2[8]Birkhead, T.R. 1985. Variation in egg quality and composition in the Mallard Anas platyrhynchos. Ibis, 127: 467-475.
3[9]Birkhead, T.R., and Nettleship, D.N. 1984. Egg size, compositionand offspring quality in some Alcidae (Ayes: Charadriiformes). J.Zool. (1965-1984), 202: 177-194.
4[10]9.Bolton, M. 1991. Determinants of chick survival in the LesserBlack-backed Gull: relative contributions of egg size and parentalquality. J. Anim. Ecol. 60: 949-960.