Sex ratio manipulation within broods of house wrens, Troglodytes aedon

Albrecht, Daniel J.

doi:10.1006/anbe.1999.1420

Cited by 41 publications

(23 citation statements)

References 53 publications

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“…However, 32% (16 out of 50) of runt chicks died before blood sampling occurred, and sex was not determined for them, so an effect of higher male mortality cannot be fully discarded in this result. In contrast, Albrecht (2000) did not report any data on sex adjustment in the first or any other positions in the laying sequence. The intrabrood model would predict a male bias for the first position more strongly than a female bias for the last one.…”

Section: Evidence So Farmentioning

confidence: 77%

Sex allocation within broods: the intrabrood sharing-out hypothesis

Carranza

2004

Behavioral Ecology

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Selection is expected to cause parents to adjust the sex of their offspring when the environment is predictable during development, and it is expected to affect each sex differently. When several offspring compete for limited resources, the environmental conditions acting on the brood are not a good predictor of the conditions affecting individual offspring. There is evidence for some species that, regardless of any bias in brood sex ratio, the sex of individual offspring within a brood may be related to its position in the hatching/birth/weight rank, in ways that might correlate with the expected share of available resources. Here I propose that parents may be selected to adjust offspring sex within the brood, provided that some depreciable environmental quality is unequally distributed among siblings in a predictable manner. I call this the ''intrabrood sharing-out'' hypothesis and present a graphical model to derive predictions about the relationship between offspring sex and positions within the brood. The model considers that sibling competition not only produces differences in the mean share of resources among siblings, but it also increases the predictability of the share obtained by high-ranking sibs and decreases the predictability of the share for low-ranking ones. Consequently, parents should be selected to deal with such a distribution by promoting the conditions to make it more predictable and then adaptively adjust the sex of particular siblings, especially in high-ranking positions within the brood, rather than to modify the sex ratio of the brood as a whole.

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Section: Evidence So Farmentioning

confidence: 77%

Sex allocation within broods: the intrabrood sharing-out hypothesis

Carranza

2004

Behavioral Ecology

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“…Under such circumstances, females might be expected to produce males first, if fledging mass influences fitness of sons more than that of daughters. A recent study on house wrens (Troglodytes aedon) indeed showed that last-hatched offspring (most probably hatched from last-laid eggs) were more likely to be females and were fledging in poorer condition relative to their siblings (Albrecht 2000). This suggests adaptive BSR manipulation to produce last-hatched chicks of the smaller, cheaper sex.…”

Section: Cases Where Evidence For Adaptive Sex Ratio Manipulation Is mentioning

confidence: 99%

Parental care and adaptive brood sex ratio manipulation in birds

Hasselquist

Kempenaers

2002

Phil. Trans. R. Soc. Lond. B

168

128

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Under many circumstances, it might be adaptive for parents to bias the investment in offspring in relation to sex. Recently developed molecular techniques that allow sex determination of newly hatched offspring have caused a surge in studies of avian sex allocation. Whether females bias the primary brood sex ratio in relation to factors such as environmental and parental quality is debated. Progress is hampered because the mechanisms for primary sex ratio manipulation are unknown. Moreover, publication bias against nonsignificant results may distort our view of adaptive sex ratio manipulation. Despite this, there is recent experimental evidence for adaptive brood sex ratio manipulation in birds. Parental care is a particularly likely candidate to affect the brood sex ratio because it can have strong direct effects on the fitness of both parents and their offspring. We investigate and make predictions of factors that can be important for adaptive brood sex ratio manipulation under different patterns of parental care. We encourage correlational studies based on sufficiently large datasets to ensure high statistical power, studies identifying and experimentally altering factors with sex-differential fitness effects that may cause brood sex ratio skew, and studies that experimentally manipulate brood sex ratio and investigate fitness effects.

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“…Given that sons and daughters have different competitive abilities under variable growth conditions (Lessells et al, 1996), it is plausible that females might actively manipulate the sex ratio of eggs in favour of the more viable sex under poor growth conditions (Whittingham and Dunn, 2000;Arnold and Griffiths, 2003;Badyaev et al, 2003;Albrecht, 2000; but see Johnson et al, 2003). Although we did not determine the sex ratio of all last-hatched nestlings, sex ratio of asynchronous chicks that hatched from last-laid eggs and survived until fledging did not diverge from parity.…”

Section: Growth Rates and Competitive Abilities Of Siblingsmentioning

confidence: 91%

Sibling Growth Patterns in Great tits: Does Increased Selection on Last-hatched Chicks Favour an Asynchronous Hatching Strategy?

Tilgar

Mänd

2006

Evol Ecol

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In birds, competitive abilities of siblings in relation to their sex and the magnitude of hatching delay are still poorly understood. We compared the sex-specific growth of the last-hatched, competitively disadvantaged chicks with that of synchronously hatched chicks in two successive years. Sons exhibited higher growth rates than daughters in a year with delayed onset of breeding, and this sex-related difference was more pronounced among the asynchronously hatched chicks. Females apparently do not selectively allocate more resources to the last-laid eggs because neonatal body mass and the growth rate of asynchronously hatched chicks did not differ between years, despite the fact that in one of the years, asynchronous chicks hatched from replaced eggs taken randomly from other nests and not from eggs laid last by the incubating female. Among chicks that survived, moderately asynchronous siblings grew at a lower rate than synchronous ones, whereas no difference in mass gain was revealed between synchronous and strongly asynchronous siblings irrespective of their contrasting competitive abilities. We suggest that selection of the fittest asynchronous chicks may improve the overall quality of asynchronous broods, thus favouring the maintenance of asynchronous hatching strategies in variable environments.

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Sex ratio manipulation within broods of house wrens, Troglodytes aedon

Cited by 41 publications

References 53 publications

Sex allocation within broods: the intrabrood sharing-out hypothesis

Sex allocation within broods: the intrabrood sharing-out hypothesis

Parental care and adaptive brood sex ratio manipulation in birds

Sibling Growth Patterns in Great tits: Does Increased Selection on Last-hatched Chicks Favour an Asynchronous Hatching Strategy?

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