Pinguino di Humboldt

Identificazione

Humboldt penguins are medium-sized penguins, growing to 56–70 cm (22–28 in) long and a weight of 2.9 to 6 kg (6.4 to 13.2 lb). The sex of the Humboldt penguin cannot be recognised via differences in plumage, as they are monomorphic. The male is heavier and larger than the females. Their sex can be determined via head width and bill length; the male has a longer bill than the female. While all the Spheniscus penguins are close to each other in size, the Humboldt penguin is the heaviest species in the genus, with 123 females weighing 4.05 kg (8.9 lb) on average and 165 males averaging 4.7 kg (10 lb). Humboldt penguins have a black head with a white border that runs from behind the eye, around the black ear-coverts and chin, and joins at the throat. They have blackish-grey upperparts and whitish underparts, with a black breast-band that extends down the flanks to the thigh. They have a fleshy-pink base to the bill. Juveniles have dark heads and no breast-band. They have spines on their tongue which they use to hold their prey.<p>The Humboldt penguin has different calls that it uses to communicate in different ways. The function of its calls are consistent among Spheniscus species. If an individual comes too close to an adult Humboldt penguin, the Yell is a warning call which is followed by pecking or chasing if ignored. A higher density of penguins leads to more territorial and aggressive behaviours, which leads to more Yells. The Throb is a soft call between pairs at the nest, used by incubating birds when their mates return to the nest. The Haw is a short call given by juveniles alone in the water and by paired birds when one is on the water and the other is on land. It has significant individual variation in duration and frequency. The Bray is a long call used to attract a mate and advertise a territory during the pre-laying and pre-hatching periods. It is an individually distinct call in all variables: syllables per call, duration, inter-syllable intervals, duration of syllables and frequency. When calling, the bird points its head upwards and flaps its flippers slowly. The Courtship Bray is similar to the Bray, however a different posture is assumed and is given synchronously by pairs during the pre-laying period: the birds stand together pointing their necks and head up, with flippers out to the side. The Peep is given by chicks begging for food.<p>Most penguins moult between mid-January and mid-February, however the initiation varies with latitude and favourable conditions such as food abundance. Humboldt penguins are confined to land until they finish moulting. They become hyperphagic during the pre-moulting period. The feathers are lost and replaced within 2 weeks.

Tassonomia

Nome scientifico

Spheniscus humboldti

Autorità

Meyen, 1834

Ordine

Sfenisciformi

Famiglia

Spheniscidae

Genere

Spheniscus

Areale e habitat

The Humboldt penguin is a top predator endemic to the west coast of South America.<p>The Humboldt penguin's breeding distribution ranges from southern Chile along the dry and arid coastal regions of the Atacama Desert to subtropical Isla Foca in north Peru. Its range is restricted to the coast and offshore islands affected by the Humboldt current, which provides a continuous supply of nutrients and food, thus supporting huge populations of seabird. In Chile, the most important breeding colony is at Isla Chañaral.

Migrazione

Complete migrants

Comportamento

The Humboldt penguin feeds predominantly on pelagic schooling fish. The consumption of cephalopods and crustaceans vary between populations. Northern colonies consume primarily Atlantic saury and garfish, whilst southern populations primarily consume anchovy, Araucanian herring, silver-side, pilchard and squid. There are seasonal differences in the Humboldt penguin's diet that reflect the changes in availability of fish species across seasons.<p>The Humboldt penguin is a visual hunter. Humboldt penguins leave their islands for foraging after sunrise and different populations have different preferred foraging distances from the colony. Their foraging rhythm depends on the light intensity. They spend more time foraging during overnight trips. Fish are mostly seized from below through short, shallow dives.<p>The foraging range of Humboldt penguins is between 2 and 92 km (1.2 and 57.2 mi) from Pan de Azúcar, with 90% of the foraging being from a range of 35 km (22 mi) around the island and 50% from a range of 5 km (3.1 mi). The maximum depth reached is 54 m (177 ft).<p>Failed breeders take longer foraging trips with longer and deeper dives. They also dive less often than breeding penguins.<p>During courtship, the Humboldt penguins bow their heads to each other and exchange mutual glances with each eye, alternatively. In the ecstatic display to attract a partner, the bird extends its head vertically, collapses its chest, flaps its wings and emits a loud call resembling the braying of a donkey. The mutual displaying consist of the pair standing side by side and repeating the actions of the ecstatic display.<p>The Humboldt penguin nests in loose colonies, with most pairs laying two eggs of the same size 4 days apart that require 41 days of incubation. Their breeding schedule is adjusted depending on the abundance of food. They breed immediately after moulting, when food is abundant and solar radiation is reduced.<p>The Humboldt penguin lay eggs from March to December, but also with peaks in April and August–September, due to individuals having a second clutch. Half of the females successfully have two clutches per year and most were double broods. If pairs lose their eggs during the first breeding season, they lay a new clutch within 1–4 months. The incubation shifts last, on average, 2.5 days, before one parent takes over and allows the other to forage. There are no differences in the contribution to provisioning from the male and female parents.<p>Chicks hatch generally 2 days apart. Chicks are semi-altricial and nidicolous and guarded by one parent while the other forages. Chicks are fed only once every day. Chicks are left unattended at the nest site after a certain age and both parents forage simultaneously.<p>The historical breeding sites of this species are burrows on guano layers. Nests of the Humboldt penguin can also be found at caverns, hollows, cliff tops, beaches and scrapes covered by vegetation. They also nest at few Peruvian islands where true soil can be found for digging. The majority of penguins breed on cliff tops.<p>Humboldt penguins are sedentary during the breeding season, staying in proximity to their nests and show fidelity to breeding site. They can cover large distances, particularly in response to food shortages or changes in environmental conditions. They are a true migrant between Peru and Chile.

Conservazione

Humboldt penguins were given legal protection in 1977 by the Peruvian Government and listed in Appendix I of the Convention of International Trade of Endangered Species (CITES). Both Peru and Chile have implemented the CITES under national law. It is categorised as vulnerable due to extreme population size fluctuations, clustered distribution and the major threats to the species not being ameliorated over time. In August 2010 the Humboldt penguin of Chile and Peru, was granted protection under the U.S. Endangered Species Act. Most penguins breed within protected areas.<p>Peruvian legislation categorises the species as endangered and prohibits the hunting, possession, capture, transportation and export of the bird for commercial purposes. Chile implemented a 30-year hunting ban in 1995 forbidding hunting, transport, possession and commercialisation of penguins.<p>In 2017 a large mining project proposed by the company Andes Iron in Chile was vetoed due to the possible environmental impact on the penguins, though that decision was subsequently overturned.<p>As of August 2018, the species is listed as Vulnerable on the IUCN Red List, noting a declining population of 32,000 mature adults. Climate change, commercial overfishing of main prey species (sardines and anchovy) and bycatch in commercial and artisanal fisheries are all contributing factors in the species' decline. Rats, feral cats and dog attacks threaten some colonies. Historically, the Humboldt penguin population was impacted by the extraction of guano from their breeding colonies, which reduced the available habitat for burrowing and nesting.

Tendenza della popolazione

declining