Ectoparasites as developmental stressors: Effects on somatic and physiological development

Area of Science:

• Avian ecology
• Developmental biology
• Parasitology

Background:

• Developmental stress impacts resource allocation in altricial birds.
• Ectoparasites pose a significant challenge to nestling development.
• European starlings (Sturnus vulgaris) are altricial birds with high resource demands.

Purpose of the Study:

• To experimentally assess the impact of ectoparasites on European starling nestling development.
• To investigate if mites act as developmental stressors affecting somatic growth, physiological development, and immunity.
• To determine the effect of mites on corticosterone concentrations in nestlings.

Main Methods:

• Experimental manipulation of ectoparasite (mite) levels in starling nests.
• Application of permethrin pesticide to reduce mite abundance.
• Monitoring of hatching success, survival rates, and somatic growth (mass, tarsus length, feather growth).
• Measurement of hematocrit, bacterial killing ability (BKA), spleen mass, and baseline corticosterone levels.

Main Results:

• Mite infestation reduced nestling survival, hematocrit, and corticosterone concentrations.
• Nestlings in mite-infested nests showed reduced bacterial killing ability (BKA) and lower mass near fledging.
• Contrary to the hypothesis, corticosterone concentrations were decreased, not elevated, in mite-exposed nestlings.
• Somatic growth was initially similar across treatments but diverged later in development.

Conclusions:

• Mites function as developmental stressors in European starling nestlings, impacting survival and immune function.
• The study challenges the prediction of elevated corticosterone in response to mite infestation.
• Early-life ectoparasite exposure can have lasting effects on physiological development and immune competence.