Abstract: Recurrence of sexual gland in relation to winter flocking in sparrows was studied by prolonging the daily photoperiod during sexual resting period in experimental populations of sparrows. Results showed that prolonged daily photoperiod did have an effect on recurrence of sexual gland, the degree of recurrence, however, not noly depended on the duration of prolonged daily photoperiod, but also on the status of flocking. Under certain conditions of photoperiod, the recurrence of sexual gland in flocking birds was more significant than that in the isolated single birds, which suggested that winter flocking in sparrow would be an essential process for later reproduction.