Help with bird identification.

Last summer i was unable to identify a bird, here are the details. Location, Shropshire Union Canal, near Nantwich, Cheshire. The bird was Robin sized, slightly darker brown than a Robin. It was in the undergrowth at the bottom of a hedge a few yards from the tow path. It was skulking about and making what i can only describe as a "whirring" noise. The bird soon disappeared when i approached. Can anyone help, please. Regards. Tom.