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In animals, events occurring early in life can have profound effects on subsequent life-history events. Early developmental stresses often produce negative long-lasting impacts, although positive effects of mild stressors have also been documented. Most studies of birds have investigated the effects of events occurring at early developmental stages on the timing of migration or reproduction, but little is known on the long-term effects of these early events on moulting and plumage quality. We exposed European starling Sturnus vulgaris nestlings to an immune challenge to assess the effects of a developmental stress on the timing of the first (post-juvenile) and second (post-breeding) complete annual moult, the length of the flight feathers, and the length and colouration of ornamental throat feathers. The nestlings were transferred to indoor aviaries before fledgling and kept in captivity until the end of post-breeding moult. Individuals treated with Escherichia coli lypopolysaccharide (LPS) started both moult cycles earlier compared to control siblings. Moult duration was unaffected by the immune challenge, but an advanced moult onset resulted in a longer moult duration. Moreover, female (but not male) throat feather colouration of LPS-injected individuals showed a reduced UV chroma. We argue that an early activation of the immune system caused by LPS may allow nestlings to better cope with post-fledging stresses and lead to an earlier moult onset. The effect of early LPS exposure was remarkably persistent, as it was still visible more than one year after the treatment, and highlighted the importance of early developmental stresses in shaping subsequent major life-history traits, including the timing of moult in birds. [ABSTRACT FROM AUTHOR]

Nest-dwelling ectoparasites represent an early stressor for birds as they impair the development of nestlings, which can adaptively respond by adjusting their growth rate to current conditions. While nest ectoparasites have long-term effects on nesting adults, no study has examined if they also have an impact on the moult patterns of juveniles. Herein, we investigated whether the presence of ectoparasites in the nest influences the start and duration of the first pre-basic moult in the European starling. To do so, we experimentally removed nest-dwelling ectoparasites from a group of nests and used another group of unmanipulated (i.e. naturally infested) nests as the control. The moult began at an earlier age and lasted longer in birds from the ectoparasite-free nests compared to their control counterparts. The timing of the moult was also affected by the hatching date (i.e. birds that fledged later had shorter moults) and the brood size (i.e. birds in larger broods started their moult at an older age). We also found evidence that the removal of nest ectoparasites influenced the condition of individuals during the course of the moult. In the control birds, we observed a decrease in hematocrit levels, but these were unaltered in the birds fledged from the ectoparasite-free nests. Our study shows that nest-dwelling ectoparasites adversely affected the timing of the moult and the individual condition of juvenile starlings, with possible major consequences for their subsequent life-history events. [ABSTRACT FROM AUTHOR]

In seasonally fluctuating environments, timing of reproduction is a crucial determinant of fitness. Studies of birds show that late breeding attempts generally result in offspring of lower reproductive value, with lower recruitment and long-term survival prospects. Several proximate mechanisms, including a seasonal decline of immune system functioning, may lead to a seasonal decline of offspring fitness. We investigated seasonal variation in offspring quality by subjecting first- and second-brood chicks of a sexually size dimorphic species, the European starling Sturnus vulgaris, to an immune challenge with a bacterial endotoxin (LPS), and evaluated their growth and physiological response in terms of total plasma antioxidant capacity (TAC), concentration of reactive oxygen metabolites and hematocrit. LPS challenge did not affect chick growth or oxidative status. However, hematocrit of second-brood chicks was higher in LPS chicks compared to controls. Body mass halfway through the rearing period (days 8-9 post-hatching), TAC and hematocrit were lower among second- vs. first-brood chicks. Interestingly, sexual dimorphism in body mass at days 8-9 post-hatching markedly differed between broods, first-brood males being 4.7% and second-brood males 22.7% heavier than their sisters, respectively. Pre-fledging mortality occurred among second-brood chicks only and was strongly female-biased. Our findings suggest that starling chicks, even if in poor conditions, are little affected by a bacterial challenge, at least in the short-term. Moreover, our study indicates that sex differences in body size, possibly mediated by sex-specific maternal investment in egg size, may heavily impact on pre-fledging survival in a different way in the course of the breeding season, resulting in sex-specific seasonal decline of offspring fitness. Finally, we suggest that levels of circulating antioxidants should be regarded among the proximate causes of the association between timing of fledging and long-term survival in avian species. [ABSTRACT FROM AUTHOR]