Factors influencing bird species numbers in small woods in south-east England

1. 151 woods, ranging in size from 0.02 to 30 ha and with differing degrees of isolation, were surveyed to determine the numbers of breeding bird species present in each of three consecutive years. Woodland and edge species were analysed separately. 2. Numbers of woodland species showed a strong relationship with woodland area which explained c. 70% of the variation in breeding species numbers. Several other features of the woods and of the surrounding landscape also had small additional influences on species numbers. 3. Numbers of edge species showed a poor relationship with woodland area, but length of perimeter explained 30-40% of the variation in species numbers. The number of structural features within a wood and isolation from other woodland also had small additional positive influences on edge species numbers. 4. Small woods held more edge species than equivalent areas of large woods, but tended to hold fewer woodland species than equivalent areas of large woods.