Laying‐sequence variation in yolk carotenoids and egg characteristics in the red‐winged blackbird Agelaius phoeniceus

Abstract

In many bird species with asynchronous hatching, smaller, later‐hatched nestlings are out‐competed for food by their larger, earlier‐hatched siblings and therefore suffer increased mortality via starvation. It is thought that female birds can either maintain or reduce the survival disadvantage of later‐hatched nestlings by differentially allocating maternal resources across the eggs of a clutch. Carotenoid pigments are an example of resources that female birds allocate differentially when producing a clutch, but laying sequence patterns for these pigments remain poorly studied in North American songbirds. We examined intraclutch variation in yolk carotenoids and egg metrics in 27 full clutches of red‐winged blackbird Agelaius phoeniceus eggs collected from eight wetlands in central Alberta, Canada. We predicted that carotenoids would decrease across the laying sequence, as in this species, later‐hatched, marginal nestlings suffer greater mortality than earlier‐hatched, core nestlings. We found nine carotenoid pigments in red‐winged blackbird egg yolks, including two that have never been described from avian yolks: α‐doradexanthin and adonirubin. As predicted, concentrations and amounts of most carotenoids decreased across the laying sequence, suggesting that female red‐winged blackbirds depleted their carotenoid resources as they laid more eggs. However, egg mass and yolk mass both increased across the laying sequence, suggesting that female red‐winged blackbirds may use other maternal resources to compensate for the size and survival disadvantage experienced by later‐hatched, marginal nestlings.

Dietary antioxidants and flight exercise in female birds affect allocation of nutrients to eggs: how carry-over effects work

“…E concentrations decreased with laying order, as has been found in many other studies with captive zebra finches (Royle et al, 2003;Williamson et al, 2006), wild passerines (barn swallow, Hirundo rustica: Saino et al, 2002; red-winged blackbird Agelaius phoeniceus: Newbrey et al, 2015) and non-passerines (gulls: Royle et al, 2001). We found, however, that exercise and diet supplementation affected the rate of decrease in egg antioxidants with laying order; that is, the treatments affected the relative amount of antioxidants that females deposited into each consecutive egg.…”

Trade-offs in the early development of tree swallows (Tachycineta bicolor): offspring characteristics, offspring quality, and parental care

“…Within clutches of tree swallows in my study, egg mass increased with laying order, which is in agreement with many previous studies of tree swallows (Zach 1982;Wiggins 1990;Ardia et al 2006;Bitton et al 2006; but see Whittingham et al 2007) and some other altricial species (Howe 1976;Ojanen 1983;Mead & Morton 1985;Hillstrom 1999;Saino et al 2004;Rosivall et al 2005;Liljesthrom et al 2012;Newbrey et al 2015). Like egg mass, yolk mass also increased with order of laying within clutches, as observed in previous studies of tree swallows (Ardia et al 2006), white-rumped swallows (Tachycineta leucorrhoa; Barrionuevo et al 2014), and red-winged blackbirds (Agelaius phoeniceus; Newbrey et al 2015), but in contrast to Chilean swallows (Tachycineta meyeni) for which size of yolk did not vary with laying order (Liljesthrom et al 2012).…”

“…Like egg mass, yolk mass also increased with order of laying within clutches, as observed in previous studies of tree swallows (Ardia et al 2006), white-rumped swallows (Tachycineta leucorrhoa; Barrionuevo et al 2014), and red-winged blackbirds (Agelaius phoeniceus; Newbrey et al 2015), but in contrast to Chilean swallows (Tachycineta meyeni) for which size of yolk did not vary with laying order (Liljesthrom et al 2012). Since both egg mass and yolk mass increased with laying order in my study, it appears that nestlings hatching from later-laid eggs could benefit from both increased albumen proteins and increased yolk lipids.…”

“…Two related potential qualityindicating traits are egg mass and yolk mass. Both egg and yolk mass have been reported to increase with laying order (Zach 1982;Wiggins 1990;Ardia et al 2006;Bitton et al 2006;Newbrey et al 2015; but see Whittingham et al 2007), which indicates that female birds may allocate more egg components, such as albumen proteins and minerals and/or yolk lipids and carotenoids, to eggs they lay later in the laying order (Ardia et al 2006;Ferrari et al 2006; but see Newbrey et al 2015). One would expect that nestlings hatching from larger eggs laid later in the laying sequence would benefit from these extra resources and show improved performance, but experimental findings do not always support this expectation.…”

Hatching asynchrony aggravates inbreeding depression in a songbird (Serinus canaria): An inbreeding-environment interaction

“…Avian females often allocate less resources to later laid eggs, in terms of quality (e.g., antioxidants such as carotenoids and vitamin E; Royle et al ; Blount et al ; Newbrey et al ), and quantity (size/weight; Williams ; Royle et al ; Nager et al ; Blount et al ). Inbreeding may have caused these chicks to be more susceptible to adverse prenatal conditions compared to those of outbred origin.…”