The effect of woodland area on avian community composition in a fragmented southern UK landscape and associated management recommendations

Capsule: Smaller woodlands not only support fewer species but also show different avian community composition due to loss of woodland interior and an increase in edge habitat. Aims: To use observed community composition changes, rather than traditional total species richness-area relationships, to make area-specific management recommendations for optimizing woodland habitat for avian communities in fragmented landscapes. Methods: 17 woodlands were selected in Oxfordshire, UK, with areas between 0.2 and 120 ha. Three dawn area searches were conducted in each woodland between 1st April and 28th May 2016 to record encounter rates for each species. The impact of internal habitat variation on woodland comparability was assessed using habitat surveys. Results: Woodlands with area less than 3.6 ha showed a significant positive relationship between total avian species richness and woodland area. Woodlands with area over 3.6 ha were all consistent with a mean (± se) total richness of 25.4 ± 0.6 species, however the number of woodland specialists continued to increase with woodland area. Woodland generalists dominated the total encounter rate across the area range, however the fractional contribution of woodland specialists showed a significant positive correlation with woodland area, while the fractional contribution of non-woodland species significantly decreased. Non-woodland species numbers peaked in mid-sized woodlands with enhanced habitat heterogeneity. Conclusions: Community composition analysis enabled more targeted recommendations than total species richness analysis, specifically: large woodlands (over 25 ha) in southern UK should focus conservation efforts on providing the specific internal habitats required by woodland specialists; medium-sized woodlands (between approximately 4 and 25 ha) should focus on promoting internal habitat variety, which can benefit both woodland species and non-woodland species of conservation concern in the surrounding landscape; small woodlands (under 4 ha) should focus on providing nesting opportunities for non-woodland species and on improving connectivity to maximize habitat for woodland generalists and facilitate movement of woodland specialists.