SEASONAL-CHANGES IN FAT AND PROTEIN RESERVES OF THE BLACK-HEADED GULL, LARUS-RIDIBUNDUS, IN RELATION TO MIGRATION

Fat and protein content in relation to age (yearlings and adults), sex and the migratory period (autumn migration, winter and spring migration) of the black-headed gull, Larus ridibundus have been determined. The omental and subcutaneous fat depots, protein and lipid content of the pectoral muscle, and total plasma lipids were lowest at the end of the autumn migratory period and highest at the vernal migratory period. The fat depots in adults were smaller than in juvenile gulls at the end of the autumn migratory period; however, adults were much fatter in spring. Age-related differences in lipid stores in relation to age-dependent variation in subsequent breeding activity is discussed.