Task partitioning increases reproductive output in a cooperative bird

Behavioral Ecology (Impact Factor: 3.18). 11/2008; 19(6):1136-1142. DOI: 10.1093/beheco/arn097
Source: RePEc


Parents often face a trade-off between the quality and quantity of young produced because terminating investment in current young could result in lower survival and future reproductive success, whereas initiating new breeding attempts could result in greater production of young. In cooperatively breeding species, helpers may alleviate this trade-off by assuming the role of primary caregivers to first broods, liberating breeders to initiate subsequent breeding attempts without compromising the level of care offspring receive. Here, we investigate the occurrence and consequences of brood overlap in the cooperatively breeding pied babbler (Turdoides bicolor). Brood overlap occurred only in groups and resulted in breeders primarily investing in second broods while helpers continued to provide care to first broods, resulting in dependent young from overlapping broods being raised simultaneously. Interbrood partitioning of care during brood overlap resulted in a greater production of young per season in groups (cf., pairs) without any effect on offspring survival, thus representing a reproductive benefit of task partitioning in cooperatively breeding species. Copyright 2008, Oxford University Press.

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Available from: Amanda R Ridley, Oct 05, 2015
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    • "The southern pied babbler is a medium-sized (70–95 g, length 26–29 cm) cooperatively breeding passerine occupying the semiarid acacia savannas of the Kalahari desert (Ridley & Raihani 2008). Groups are stable, comprising a dominant male and female and between 1 and 12 adult subordinates that help to raise young produced by the dominant pair (Ridley & Raihani 2008). Each group occupies a territory that they defend year-round from neighbouring groups (Golabek, Ridley & Radford 2012). "
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    • "Group size in the study period ranged from 2 to 13 (mean ± SD 6.1 ± 2.6) adults (individuals > 365 days old). Birds were sexed using DNA from blood collected when ringing (for capture details, see Radford & Ridley, 2008) using the technique described in Griffiths et al. (1998). Groups defend year-round territories (Golabek et al., 2012) and move around these as a tight unit throughout the day. "
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    • "Individual behavioural variation within groups of social animals can be highly advantageous in terms of overall increase in group fitness (Oster & Wilson, 1978; Wallace , 1982). In particular, task specialization is expected to result in enhanced colony efficiency and productivity , decreased individual energy expenditure to reach a communal outcome and improved resource allocation between colony members (Wilson, 1987; Schmid-Hempel, 1991; Rypstra, 1993; Ridley & Raihani, 2008). Task specialization can take many forms, from behavioural asymmetry in task performance to strict division of labour as seen in the eusocial insects, where behaviourally or morphologically specialized castes determine the limited behavioural repertoire of individuals. "
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