The biology of the Alpine Accentor Prunella collaris. V. The sex ratio and transmission of lice Philopterus emiliae

Abstract

Of the 105 inspected accentors, 52 birds yielded lice. Species Philopterus emiliae highly prevailed to Ricinus subpallidus. Only four birds were infested by both species. There was an apparent decrease in the number of lice Ph. emiliae in August and late autumn (October - November) but 85 percent of the accentors caught in September yielded Philopterus lice. In total, we collected 221 specimen of lice, 89 % (196) of all individuals were Ph. emiliae and only 11 % were R. subpallidus. The ratio males: females of Ph. emiliae was biased towards females from summer to winter. The average number of louse individuals was the lowest in summer, 1.8 on individual alpine accentors. Among adult birds, the female accentors were more often infested by females than males of Ph. emiliae. The female-biased sex ratios of lice and female louse loads of the females of accentors clearly signalize that there is the vertical transmission in lice in summer and autumn. The same sex ratio of lice, approximately 2:1 towards the lice females, was also found in wintering males of accentors. We hypothesize that these findings may result from the increased frequency of horizontal transmission via increased body-to body contacts among nighting accentors in winter.