Previous studies have suggested that availability of high quality habitat rather than habitat connectivity or species mobility was the limiting factor in the distribution of grassland butterflies, but were mostly undertaken on specialist species in rural areas. Consequently, this project tests the hypothesis that the quality of available habitat is more important than patch size or connectivity to the persistence of four grassland butterfly species in the West Midlands conurbation.
Two of the study species are widespread (Polyommatus icarus and Coenonympha pamphilus) whilst two have a more restricted distribution (Erynnis tages and Callophrys rubi). However, unlike species with very specific requirements, all are polyphagous and can tolerate a wide range of conditions, making habitat quality difficult to quantify. Several means of assessing habitat quality were developed and tested. A detailed vegetation quadrat sampling method had the best predictive abilities for patch occupancy and summarised the habitat preferences within the urban context. A model based upon habitat quality and connectivity was devised, with the ability to rank each patch according to potential suitability for each species.
For all four species, habitat quality accounted significantly for the greatest variance in distribution. Connectivity had only a small significant effect whilst patch area had almost none. This suggests that conservation efforts should be centred upon preserving and improving habitat quality.