Date of Award
Master of Science (MS)
School of Biological Sciences
Joseph M Casto
The developmental stress hypothesis suggests that birdsong can reflect the current condition and developmental history of a songbird. Developmental stressors such as food restriction or ectoparasitism can hinder normal song development, leading to altered song quality in adulthood. Previous research has demonstrated that early food restriction results in reduced growth of song control nuclei, which may account for the effects of early food restriction on adult song quality. However, the neural mechanisms underlying the effects of early ectoparasitism on birdsong have not been directly investigated. In this study, we examined the development of song control nuclei in European starling (Sturnus vulgaris) nestlings under varying levels of ectoparasitic infestation. We subjected nests to either the addition of Northern fowl mites (Ornithonyssus sylviarum) or the use of a miticide, Permethrin, to reduce ectoparasites. We followed nestlings throughout pre-fledging development and assessed physical growth and hematological titers on brood-days 10 and 20. On brood-day 20, we harvested nestling brains for later histological analysis. We found that nestlings from nests with added mites had significantly shorter wing chord and lower body mass on brood-day 10, but on brood-day 20, structural growth was similar to that of nestlings in miticide-treated nests. Our analyses revealed that, relative to miticide-treated nests, hematocrit, brain mass, and the volumes of two song control nuclei (HVC and the robust nucleus of the archipallium) were significantly reduced in nests with added ectoparasites on brood-day 20. These findings suggest that early ectoparasitism can affect the development of song control nuclei, potentially resulting in altered song quality in adulthood.
Lusk, Elliot Parker, "Of Mites and Brains: Ectoparasitism in Nestlings Alters the Development of Song Control Nuclei in European Starlings" (2022). Theses and Dissertations. 1684.