Family structure and variation in reproductive success in blackbirds

Forbes, Scott

doi:10.1007/s00265-009-0863-x

Cited by 17 publications

(22 citation statements)

References 25 publications

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“…Previous studies have also shown betweenyear variation in estimated moult duration (Bensch and Grahn 1993;Smith and Sheeley 1993), while other studies have reported that moult speed did not vary across years (Borras et al 2004). On the other hand, inter-annual variation in breeding success has also been reported in wild birds (Pajuelo et al 1992;Cézilly et al 1995;Forbes 2010). Such differences could be explained by annual variations in environmental factors such as climate or food availability that can affect moult phenology and/or key reproductive traits of birds (Bryant 1975;Murphy 1986;Smith and Sheeley 1993;Renfrew et al 2011).…”

Section: Discussionmentioning

confidence: 94%

Malaria infection and feather growth rate predict reproductive success in house martins

et al. 2012

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Carry-over effects take place when events occurring in one season influence individual performance in a subsequent season. Blood parasites (e.g. Plasmodium and Haemoproteus) have strong negative effects on the body condition of their hosts and could slow the rate of feather growth on the wintering grounds. In turn, these winter moult costs could reduce reproductive success in the following breeding season. In house martins Delichon urbica captured and studied at a breeding site in Europe, we used ptilochronology to measure growth rate of tail feathers moulted on the winter range in Africa, and assessed infection status of blood parasites transmitted on the wintering grounds. We found a negative association between haemosporidian parasite infection status and inferred growth rate of tail feathers. A low feather growth rate and blood parasite infections were related to a delay in laying date in their European breeding quarters. In addition, clutch size and the number of fledglings were negatively related to a delayed laying date and blood parasite infection. These results stress the importance of blood parasites and feather growth rate as potentially mechanisms driving carry-over effects to explain fitness differences in wild populations of migratory birds.

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Section: Discussionmentioning

confidence: 94%

Malaria infection and feather growth rate predict reproductive success in house martins

et al. 2012

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“…Daily censuses were conducted at an average of 278 nests each year with the assistance of a field crew. Detailed methods have been described elsewhere [15,16] and I present only a précis here. Nests were visited from egg-laying until nestlings reached at least 8 days of age (hatching ¼ day 1).…”

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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“…Daily censuses were conducted at between 135 and 511 nests each year (mean = 278) with the assistance of a field crew. Detailed methods have recently been described elsewhere (Forbes 2009(Forbes , 2010 and I present only a précis here. Nests were visited at least daily from the onset of egg-laying until the youngest nestlings reached at least 8-days of age, and/or eldest nestlings reached 10 (hatching = day 1).…”

Section: Study Area and Populationmentioning

confidence: 99%

“…These blackbirds create structured families via hatching asynchrony laying the foundation for an asymmetric sibling rivalry among contemporary siblings (Forbes 2009(Forbes , 2011. Older and larger nestlings frequently outcompete younger nestmates in non-aggressive begging competitions for food delivered by parents (Teather 1992;Forbes et al 1997Forbes et al , 2001Glassey and Forbes 2002b;Forbes 2010Forbes , 2011Hall et al 2010).…”

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confidence: 99%

Parental preference for investment risk incites family strife

Forbes

2011

J Bioecon

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Older stronger siblings in many birds and mammals enjoy decisive and often lethal advantages in sibling competitions by virtue of being born or hatching first. Asynchronous hatching in birds divides the brood into core (advantaged) and marginal (disadvantaged) elements generating an asymmetric sibling rivalry with often fatal outcomes. Given that these asymmetries are under parental control, the obvious question is why parents seem to incite family conflict. Here I show in a model system (an altricial songbird) that family strife in the form of fatal sibling rivalry arises as a consequence of parental investor's appetite for risk: in accord with an axiom of investment theory, obtaining greater potential rewards required taking greater risks. I analyze the risk and reward of investment in different family structures using a tool borrowed from modern portfolio theory, and show that the most successful parents gambled with brood size, placing bets on incipient families that often proved too large. Failed bets triggered a fatal sibling rivalry for insufficient resources. Parents driven to maximize reproductive success incited family strife among their offspring.

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Family structure and variation in reproductive success in blackbirds

Cited by 17 publications

References 25 publications

Malaria infection and feather growth rate predict reproductive success in house martins

Malaria infection and feather growth rate predict reproductive success in house martins

Social rank governs the effective environment of siblings

Parental preference for investment risk incites family strife

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