Kororā were once common on the mainland coast. Now, most are found on offshore islands where there is less disturbance from humans, dogs, and introduced predators.
Despite this, kororā can be found on beaches around the country, and their population is increasing in areas where there is predator control.
Every year starting around November, DOC begins to receive reports of dead kororā washing up on beaches, and bird rescue centres get an influx of sick and injured birds to care for.
The summer of 2020/21 is a La Niña year. This brings increased sea-surface temperatures and onshore winds to New Zealand. These conditions can make it more challenging for kororā to nest and feed.
However, some level of mortality is natural and to be expected.
Possible high number of dead penguins this summer
It's possible that this will be a high mortality year for little kororā because of the La Niña weather system bringing warmer than average seas to northern New Zealand.
Breeding season is a very stressful time for adult and juvenile kororā. Not all fledging chicks will make it through to adulthood because of predation and lack of food. Breeding during a La Niña year is even more stressful and difficult on seabirds.
Adult birds find breeding stressful because they need to find food for both themselves and their chicks. This extra stress and exhaustion may make some birds more prone to illness, or increase the risk of a predator attack as they dive deeper for food.
Juveniles that have left the nest are independent from their parents. They need to learn where and how to find food. A chick’s condition at fledging is crucial to their survival in the first difficult month at sea. Body fat reserves give them a chance to learn how to feed. Underweight juveniles may struggle to find enough food, or get caught up in stormy seas with low water clarity and die.
High juvenile mortality is unfortunate but natural for kororā, particularly at this time of year. Often penguins simply need to rest, especially after a storm. However, many can not fend for themselves and die of exhaustion or starvation.
Studies in the South Island have shown that typically only 30% of chicks survive to adulthood. During a difficult season when little food is available, the survival rate can be even lower. Some chicks are found washed up on beaches, but the majority are washed away by the sea currents.
Effects La Niña could have on penguin survival
La Niña brings warmer waters. This means the fish that seabirds feed on stay in cooler, deeper waters as surface temperatures rise.
Penguins and petrels respond to these changes by foraging further away and diving deeper to find food. Starvation is a risk for themselves and their chicks if food is in short supply. The recent reports of starved kororā all point to a lack of small fish that all these species depend on.
Dead penguins can start turning up on beaches as early as November, when the first chicks begin to depart the nest. Reports so far have confirmed that some kororā are dying of starvation.
When we'll know if this level of mortality is normal
Most penguin chicks fledge during November and December. If juvenile kororā are struggling, we will begin to see evidence of this in January. We are monitoring the situation quite closely, as are many conservation groups.
Higher than usual deaths were reported to northern North Island bird rescue centres in the summer of 2017/18. This was also a La Niña year.
Other historical mass die-off events happened in 1974 (4,737 penguins), 1985 (5,386 penguins), and 1998 (3,517 penguins). A mass die-off event (when more than 1,000 birds wash up annually) is typical about every decade. While current reports are well below this number, it is early days and may yet occur.
The lack of kororā washed up on beaches does not mean that all is well with this species. Sometimes failure occurs within the nest (lost eggs and small chicks that fail to grow) so very few healthy chicks make it out to sea. In years when the winds blow offshore away from breeding colonies, dead birds float further out to sea and are not noticed by the public.
More work is needed to determine the status and trends of kororā colonies in northern New Zealand
How climate change is expected to affect kororā
Mass die-offs with more than 1,000 dead penguins used to be a once in a decade event.
Climate change is likely to increase the frequency of marine heatwaves. These warm water events are likely to increase the number of poor breeding seasons for kororā in northern New Zealand.
Marine heatwaves are a major threat for many other marine species. Localised extinctions following marine heatwaves have occurred in species such as bull kelp and starfish.
As climate change effects continue, heatwaves, and other adverse weather events such as storms, will become stronger and more frequent. We may expect to see a corresponding increase in the amount of mass die-offs of penguin and other sea creatures.
You can help
With the potential food shortages this year, you may encounter penguins that are very weak. These birds are extra vulnerable to dog attacks. It's crucial you keep your dogs on leashes while in coastal areas.
Keep our penguins safe
- Leave penguins alone. Usually scruffy birds are simply moulting.
- Put your dog on a leash around penguin areas.
- Keep your dog away from nests, and warn others nearby of the location.
- Donate your time or money to help penguin protection groups, such as the Yellow-eyed Penguin Trust and Forest & Bird.
If you find a dead or injured penguin
If you find a dead penguin, leave it alone. Community groups regularly count dead seabirds and will remove them from beaches.
If a sick penguin is at risk from attack by dogs or other predators, place it under vegetation in the rear-dune well away from people. Or you can take it to a local bird rescue centre.
Do not give emaciated penguins food. The rehabilitation of seabirds requires specialist knowledge and training.
If a penguin is clearly injured or in immediate danger, contact the emergency hotline 0800 DOC HOT (0800 362 468). Try and give the exact location and take photos to help us make an assessment.