Oakwoods in western Wales have long been regarded as the seminatural remnants of the region's climax vegetation, and several of the less fragmented examples have been acquired by various conservation bodies for management as nature reserves. The botany of many of these woods is quite well documented, but in only a few cases has anything been recorded on their animal life beyond the listing of many vertebrate, and some invertebrate, species. Quantitative work on birds in Welsh oakwoods was initiated in the early 195o's, and the results of extensive transect counts, later summarised by Yapp (1962), provided figures on the percentage frequency and relative abundance of many of the species recorded. The work reported in this paper was planned to provide information on breeding bird population densities in different types of oakwood in western Wales, and to help in the formulation of management policies for such woods.In much of north-west and mid-west Wales, woods of sessile oak Quercus petraea tend to occur on the steep sides of valleys between the open grassland, moorland or fell of the uplands and the cultivated fields of the valleys. The woods have long been utilised as a ready source of timber, and over the past half-century have been used extensively as winter shelter and feeding for sheep brought down off the hills. The better trees have, in general, been removed as timber, and the remainder are often little more than tall scrub, biologically still quite interesting but economically of very little value. In recent