Chick development in free-living great tits Parus major in relation to calcium availability and egg composition.
Evidence from a number of avian studies suggests that limitation of exogenous calcium (Ca) may reduce egg quality and retard nestling growth. However, it is poorly understood whether reduction in chick growth in Ca-poor areas is due to insufficient intake of dietary Ca or caused by maternal Ca limitation mediated through subtle changes in composition of eggs. In this study, we provide new evidence that Ca availability during egg formation may indeed affect egg composition and influence chick development of the great tit Parus major at early developmental stages. Ca-supplemented birds breeding in base-poor pine forests produced eggs with elevated yolk Ca concentration compared with controls, while no such effect of supplementation was detected in case of eggshell thickness. Nestling tarsus length in the first half of the nestling period was positively influenced by both yolk dry mass and yolk Ca concentration. The effect of supplementary Ca did not persist throughout the nestling period; initial effects of egg components disappeared as nestlings aged. We conclude that apparently normal eggs may harbor poor nutrient and mineral conditions for chick growth. Such subtle changes in composition of eggs can depress chick growth, especially in harsh years.
Tilgar
Vallo
V
Institute of Zoology and Hydrobiology, Centre of Basic and Applied Ecology, Tartu University, Vanemuise 46, 51014 Tartu, Estonia. wallo@ut.ee
Mand
Raivo
R
Kilgas
Priit
P
Reynolds
S James
SJ
D000704:Analysis of Variance; D000818:Animals; D001682:Biological Availability; D001837:Body Weights and Measures; D002118:Calcium / Q000493:pharmacokinetics* / Q000494:pharmacology; D004957:Estonia; D048788:Growth and Development / Q000187:drug effects*; D016014:Linear Models; D010063:Ovum / Q000378:metabolism*; D046109:Passeriformes / Q000254:growth & development* / Q000378:metabolism
D002118:Calcium