From a zoonotic perspective, Ixodes ticks are of biological significance given their role in the transmission of a range of diseases across taxa, including, Lyme disease and tick typhus. Understanding the life-history impacts of ticks on their avian hosts is important to identify possible fitness costs of ticks for their hosts to inform the conservation management of endemic fauna and risks to disease transmission. Here, we test for effects of I. Hirsti ticks on its endemic songbird host, the New Holland Honeyeater (Phylidonyris novaehollandiae). We mist-netted 293 adult and 45 juvenile birds from 11 sites across South Australia to test for effects of ticks on adult versus juvenile birds in relation to (i) host body condition (a measure of fitness), (ii) tail feather symmetry, and (iii) haemoglobin concentration. We predicted that juvenile and adult birds in tick-infested areas would have lower body conditions, greater feather asymmetry and lower haemoglobin concentration. The results showed different effects of ticks across age classes. Compared with tick-free birds, tick-infested adult birds had lower body condition (no significant difference in juvenile birds) and tick-infested juvenile birds had greater tail asymmetry (no significant difference in adult birds). Haemoglobin concentration did not differ significantly across age class or study site. These findings show age-specific effects of ticks on hosts and point to the role of parasites to alter host phenotype during ontogeny.