Most of the predation in ground habitats were from rodent teethmarks, most likely mice or rats.
Discussion
One of the issues with this experiment is the use of artificial nests over natural ones, which has been shown to overestimate predation rates and does not mimic the seasonal variation in predation rates observed in natural nest experiments \cite{Zanette_2002}.
Over X% of ground nesting birds in the U.K. are endangered, or critically endangered, and X% of those live in deciduous woodland.