1. In Great Britain the distribution of the riverine damselfly Calopteryx splendens is predominantly southern. However, the last decade has seen records of the species in previously unoccupied areas in the northeast of England, prompting speculation regarding northward range expansion. The current study is the first to quantify the physical features of the habitat that influence the presence of C. splendens.
2. A field survey was carried out on the physical characteristics of habitat supporting C. splendens along a section of the River Wharfe, West Yorkshire, U.K. Adult C. splendens were marked uniquely for individual identification in order to assess the occurrence of the species within different habitat patches of the study area.
3. A multiple logistic regression was used to identify the significant habitat variables in explaining the occurrence of adult C. splendens.
4. The most important habitat factor in determining the presence of C. splendens was the height of the vegetation at the edge of the river. Significant negative relationships were found between the presence of C. splendens and tree coverage along the bank, and between its presence and increased bank height.
5. The distribution of C. splendens is affected by the natural physical features of the habitat, anthropogenic disturbance and the behaviour of the species itself.
6. The importance of quantitative habitat data in species conservation, particularly with regard to range expansion, is discussed.