“…Almost all bird species harbour species-or genus-specific feather mites (Doña, Proctor, Mironov, Serrano, & Jovani, 2016;Gaud & Atyeo, 1996;Proctor, 2003). Feather mites are highly specialized symbionts due to their (i) life cycle (i.e., they are permanent ectosymbionts, Dabert & Mironov, 1999;Proctor, 2003); (ii) high host specificity (Doña, Proctor, Mironov, Serrano, & Jovani, 2017); (iii) specific distribution on particular feathers and microsites on feathers (Fern andez-Gonz alez, P erez-Rodr ıguez, de la Hera, Proctor, & P erez-Tris, 2015;Jovani & Serrano, 2001Stefan et al, 2015); and (iv) mainly vertical mode of transmission (Doña, Potti, et al, 2017;Jovani, Tella, Sol, & Ventura, 2001;Mironov & Malyshev, 2002). However, as with many other symbionts, they are challenging to study, and this has strongly hampered our comprehension of this system (Doña, Diaz-Real, et al, 2015;Proctor, 2003;Proctor & Owens, 2000).…”