On the wild and rugged coast of South Westland, remote colonies of Fiordland Crested Penguins or tawaki breed each year between July and December. We have been monitoring up to three of those colonies since 2014.
The early focus of this study was to identify and understand any predation trends on tawaki eggs and chicks by introduced mammals. Now, over a decade later, our main focus at our study sites is tawaki breeding success: monitoring nesting behaviour, chick growth and health, and indications of overall colony growth or decline. In addition, at one of the three sites, we monitor predator presence and activity.
Monitoring breeding success at Gorge River
The 2025 breeding season was a successful one at our key study site at Gorge River, though results varied between nests that were monitored by camera and those that were not.
With all birds sitting on eggs from August 22, the season ran at average to late timing compared to previous years. Over the course of three months, chicks were seen to be well-fed and growing at an average rate.
Our method:
- 24 nests checked over 3 months, from August to November
- 10 additional camera monitored nests, providing the most accurate results
- 2 cameras were lured & baited to assess predator activity in the area (mainly stoats).
Breeding success for Little Penguins or kororā is measured by the number of chicks fledged from both eggs laid (two = 100%). However, for tawaki, with a very different breeding strategy, breeding success is measured by the number of chicks assumed to have fledged per two eggs, and 100% = 1 per nest. In years or locations where food is plentiful, two chicks can occasionally be raised, but that’s the exception rather than the rule.
Here’s how the results unfolded.
10 camera-monitored nests, high accuracy results:
- 10 breeding attempts
- 2 nests attempted to raise 2 chicks
- 1 failed nest
- 9 fledged chicks
- 90% breeding success
24 nests not camera-monitored, lower accuracy results:
- 24 breeding attempts (assumed)
- 7 failed nests (cause undetermined)
- 17 fledged chicks (estimated)
- 65% breeding success
For nests not camera-monitored, the true number of failed nests is undetermined, as it is difficult to check for eggs without disturbing the penguins. At the time of nest checks during the incubation stage, tawaki that appeared to be sitting on eggs may not have had eggs in the nest at all.
Therefore, the most accurate indication of breeding success is from camera-monitored nests. And, from the 90% success rate recorded from camera-monitored nests this year, the results look good.
This is a significant improvement from 2024, when camera-monitored tawaki nests had a 66% breeding success rate. From 2019-2025, the average breeding success assessed using cameras in this colony is 92%.
There is another challenge in terms of counting fledged tawaki chicks. Chicks congregate in crèches, or a communal nursery, from about 3 to 4 weeks old. They leave their nests to huddle and socialise in small groups while both parents head out to sea to forage and meet the needs of their hungry, growing chicks.
Mystery chick deaths at camera-monitored site
Two of the camera-monitored nests in 2025 attempted to raise two chicks instead of one. One nest showed particular promise: both chicks were growing healthily, and at equal size to each other. It appeared that both were headed to fledging.
However, in early October, Gorge River tawaki ranger, Catherine, found both chicks in this nest dead, and unfortunately the camera had failed. There were no signs of predation, and one parent was present at the nest.
The cause of the chicks’ death is unexplained. Besides predation, the likely cause of chick death in tawaki is the death or abandonment of a parent, leading to loss of food supply and starvation.
Though both chicks were at a healthy weight, it is possible that one parent died at sea or abandoned the nest, leading to starvation in the chicks that happened too quickly to show signs of emaciation. Another possible explanation is that one parent brought home something poisonous.
In another nest raising two chicks, one chick was unfortunately growing slower than the other, and did not make it. Again, with no sign of predation, the likely cause of death was competition for food from the other, stronger chick.
Predator assessment: lured and baited cameras
We have used cameras to monitor the risk of predation since 2014. From earlier monitoring, we found that stoats are a major threat to tawaki eggs and chicks when stoat numbers are at plague proportions.
This year, our predator monitoring showed encouraging news. No stoats were seen at the two baited cameras or any nest cameras this season, demonstrating the success of DOC’s landscape-scale predator control efforts earlier in 2025.
Secondary study sites
Alongside our key study site in the early years of our research, we monitored for predators and predation at two other South Westland colonies. Since 2019, we have monitored tawaki breeding success at these colonies.
In 2025, our ranger, Lucy, along with her volunteer assistants, monitored breeding success at these colonies through two nest checks:
- The first nest check takes place during the incubation stage, when penguins are sitting on eggs and taking it in turns to feed themselves or keep the eggs warm.
- For the second check, we aim at the chick-guard stage, where, after hatching, one parent stays behind in the nest to warm and protect the vulnerable chick, while the other parent hunts for food. It is desirable to check as late as possible in this approximately three-week stage to ensure the most accurate representation of chick survival.
It was a steady year for breeding across both colonies.
Let’s start with our largest one.
Colony 1 (Jackson Head):
- 30 nests checked
- 22 active nests
- 20 breeding attempts
- 0 failed nests
- 20 fledged chicks
- 100% breeding success
This colony has shown real promise over the last two years, repeating its 100% breeding success from 2024 (one chick raised per breeding attempt). Overall, this site has an average breeding success rate of 97% from 2020 to 2025.
Colony 2 (Knights Point area):
- 19 nests checked
- 10 active nests
- 10 breeding attempts
- 1 failed nest
- 9 fledged chicks
- 90% breeding success
In 2025, this colony saw a 10% increase in breeding success compared to 2024, which is again encouraging. The overall breeding success average here is 90% from 2019 to 2025.
Accuracy of results
It’s important to note, however, that due to the remote location of these colonies and the variable timing of the tawaki breeding season, it is difficult to predict optimal timing for nest checks, which can interfere with the accuracy of our results.
The tawaki breeding season started a little later in 2025 than it did in 2024. Lucy checked nests on the same dates as the previous year, but the second visit during the chick-guard stage was not sufficiently far enough into chick growth to give us strong confidence that the chicks would survive. Many chicks were still small, and it is not clear whether they would have survived to fledging, so the number of fledged chicks is assumed.
Our results are therefore informed guesses for tawaki breeding success across these two South Westland colonies.
Importance of monitoring multiple sites
No pattern or consistency is shown across our tawaki study colonies, showing that monitoring multiple sites is necessary. One colony cannot represent the rest.
What’s happening in 2026?
In 2026, we aim to establish the timing of egg laying if possible, in order to visit tawaki nests later in the chick-guard stage, when the chicks are larger. This will help us better determine chick survival to the fledging stage and provide greater data accuracy for overall breeding success.
We will continue to monitor breeding success at our three sites, using cameras at Gorge River for both monitoring and predator observations.
