Effects of woodland structure on breeding bird populations in stands of coppiced lime (Tilia cordata) in western England over a 10-year period

Bird populations were estimated in three adjacent stands of small-leaved lime (Tilia cordata) at Shrawley Wood, Worcestershire between 1984 and 1993. The stands were old coppice, recent coppice cut in the late 1970s and thinned coppice that had been singled probably in the 1970s. It is thought that the stands were all previously coppiced in the 1940s. The study area presented an unusual opportunity to (1) assess effects of woodland structure on bird populations in the absence of any major differences in tree species, (2) to compare the dynamics of bird populations, and hence assess habitat preferences, within large samples of each habitat. Overall densities of birds were consistently lowest in the old coppice and generally highest in the recent coppice. The singled coppice supported the least diverse bird communities as measured by a simple diversity index and the expected numbers of species within standardized samples of individuals. Warblers (Sylviidae) were strikingly more abundant in recent coppice than other habitats, being virtually absent from the old coppice. Wrens were by far the most abundant species in the singled coppice. There was strong evidence that the old coppice was the least preferred habitat of wren and robin. The most striking change during the study was the collapse of the warbler populations in the recent coppice after some 11 to 12 years of coppice growth. This was predictable from previous studies, but the timing of the warbler decline occurred later than expected and was probably a consequence of the relatively slow canopy closure of the coppice at Shrawley Wood. Differences between stands, and changes over the 10 years within stands, were interpreted in terms of habitat structure and effects of winter weather on survival of resident species. The findings are discussed in relation to management of abandoned coppice; it is suggested that for conservation purposes thinning should be regarded as a complementary approach, alongside coppicing and non-intervention.