THE following observations were made in late June and early July 1952-56, round Westleton in Suffolk, where Nightjars (Caprimulgus europaeus) breed not uncommonly on sandy heaths similar to those where I studied the species fifty miles N . N . W . , round Holt in Norfolk, twenty-five years earlier (Lack, i93oa,b, 1932). At Holt, most nests were found by tramping, especially through ground previously burnt and covered with light bracken on the edge of a stretch of heather. Round Westleton, with denser and more varied vegetation, tramping proved quite unrewarding. Several nests with eggs were found by watching the male fly up to relieve the female at dusk. A few with young were found because the parents came clucking round after dark, but some pairs did this well over a hundred yards from their nest, necessitating a long search afterwards. The nests were placed in heather or bracken, sometimes amid young birch trees. In 1955 and 1956, Head Forester Parker of Dunwich State Forest showed me several other nests found during Forestry operations in young plantations on the heaths. In 1954, a bird with a clutch of two dissimilar and distinctive e g g s laid only four feet from where a similar clutch was laid two years earlier, presumably by the same individual. In 1955, a pair bred some ten yards from where there had been a clutch two years before. Other sites were not re-occupied in this way.Assuming an incubation period of 17 days (see later), and