One of the more unusual results from this experiment is the spatial autocorrelation between arboreal nest proximity and location, which is not present on ground nests. Particularly given that the dispersal constraints of terrestrial predators are usually larger than those of arboreal predators. As there is a smaller diversity of arboreal predators in the U.K., the autocorrelation could be due to a smaller number of individuals predating the nests, limited by their dispersal constraints. In conjunction, the ground nests were predated on by more individuals, disguising individual dispersal patterns. This could be an avenue of future study, however it should be noted the spatial autocorrelation was quite weak (r = 0.0889), so the result may not be ecologically significant.
Limitations
Artificial nest experiments have inherent flaws, and the results are not always directly applicable to wild bird populations. Artificial nests can overestimate predation rates, by attracting different predators and do not mimic the seasonal variation in predation rates observed in natural nest experiments \cite{Zanette_2002,WEIDINGER_2008}. The cryptic nature of artificial nests may provide a source of bias during fixed nest experiments, especially if there are associated sensory cues. While olfactory cues from the plasticine eggs in this experiment was controlled for, the artificial nests were made from non-native conifer leaves, which may have guided predators towards the nests.
Acknowledgements
I would like to thank Cristina Banks-Leite of Imperial College London for help and advice regarding the pilot study, statistical analysis and invaluable guidance. I would also like to thank the technical staff at Silwood Park for their assistance using the GPS unit for spatial analysis. Many thanks to the Biology Undergraduate department, without whom this project could not be possible.