Penguins are birds, and therefore it makes sense that their physiology and mating habits will be similar to other birds. The short answer is no. Like 90% of all bird species, many species of penguins are serially monogamous which means that they are with one partner, but wont necessarily stay with the same partner over multiple breeding seasons.
Some species of penguins such as the Adelie Penguins shown in the video are generally monogamous and will stay with the same partner over multiple seasons. Saying that penguins "mate for life" can be misleading because when a partner dies, they will usually be replaced by another. The greatest advantage of being monogamous over multiple breeding seasons is that instead of expending time and energy trying to attract a mate, it can be put towards reproduction.
Many species of penguin make nests by starting with hollows in the ground that they fortify with rocks, mud, sticks or grass. Some penguins burrow into the ground or use caves, crevices or holes to nest. Penguins have a variety of mating rituals that vary between species. They call, bow and wave their flippers and preen one another.
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. UV light, invisible to the human eye, can be perceived by most birds. In adult penguins, UV reflection in bills is one of the cues used in mate selection. The bills of sexually mature 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 Selection and Nesting Habits
Nest site fidelity is strong in many penguin species. Studies have shown that most penguin species tend to be faithful to the same rookeries and return each year. 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 of weather or environmental changes from the previous season. When it is time to breed, mature birds return to the rookery where they hatched, resulting in large numbers of penguins at a single rookery rather than 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 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 from the edge of the sea ice on the Antarctic continent and nearby 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 rainforest 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. 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 brood patch, which transfers body heat to the eggs.
Eggs and Incubation
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. Emperor penguin eggs measure 11.1 to 12.7 cm long and weigh 345 to 515 g, while Adélie penguin eggs measure 5.5 to 8.6 cm long and weigh 61 to 153.5 g. A nest of eggs is called a clutch, and with the exception of emperor and king penguins, clutches usually contain two eggs. In the Eudyptula, Spheniscus, and Pygoscelis genera, the first-laid egg is generally larger than the second, and usually hatches first. The second, usually smaller, chick cannot compete with the larger chick for food and may perish in times of scarce resources. In the Eudyptes genus, the second-laid egg and the subsequent chick is usually the larger of the two and usually the survivor. 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. The incubation temperature is approximately 36°C, a bit lower for larger species. Emperor penguins can maintain an incubation temperature of 31°C in an environment that is -60°C. 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.
Parental Care, Hatching, and Chick Rearing
In emperor penguins, the female transfers a single egg to the top of her mate's feet, after which she goes to sea to feed while the male incubates. He fasts throughout courtship, nesting, and incubation periods, relying on fat reserves that may constitute up to 45% of his body mass. Hatching takes place after 65 to 75 days, and the male often remains with the egg for months while the female returns to feed and later relieves him. The chicks are very small at hatching, weighing about 150-200 g, with only a thin layer of down, and require about 50 days to develop temperature regulation. Both parents brood the chicks and bring food to the youngsters until they can stand on the ice by themselves. By September, the chicks have grown a thick down and are rapidly developing, necessitating both parents to collect food.
During chick rearing, there is significant colony activity, with parents coming and going, chicks calling for food, and huddling at night to stay warm. In December, chicks are nearly as big as their parents, and black patches begin to appear on their flippers as they shed down for real feathers. The number of adults in the colony declines as some go out to sea to fatten for their annual moult. The end of the cycle involves moulting, during which penguins replace all feathers; this is energetically costly, and penguins must stay out of the water to keep their new plumage dry and waterproof. The molt period can take about a month, and replacing every feather is extremely energy-intensive. By the time the new plumage grows, penguins have lost nearly half their body mass.
Special Cases and Notable Details
Some interesting behaviors include the ritual of "pebble proposals" in which males collect stones to present to females as part of courtship. In many species, the female may trigger courtship by selecting a mate, while in others the male establishes a nest site first. Emperor penguins breed on the sea-ice in winter and the males may travel far inland to reach rookeries, where eggs are kept warm on the feet under a brood patch. The timing of breeding varies by species: emperor penguins breed during the Antarctic winter, king penguins and other subantarctic species have longer cycles, and temperate penguins may nest year-round. Nesting materials range from stones to vegetation, feathers, and other available items, and some species even nest in underground burrows or guano-deposited sites.
