Nutritional Condition and Muscular Features of Wintering Long-Billed Murrelets in Japan

Abstract

Abstract We analyzed the nutritional condition and morphological characteristics of wintering Long-billed Murrelets (Brachyramphus perdix) in Japan. These birds were well nourished with an average body mass of 293 g, composed of a mean total body fat of 40.7 g (14%). The fat deposit was equivalent to an average energy reserve of 2.5 days at the estimated energy consumption of 615 kJ day−1 or 2.1 kJ g−1 day−1. Muscle mass consisted mainly of water (73%) and fat-free dry matter (26%), with small amounts of fat. Uropygial glands consisted of 33% fat and 17% fat-free dry matter, with 48% water. Long-billed Murrelets were characterized by large pectoral (26% of fat-free body mass) and small leg muscles (2% of fat-free body mass). We believe that these muscular traits, which contrast with those of alcids breeding at coastal colonies, reflect specific adaptations to inland nesting and long-distance foraging. Condicion Nutricional y Caracteristicas Musculares durante el Periodo de Invernada de Brachyramphus perdi...