Fiordland Penguin surveys reveal a larger population than previously indicated
Twelve years of nest mapping suggest New Zealand's forest-breeding penguin is about three times more numerous than earlier surveys indicated.
A twelve-year effort to map the Fiordland Penguin's (Fiordland Crested Penguin's) scattered forest nests has recorded 1,200 breeding sites across nine New Zealand fjords and suggests the population may be roughly three times larger than older surveys indicated.
The latest field season took the Tawaki Project into remote parts of Fiordland, where researchers mapped 93 nests on two islands during September 2026. Unlike most penguins, Fiordland Penguins do not usually gather in conspicuous open colonies; pairs often breed in isolated burrows beneath dense rainforest.
That behaviour makes conventional counts unreliable. A boat-based observer can pass close to nesting habitat without seeing a bird, while steep slopes, thick vegetation and long stretches of inaccessible coast limit ground searches. A higher modern estimate may therefore reflect better coverage rather than a recent biological increase.
The programme combines repeated nest mapping with individual identification and tracking. At a central Fiordland sea cave known to researchers as the Hive, more than 25 pairs use a single narrow entrance. A transponder gate reads passive tags as birds pass, offering low-impact records of arrival, breeding and survival.
Elsewhere, researchers must retrieve logging devices directly. One female on Eleanor Island dug several exits from her burrow, repeatedly avoiding the team trying to recover her tag. The episode illustrates both the practical difficulty of the work and the limits of short deployments on wary birds.
Dr Thomas Mattern, a University of Otago researcher and Tawaki Project co-leader, told the Guardian that it took four days to recapture that individual and recover the instrument.
It took us about four days to recapture that bird.
Dr Thomas Mattern, Tawaki Project
Long-term monitoring is intended to separate one productive season from a genuine population trend. Automated gates can record when tagged adults return, whether young birds recruit and how survival changes between years. Nest maps provide the denominator needed to understand what those individual histories mean at population scale.
Recent genetic work adds a more encouraging line of evidence. A University of Otago-led study found Fiordland Penguins forming a single, genetically diverse population without clear isolation between colonies. Researchers linked that resilience to the species' ability to forage in environments ranging from enclosed fjords to coastal and oceanic waters.
That contrast is important because related New Zealand crested penguins face very different prospects. Eastern Rockhopper Penguins on the Antipodes Islands showed very low genetic diversity, while Erect-crested Penguins were divided into distinct island populations, one of which is shrinking.
The revised Fiordland estimate does not remove conservation concerns. Marine heat, changing prey, fisheries interactions and introduced predators around nest sites could still affect survival. A species can be more numerous than previously counted while remaining vulnerable because much of its breeding range is difficult to monitor.
The field programme also depends on access and repeated effort. Ninety-three nests mapped in one month cannot be extrapolated without accounting for unsurveyed habitat, missed burrows and whether old nest sites were active. Publication of the sampling design and confidence intervals will be essential when a formal population estimate appears.
For now, the best conclusion is not that Fiordland Penguins have tripled, but that researchers are finally measuring a cryptic population at the scale its unusual ecology demands. The forest that hides these penguins has also hidden how many there are.
17 Oct 2026
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