title: Effects of egg size on Double-crested Cormorant (Phalacrocorax auritus) egg composition and hatchling phenotype.
abstract: Maternal investment of yolk and albumen in avian eggs varies with egg mass and contributes to variation in hatchling mass. Here we use the natural variation in mass and composition of Double-crested Cormorant (Phalacrocorax auritus) eggs to examine consequences of variation in yolk and albumen mass on hatchling phenotype. The Double-crested Cormorant, a large bird with altricial young, lays eggs ranging in mass from 40 to 60 g and containing an average of 82% albumen and 18% yolk. Variation in Cormorant egg mass arises primarily from variation in the amount of albumen and water in the eggs; yolk mass remains relatively constant, contributing only 10% to egg mass variation. Likewise, variation in hatchling mass correlates positively with albumen mass and albumen solids contribute to hatchling dry mass. Thus, variation in Cormorant egg mass is primarily the result of variation in the amount of egg albumen, which contributes most to variation in hatchling mass. Similarities in egg composition of altricial birds, along with data presented here, suggest that variation in hatchling mass of all altricial birds may depend most on the amount of egg albumen, unlike species with precocial young that hatch from eggs with substantially more yolk.
authors.affiliation: Department of Biological Sciences, University of North Texas, Denton, TX 76203, USA. edzial@unt.edu
authors.forename: Edward M
authors.initials: EM
authors.lastname: Dzialowski
authors.forename: Wendy L
authors.initials: WL
authors.lastname: Reed
authors.forename: Paul R
authors.initials: PR
authors.lastname: Sotherland
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D001717:Birds / Q000196:embryology / Q000378:metabolism*; D001724:Birth Weight; D004530:Egg Yolk / Q000378:metabolism*; D004625:Embryo, Nonmammalian / Q000378:metabolism; D004734:Energy Metabolism; D005260:Female; D039382:Maternal Nutritional Physiological Phenomena; D010047:Ovalbumin / Q000378:metabolism*; D052287:Oviparity; D010058:Oviposition; D010101:Oxygen Consumption; D010641:Phenotype
chemical_list: D010047:Ovalbumin