Meeting Abstract

29.8  Jan. 5  Intraclutch Variation in Carotenoid Concentrations in Yellow-headed Blackbird Eggs NEWBREY, J.L.**; REED, W.L.; FOSTER, S.P.; ZANDER, G.L.; North Dakota State University, Fargo; North Dakota State University, Fargo; North Dakota State University, Fargo; South Milwaukee, WI jennifer.newbrey@ndsu.edu

Asynchronous hatching creates a size hierarchy among siblings and a survival disadvantage for last-hatched nestlings. Female birds can either maintain (brood reduction strategy) or reduce this survival disadvantage (brood survival strategy) by differentially investing maternal resources, such as carotenoids, across the laying sequence. We quantified intraclutch variation in the concentrations of four carotenoids, beta-carotene, beta-cryptoxanthin, lutein, and zeaxanthin, in Yellow-headed Blackbird eggs collected from five free-living breeding colonies. We also quantified the relationship between egg metrics (i.e., egg mass, yolk mass, and yolk water content) and carotenoid allocation to eggs. Concentrations of four yolk carotenoids were significantly related to egg laying order, but there were differences in their patterns. The concentration of lutein decreased from first to last-laid eggs, supporting a brood reduction strategy, whereas the concentrations of beta-carotene, beta-cryptoxanthin, and zeaxanthin increased from first to last-laid eggs, supporting a brood survival strategy. The differences in carotenoid-concentration patterns we observed across Yellow-headed Blackbird clutches suggest that the carotenoids may compete with each other during absorption, they may be of different value to the developing embryo due to differences in antioxidant function, or they may be differentially available in the diets of females during egg production. Carotenoid concentrations were not significantly related to any of the egg metrics measured despite previous research that has found an effect of egg size on carotenoid allocation to eggs.