Summary
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.
Zusammenfassung
In klaren Gewässern in Chile tauchende Humboldt-Pinguine zeigten zwei deutlich verschiedene Verhaltensweisen. Während kurzer Tauchgänge\((\bar x = 13,3 s)\) blieben die Tiere im Bereich von 1 m unter der Oberfläche. Tauchgänge durch unmittelbares Abtauchen in einem Winkel von 45° eingeleitet, führten direkt zum Meeresboden; die Vögel kehrten sofort wieder an die Oberfläche zurück. In diesem Fall war die Tauchzeit von der Wassertiefe abhängig. Pinguine, deren Magen durch Auspumpen untersucht wurde, hatten vorwiegend pelagische Schwarmfische gefressen:Scomberesox, Engraulis undSardinops. Die Mehrzahl der Fische (94 %) wurde von unten kommend erfaßt. Nach unserer Auffassung sind die kurzen und flachen Tauchgänge typisch für nicht jagende Pinguine, die längere horizontale Strecken zurücklegen. Das tiefe Abtauchen dagegen ermöglicht jagenden Pinguinen, die ein besonders gutes Fernsichtvermögen oberhalb des Schnabels besitzen, nahe der Oberfläche schwimmende Beute leichter zu erfassen. Die sonst silbrigen clupeiden Fische sind als dunkle Silhouetten gegen die Wasseroberfläche besser zu erkennen.
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Wilson, R.P., Wilson, MP., Duffy, D.C. et al. Diving behaviour and prey of the Humboldt Penguin (Spheniscus humboldti). J Ornithol 130, 75–79 (1989). https://doi.org/10.1007/BF01647164
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DOI: https://doi.org/10.1007/BF01647164