The frequency distributions of 15 species of avian lice among individuals within host populations are described and 12 previously described distributions are reviewed. All of these distributions were aggregated, but some of them do not conform to the negative binomial model (4 at P <0.05 out of the 25 examined). Distribution measures (prevalence, mean and variance of louse subpopulations. the exponent k of the negative binomial distribution. and the index of d~screpancy)01' lice of colonial birds are compared to those of territorial ones. Minimum ;ampie size requirement is calculated for each case study. Louse subpopulation size and variance do not correlate with host social system, however, residuals from the log mean-log variance regression do. Lice of territorial hosts tend to form more variable subpopulations than those predicted by the regression curve, while those of colonial birds tend to form less variable subpopulations. Prevalence and k are higher, while the index of discrepancy is lower, for the distributions of lice of colonial hosts, indicating less aggregated louse distributions compared to those of territorial host species.