Humboldt penguins are medium-sized seabirds found along the Pacific coast of South America, from Peru down through Chile, where the cold, nutrient-rich Humboldt Current supports their food supply. They belong to the genus Spheniscus, a group of four banded penguin species recognizable by the black horseshoe-shaped band across their white chests and the fleshy pink patches at the base of their bills. Listed as Vulnerable by the IUCN, the Humboldt penguin sits at the intersection of several pressures: shifting ocean conditions, direct human contact, disease, and industrial fishing. Understanding how these birds are built, how they live, and what threatens them is central to figuring out whether their populations can recover.
Built for Swimming, Not Flying
Like all penguins, Humboldt penguins lost the ability to fly millions of years ago and repurposed their wings into rigid, flattened flippers optimized for underwater propulsion. Their skeletal anatomy reflects this trade-off. The humerus is flattened, the scapula is greatly elongated (its length reaches about 150% of the humerus length), and the coracoid and furcula are robust, all features driven by the high physical demands of rowing through water rather than gliding through air.1Scientific Messenger of LNU of Veterinary Medicine and Biotechnology. Біоморфологічні особливості скелетних елементів плечового суглоба пінгвіна Гумбальта Moving underwater requires far more effort than moving through air, and the entire shoulder joint has been remodeled to handle those loads.
Comparative studies of Humboldt and Magellanic penguins, their closest relative and a species whose range partially overlaps theirs, found that wing shape was strikingly similar between the two species even though beak shape varied more. That consistency in wing form suggests the locomotion demands of the Humboldt Current system impose a narrow set of constraints: both species swim in the same waters and have converged on roughly the same flipper design. Beak differences, by contrast, hint at different prey-handling strategies despite a broadly overlapping diet.2PubMed. Ecomorphology of South American Penguins
Their eyes are another impressive adaptation. Penguins need to see well both above and below the water line, a challenge because the optical properties of air and seawater are very different. Humboldt penguins, like other penguins, manage this with a relatively flat cornea that minimizes the refractive shift when they submerge. All penguins are trichromats, meaning they see three color channels, but they have lost one of the visual pigments typical of birds, a trait associated with dim-light performance. Deeper-diving species show additional adaptations like pale oil droplets and more rod cells in the retina, which boost sensitivity in low light.3PubMed Central. An Overview of the Penguin Visual System Humboldt penguins are relatively shallow divers compared with their Antarctic cousins, but they still forage in murky, sediment-laden coastal waters where good underwater vision matters.
What and How They Eat
Humboldt penguins are fish specialists, feeding primarily on small schooling species that concentrate where the cold Humboldt Current drives upwelling. Observational studies at colonies in Chile found that diet composition varies by location. At Chañaral Island, garfish made up about 94% of prey by number, with small amounts of anchovy and sardine. At Algarrobo, anchovy dominated at roughly 72%, supplemented by sardine and squid.4Journal of Ornithology. Diving behaviour and prey of the Humboldt Penguin This flexibility in prey choice is likely what allows the species to persist across a wide coastal range with varying local conditions.
Their foraging dives are generally shallow and short by penguin standards. At Chañaral, where the water was clear enough for direct observation, birds dove to the seabed at roughly 45-degree angles and returned immediately, with dives in the deepest zones (up to about 30 meters) averaging around 26 seconds. In deeper Peruvian waters, dives have been recorded lasting more than a minute on average. At Algarrobo, where the water was more turbid, penguins often swam within a meter of the surface for the entire duration of a dive, and average dive time was about 13 seconds.4Journal of Ornithology. Diving behaviour and prey of the Humboldt Penguin Almost all freshly caught fish showed tooth marks indicating the penguin had seized them from below, a hunting technique consistent with attacking silhouetted prey from underneath, where the fish is backlit against the brighter surface.
Breeding and Nesting
Unlike many penguin species that breed once per year in a sharply defined season, Humboldt penguins can attempt two breeding cycles annually. In Peru, the reproductive period stretches from March to December and can be split into an early season (March through July) and a late season (August through December). A full reproductive attempt takes roughly four months: adults occupy nests for one to two months, incubate a clutch of two eggs for about six weeks, and then brood chicks for 10 to 12 weeks.5Global Ecology and Conservation. Have we achieved a sustainable balance? Evaluating the effects of regulated guano extraction on an important penguin breeding colony (2008–2019)
Nesting sites are typically burrows dug into guano deposits, soil, or crevices in coastal rock. Guano burrows are historically preferred because the material is soft enough to excavate but sturdy enough to maintain structure, and the insulation helps buffer temperature extremes. Where guano has been stripped away by industrial extraction, penguins are forced into less suitable surface nests that leave eggs and chicks exposed to predators and sun. This is one of the quieter but chronic pressures on the species: centuries of guano harvesting along the Peruvian and Chilean coasts have degraded nesting habitat that would otherwise be available.
The Annual Molt
Every year, Humboldt penguins undergo a complete feather replacement, and this is one of the most energetically demanding events in their lives. Because new feathers push out old ones all at once rather than gradually, the birds lose their waterproofing for about two weeks and cannot enter the water to feed. In captive studies, molting lasted an average of about 13 days for males and 13 days for females, with males typically starting slightly earlier.6Zoological Science. Changes in Circulating LH, Sex Steroid Hormones, Thyroid Hormones and Corticosterone in Relation to Breeding and Molting in Captive Humboldt Penguins Kept in an Outdoor Open Display
To prepare, the birds go through a pre-molt fattening phase. Males in one captive colony held steady at around 5 kg for most of the year, then gained weight to peak at roughly 5.9 kg just before molt onset. Females climbed from around 4.3 kg to about 4.9 kg over the same pre-molt window. After molting, body mass dropped back to baseline levels.6Zoological Science. Changes in Circulating LH, Sex Steroid Hormones, Thyroid Hormones and Corticosterone in Relation to Breeding and Molting in Captive Humboldt Penguins Kept in an Outdoor Open Display The increase in flipper thickness tracked alongside body mass, suggesting the extra weight was primarily fat stored as an energy reserve for the fasting period.7PubMed. Hormonal correlations at transition from reproduction to molting in an annual life cycle of Humboldt penguins (Spheniscus humboldti) A penguin that enters molt in poor body condition, whether from a bad foraging season or repeated breeding attempts, faces real danger of not making it through.
Talking to Each Other
Humboldt penguins are vocal birds, and their calls carry individually distinct acoustic signatures. Researchers analyzing display songs found that a statistical classification method could assign individual calls to the correct bird with about 77% accuracy, dropping to about 74% under stricter cross-validation. Both the timing of the call (how long different syllables lasted) and frequency-related features (pitch and resonance patterns shaped by the vocal tract) contributed to making each bird’s voice recognizable.8PLOS ONE. Acoustic correlates of body size and individual identity in banded penguins
This vocal individuality extends to simpler contact calls as well, not just the elaborate display songs used during courtship. Studies comparing Humboldt, Magellanic, and African penguins showed that contact calls also allow individual discrimination and that the calls of these closely related species differ in ways that suggest natural selection has pushed each species toward distinctiveness, possibly to reduce the risk of hybridization where ranges overlap.9PubMed. Vocal individuality and species divergence in the contact calls of banded penguins For a bird returning to a noisy, crowded colony after days at sea, being able to pick out its mate’s or chick’s voice from hundreds of calling neighbors is not a luxury. It is a basic survival tool.
El Niño and Ocean Disruption
The Humboldt Current system is one of the most productive marine ecosystems on earth, but it is also periodically upended by El Niño events. During El Niño, warm water displaces the cold, nutrient-rich upwelling that sustains the anchovies and sardines Humboldt penguins depend on. The fish scatter or move to deeper, colder layers, and the penguins struggle to find food.
The consequences can be severe. During the 1982–83 El Niño, anchovy schools became unavailable to seabirds along the Peruvian coast, triggering massive mortality (especially among juveniles), widespread nest desertion, and a near-total collapse of reproduction.10Biological Conservation. Effects of the 1982–1983 El Nino on Humboldt penguin colonies in Peru The 1997–98 El Niño was similarly devastating. At Pan de Azúcar Island in Chile, a January 1998 count found just 312 Humboldt penguins compared with 2,276 the previous January, and at Punta San Juan in Peru, all chicks were deserted by January 1998.11Journal of Experimental Biology. Humboldt Penguins Outmanoeuvring El Niño Some individual penguins responded by shifting foraging strategies, but these adjustments were not enough to sustain breeding, and nest desertion accompanied the behavioral changes.
El Niño events are natural, and Humboldt penguins have weathered them for millennia. The worry now is that these events may be intensifying or becoming more frequent against a backdrop of ongoing climate change, while penguin populations are already reduced by other pressures and have less capacity to bounce back between episodes. Species distribution modeling suggests that several penguin species in the region, including Humboldt penguins, face strong declines in suitable habitat under future climate scenarios.12Journal of Biogeography. Past and Future Shifts in Marine Species Distributions Across Two South American Large Marine Ecosystems
Fisheries Bycatch
Getting tangled in fishing gear is one of the most direct and quantifiable threats to Humboldt penguins. A rapid assessment across both Peru and Chile estimated that roughly 4,000 penguins were caught as bycatch in 2023, with the majority taken in Peruvian waters. Gillnets were the primary culprit: about 40% of the fishers interviewed in Peru and 29% in Chile reported having caught Humboldt penguins in their gear. Larger mesh sizes and certain target fish species, such as corvina drum and Peruvian grunt, were strongly associated with bycatch events.13PubMed Central. Use of rapid assessments of fishery bycatch of Humboldt penguins Spheniscus humboldti in Peru and Chile to help identify conservation priorities
Four thousand birds per year is a substantial number for a species whose total wild population is estimated in the low tens of thousands. Not all bycatch is fatal, but many entangled penguins drown or sustain injuries that reduce survival. Because the bycatch is spread across thousands of small-scale fishing operations rather than concentrated in a few industrial fleets, addressing it requires engagement with individual fishing communities, not just top-down regulation. Identifying which gear types and fisheries cause the most damage is the first step toward designing interventions, whether that means modified net designs, seasonal closures, or compensation programs for fishers who adopt penguin-safe practices.
Disease in Wild and Captive Populations
Avian malaria is one of the most discussed disease threats to penguins in captivity, and Humboldt penguins are no exception. In zoos, where mosquitoes carrying Plasmodium parasites can be difficult to exclude, outbreaks have been documented repeatedly. A mortality event at a UK zoo identified avian malaria as a confirmed or suspected cause of death in several birds, alongside aspergillosis, a fungal lung infection that frequently co-occurs and complicates diagnosis.14International Journal for Parasitology: Parasites and Wildlife. Molecular and epidemiological surveillance of Plasmodium spp. during a mortality event affecting Humboldt penguins (Spheniscus humboldti) at a zoo in the UK In Thailand, molecular screening of captive penguins found blood parasite DNA in about 27% of samples, indicating widespread low-level infection even in birds that appeared healthy.15Current Research in Parasitology & Vector-Borne Diseases. Malaria outbreaks in Humboldt penguins and haemosporidian infections in avian hosts in zoos across Thailand
In wild colonies, the picture is different and somewhat reassuring. A molecular survey of wild Humboldt and Magellanic penguin colonies across South America found avian malaria to be absent from most sites. The one exception was the Punta San Juan colony in Peru, where at least two new parasite lineages were detected at a prevalence of just 0.6%.16PubMed. Molecular Epidemiology of Avian Malaria in Wild Breeding Colonies of Humboldt and Magellanic Penguins in South America Researchers cautioned that the low detection rate could mean either genuinely low incidence or that infected birds die quickly and are not sampled, or that chronically infected birds carry parasites at levels too low to detect in blood. The practical takeaway is that wild Humboldt penguins appear to have limited natural exposure to malaria, which means they likely have little acquired resistance and could be devastated if the parasite were to spread more widely, for example, as mosquito ranges expand with warming temperatures.
Sensitivity to Human Presence
Humboldt penguins react to people more intensely than any other penguin species studied so far. Heart rate telemetry experiments showed that an incubating penguin’s heart rate increased significantly when a person passed at just 150 meters, a distance at which many other penguin species show no measurable response. After a direct approach, recovery times lasted up to half an hour, during which the bird’s heart rate stayed elevated and energy expenditure increased even though the penguin showed no outward behavioral reaction like fleeing or calling.17Biological Conservation. Physiological and reproductive consequences of human disturbance in Humboldt penguins: The need for species-specific visitor management
This invisible stress has real reproductive consequences. Breeding success was significantly lower at frequently visited colony sites compared with undisturbed ones. The lack of obvious behavioral alarm makes the problem insidious: a tourist watching a penguin sitting calmly on its nest might assume the bird is unbothered, when in fact it is burning through energy reserves it cannot afford to waste. The researchers who documented this response argued that Humboldt penguins show little evidence of habituating to repeated human presence, making them a particularly difficult species around which to build ecotourism operations. Any visitor management plan needs wider buffer zones than would work for other penguins.
Protected Areas and Population Recovery
Where protections have been put in place, there is evidence that Humboldt penguin numbers can rebound. A mixed colony of Humboldt and Magellanic penguins in southern Chile was monitored before and after a protected area was established. By 2008, Humboldt penguin burrow counts had risen 13% above the 1997 baseline, while Magellanic penguin burrows increased by 64%. Total burrow numbers across both species grew by 63% over the same period. The improvements were attributed to removing feral goats from the nesting islets and excluding tourist foot traffic.18Avian Conservation and Ecology. Population Trends of a Mixed-Species Colony of Humboldt and Magellanic Penguins in Southern Chile after Establishing a Protected Area
The differential response between the two species is worth noting. Magellanic penguins bounced back faster, possibly because they were already in a stronger position demographically or because the habitat improvements disproportionately benefited their nesting preferences. Still, the Humboldt penguin increase, while more modest, is encouraging. It suggests that when the most immediate pressures (disturbance, habitat degradation from livestock) are lifted, these birds can begin recovering on their own. The challenge is scaling that kind of protection across the species’ long, fragmented coastal range, where competing uses like fishing, guano extraction, and tourism are deeply embedded in local economies.
Marine Pollution Along the Humboldt Current
Plastic debris is an emerging concern for marine megafauna throughout the Humboldt Current system, Humboldt penguins included. Plastic items in the ocean do not just pose ingestion or entanglement risks on their own. As they degrade, they absorb heavy metals and organic pollutants from the surrounding water and can become colonized by pathogenic microbes, turning each fragment into a concentrated package of contaminants that an animal may swallow along with or instead of food. The scale of plastic pollution in the Humboldt Current region is only beginning to be characterized, but the pathway from environmental contamination to individual animal harm is well established in marine systems worldwide.
For a species that already juggles El Niño disruptions, bycatch mortality, disease vulnerability, and extreme sensitivity to human disturbance, the additive burden of pollution is concerning even if its effects are harder to quantify than, say, the number of birds drowned in gillnets. Conservation planning for Humboldt penguins increasingly needs to account for these cumulative, interacting stressors rather than treating each one in isolation.