The breeding biology of Plain Swift Apus unicolor was quantitatively studied on Gran Canaria. Mean laying date of the first clutch was 21 April and that for the second clutch 24 June (a third clutch was also recorded), extending the previously suspected breeding period by c. 1.5 months. The mean sizes of the first and second clutches were very similar (1.97 eggs ±0.06 vs. 1.95 eggs). The percentage of second broods was 70% and the mean breeding success of first and second broods was 74.44±6.77 and 64.29+5.05 respectively. These intermediate life-history traits reflect the geographical location and oceanic aspect of the Canaries compared to the northern temperate region and tropical Africa.