Habitat preference, escape behavior, and cues used by feather mites to avoid molting wing feathers

Abstract

We analyzed the pattern of distribution and the effect of molting on the escape behavior of feather mites on the wing feathers during the nonmolting and molting season of the barn swallow Hirundo rustica. Feather mites showed consistent preference for the second outermost primary, with a steady decrease in proximal distance and avoidance of the outermost primary. Several explanations are suggested to explain this unusual distribution. Further, analyzing the escape behavior of feather mites on molting primaries, we show that mites avoid the feathers destined to be dropped next on molting barn swallows, and in the case of the outermost primary, mites use the “last moment” strategy, namely, leaving feathers shortly before it is dropped. Next, we performed an experiment in which we simulated shedding feathers or feathers about to be shed on nonmolting barn swallows, in order to test cues used by feather mites in avoiding molting primaries. Both the vibration of the incised feather and the gap of the pulled feather induced mites to leave primaries situated distally, at two-feathers distance from the manipulated primary, related to the control group. Our results show that feather mites have the ability to perceive the signal produced by the feather that will drop next and by the gap of the missing feather. It remains to be demonstrated, whether feather mites have the ability to perceive the vibration of the feather per se or they perceive the altered airflow caused by the vibrating feathers.