Does the abundance of ectoparasite in the nest affect nestling condition and fledging success?

Abstract

Nestlings of most passerine species face many stressors including early exposure to ectoparasites. Ectoparasites negatively impact the health of nestlings by feeding on their blood and feathers, leaving the nestlings in poor condition, and reducing their chance to fledge. European Starlings (Sturnus vulgaris) are cavity-nesting passerines; they nest in the holes of trees and artificial nest boxes which accumulate ectoparasites. Parents are known to line their nest with feathers to serve as a barrier to ectoparasites. Only one study on the ectoparasite community of European Starlings exists and it was done in Halifax, Nova Scotia (Fairn et al. 2014). My objectives were to 1) identify the abundance and types of ectoparasite in starling nests, 2) determine whether ectoparasite abundance reduces nestling condition and fledging success, and 3) determine whether the mass of feathers in the nest reduces ectoparasite abundance and to quantify the number of cigarette butts present in nests. This study was conducted in June 2020 on nine nests from the late broods of European Starlings. The number of ectoparasites per nest ranged from 8-31. The only ectoparasites found were adult hen fleas (Ceratophyllus gallinae). I found no relationship between ectoparasite abundance and a) mean nestling condition in the brood, b) proportion of nestlings that fledged and c) mass of feathers. These results suggest that nestlings were not affected by this particular prevalence of ectoparasites. It also suggests that feathers do not serve as a barrier which may instead be present in the nest to attract the opposite sex. Future studies should examine the effects of different ectoparasite prevalences on nestlings.