Birds of Indian Subcontinent

Influence of Diet on Egg Size in American Coots (Fulica americana): Evidence from Food Supplementation and Biochemical Markers (Influencia de la Dieta sobre el Tamaño de los Huevos en Fulica americana: Evidencia Provista por Alimento Suplementario y por

Publication Type:Journal Article
Year of Publication:2009
Authors:Bortolotti, GR, Hobson, KA, Butt, UJ, Surai, PF
Journal:The Auk
Date Published:2009
ISBN Number:00048038
Keywords:Fulica, Fulica americana, Fulica atra, Rallidae
Abstract:Abstract Food-supplementation studies on birds during egg laying have generally manipulated macronutrients and energy. Such studies have shown variable effects on egg size in American Coots (Fulica americana). We determined the relative influences of local environment, food quantity, and food quality on egg size in American Coots by supplementing food and carotenoids at three sites in Saskatchewan. Eggs were collected and analyzed for carotenoid content and stable isotopes (δ15N and δ13C) in the yolk to determine whether variation in the type of food eaten contributes to egg size. We also report on the isotopic analysis of American Coot tissues and their eggs to assess evidence of endogenous versus exogenous protein and lipid allocations to reproduction. We provide isotopic evidence that American Coots used endogenous lipid, but not protein, reserves for egg formation and that egg size is more dependent on exogenous sources of nutrients. Laying sequence was the only variable across nesting locales that had a significant influence on the size of eggs. There was an effect of provisioning food at only one site; however, this response was driven by a component of diet quality other than carotenoids. Yolk δ13C values were positively correlated with egg volume, which further suggests the importance of diet quality in determining egg size in American Coots.
Short Title:The Auk
Scratchpads developed and conceived by (alphabetical): Ed Baker, Katherine Bouton Alice Heaton Dimitris Koureas, Laurence Livermore, Dave Roberts, Simon Rycroft, Ben Scott, Vince Smith