Magellanic penguin Biology


Common Name: Magellanic penguin

Species Name: Spheniscus magellanicus













Punta Tombo Population Trend







Descriptive Characteristics 


Adults have black backs and white fronts with two black bands across their upper chest and neck. Their faces have white crescents arching from their eyes, around their cheeks, and joining on their neck. Juveniles and chicks have one large band separating their face and their stomach. Their faces have cheek patches that range in color from white to dark grey.




Magellanic chick


Chicks go through two layers of down (hatching and cloverdown) before growing their juvenile plumage.






Penguin weights differ depending on time of the season (see weight range on the diagram below) and how long each individual has been fasting. Generally, penguins will weigh the most when beginning the molt since they have bulked up in preparation for the several weeks of fasting that accompanies the molt.

Males are generally bigger than females




Breeding Biology

The breeding biology information presented was obtained during more that 30 years of research on the Magellanic penguins of Punta Tombo (Boersma unpublished data); each Magellanic penguin colony will differ.

Average Arrival Date: Early September

Average Egg Laying Date: October 18

Incubation Period: 40 – 42 days

Chick Rearing Period: 60 – 120 days

Fledging Period: January 10 to March 05

Average Annual Reproductive Success: 0.52 chicks/nest

Nest: Burrows, Bushes, Scrapes

Age at First Breeding: 4 years

Maximum Lifespan: 30+ years

Egg Weight:  124.8 (+/- 11.1) grams

Egg Length:  7.5 (+/- 0.3) cm

Egg Breadth:  5.5 (+/- 0.2) cm

Second Egg Weight:  124.4 (+/- 10.9) grams

Second Egg Length:  7.3 (+/- 0.3) cm

Second Egg Breadth:  5.6 (+/- 0.2) cm


Magellanic Penguins undergo an annual catastrophic molt during which they are confined to land and unable to replenish fat stores. Penguins must therefore begin the process at or above an appropriate body condition.  If penguins are too thin to complete the molt-fast when they arrive they will starve before returning to sea. However, if they return in too high of a condition they can succumb to heat stress in the Patagonian desert. Juvenile penguins begin molting in January, followed by young adults beginning their molt in late February, and finally older adults in late March. It takes approximately 19 days for an individual to complete the molt.


Penguins prey upon anchovy (Engraulis anchoita), hake (Mercluccius hubbsi), Falkland sprat (Sprattus fueguenis), cod (Micromesistius australis), squid (Gonatus antarticus and Loligo gahi) and krill (Munida gregaria).


Kelp gulls, Antarctic skuas, little grison and large, hairy armadillos prey upon penguin eggs and small chicks. Red Foxes, grey foxes, pampas cat and pumas prey upon larger chicks, juveniles and adults on land. Giant petrels, South American sea lions, and orcas prey upon fledglings, juveniles and adults while at sea.

Conservation Concerns

Illegal ballast water dumping: In the 1980’s and early 1990’s approximately 20,000 adults and 22,000 juveniles died each year from oil pollution caused by illegally dumped ballast water (Gandini et al 1994). In 1997 based on data we collected showing the extent of the oil pollution problem, the provincial government of Chubut moved tanker lanes 40km farther off shore. The number of oiled penguins along the coast of Chubut dramatically decreased  but large numbers of penguins are oiled in northern Argentina, Uruguay, and southern Brazil during their winter migration.

Fisheries: We know little about how fisheries impact the penguins of Punta Tombo. If fisheries alter the productivity of the ecosystem, remove penguin prey, or take fish where penguins like to forage, penguins may move and be less successful finding prey.  Penguins are caught and killed in fishing nets. Nets, plastic and other debris can entangle penguins and kill them.

Tourism: When not managed responsibly, tourism can harm penguins because they may disrupt the penguin’s ability to return to their nests and feed their chicks, or cause stress that may result in slower growth of chicks and more exposure to predators.

Climate change: Climate change has increased the frequency of storms and rainfall. If a chick’s down becomes wet from rain its nest floods, it is at risk of dying of hypothermia. Global warming may also impact the abundance and location of penguins prey. Magellanic penguins are traveling further to find food for their chicks.

For more information on the penguins, threats, and conservation pick up a copy of Penguins: Natural History and Conservation by Dr. Pablo Garcia Borboroglu and Dr. P. Dee Boersma (University of Washington Press).

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