Typescript. Includes vita and abstract. Bibliography: Includes bibliographical references (leaves 95-99). Description: xii, 99 leaves : ill. ; 29 cm. / Blood oxygen carrying capacity, myoglobin levels and LDH isozyme compositions in the heart, gastrocnemius and pectoralis muscles were determined in Common Murre adults and during maturation of the chick at sea. Oxygen stores in the chick (hemoglobin, hematocrit, muscle myoglobin) increased significantly with growth. High levels of the aerobic isozyme, LDH 1, were maintained throughout maturation in the heart. All five LDH isozymes were maintained at similar levels in the gastrocnemius muscle. The pectoralis showed an increase in LDH 1, 2, 3, and 4, yet retained relatively high levels of LDH 5 throughout maturation. Upon leaving the nesting colony, metabolic capacities in the heart and gastrocnemius of the chick are similar to those of adults. The chick pectoralis tissue, however, gains aerobic capacities with maturation which is concomitant with the needed capacity for aerial and aquatic flight upon fledging.