No effects of a feather mite on body condition, survivorship, or grooming behavior in the Seychelles warbler, Acrocephalus sechellensis

A common assumption of studies examining host-symbiont interactions is that all symbiotic organisms are parasitic. Feather mites are widespread symbio nts of birds that do not appear to deplete the host of any vital resources. Instead they feed on the oily secretions that cover the feathers and the d etritus caught in these secretions. Therefore, a more logical assumption mi ght be that feather mites are non-parasitic. We investigated whether infest ation by a feather mite, Trouessartia sp. (Trouessartiidae), has any detrim ental effects on the Seychelles warbler, Acrocephalus sechellensis. Feather mite load was not correlated with body condition. Survivorship of birds pe r territory was lower for birds with lower mite loads, but this result is e xplained by these birds also living in low-quality territories with low foo d availability. The amount of time birds spent grooming was not related to feather mite load and grooming did not decrease following the experimental removal of mites. Additionally, although males groom more than females, the y do not have larger mite loads than females. Although this study is largel y non-experimental, the combined results indicate that the relationship bet ween these feather mites and the Seychelles warbler is probably benign.