Feather mites (Astigmata) avoid moulting wing feathers of passerine birds

Abstract

The moult of birds could greatly perturb the life cycle of feather mites (Astigmata). These mites live on the surface of feathers and are unlikely to survive if they are on one when it is moulted. Therefore, we hypothesized that they would escape to other feathers to avoid this risk of mortality. We analysed the distribution of feather mites on the wings of 63 moulting individuals of 13 species of passerine birds. We used generalized linear mixed models to test whether the distribution of feather mites depends on the stage of moult of feathers. Feather mites were significantly less abundant on the next feather to fall out than on the other feathers. This ability to escape seems to be higher on primaries and secondaries than on tertials. At least on primaries, feather mites avoided not only the next feather to be moulted but also the second one. For primaries and secondaries the new full-grown feathers harboured more feather mites than those still growing. This study shows that feather mites have an escape behaviour from moulting wing feathers in passerine birds that is consistent with a model of adaptive behaviour.