1. Department of Statistics; University of Oxford; Oxford OX1 3TG UK
2. School of Mathematics, Statistics and Actuarial Science; University of Kent; Canterbury CT2 7NZ UK
3. Centre for Ecology and Hydrology; Crowmarsh Gifford Wallingford OX10 8BB UK
4. Butterfly Conservation; East Lulworth Wareham Dorset BH20 5QP UK