- 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.
- 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 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 three distinct types of displays.
These gentoo penguins enact the "bowing" display. This behavior
appears to strengthen the bond between breeding pairs.
- 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.
- 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.
- Nest site fidelity.
- Studies have shown that individuals of most penguin species return each year to the same rookeries. In addition, most penguins return to the same nesting site within the rookery. Studies have indicated that fidelity to the previous year's nest site was 99% for male Adélie penguins, 94% for chinstraps, and 63% for gentoos.
- 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.
- 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.
- Nesting habitats vary among species.
- Emperor penguins form colonies on the Antarctic continent. They prefer sites on a fairly level surface of land-fast sea ice sheets in areas sheltered from wind, with easy access to feeding areas. Rookeries must be far enough inland that the ice does not melt under them prior to the chicks being ready to go to sea.
- 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 (31.1-37.3 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.
Cape Adare is home to the largest single colony of Adélie penguins
with an estimated population of 282,000 breeding pairs.
- 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.
Gentoo penguins nest in-land or on coastal peninsulas and islands.
- Chinstrap penguins nest on fairly steep slopes.
The South Sandwich Islands have the largest population of nesting
chinstraps with an estimated 5 million pairs.
- Fiordland crested penguins nest in a wet, coastal rain forest habitat, under bushes, between tree roots, in holes, or on rocky coasts among rocks or in caves.
- 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.
Temperate penguins nest in underground burrows.
- Some Humboldt penguins burrow and create nesting sites in guano (fecal) deposits.
- Nesting materials vary from species to species and from location to location.
- Adélies 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.
Male and female Adélie penguins build their nests
out of pebbles, bones, and moss.
- 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.
This gentoo penguin has constructed its nest out of pebbles.
The eggs of emperor penguins are incubated on the tops of
their feet and under their abdominal brood patch.
- 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 (4.4-5 in.) long and weigh 345 to 515 g (12.1-18 oz.), and Adélie penguin eggs measure 5.5 to 8.6 cm (2.2-3.4 in.) long and weigh 61 to 153.5 g (2.1-5.4 oz.).
A sample of penguin eggs. Clockwise from top center: king, emperor,
Magellanic, Adélie, and gentoo. King and emperor penguins incubate
eggs on the topes of their feet. The elliptical shape fits snugly.
In addition, if the egg happens to fall off, it will roll in a circle instead of
a straight line away from the parent bird.
- 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.
- 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.