Effects of carnus hemapterus, a hematophagous ectoparasite on nestling European starlings (Sturnus vulgaris)

Hematophagous ectoparasites on nestlings can cause poor body condition, reduced hematocrit levels, increased heterophil/lymphocyte (H/L) ratios, decreased parental investment, and reduced fledging success. Carnus hemapterus is a common ectoparasite of cavity-nesting species, such as European Starlings (Sturnus vulgaris) and leave red-brown spots on eggs. Egg spot density and Carnus abundance were positively correlated, so I used spot density as a proxy for Carnus abundance. I studied Carnus effects on 54 broods (191 nestlings) of European Starlings and predicted that nestlings from nests with more egg spots would be in poorer condition, have lower hematocrit, higher H/L ratios, lower parental provisioning rates, and lower fledging success than nestlings from nests with fewer egg spots. As predicted, Carnus abundance was negatively correlated with hematocrit, male provisioning effort, and fledging success. However, no relationship existed with nestling condition, which may be explained by females compensating for reduced male provisions to nestlings from heavily spotted-egg nests.