Penguins for the most part breed in large colonies, the exceptions being the yellow-eyed and Fiordland species; these colonies may range in size from as few as a 100 pairs for gentoo penguins, to several hundred thousand in the case of king, macaroni and chinstrap penguins.[54] Living in colonies results in a high level of social interaction between birds, which has led to a large repertoire of visual as well as vocal displays in all penguin species.[55] Agonistic displays are those intended to confront or drive off, or alternately appease and avoid conflict with, other individuals.[55]
Penguins form monogamous pairs for a breeding season, though the rate the same pair recouples varies drastically. Most penguins lay two eggs in a clutch, although the two largest species, the emperor and the king penguins, lay only one.[56] With the exception of the emperor penguin, where the male does it all, all penguins share the incubation duties.[57] These incubation shifts can last days and even weeks as one member of the pair feeds at sea.
Penguins generally only lay one brood; the exception is the little penguin, which can raise two or three broods in a season.[58]
Penguin eggs are smaller than any other bird species when compared proportionally to the weight of the parent birds; at 52 g (2 oz), the little penguin egg is 4.7% of its mothers' weight, and the 450 g (1 lb) emperor penguin egg is 2.3%.[56] The relatively thick shell forms between 10 and 16% of the weight of a penguin egg, presumably to minimize the risk of breakage in an adverse nesting environment. The yolk, too, is large, and comprises 22–31% of the egg. Some yolk often remains when a chick is born, and is thought to help sustain the chick if the parents are delayed in returning with food.[59]
When mothers lose a chick, they sometimes attempt to "steal" another mother's chick, usually unsuccessfully as other females in the vicinity assist the defending mother in keeping her chick.[citation needed] In some species, such as emperor penguins, young penguins assemble in large groups called crèches.
Penguins for the most part breed in large colonies, the exceptions being the yellow-eyed and Fiordland species; these colonies may range in size from as few as a 100 pairs for gentoo penguins, to several hundred thousand in the case of king, macaroni and chinstrap penguins.[54] Living in colonies results in a high level of social interaction between birds, which has led to a large repertoire of visual as well as vocal displays in all penguin species.[55] Agonistic displays are those intended to confront or drive off, or alternately appease and avoid conflict with, other individuals.[55]Penguins form monogamous pairs for a breeding season, though the rate the same pair recouples varies drastically. Most penguins lay two eggs in a clutch, although the two largest species, the emperor and the king penguins, lay only one.[56] With the exception of the emperor penguin, where the male does it all, all penguins share the incubation duties.[57] These incubation shifts can last days and even weeks as one member of the pair feeds at sea.Penguins generally only lay one brood; the exception is the little penguin, which can raise two or three broods in a season.[58]Penguin eggs are smaller than any other bird species when compared proportionally to the weight of the parent birds; at 52 g (2 oz), the little penguin egg is 4.7% of its mothers' weight, and the 450 g (1 lb) emperor penguin egg is 2.3%.[56] The relatively thick shell forms between 10 and 16% of the weight of a penguin egg, presumably to minimize the risk of breakage in an adverse nesting environment. The yolk, too, is large, and comprises 22–31% of the egg. Some yolk often remains when a chick is born, and is thought to help sustain the chick if the parents are delayed in returning with food.[59]When mothers lose a chick, they sometimes attempt to "steal" another mother's chick, usually unsuccessfully as other females in the vicinity assist the defending mother in keeping her chick.[citation needed] In some species, such as emperor penguins, young penguins assemble in large groups called crèches.
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