually fledge at 8 weeks and are independent from then on.Blue penguins usually breed for the first time at 2-3 years of age. Long term partnerships are the norm, but divorce is not uncommon. There is a high rate of juvenile mortality, but individuals can reach up to 25 years of age.Blue penguins are very faithful to their home site. Chicks will often return to within a few metres of where they were raised and once settled in an area never move away. A small number (<1%) of juveniles disperse to other breeding sites.
These birds feed by hunting fish, squid and other small sea animals, for which they travel and dive quite extensively. They are generally inshore feeders. The use of dataloggers has provided information of the diving behaviour of Little Penguins. 50% of their dives go no deeper than 2 m and the mean diving time is 21 seconds. Yet, they are able to dive as deep as 20m and remain submerged as long as 60 sec.
The species is not considered endangered, except for the White-Flippered subspecies found only on Banks Peninsula and nearby Motunau Island in New Zealand. Since the 1960s, the mainland population has declined by 60-70%; though there has been a small increase on Motunau Island. But overall Little Penguin populations have been decreasing as well, with some colonies having been wiped out and other populations continuing to be at risk. However, new colonies have been established in urban areas. The greatest threat to Blue Penguin populations has been predation (including nest predation) from cats, dogs, mustelids, foxes, large reptiles, and possibly ferrets and stoats. Due to their diminutive size and the introduction of new predators, some colonies have been reduced in size by as much as 98% in just a few years, such as the small Fairy colony on Australia's Middle Island, which was reduced from 5000 penguins to 100. Because of this threat of colony collapse, conservationists pioneered an experimental technique using Maremma Sheepdogs to protect the colony and fend off would-be predators.