Reproduction

Sexual Maturity

Like most seabirds, penguins tend to be long-lived. They may take three to eight years to reach sexual maturity.

With some of the smaller species, breeding may begin at three to four years, but most larger species are not accomplished breeders until much later. On average, breeding does not begin until the fifth year, and a few males do not breed until the eighth year.

Mating Activity

Breeding seasons differ from species to species.

• Most species have an annual breeding season - spring through summer.
• The king penguin has the longest breeding cycle of all the penguin species, lasting 14 to 16 months. A female king penguin may produce a chick during alternate breeding seasons.
• Emperor penguins breed annually during the antarctic winter, June through August.
  • During the emperor breeding season, air temperature may drop to -60°C (-76°F) and winds may reach speeds up to 200 kph (124 mph.)
  • For most of the winter, antarctic penguins live in an environment of darkness or half-light. Why emperors breed during the harshest season of the year is unknown, but some scientists speculate that when the chicks become independent five months later (in January and February, the antarctic summer), environmental conditions are more favorable for the young birds.

• The little penguin breeds throughout the year and has the shortest breeding cycle, which lasts about 50 days.

• Some of the temperate penguins, like the Humboldt and the African, tend to nest throughout the year.

Courtship.

Courtship varies among species. It generally begins with both visual and auditory displays. In many species, males display first to establish a nest site and then to attract a mate. Not all species exhibit all displays, but in general there are 3 distinct types of displays.

• Ecstatic. Also called trumpeting, head swinging or advertisement, this display establishes possession of a nest site, attracts females and warns other males to stay away. Males at the nest site commonly exhibit the ecstatic display before females arrive or when building nests. The male may dip its head low and then stretch its head
  and neck upward with flippers held outstretched and squawk or “bray”. Male penguins can perform the ecstatic display in a sitting or standing position. Some species, like the Adélie, chinstrap and crested penguins, may swing their head or flap their flippers while calling.
• Mutual ecstatic. Once paired, male and female penguins perform the mutual ecstatic display together. This display seems to strengthen the pair bond, coordinate nesting behavior, and advertise a nesting territory. The mutual display is similar to the ecstatic display—head and neck stretched upward with a braying vocal.
  • Crested, brush-tailed, and temperate penguins, stand facing each other, performing the action in unison. Within these species there are some behavior differences. For example, gentoos generally hold their outstretched head and flippers still, while macaronis flap flippers and roll their heads from side to side.
  • Emperor penguins have a unique mutual display position: Standing face-to-face, individuals hold their heads down with bills pointed to the ground while braying. Mutual displays continue throughout the breeding season, often taking place at the nest when parents switch places for egg incubation and chick feeding.

 

 

• Bowing. Bowing displays may lessen the likelihood of aggression and strengthen recognition between partners. One or both of the penguins dips its head and points its bill at the nest or at the other bird’s bill. The call is a low hiss or growl.
• Crested penguins may vibrate their bills while pointing in a type of display called “quivering.”

 

 

• Emperor and king penguins are the only known marine birds to reflect ultraviolet (UV) light from their bills, and a male king penguin's bill may be used as a cue in finding and selecting a mate.
  • UV light, invisible to the human eye, can be perceived by most birds. UV reflection off the feathers of studied songbirds has been a recognized factor for mate selection.
  • During courtship, king penguin males come face-to-face and flaunt their bills to possible mates. The strong contrast of the black background of their bills is believed to augment UV light reflection.
  • The bills of sexually immature king juveniles do not reflect UV light, adding to the hypothesis that UV reflection in adult males is used to attract mates.

 

The strong contrasting black background of this king penguin's bill is believed to augment UV light reflection.

 

Most penguin species are monogamous (one male breeds with one female during a mating season); however, research has shown that some females may have one to three partners in one season and some males may have one or two partners.

Mate selection is up to the female, and it is the females that compete for the males.

In some penguin species, a female selects the same male from the preceding season to mate with. Adélie penguins have been documented re-pairing with the previous year's mate 62% of the time. Chinstraps re-paired in 82% of possible cases, and gentoos re-paired 90% of the time. In one study of Adélies, females paired with males within minutes of arriving at the colony.

When a female selects a different mate it is usually because her mate from the previous season fails to return to the nesting area. Another reason may be mistiming in returning to the nesting area. If they arrive at different times and miss each other, one or both penguins may obtain new mates.

Eudyptes penguins are closely related and some in this genus are known to crossbreed with different Eudyptes members. Rockhoppers are known to interbreed with macaroni, royal, and erect-crested penguins, for example, with matings producing hybrid offspring that in some cases have successfully reproduced as well.

 

 

Nesting

Nest site fidelity.

• Studies have shown that most penguin species tend to be faithful to the same rookeries and return each year. Most penguins return to the same territory within the rookery. Male Adélie penguins were 99% faithful to the previous year’s territory, chinstraps were 94% faithful and gentoos 63% faithful.
• Rockhoppers appear to have an amazingly precise breeding timetable, with males returning to the spot of their former nest virtually on the same day each year, Regardless if weather or environmental factors have changed from the previous breeding season.
• Males arrive first to the rookeries to establish and defend their nesting sites.
  • In a study on Adélie and chinstrap penguins, females arrived one day and five days after the males, respectively.
• When it is time to breed, mature birds return to the rookery where they hatched. This results in large numbers of penguins at a single rookery rather than penguins colonizing new areas. Some penguin rookeries number millions of birds.
• When it is time to breed, mature birds return to the rookery where they hatched. This results in large numbers of penguins at a single rookery rather than penguins colonizing new areas. Some penguin rookeries number millions of birds.
• Various penguin species may share a particular rookery site. It is not uncommon to find gentoos nesting near Adélie and chinstrap penguins for example, but nesting areas within the rookery are kept segregated by each species.

 

Cape Adare is home to the largest single colony of Adélie penguins with an estimated population of 282,000 breeding pairs.

 

Gentoo penguins nest inland or on coastal peninsulas and islands.

 

 Nesting habitats vary among species.

• Emperor penguins form colonies around the shoreline of the antarctic continent and adjacent islands. They prefer sites on a fairly level surface of ice in areas sheltered from wind, with easy access to feeding areas.
• King penguins nest and breed on subantarctic and antarctic islands. They prefer beaches and valleys of level ground or gentle slopes, free of snow and ice and accessible to the sea.
• Adélies often nest 50 to 60 km (31.1 to 37.3 mi.) from the edge of the sea ice on the antarctic continent and nearby on rocky islands, peninsulas, beaches, hillsides, valleys, and other areas free of ice.
• Gentoo penguin colonies can be inland or coastal on antarctic and subantarctic islands and peninsulas. They tend to breed on ice-free ground on beaches, in valleys, on inland hills and on cliff tops.
• Chinstrap penguins nest on fairly steep slopes.

 

The South Sandwich Islands have the largest population of nesting chinstraps with an estimated 5 million pairs.

 

Temperate penguins nest in underground burrows.

 

• Fiordland crested penguins nest in a wet, coastal rain forest habitat, under bushes, between tree roots and in holes.
• Galápagos penguins nest in volcanic caves or cracks in rock.
• The temperate penguins and the little penguin often nest underground in burrows, rock crevices, caves, under shrubs or in scrapes in the ground. These species breed in areas where the climate can range from tropical to subantarctic. Underground or other sheltered burrows provide an environment with a relatively constant air temperature for the eggs and chicks.
• Some Humboldt penguins burrow and create nesting sites in guano (fecal) deposits.

 Nesting materials vary from species to species and from location to location.

• Adelies build nests of small stones that they use to line depressions in the ground. Some chinstrap and gentoos also construct nests out of stones. The stones help keep the eggs above the surface when the rookery floods from melting snow. Adélie, gentoo, and chinstrap penguins are known to take stones from other nests. A penguin returning to the nest sometimes brings its mate a stone as a courtship gesture.
• Chinstrap penguins usually construct nests with perimeters of eight to ten stones, just enough to prevent eggs from rolling away.
• Gentoo penguins use nesting materials ranging from pebbles and molted feathers in Antarctica to vegetation on subantarctic islands. One medium-sized gentoo nest was composed of 1,700 pebbles and 70 molted tail feathers.
• Emperor and king penguins build no nests. They stand upright while incubating a single egg on the tops of their feet under a loose fold of abdominal. Under this loose fold is a featherless patch of skin called a brood patch, which occurs in all incubating birds. The brood patch contains numerous blood vessels that, when engorged with blood, transfer body heat to the eggs.

 

 

 

Eggs

Eggs may be white to bluish or greenish. The shape varies among species. In Humboldt and Adélie penguins the egg is more or less round. In emperor and king penguins the egg is rather pear-shaped, with one end tapering almost to a point. With this elliptical shape, if an egg falls off of the feet of a parent bird, the egg will roll in a circle instead of away from the parent. 

Egg size and weight varies with species. From the records of SeaWorld's successful penguin breeding programs, emperor penguin eggs measure 11.1 to 12.7 cm (4.4 to 5 in.) long and weigh 345 to 515 g (12.1 to 18 oz.), and Adélie penguin eggs measure 5.5 to 8.6 cm (2.2 to 3.4 in.) long and weigh 61 to 153.5 g (2.1 to 5.4 oz.).

A nest of eggs is called a clutch, and with the exception of emperor and king penguins, clutches usually contain two eggs. (Emperor and king penguins lay a single egg.) A clutch with more than one egg presents a better chance of at least one chick surviving.

• In the Eudyptula, Spheniscus, and Pygoscelis genera, the first-laid egg is generally larger than the second, and usually hatches first (except in the chinstrap species.) Usually the first chick to hatch has the survival advantage since it will already have fed and will be larger by the time the second egg hatches. The second, usually smaller, chick cannot compete with the larger chick for food and may perish in times of scarce food resources.
• In the Eudyptes genus, the second-laid egg and the subsequent chick is usually the larger of the two and usually the survivor. It typically hatches first or at the same time as the chick from the first-laid egg. The first-laid egg is often kicked out of the nest by the adults prior to hatching time.
• The chinstrap and yellow-eyed species usually lay two eggs. Parents typically raise both chicks, which are nearly equal in size.

 

Penguin eggs from left to right: gentoo, king, and emperor.

Incubation

Incubation is the time spent warming the egg before it hatches. With the exception of emperor penguins, partners take turns incubating eggs, allowing each mate to leave to feed for several days at a time.

A female emperor penguin transfers a single egg to the top of her mate's feet. The female goes to sea to feed while the male incubates the egg. She returns several weeks later, usually just before the egg is ready to hatch, to relieve her mate so that he may feed. The male fasts throughout the courtship, nesting, and incubation periods. He lives off reserves of body fat which may be 3 to 4 cm (1.2-1.6 in.) thick, and loses up to 45% of his body weight.

The incubation period varies with species. It may be as short as one month, as in the erect-crested penguins, or as long as 62 to 66 days for emperor penguins.

The incubation temperature for penguins is approximately 36°C (96.5°F); it is a bit lower for the larger species. Emperor penguins can maintain an incubation temperature of 31°C (87.8°F) in an environment that is -60°C (-76°F.)

The greatest single cause for reproductive failure in some species is the mistiming between parents for nest relief during incubation. This usually occurs when the female fails to return from a foraging trip before the male deserts the nest. A male will spontaneously leave the nest and eggs when the motivation to feed overcomes that for incubating eggs.