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19 December 2015

Penguins, Predators and Prey

Magellanic Penguin (麥哲倫企鵝) ; Falkland Skua (福克蘭賊鷗)
Falkland Islands (2015)
21st August, 2015. Stanley

Magellanic penguins are opportunistic feeders, taking roughly equal proportions of fish, squid and crustaceans. During chick-rearing, foraging trips take place on a daily basis during daylight hours. Birds generally hunt at depths of less than 50m, but may dive up to 100m. One of the more common prey species is the Falkland Sprat or Fuegian Sardine Sprattus fuegensis. This a small fish about 150mm in length which breeds in spring and early summer in the coastal shelf waters around the Falkland Islands and feeds on copepods, euphausiids, mysids, pelagic amphipods, chaetognaths, eggs and fish larvae. Large numbers appear close inshore during the summer making them ideal prey for penguins. The maximum recorded age is five years. The Falkland Sprat also lives along the Patagonian coast between 43° 30'N and 55° S.

Magellanic penguins encounter a number of predators at sea such as sea lions, leopard seals and orcas. They also face predation of chicks and eggs by avian predators such as caracaras, gulls and skuas although, by nesting in burrows, such predation is greatly reduced. The Falkland Skua is amongst the fastest and most skilled of all the flying birds. Add to that power and strength, high intelligence and longevity and the penguins have a formidable foe. Skuas are quick to spot any weak or infirm “Jackasses” and often attack them in mobs. Being without the claws and hooked beaks of hawks, skuas have to rely on each other to take hold of different parts of their prey in order to tear it apart. Falkland Skuas are entirely pelagic during the southern winter and come ashore in the Falklands only between October and April. The illustration shows part of their distinctive “courtship walk”. They nest in loose colonies, often close to their prey which, in addition to Magellanic Penguins, also includes other penguins and prions. They also specialize in harrying and forcing shags to re-gorge their food in flight over the ocean.

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