Dataset Information

Looking after your partner: sentinel behaviour in a socially monogamous bird.

ABSTRACT: Natural selection favours those individuals with effective anti-predator defences. The presence of sentinels is known to be an effective form of defence amongst stable groups of individuals within cooperative and polygynous breeding systems. However, the presence of sentinels in the more prevalent socially monogamous breeding systems remains overlooked as an important benefit of such partnerships. Here, we describe a study in which we examined the presence and effectiveness of sentinels in a wild population of the socially monogamous zebra finch (Taeniopygia guttata). We found that when experimentally approached by a human observer during incubation, birds flushed from their nests at significantly greater distances when their reproductive partner was acting as a sentinel than when the partner was absent. The distance at which birds flushed was not influenced by the approach direction of the human observer, the gender of the incubating bird, the presence of conspecifics, the habitat type or the size of the breeding colony. Our results indicate that sentinels are an effective anti-predator defence amongst socially monogamous birds, and may represent a neglected benefit of the formation of stable social partnerships in birds. We suggest that whilst recent work has focused on the sexual conflicts that occur between males and females in socially monogamous pairs, we should not lose sight of the benefits that individuals may gain from their partner.

SUBMITTER: Mainwaring MC

PROVIDER: S-EPMC3678116 | biostudies-literature | 2013

REPOSITORIES: biostudies-literature

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Looking after your partner: sentinel behaviour in a socially monogamous bird.

Mainwaring Mark C MC Griffith Simon C SC

PeerJ 20130604

Natural selection favours those individuals with effective anti-predator defences. The presence of sentinels is known to be an effective form of defence amongst stable groups of individuals within cooperative and polygynous breeding systems. However, the presence of sentinels in the more prevalent socially monogamous breeding systems remains overlooked as an important benefit of such partnerships. Here, we describe a study in which we examined the presence and effectiveness of sentinels in a wil ...[more]

PMID: 23761856

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Project description:INTRODUCTION: In biparental birds testosterone levels of males are typically high during the mating phase and decrease during the parental phase. Testosterone implants may enhance mating behaviors, increase the likelihood of males to engage in extra-pair mating behavior and may reduce paternal care. Thus, sex steroids such as testosterone influence reproductive behaviors. Little is known, however, as to whether the more subtle differences in physiological concentrations of testosterone that occur between individuals are related to differences in paternal care, extra-pair behavior, and genetic paternity between those males. Here, we investigate these relationships in the male black redstart (Phoenicurus ochruros), a socially monogamous songbird with a low breeding synchrony. We used nestling provisioning as a proxy for parental care behavior and genetic paternity loss as a proxy for the efficiency of mate-guarding. RESULTS: There was no relationship between nestling provisioning and paternity loss of males. Baseline and gonadotropin releasing hormone (GnRH)-induced levels of testosterone, but not baseline corticosterone, were significantly higher during the mating than during the provisioning phase. Males fed more often when temperatures decreased and fed less when they sang more, but we found no correlation between parental behavior and baseline or GnRH-induced testosterone, and baseline corticosterone - both measured during either the mating or the parental phase. However, males that experienced loss of paternity had lower levels of testosterone during the provisioning phase than males that did not lose paternity. Further, males that lost paternity also expressed higher baseline levels of corticosterone. CONCLUSIONS: Physiological differences in testosterone or baseline corticosterone were not related to differences in parental care, suggesting that the variation of testosterone within a physiological range may not relate to the degree of paternal care in this species. However, the profile of both hormones may indicate quality traits that influence the likelihood of the respective male to lose paternity.

Project description:Female mate choice is thought to be responsible for the evolution of many extravagant male ornaments and displays, but the costs of being too selective may hinder the evolution of choosiness. Selection against choosiness may be particularly strong in socially monogamous mating systems, because females may end up without a partner and forego reproduction, especially when many females prefer the same few partners (frequency-dependent selection). Here, we quantify the fitness costs of having mating preferences that are difficult to satisfy, by manipulating the availability of preferred males. We capitalize on the recent discovery that female zebra finches (Taeniopygia guttata) prefer males of familiar song dialect. We measured female fitness in captive breeding colonies in which one-third of females were given ample opportunity to choose a mate of their preferred dialect (two-thirds of all males; "relaxed competition"), while two-thirds of the females had to compete over a limited pool of mates they preferred (one-third of all males; "high competition"). As expected, social pairings were strongly assortative with regard to song dialect. In the high-competition group, 26% of the females remained unpaired, yet they still obtained relatively high fitness by using brood parasitism as an alternative reproductive tactic. Another 31% of high-competition females paired disassortatively for song dialect. These females showed increased levels of extra-pair paternity, mostly with same-dialect males as sires, suggesting that preferences were not abolished after social pairing. However, females that paired disassortatively for song dialect did not have lower reproductive success. Overall, females in the high-competition group reached equal fitness to those that experienced relaxed competition. Our study suggests that alternative reproductive tactics such as egg dumping can help overcome the frequency-dependent costs of being selective in a monogamous mating system, thereby facilitating the evolution of female choosiness.

Dataset Information

Looking after your partner: sentinel behaviour in a socially monogamous bird.

Publications

Looking after your partner: sentinel behaviour in a socially monogamous bird.

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