Egg size and asymmetric sibling rivalry in red-winged blackbirds

Forbes, Scott; Wiebe, Mark

doi:10.1007/s00442-010-1629-x

Cited by 28 publications

(26 citation statements)

References 35 publications

(59 reference statements)

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“…Forbes and Wiebe (2010) recently found in Red-winged Blackbirds that small last-laid eggs were associated with a different form of brood reduction than that occurred most of the time. These 'marginal' nestlings from small last-laid eggs were more often victims of 'instant' brood reduction, which occurred within 24 h of hatching.…”

Section: Discussionmentioning

confidence: 98%

Giant Babaxes mix brood reduction and brood survival strategies

Liu

Guan

et al. 2011

J Ornithol

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Altricial birds may vary their relative reproductive investment at the egg versus nestling stages as an adaptive strategy to deal with variable or unpredictable food availability between stages. We investigated the parental investment strategies of Giant Babax (Babax waddelli) breeding in a harsh, high-altitude environment on the Tibetan plateau. In the modal clutch size of three, egg size declined strongly with laying order, resulting in an intra-brood size hierarchy throughout the nestling period. However, provisioners counteracted the initial handicapping of smaller, last-hatching young by two means: (1) preventing siblings from competing over a predictable feeding site; and (2) preferentially feeding the smallest nestling. Consequently, nestling growth curves differed near significantly by hatching order. We suggest this contrasting investment during the egg and nestling stages may be a strategy to maximize reproductive success in a harsh and unpredictable, high-altitude environment. The handicapping of last-laid eggs provides the opportunity for more efficient brood reduction in unfavorable conditions, but can be counteracted by preferential feeding under favorable conditions.Keywords Babax waddelli Á Parental investment strategy Á Brood reduction Á Brood survival Á Size hierarchy Zusammenfassung Riesenbabaxe (Babax waddelli) vermischen Strategien zum Brutverkleinern und Brutü berlebenNesthocker variieren ihre relativen Fortpflanzungs-Investitionen während der Ei-und Nestlings-Phasen als eine Anpassungsstrategie, um das wechselnde, oder nicht vorhersagbare, Nahrungsangebot in den unterschiedlichen Stadien in den Griff zu bekommen. Wir untersuchten die elterlichen Investitionsstrategien des in einer rauen Umgebung auf dem Tibetischen Hochplateau brütenden Riesenbabax. Bei einer modalen Gelegegröße von drei Eiern nahm die Größe der Eier stark mit der Reihenfolge, in der sie gelegt wurden, ab, was in einer brutinternen Größen-Hierarchie während der gesamten Nestlingszeit resultierte. Die Fütternden wirkten diesem anfänglichen Handicap der kleineren, später geschlüpften Jungen aber auf zwei Arten entgegen, indem sie: (1) die Jungen davon abhielten, an einem Futterplatz miteinander zu konkurrieren und (2) die kleineren Nestlinge beim Füttern bevorzugten. Die Wachstumskurven der Nestlinge unterschieden sich beinahe signifikant entsprechend der Reihenfolge des Schlüpfens. Unserer Meinung nach könnte dieses sich voneinander abhebende Investieren während der Ei-und Schlüpf-Stadien eine Strategie zur Maximierung des Fortpflanzungserfolgs in einer rauen, unberechenbaren und hoch gelegenen Umwelt sein. Diese Benachteiligung der später gelegten Eier bietet eine Gelegenheit für eine effizientere Brutverkleinerung bei ungünstigen Bedingungen, der aber bei günstigen Bedingungen durch eine Bevorzugung beim Füttern entgegengesteuert werden kann. Communicated by T.

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Section: Discussionmentioning

confidence: 98%

Giant Babaxes mix brood reduction and brood survival strategies

Liu

Guan

et al. 2011

J Ornithol

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“…Similar patterns of increasing egg size with laying position have been found in other populations of red‐winged blackbirds (Blank and Nolan , Weatherhead ). Egg mass is positively linked to hatching mass and growth rates of red‐winged blackbirds nestlings (Blank and Nolan , Forbes and Wiebe ), and is strongly correlated with the survival of marginal nestlings (Forbes and Wiebe ). Marginal nestlings from larger eggs tend to survive longer in the nest, likely because they have larger nutrient reserves, which allow them to better survive early food deprivation (Forbes and Wiebe ).…”

Section: Discussionmentioning

confidence: 99%

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

Newbrey

Paszkowski

McGraw

et al. 2014

Journal of Avian Biology

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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.

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“…If groups are sufficiently successful, then individual genetic differences creating within-group reproductive skew can be evolutionarily stable [9]. Alternatively, parental manipulation can bias offspring to assume otherwise reproductively disadvantageous roles [10-12]. If such groups remain intact over generations of shared reproduction, then high relatedness may be a consequence and not a cause of cooperation.…”

Section: Introductionmentioning

confidence: 99%

Monogamy and high relatedness do not preferentially favor the evolution of cooperation

Nonacs

2011

BMC Evol Biol

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BackgroundPhylogenetic analyses strongly associate nonsocial ancestors of cooperatively-breeding or eusocial species with monogamy. Because monogamy creates high-relatedness family groups, kin selection has been concluded to drive the evolution of cooperative breeding (i.e., the monogamy hypothesis). Although kin selection is criticized as inappropriate for modeling and predicting the evolution of cooperation, there are no examples where specific inclusive fitness-based predictions are intrinsically wrong. The monogamy hypothesis may be the first case of such a flawed calculation.ResultsA simulation model mutated helping alleles into non-cooperative populations where females mated either once or multiply. Although multiple mating produces sibling broods of lower relatedness, it also increases the likelihood that one offspring will adopt a helper role. Examining this tradeoff showed that under a wide range of conditions polygamy, rather than monogamy, allowed helping to spread more rapidly through populations. Further simulations with mating strategies as heritable traits confirmed that multiple-mating is selectively advantageous. Although cooperation evolves similarly regardless of whether dependent young are close or more distant kin, it does not evolve if they are unrelated.ConclusionsThe solitary ancestral species to cooperative breeders may have been predominantly monogamous, but it cannot be concluded that monogamy is a predisposing state for the evolution of helping behavior. Monogamy may simply be coincidental to other more important life history characteristics such as nest defense or sequential provisioning of offspring. The differing predictive outcome from a gene-based model also supports arguments that inclusive fitness formulations poorly model some evolutionary questions. Nevertheless, cooperation only evolves when benefits are provided for kin: helping alleles did not increase in frequency in the absence of potential gains in indirect fitness. The key question, therefore, is not whether kin selection occurs, but how best to elucidate the differing evolutionary advantages of genetic relatedness versus genetic diversity.

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Egg size and asymmetric sibling rivalry in red-winged blackbirds

Cited by 28 publications

References 35 publications

Giant Babaxes mix brood reduction and brood survival strategies

Giant Babaxes mix brood reduction and brood survival strategies

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

Monogamy and high relatedness do not preferentially favor the evolution of cooperation

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