The Impacts of Rock Dove (Columba livia) Preen Oil on Wing Louse (Columbicola columbae) Behavior and Survival

The avian uropygial gland secretes preen oil, a complex blend of lipids that birds spread on their feathers during preening. Although preen oil is known to help birds maintain feather condition, there has been increasing evidence suggesting preen oil also affects other organisms that reside on bird feathers, such as bacteria, mites, and lice. In a series of experiments, we investigated the effects of Rock Dove (Columba livia) preen oil on the behavior and survival of feather-feeding wing lice (Columbicola columbae). These lice spend the majority of their lives hidden between flight feather barbs to avoid bird preening. However, because lice cannot feed on flight feathers, they regularly migrate to bird body regions to consume thinner insulative feather barbs. We found that lice strongly preferred to spend time on body feather regions treated with preen oil compared with untreated feather regions, but this preference disappeared when lice encountered preen oil on either flight feathers or on filter paper arenas. As lice are only known to feed on body feathers, our data suggest that preen oil may be consumed by lice or that lice prefer to feed in preen oil-rich regions to increase the chances of encountering and perhaps consuming bacteria or mites that feed on preen oil. Contact with preen oil also influenced louse locomotion, with lice reducing the turn rate (though not velocity) while walking on arenas treated with preen oil, which is also consistent with a preference for preen oil. However, in vitro survival analyses showed that lice kept on preen oil-treated body feathers experienced a moderate but significant reduction in survival compared with lice on untreated body feathers. In contrast, lice on treated and untreated flight feathers showed similar rates of survival. Overall, our behavioral data and survival analyses suggest that louse interactions with preen oil are more complex than previously thought. Further research is needed to determine how these in vitro impacts of preen oil on louse behavior and survival influence bird-louse interactions in more natural settings.