Data from: Do parasites and antioxidant availability affect begging behaviour, growth rate and resistance to oxidative stress?

Early-life trade-offs faced by developing offspring can have long-term consequences for their future fitness. Young offspring use begging displays to solicit resources from their parents and have been selected to grow fast to maximize survival. However, growth and begging behaviour are generally traded-off against self-maintenance. Oxidative stress, a physiological mediator of life-history trade-offs, may play a major role in this trade-off by constraining, or being costly to, growth and begging behaviour. Yet, despite implications for the evolution of life-history strategies and parent-offspring conflicts, the interplay between growth, begging behaviour and resistance to oxidative stress remains to be investigated. We experimentally challenged wild great tit (Parus major) offspring by infesting nests with a common ectoparasite, the hen flea (Ceratophyllus gallinae), and simultaneously tested for compensating effects of increased vitamin E availability, a common dietary antioxidant. We further quantified the experimental treatment effects on offspring growth, begging intensity and oxidative stress. Flea-infested nestlings of both sexes showed reduced body mass during the first half of the nestling phase but this effect vanished short before fledging. Begging intensity and oxidative stress of both sexes were unaffected by both experimental treatments. Feeding rates were not affected by the experimental treatments but parents of flea-infested nests fed nestlings with a higher proportion of caterpillars, the main source of antioxidants. Additionally, female nestlings begged significantly less than males in control nests, while both sexes begged at similar rates in vitamin E supplemented nests. Our study shows that a parasite exposure does not necessarily affect oxidative stress levels or begging intensity, but suggests that parents can compensate for negative effects of parasitism by modifying food composition. Furthermore, our results indicate that the begging capacity of the less competitive sex is constrained by antioxidant availability.发育中的幼体所面临的早期生活史权衡（life-history trade-offs），会对其未来的适合度（fitness）产生长期影响。幼雏通过乞食展示（begging displays）向亲代索取资源，并演化出快速生长的策略以最大化存活概率。然而，生长与乞食行为通常会与自我维持产生权衡。作为生活史权衡的生理介导因子，氧化应激（oxidative stress）可能通过限制生长与乞食行为（或使其付出高昂代价）在该权衡中发挥核心作用。尽管这一关系对生活史策略演化与亲子冲突具有重要启示，但生长、乞食行为与氧化应激抗性之间的相互作用仍有待研究。 本研究以野生大山雀（Parus major）幼雏为研究对象，通过在巢箱中接入常见体外寄生虫（ectoparasite）禽蚤（Ceratophyllus gallinae）构建感染模型，并同时测试膳食中常见抗氧化剂维生素E的补充能否抵消寄生虫感染的负面影响。此外，我们量化了实验处理对幼雏生长、乞食强度与氧化应激水平的影响。 感染禽蚤的雌雄幼雏在育雏期前半段的体重均出现下降，但该效应在离巢前的短时间内消失。两项实验处理均未对雌雄幼雏的乞食强度与氧化应激水平产生影响。实验处理未改变亲代的喂食频率，但寄生巢的亲代会向幼雏提供更高比例的毛虫——这是抗氧化剂的主要来源。此外，在对照组巢箱中，雌性幼雏的乞食频率显著低于雄性；而在补充维生素E的巢箱中，雌雄幼雏的乞食频率无显著差异。本研究表明，寄生虫暴露未必会影响氧化应激水平或乞食强度，但提示亲代可通过调整食物组成抵消寄生带来的负面影响。此外，本研究结果还显示，竞争力较弱的性别的乞食能力受抗氧化剂可获得性的限制。