Alpine accentors (Prunella collaris) and dunnocks (P. modularis) are closely related species of Prunellidae, which often breed in polygynandrous groups and have specific types of mating behaviour. The alpine accentor lives at high altitudes, in an extreme alpine environment; the dunnock is widely dispersed from lowland to tree line in the mountains. Both species are hosts of the related species of wing lice Philoptersus emiliae and Ph. modularis, respectively. Behavioural differences between these two host species may have resulted in different breeding and seasonal adaptations by their parasites. The main goal of this paper was to test this hypothesis. Sixty five alpine accentors Prunella collaris (Scopoli, 1769) and eighty four dunnocks Prunella modularis (Linnaeus, 1758) were examined for Ischnocera lice in the West Carpathians, Slovakia from 1988 to 2001, and from 2007 to 2010, respectively. Birds were found to be infested with two species of Ischnoceran lice: the parasite species are not competing as they each have their own host Philopterus emiliae Balát, 1955 /P. collaris and Philopterus modularis (Denny, 1842) /P. modularis. Significant differences in abundance and prevalence existed between these two species of lice. High number of Ph. modularis nymphs in the comparison to Ph. emiliae nymphs reflects the different ecological, behavioural and phylogenetic trajectories of their host bird species. This work is the first to assess the louse breeding strategies on two closely related bird species in the high mountain environment.