Hatching asynchrony in birds is considered an adaptation to facilitate brood reduction because under conditions of food scarcity, the smallest nestling usually dies soon after hatching, thereby minimizing parental eff...Hatching asynchrony in birds is considered an adaptation to facilitate brood reduction because under conditions of food scarcity, the smallest nestling usually dies soon after hatching, thereby minimizing parental effort. However, in species with extreme hatching asynchrony, the last hatchlings paradoxically experience a very low probability of survival and death can take so long that it can hardly be considered an adaptation. Here, we propose and experimentally tested a new adaptive hypothesis explaining the brood reduction paradox, namely the“Male Manipulation Hypothesis”. Our hypothesis suggests that by inducing asynchronous hatching,females increase the feeding requirements of the brood, which will induce males to increase provisioning effort. In addition, females may extend the period of male manipulation by feeding the smallest nestling just enough to sustain life. Our study showed that male common blackbirds(Turdus merula) increased their effort(i.e., number of food items per hour) in experimental asynchronous broods compared to synchronous broods, while females reduced their contribution, as predicted by the hypothesis.展开更多
Egg rejection is the most effective and widespread defense used by host species to counteract the extreme fitness costs frequently imposed by obligate avian brood parasites.Yet,the proximate mechanisms underlying betw...Egg rejection is the most effective and widespread defense used by host species to counteract the extreme fitness costs frequently imposed by obligate avian brood parasites.Yet,the proximate mechanisms underlying between-and within-individual variation in host responses remain poorly explored.Emerging evidence suggests that egg rejection is dependent on individual physiological states,and draws attention to the role of hormones as mediators of flexible antiparasitic responses.In this perspective article,I outline recent advances in our understanding of the proximate factors that mediate egg rejection.I also point out some areas where knowledge remains still lacking,especially those related to the development and maintenance of effective cognitive functions,the potential role of oxidative stress,immunological state,and developmental stressors.I propose new hypotheses that stimulate future research on behavioral host responses toward brood parasitism.展开更多
基金supported by the Consejeria de Economia, Innovacion, Ciencia y Empleo, Junta de Andalucia(research project CVI-6653 to M.S.)。
文摘Hatching asynchrony in birds is considered an adaptation to facilitate brood reduction because under conditions of food scarcity, the smallest nestling usually dies soon after hatching, thereby minimizing parental effort. However, in species with extreme hatching asynchrony, the last hatchlings paradoxically experience a very low probability of survival and death can take so long that it can hardly be considered an adaptation. Here, we propose and experimentally tested a new adaptive hypothesis explaining the brood reduction paradox, namely the“Male Manipulation Hypothesis”. Our hypothesis suggests that by inducing asynchronous hatching,females increase the feeding requirements of the brood, which will induce males to increase provisioning effort. In addition, females may extend the period of male manipulation by feeding the smallest nestling just enough to sustain life. Our study showed that male common blackbirds(Turdus merula) increased their effort(i.e., number of food items per hour) in experimental asynchronous broods compared to synchronous broods, while females reduced their contribution, as predicted by the hypothesis.
基金supported by the Spanish MINECO’s Juan de la Cierva-Formaci/En programme(grant FJC2018-037157-I).
文摘Egg rejection is the most effective and widespread defense used by host species to counteract the extreme fitness costs frequently imposed by obligate avian brood parasites.Yet,the proximate mechanisms underlying between-and within-individual variation in host responses remain poorly explored.Emerging evidence suggests that egg rejection is dependent on individual physiological states,and draws attention to the role of hormones as mediators of flexible antiparasitic responses.In this perspective article,I outline recent advances in our understanding of the proximate factors that mediate egg rejection.I also point out some areas where knowledge remains still lacking,especially those related to the development and maintenance of effective cognitive functions,the potential role of oxidative stress,immunological state,and developmental stressors.I propose new hypotheses that stimulate future research on behavioral host responses toward brood parasitism.
