THE EFFECT OF DIETARY AMINO-ACID-COMPOSITION ON EGG-PRODUCTION IN BLUE TITS

Most studies on the interaction between food supply and reproduction i n animals have assumed that energy is likely to be the factor limiting egg number and/or size. In this paper, we investigate whether dietary protein proximately constrains egg production in birds. We provisione d breeding blue tits with two food supplements that differed only in t he concentration of five essential amino acids. Birds receiving a supp lementary diet containing an amino acid balance close to that required for egg protein formation laid significantly larger clutches (18% gre ater) than control birds, whereas birds receiving an otherwise identic al supplementary diet but without a favourable amino acid balance did not increase egg production. To our knowledge, this is the first demon stration that dietary amino acid composition may limit egg production in free-living birds.