Season and ambient air temperature influence the distribution of mites (Proctophyllodes stylifer) across the wings of blue tits (Parus caeruleus)

Changes in the distribution of the wing-feather mite Proctophyllodes stylif er (Buckholz 1869) on the flight feathers of blue tits (Parus caeruleus) we re studied throughout the seasons and in relation to ambient air temperatur e at three combinations of study sites (Lancashire, West Midlands, and Sout h Midlands). We tested the hypotheses that the distribution of mites is inf luenced in part by season and ambient air temperature. In the winter months mites clustered predominantly on the tertiary feathers, whereas in late sp ring, summer, and autumn, mite-infestation scores were higher on the proxim al primary and secondary feathers. Three approaches were employed to determ ine whether this seasonal redistribution of mites arose as a response to ch anges in microclimate, probably ambient air temperature, rather than to sea son per se. Firstly, meteorological data for the Lancashire study sites, an d our own monitoring of the precise air temperature at the time of handling and inspection at the West Midlands study sites, enabled us to establish a link between distribution pattern and ambient temperature. Secondly, limit ed observations on the distribution of mites on birds recaptured when ambie nt air temperatures differed by 5%C or more between first and second nettin gs, one temperature being below 10%C and the other above, supported the ide a that the change in distribution was associated with air temperature. Fina lly, the results of a small experiment in which heavily infested birds caug ht on a day when air temperatures ranged from 9 to 11%C were taken indoors and temporarily subjected to a higher ambient air temperature (20 min) prio r to re-inspection and release also confirmed that mite movement was associ ated with the temperature of their environment. We conclude that the season al changes in distribution were driven by microclimatic changes, in part by temperature.