Diving behaviour and prey of the Humboldt Penguin (Spheniscus humboldti)

Abstract

Humboldt Penguins diving in clear water in Chile had two distinct behaviours; short dives\((\bar x = 13.3 s)\) where the birds remained within a metre of the surface and bounce dives, where the penguins descended the water column to the sea bed where they immediately returned to the surface. Here, dive time was correlated with water depth. Stomach pumped penguins had eaten predominantly pelagic school fish,Scomberesox, Engraulis andSardinops. Most prey (94 %) had been seized from below. We suggest that short, shallow dives are typical of travelling penguins. Bounce dives, however, would enable foraging penguins, which have an enhanced binocular field above the line of the bill, to perceive surface-swimming prey more easily because silvery clupeid fish appear as silhouettes.