“…In birds, blood parasites can have negative effects on important aspects of host life history and fitness components. Clutch size (Marzal et al, 2005 ), hatching success (Knowles et al, 2010 ; Sanz et al, 2001 ), fledgling success (Knowles et al, 2010 ; Merino et al, 2000 ; Pigeault et al, 2020 ), and offspring size (Szép & Møller, 2000 ) have all been found to be reduced by parasite infections, as have other aspects of reproductive behavior such as parental care (Ganser et al, 2020 ; Parejo‐Pulido et al, 2020 ). Ectoparasites, on the other hand, have been found to impose fitness costs on reproduction by affecting nestling body size and condition, and overall reproductive success in terms of fledgling success, fledgling survival, and thermogenic and metabolic capacities (Dufva & Allander, 1995 ; Fitze et al, 2004 ; Richner et al, 1993 ; Simon et al, 2004 ; Szép & Møller, 2000 ).…”