Individual variation and environmental context in avian life-history evolution: An experimental approach using mountain bluebirds (Sialia currucoides).

O'Brien, Erin Lea

doi:10.24124/2011/bpgub732

Cited by 1 publication

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References 189 publications

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“…1b). Male nestlings are heavier at fledging compared to females in our study population (O’Brien 2010), and this mass difference at day 15 was similarly evident among control birds in this study (marginal means ± SE, mass at day 15, males: 31.49 ± 0.24 g; females: 30.63 ± 0.23 g). However, methionine supplementation resulted in males fledging at a mass comparable to that of females, and lower than control males (Table 2, treatment × sex; males: 30.62 ± 0.29 g; females: 30.78 ± 0.30 g).…”

Section: Resultssupporting

confidence: 72%

Nestling sex predicts susceptibility to parasitism and influences parasite population size within avian broods

O’Brien¹,

Dawson²

2013

Journal of Avian Biology

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Vertebrate hosts differ in their level of parasite susceptibility and infestation. In avian broods, variation in susceptibility of nestlings to ectoparasites may be associated with non‐uniform distributions of parasites among brood mates, with parasites concentrating feeding on the most vulnerable hosts. The presence of a highly susceptible nestling in a brood can benefit the remaining young by reducing the parasite pressure they experience; however, from a parasite’s perspective, broods with fewer susceptible hosts may provide effectively fewer resources than broods of the same size containing a greater abundance of susceptible hosts, and this could limit the number of parasites that a host brood can sustain. To test whether variation in number of susceptible hosts affects the number of parasites in bird nests, we first examined the role of host sex and induced immunity (via methionine supplementation) on susceptibility of mountain bluebirds Sialia currucoides to parasitism by blow flies Protocalliphora spp. We then assessed the effect of variation in number of susceptible hosts on the number of parasites inhabiting the nest. Only females showed a benefit of methionine supplementation, gaining mass more rapidly following supplementation compared to males. This suggests that females are more susceptible to parasites in this system; this was further supported by parasite feeding trials, in which parasites extracted larger blood meals from female than male hosts. Finally, the abundance of parasites in nests was predicted by brood sex ratio: broods containing more female young harboured more parasites. Hence, within‐brood variation in host susceptibility to parasites can not only influence the costs of parasitism for individual nestlings, but may also have consequences for the size of parasite populations within nests. If patterns of maternal investment affect the abundance of nest‐dwelling parasites, these interactions may be important for understanding fitness consequences of maternal resource allocation in many vertebrate hosts.

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Section: Resultssupporting

confidence: 72%