We recorded the timing and frequency of copulation and mate-guarding behaviour during the fertile period in relation to day of first ovulation and time of day in the facultatively polygynous European starling, Sturnus vulgarisAll within-pair copulations were female-solicited. Females solicited them at a high rate during both the pre-ovulatory and ovulatory period, but there were differences in solicitation rates between monogamous, primary and secondary females. Extra-pair copulation attempts were all male-initiated and females rarely engaged in them. Attempts by males were most frequent during the ovulatory period, when the probability of extra-pair fertilization was highest. Males intensively guarded their mate during both the pre-ovulatory and ovulatory period. In contrast to most other passerines, female starlings lay their eggs not at dawn but usually between 0900 and 1100 hours, implying that they may be most fertile in the late morning. During the ovulatory period, extra-pair copulation attempts were more frequent in the late morning than in the early morning, suggesting that males try to take advantage of this putative 'insemination window'. Accordingly, there was some indication that mate guarding during the ovulatory period was more intense in the late than early morning. Females solicited within-pair copulations at a higher rate in the early morning than in the late morning, but copulation rate did not differ between early and late morning. The proportion of monogamous and polygynous males attempting extra-pair copulations did not differ significantly, but mate-guarding intensity differed significantly between female categories. Primary females were guarded less intensively than monogamous females suggesting that males trade mate guarding against mate attraction/courting additional females.