Why parent birds play favourites

Forbes, Scott; Thornton, Suzanne; Glassey, Barb; Forbes, M.A.; Buckley, Neil J.

doi:10.1038/37025

Cited by 107 publications

(82 citation statements)

References 3 publications

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“…I divide the brood into core and marginal elements [17,18] based upon the hatching pattern of individual offspring. All nest-mates hatching on the first day of the nestling period are core offspring; nestlings hatching one or more days later are marginal offspring (see [16] for detailed methods of classifying core versus marginal progeny).…”

Section: Methodsmentioning

confidence: 99%

Social rank governs the effective environment of siblings

Forbes

2010

Biol. Lett.

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Siblings within the same family often differ dramatically in phenotype. Some differences are attributable to initial maternal handicaps (birth or hatching asynchrony, differences in egg or neonate size and hormonal or antioxidant titre); but differences among siblings may also arise from differences in the brood-rearing environment that offspring experience. Here, I use a model system-a long-term study of nestlings in an altricial bird-to study how an initial maternal handicap, hatching asynchrony, regulates the effective social environment of siblings in the same family as measured by offspring survival. The interaction of family size and structure generated wide differences in the effective environments of siblings living in the same physical space (a nest), and reared by the same parents, in the same family structure. Social rank was the key component of the unshared environment of contemporary siblings, and was alone sufficient to generate near-maximal differences in offspring performance. Nestlings sitting side-by-side effectively lived in different worlds.

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Section: Methodsmentioning

confidence: 99%

Social rank governs the effective environment of siblings

Forbes

2010

Biol. Lett.

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“…The inevitable victory of the core chick is fixed in advance by the mother via an insurmountable size advantage caused by extreme hatching asynchrony (Forbes and Mock 2000). Insurance value for marginal young has also been documented for a wide range of facultative brood reducers, including raptors, parrots, and passerines (Wiebe 1996;Forbes et al 1997). Evolutionary models demonstrate that producing insurance offspring benefits species with large clutches (Forbes 1990), which have a higher cumulative probability of failure of a core offspring.…”

Section: Introductionmentioning

confidence: 99%

Within-Clutch Variation in Yolk Testosterone as an Adaptive Maternal Effect to Modulate Avian Sibling Competition: Evidence from a Comparative Study

Müller

Groothuis

2013

The American Naturalist

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Dryad data: http://dx.doi.org/10.5061/dryad.b87j7.abstract: In many species, embryos are exposed to maternal hormones in utero, in the egg, or in the seed. In birds, mothers deposit substantial testosterone into their eggs, which enhances competitive ability of offspring. These maternal testosterone concentrations vary systematically within clutches in different patterns and may enable mothers to adaptively fine-tune competitive hierarchies within broods. We performed a comparative analysis to investigate this hypothesis using a broad set of avian species. We expected species with small size differences among siblings (arising from small hatching asynchrony or slow growth rates) to aim for survival of the whole brood in good years and therefore compensate last-hatching eggs with relatively more testosterone. We expected species with large size differences among siblings (large hatching asynchrony or fast growth rates) to produce surplus young as insurance against failed offspring and to facilitate elimination of redundant surplus young by bestowing last-hatching eggs with relatively less testosterone. As predicted, we found that maternal testosterone compensation to last-hatching eggs is stronger when size differences among siblings become smaller. Maternal testosterone compensation to last-hatching eggs also correlated negatively with hatching asynchrony and growth rates. These findings provide evidence for correlated evolution of several maternal effects that together support different maternal reproductive strategies.

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“…Nestling blackbirds engage in non-aggressive begging competitions for parentally delivered food and older, stronger nestlings are more successful than their younger nestmates by virtue of their ability to stretch their necks higher, and present themselves as more conspicuous targets for parents with food. Crowding is evident in larger broods as nestlings generally grow more slowly and suffer higher mortality (Forbes, Thornton, Glassey, Forbes, & Buckley, 1997;Forbes & Glassey, 2000;Forbes, Glassey, Thornton, & Earle, 2001). But the costs of crowding do not befall all nestlings equally.…”

Section: Despotism In Sibling Triadsmentioning

confidence: 99%

Sibling Rivalry in the Birds and Bees

Forbes

2010

Handbook of Jealousy

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Families are complex social structures that are forums for often-spectacular cooperation and altruism among close kin. We find myriad examples of selfsacrificial behavior across the full spectrum of nature, from simple social insects where sisters forgo their own reproduction, and sometimes forfeit their lives to aid their close relatives, to mother hippos, bears, and crocodiles that are both fearless and lethal in the protection of their progeny. Nurturing parents and affectionate siblings match our expectations of family harmony, and biologists on the basis of shared genetic interests expect cooperation and altruism among close relatives.Inclusive fitness theory, first proposed by biologist William D. Hamilton (Hamilton, 1964a(Hamilton, , 1964b, provides the conceptual framework for understanding interactions among kin. Close relatives have a high probability of sharing identical copies of genes by recent common ancestry, and promoting the interests of relatives also promotes one's own (shared) genetic interest; the closer the relationship, the higher the probability of sharing identical genes. Thus from a genetic perspective, altruism within the family is easy to understand. But families are also venues for extremes of violence and selfishness, and Robert Trivers (1974), building upon Hamilton's work, showed how parents and offspring might disagree over how resources within the family should be shared, defining the concept of parent-offspring conflict (Trivers, 1974)

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Why parent birds play favourites

Cited by 107 publications

References 3 publications

Social rank governs the effective environment of siblings

Social rank governs the effective environment of siblings

Within-Clutch Variation in Yolk Testosterone as an Adaptive Maternal Effect to Modulate Avian Sibling Competition: Evidence from a Comparative Study

Sibling Rivalry in the Birds and Bees

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