The separate effects of egg size and parental quality on the development of ornamental plumage coloration

Abstract

The fitness‐related consequences of egg size, independent of the influences of parental quality, are poorly understood in altricial birds. Not only can egg size and parental quality influence growth and survival, but each could influence the development of condition‐dependent plumage coloration in offspring. The Eastern Bluebird Sialia sialis is an altricial, multi‐brooded, cavity‐nesting passerine in which juveniles display dichromatic UV‐blue plumage. Previous research suggests that plumage coloration acts as a signal of individual quality among juvenile and adult Eastern Bluebirds. Here, we separate the effects of egg size and parental quality (defined by egg size laid) on nestling growth and plumage ornamentation by exchanging clutches of large eggs with clutches of small eggs. Nestlings were significantly larger immediately post‐hatching when hatched from a large egg, but to maintain a larger size, nestlings needed to have hatched from a large egg and to have been reared by high‐quality parents. Nestlings were brighter when reared by high‐quality parents and this relationship was strongest later in the breeding season. Nestlings exhibited greater UV chroma if hatched early in the season, but UV chroma was not significantly affected by egg size or parental quality. These findings demonstrate varying influences of both egg size and parental quality on offspring growth and plumage ornamentation but suggest that quality of post‐hatching investment is more influential than pre‐hatching investment.

Effects of parental and nest-site characteristics on nestling quality in the Tree Swallow (Tachycineta bicolor)

“…García-Navas and José Sanz 2011; Jacquin et al 2012;Robinson et al 2014). Parental quality also affects fitness traits, such as nestling survival (Voltura et al 2002;Sasvari et al 2004).…”

The ecological consequences of solitary breeding in a species with bi-parental care

“…We do not know whether uni-parental broods were caused by a predation or a desertion. However, the lack of differences in egg masses and brood sizes between uni-parental and bi-parental nests indicates similar condition of adults, as above features have the potential to re-flect quality of parent birds (Slagsvold & Lifjeld 1990, Rish & Rohwer 2000, Silva et al 2007, Robinson et al 2014. It should also be noted that we did not control for the prey size delivered by single parents and pairs.…”