Final answer:
Male barn swallows serve as hosts for ectoparasites in Biology.
Step-by-step explanation:
In the context of Biology, the relationship between male barn swallows and ectoparasites is that males serve as hosts for ectoparasites. Ectoparasites are organisms that live on the external surface of another organism and derive nutrition from it. In this case, male barn swallows provide a habitat and resources for ectoparasites such as ticks, fleas, and lice. These ectoparasites consume host-derived resources, such as blood and skin cells, for their survival and reproduction.