Coquimbo, Landau, 12 August 2026.
Since 2021, a research group led by Dr. Alejandro Simeone (1) has been conducting research on the population, breeding success and foraging of the Humboldt penguin in Chile on behalf of Sphenisco. The project is funded by the Karlsruhe Zoo Conservation Foundation, Dresden Zoo and the Hagenbeck Zoo Association. Guillermo Luna-Jorquera (2), Nicolás Luna (2) (3), Karen Lau (2), Mylene Seguel (2) (4) submitted a final report in August 2026 regarding the breeding success in the period 2021 to 2025. The report is entitled "Reproductive behaviour of the Humboldt penguin (Spheniscus humboldti) on the islands of Chañaral and Choros in the "Pingüino de Humboldt" National Reserve, period 2021–2025" (see PDF file). The researchers plan to publish the report in a journal. Excerpts and short chapters are reproduced below:
"Summary
Between 2021 and 2025, we tracked the brood of the Humboldt penguin (Spheniscus humboldti) nest by nest on the two main islands of the Pingüino de Humboldt National Reserve, Isla Chañaral and Isla Choros. In total, we checked 257 nests, in which 440 eggs were registered, 343 chicks hatched and 305 chicks reached a size that corresponds to fledge, i.e. leaving the nest towards the sea.
The results contain two very different but equally important pieces of information: 1. When the penguins breed, they do it successfully. In normal breeding seasons, the majority of eggs hatch (74–90%) and the majority of hatched chicks fledged (83–95%). The island of Choros stands out throughout: two thirds of the eggs and three quarters of the chicks of the entire study were concentrated there. The problem is not the success per nest, but how many pairs make a breeding attempt at all. The number of pairs with clutches fell from 117 in 2021 to 91 in 2022, to zero in 2023, to a single pair in 2024 and to 38 in 2025. In 2023 and 2024, reproduction came to an almost complete standstill, and in 2025 the recovery reached only a third of the 2021 level.
This pattern coincides with two events that are outside the colonies: the emergence of highly pathogenic avian influenza (H5N1) in northern Chile at the end of 2022 and the El Niño event in 2023–2024. The combination of adult mortality and lack of food explains what has been observed better than any problem on the islands themselves, which still offer good conditions for nesting. (...)
Results
Table 1: Breeding activity of the Humboldt penguin on the islands of Chañaral and Choros, seasons 2021–2025. Eggs/nest as an average (standard deviation).
(...) Comparison between the islands
If you compare the summed up values of the five periods, the difference between the two islands is clear:
Table 2: Cumulative values 2021–2025 per island.
The Isle of Choros yielded almost twice as many nests as Chañaral (161 vs. 96), nearly twice as many eggs (290 vs. 150), and nearly three times as many hatched chicks (256 vs. 87) and fledged juveniles (229 vs. 76). Of the 440 eggs in the study, 66% were laid on Choros; of the 343 chicks hatched, 75% hatched on Choros; and of the 305 fledged birds, 75% came from Choros.
Part of this difference is simply explained by the higher number of nests tracked on Choros, but not the entire reason: the pairs on Choros laid more eggs per nest (1.91 and 1.96 in 2021 and 2022 compared to 1.70 and 1.63 on Chañaral) and had higher and more stable hatching rates. Chañaral was also the island where the slump of 2023–2024 was most visible: from 40 pairs in 2021 to a single one in 2024.
However, once the chicks have hatched, the two islands behave in the same way: the cumulative fledge rates were 87% on Chañaral and 89% on Choros. The bottleneck is not in the rearing, but in the fact of whether the pairs can lay their eggs in the first place.
(...) The breeding failure of 2023 and 2024
The years 2023 and 2024 do not show bad breeding success — they show the lack of reproduction. In 2023, not a single clutch was recorded on either island, and in 2024 there was only one pair with an egg on Chañaral, which gave birth to a chick. A result of this magnitude cannot be explained by predation (5), bad weather or nesting habitat problems, because the hatching and fledging rates of the near periods were high. It can be explained by the fact that the adults simply did not attempt to breed — or were not there.
Penguins are long-lived birds that put their own survival above the success of a single season. When food is scarce, the adaptive response is to suspend the brood and try again the following year. This is exactly what seems to have happened, and it coincides with observations from other Chilean colonies in the same years, from which drastic declines in the number of breeding pairs were also reported.
(...) The partial recovery in 2025 — 38 pairs with clutches of normal hatching and fledging rates — is an encouraging but modest signal: it corresponds to only a third of the pairs of 2021. With a fertility of about 1.5 eggs per nest and sexual maturity at two to three years of age, returning to 2021 levels will require several consecutive breeding seasons with good oceanographic conditions.
Consequences for management
- The nesting habitat is not the limiting factor.
The high hatch and fledging rates on both islands shows that the protection of the reserve works: When the couples lay eggs, the chicks come through. This justifies the control of introduced predators (5) and the regulation of tourism; however, at the same time warns that no measure on land can compensate for the lack of food in the sea.
- The Isle of Choros deserves a priority status.
It accounted for 75% of the chicks and fledged young birds in the study, and has the largest clutches.
- Monitoring must be continuous.
A stable protocol of five to six inspection rounds per season and beyond that, a continuation of monitoring over several years are needed.
- Alert remains in place.
In Chile, new cases of avian influenza were detected in 2026, and the climate projections point to the occurrence of a strong El Niño event — a scenario that requires the maintenance and reinforcement of ongoing monitoring (open letter from the scientific community).
W.K.
Notes
For better readability, the generic masculine is used in this article. The personal names used in the article refer to all genders – unless otherwise indicated.
(1) Instituto One Health, Universdad Andrés Bello, Santiago, Chile.
(2) Center for Ecology and Sustainable Management of Oceanic Islands, Departamento de Biología Marina, Universidad Católica del Norte, Coquimbo Chile.
(3) ECOLAB, Animal Ecology, Conservation & Science Communication, Research and Technology Centre, Kiel, Germany.
(4) Medicina Veterinaria, Facultad de Agronomía, Universidad del Alba, La Serena, Chile. (5) In biology, predator refers to an organism that uses another for the purpose of eating and usually kills in the process.
translated by Erich Greiner