Written By: Cindy Gentry, Biology 487, Winter 2009
Status (IUCN v3.1)
Population estimates range from 8,000,000-15,000,000 individuals in the wild, with some evidence of population increase in recent years.
Adults have a white belly, throat and face, with a black back and black beak. Their distinguishing characteristic is a black stripe running under the chin from ear to ear. Juveniles are similar to adults, but with dark spotting over their faces. Chicks are completely grey with black beaks and pink feet.
Vocalizations: Three vocalizations have been studied in adults: ecstatic, mutual, and bowing. Ecstatic displays occur during incubation or brooding of chicks; the adult stretches upwards and flaps its wings while emitting loud, shrill repeated series of syllables. Mutual display songs occur during nest relief and are important for mate recognition; they involve a loud cackling as well as a soft humming sound. The bowing display is between members of a pair; the individuals bow towards each other while emitting a “hissing” sound.
Males tend to be heavier, have longer flippers, and deeper bills than females. Average bill depth is 1.9 cm for females, and 2.1 cm for males.
Weight: 4.0 kg
Beak: 4.9 cm
Flipper: 19.3 cm
Weight: 3.7 kg
Beak: 4.6 cm
Flipper: 18.7 cm
Breeding information taken from King George Is., South Shetland Is.
Average Arrival Date: November 02
Average Egg Laying Date: November 27
Incubation Period: 36 days (First Egg), 34 days (Second Egg), Chinstraps will not lay a third egg in a season unless the first egg is lost before the second is laid.
Chick Rearing Period: 53 days
Fledging Period: Late February to Early March
Average Annual Reproductive Success: Reproductive success can vary greatly from year to year, depending on ice conditions (extensive sea-ice can limit abilities of foraging adults.) Values recorded by Williams varied from 1.02 chicks/pair to 0.56, depending on the year.
Nest: Nests are built of small stones on high, typically snow-free slopes.
Age at First Breeding: Age at first breeding can vary from 3-7 years of age
Egg Length (First Egg): 6.7 cm
Egg Breadth (First Egg): 5.2 cm
Egg Length (Second Egg): 6.7 cm
Egg Breadth (Second Egg): 5.2 cm
Molt: Adults molt in early March, for about 13 days. Juveniles have their first complete molt at around 14 months of age.
Mainly krill (up to 96% of diet by weight) but also small fish and crustaceans.
Skuas, gulls, and Sheathbills are predators on land of eggs and chicks. Leopard Seals predate upon adults at sea.