Ectoparasitism and the role of green nesting material in the European starling

Summary

The use of green nesting material is widespred among birds. Recent evidence suggests that birds use secondary chemicals contained in green plants to control ectoparasites. We manipulated green nesting material and ectoparasites of European starlings (Sturnus vulgaris) to test two hypotheses: (1) ectoparasites adversely affect prefledging survival and morphometrics or postfledging survival, and (2) green nesting material ameliorates the effects of ectoparasites. We recorded fat score, numbers of scabs, tarsal length, body mass, and hematocrit level on each nestling 17 days after hatching. We also fitted each nestling with unique patagial tags and resighted the starlings for 6–8 weeks after fledging to estimate survival and sighting rates. Nests devoid of green nesting material and dusted with the insecticide, carbaryl, had fewer high ectoparasite infestations, and nestlings had significantly lower scab scores, and significantly higher body masses than nestlings in undusted boxes. However, there was no difference in postfledging survival between birds from carbaryl-treated and undusted nests. There also was no difference in prefledging survival and morphometrics or postfledging survival between nestlings from boxes with and without green nesting material. These results do not support the hypothesis that starlings use green nesting material to control nest ectoparasites. We suggest an alternative hypothesis; green nesting material is used for mate selection or pairbonding in the starling.