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Journal Article

Foraging Behaviors of Surf Scoters and White-Winged Scoters during Spawning of Pacific Herring

Tyler L. Lewis, Daniel Esler and W. Sean Boyd
The Condor
Vol. 109, No. 1 (Feb., 2007), pp. 216-222
Stable URL: http://www.jstor.org/stable/4122549
Page Count: 7
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Foraging Behaviors of Surf Scoters and White-Winged Scoters during Spawning of Pacific Herring
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Abstract

Winter diets of Surf (Melanitta perspicillata) and White-winged Scoters (M. fusca) are composed primarily of bivalves. During spawning of Pacific herring (Clupea pallasi) in early spring, scoters shift their diets to herring eggs. Using radio-telemetry, we contrasted scoter foraging behaviors between winter and herring spawning periods. Scoters increased their dive durations during herring spawning, likely to maximize the amount of roe consumed per dive; in winter, dives were typically terminated upon clam capture. Scoters spent approximately 50% less time foraging ($min underwater hr^{-1}$) and decreased their dive rate (dives hr-1) by 70% when feeding on roe. The observed reduction in time spent foraging was presumably caused by the abundance of herring eggs, and thus a reduction in prey search-time. Scoters were able to meet energetic requirements with reduced effort, despite potentially increased demands related to spring fattening. Less time spent foraging may also allow more time for premigratory courtship behaviors. /// Las dietas de invierno de los patos Melanitta perspicillata y M. fusca están compuestas principalmente por bivalvos. Durante el desove del arenque del $Pac\acute{i}fico$ (Clupea pallasi) al inicio de la primavera, estas especies cambian su dieta y se alimentan de huevos de arenque. Utilizando $radio-telemetr\acute{i}a$, contrastamos los comportamientos de forrajeo entre los $per\acute{i}odos$ de invierno y de desove del arenque. Los patos incrementaron la $duraci\acute{o}n$ de sus inmersiones durante el $per\acute{i}odo$ de desove, probablemente para maximizar la cantidad de huevos consumida por $inmersi\acute{o}n$. En el invierno, las inmersiones $t\acute{i}picamente$ terminaron una vez que las aves capturaron almejas. Los patos invirtieron cerca de un 50% menos de tiempo forrajeando (minutos bajo el agua por hora) y disminuyeron su tasa de buceo (inmersiones por hora) en un 70% cuando se alimentaron de huevos. Presumiblemente, la $reducci\acute{o}n$ en el tiempo de forrajeo observada fue causada por la abundancia de huevos de arenque, la cual condujo a una $reducci\acute{o}n$ en el tiempo de $b\acute{u}squeda$ de presas. Los patos fueron capaces de suplir sus requerimientos $energ\acute{e}ticos$ con un esfuerzo reducido, a pesar de que potencialmente $exist\acute{i}an$ mayores exigencias relacionadas con el engordamiento de primavera. Invertir menos tiempo en forrajear $tambi\acute{e}n$ $podr\acute{i}a$ permitir dedicar más tiempo a comportamientos de cortejo previos a la $migraci\acute{o}n$.

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