The effect of ectoparasite load on the condition of nestling European starlings (Sturnus vulgaris)

Abstract

Nest-dwelling ectoparasites are commonplace among-cavity nesting birds such as the European starling (<i>Sturnus vulgaris</i>), and can be detrimental to the health of nestlings. To determine if this was also the case for <i>Sturnus vulgaris</i>, ectoparasite load and evidence of ectoparasites such as tiny blood spots found on eggs were compared to brood condition in 12 nests. Nests were divided into early and late broods to determine if time of breeding played a role in ectoparasite load. Egg spot and nestling data were collected between April and July of 2021 from nest boxes found throughout the Saint Mary’s University campus. Nest material from six early brood nests and six late brood nests were taken for analysis once nestlings had fledged and frozen for a week before dissection. Nest material was filtered through a 250 micrometer sieve with water and ectoparasites were identified, documented and removed under a dissecting microscope. There were significantly more ectoparasites found in the later broods than in early broods, possibly due to the colder temperatures in April and early May. The number of egg spots was positively correlated with <i>Carnus</i> spp. load, and positively correlated to other ectoparasites as well but this could be due to all ectoparasites increasing in the later broods. While there was a trend towards lower condition with increased ectoparasite load, no significant effect of ectoparasite load on nestling condition was found.