“…Before discussing the implications of our findings, we should briefly consider if extra-pair fertilisations, which being relatively frequent in pied flycatchers (Lifjeld et al, 1991;Gelter and Tegelströ m, 1992;Brü n et al, 1996;Moreno et al, 2010), could be biasing our estimates of resemblance. Our data on extra pair fertilisations (D Canal, J Potti and JA Dávila, paper under review) do not allow for a proper estimation of their effect on trait heritability because of a combination of two events with low frequency, that is, recruiting to adult age (which is needed for the ornament being measured; average recruitment rate ¼ 14%, both sexes combined; N ¼ 14 years and 4536 fledglings; Montalvo, 1991b, Lehtonen et al, 2009) and being sired by a male other than the social 'father' (average rate of extra-pair paternity about 15%; D Canal and J Potti, unpublished data).…”