Breeding sites It nests on islands and rocky coastal stretches, using a variety of nest types including guano and dirt burrows, surface nests, vegetation- and rock-covered scrapes, rock crevices, sea caves and under rocks at breakwater walls (Battistini and Paredes 1999, Simeone and Bernal 2000, Paredes and Zavalaga 2001). It apparently prefers to breed on slopes at high elevation sites where guano deposits are available for burrow excavation (Paredes and Zavalaga 2001).

Reproductive behaviour Breeding occurs year-round, but has two peaks, in autumn-winter (April through July) and in spring (August through December), with latitudinal shifts in dates between Peru and Chile (Paredes et al. 2002, Simeone et al. 2002, de la Puente et al. 2013).

Moult Birds moult mainly during January and February, but moult in juveniles is less synchronous (Simeone et al. 2002, Paredes et al. 2003, de la Puente et al. 2013).

Migratory range It is uncertain whether this is a migratory species, but a part of the population migrates after moult (March), with birds from Pan de Azúcar migrating over 600 km (Culik and Luna-Jorquera 1997b) and birds from Puñihuil over 1,000 km (Pütz et al. 2016) northwards from their colonies.

Diet Depending on locality, it feeds on a variety of fish species including Peruvian Anchovy (Engraulis ringens), Araucanian Herring (Strangomera bentincki), Silverside (Odontesthes regia), Common Hake (Merluccius gayi), Inca Scad (Trachurus murphyi), Garfish (Scomberesox saurus scombroides) and South American Pilchard (Sardinops sagax). Diet also includes squid: Dosidiscus gigas and Loligo gahi (Herling et al. 2005).  

Foraging behaviour Humboldt Penguins are highly dependent on predictable food resources in coastal waters near the nesting sites (Taylor et al. 2002). During the chick-rearing period, adults forage within 20-35 km around the colony, while incubating birds may reach up to 72 km from the colony (Culik and Luna-Jorquera 1997a, Culik et al. 1998, Chiu et al. 2011). The species typically makes short, shallow dives within 30 m of the surface (Taylor et al. 2002). At Isla Pan de Azúcar, Chile, it was found that maximum dive depth was 53 m.

Population health Health surveys conducted on breeding adults from Punta San Juan showed that birds are in good condition. Haematology, plasma chemistries, and plasma mineral levels varied between years. Positive antibody titers for Chlamydophila psittaci (62%), avian adenovirus (7%), paramyxovirus-2 (7%) and Salmonella pullorum (7%) were found (Smith et al. 2008). Sallaberry-Pincheira et al. (2015) detected Haemoproteus sp. in wild ranging Humboldt Penguins at Punta San Juan, but it is unclear whether Haemoproteus sp. sporozoites are able to infect and develop in penguin cells (see Levin et al. 2013, Valkiunas et al. 2014) and, until this has been conclusively demonstrated, it seems unlikely that these parasites pose a significant threat for their conservation (Vanstreels et al. 2016).

Pollution Humboldt Penguins at Punta San Juan were evaluated for 55 important trace elements, including Hg [maximum Hg concentrations in serum (0.0056 ± 0.001 µg/g), whole blood (0.297 ± 0.0683 µg/g), and feathers (1.8 μg/g dw)], but at levels generally not considered to cause health impairment. Plasma samples from the same animals were analysed for 31 polychlorinated biphenyls (PCB) and 11 organochlorine (OC) residues using gas chromatography coupled to an ion trap mass spectrometer and for 15 polybrominated diphenyl ethers (PBDE) using gas chromatography high-resolution mass spectrometry. The detection rate for PCBs was 69%, with congeners 105, 118, 180, and 153 most commonly detected (Adkesson unpubl. data).   

Historically, the population suffered a severe decline starting in the mid-1800s due to the extensive guano harvest in Peru and northern Chile, which removed the preferred nesting habitat (Murphy 1936). According to Johnson (1965), the Humboldt Penguin occurred by the “hundreds of thousands” before the guano exploitation started. In the early 1980s, just prior to the 1982-83 El Niño event, the global population was estimated at 16,000-20,000 birds (Hays 1986, Araya and Todd 1987). After this El Niño event, numbers dropped to 5,000-6,000 individuals, but it is uncertain whether this reduction actually represented mortality or dispersal or a combination of both (Hays 1986, Araya and Todd 1987).

Evidence from satellite-tracked individuals suggests that part of the population migrate between 600-1,000 km northwards during the winter. This has been observed from colonies in northern Chile (Culik and Luna-Jorquera 1997a) and southern Chile (Pütz et al. 2016). Based on band recoveries, Wallace et al. (1999) showed dispersal of penguins from a colony in central Chile up to 600 km to the south and 80 km to the north. Recent geolocation sensor data for Peru indicates post moult movements from breeding individuals at Punta San Juan (15º 22'S) southward up to the Magellan Region (49º 51'S) in Chile (Paredes et al. unpubl. data).

Conservation Actions Underway
Colonies in Peru and Chile are monitored regularly. In January 2010, the Peruvian government established the Guano System National Reserve (Decreto Supremo 024–2009-MINAM) (Ministerio de Ambiente 2012, http://www.minam.gob.pe/wp-content/uploads/2013/09/decreto_supremo_024-2009.pdf). This network of headlands, capes and islands harbours nesting sites of Humboldt Penguins and protects major foraging areas around them. The San Fernando National Reserve (established in July 2011 by the Decreto Supremo 017–2011-MINAM) is also a major site for penguins. Monitoring and removal of rodents has recently begun at Punta San Juan (Cárdenas-Alayza unpubl.). Recently, the Chilean Forest Service eradicated rabbits from Isla Choros in northern Chile, and they have developed an Action Plan (CONAF 2016) for the species aiming to improve its conservation in the country and particularly within the protected area network. Currently, the National Zoo in Santiago (Chile) is successfully developing an ex-situ programme by raising chicks from neglected eggs taken from wild populations. Recently, the Shimonoseki Marine Science Museum (Japan) succeeded in artificially inseminating female penguins from frozen sperm (K. Ueda pers. comm.).

Conservation Actions Proposed
Currently, population estimates for Peru and Chile are determined by different methods and this prevents comparisons and estimates of the global population. Therefore, a consolidated census methodology for both Peru and Chile should be established. Determine the optimum survey times and methods for assessing the population size of the species in both countries (e.g. define whether censuses of breeding or moulting birds [or both] should be conducted for the species). Quantify the impact of identified threats on distribution, abundance, and breeding success. Identify and quantify the impacts of climate change on population size, distribution, and breeding success. Determine basic life history parameters at strategic colonies along the species's distribution, including juvenile dispersal and survival, breeding success and population size. Identify critical areas for conservation, both inland (breeding) and at sea (foraging), and monitor strategic colonies to detect changes in abundance and how colonies behave during periods of food abundance and scarcity. Determine whether the fluctuations in numbers observed during El Niño are caused by mortality, dispersion or a combination of both. Generate relevant information for industrial fishery management and policy (define catch quotas and fishery bans based on ecosystem parameters) and monitor targeted prey species. Generate a baseline of health parameters across the species's distribution. Assess whether the current Marine Protected Area (MPA) system effectively protects penguins, and establish further MPAs around strategic colonies to secure feeding grounds of penguins, at least during the breeding season. At colonies where MPAs already exist, enforcement should be coupled with management plans and measurable objectives, so that conservation practitioners can monitor the efficiency of MPAs and adapt to changes as necessary. It is urgent to reduce bycatch in gillnets along the entire distribution of the species. The industrial anchovy fishery is a threat to Humboldt Penguins, so total allowable catches should be set based on trophic and oceanographic models that include ecological parameters and a precautionary approach, reducing fishing pressure during El Niño years. Implement a sustainable guano harvest method in order to minimize disturbance at the breeding colonies and better preserve nesting habitat. Continue eradication of invasive species, particularly rats. Develop educational programmes on fish and seabird conservation for adults and children to better understand economic and conservation trades-offs with human well-being.