This dataset contains bird and butterfly abundance data from field-surveyed transects at Hillesden, UK (2006-2017). Over this time period, Hillesden hosted two five-year experimental manipulations of agri-environmental habitats, alongside monitoring of their impacts on biodiversity and agronomic indicators. This dataset contains data suitable for analysis of ten-year interannual population trends across both 5-year phases of experimental work at Hillesden, and subsequent comparison with equivalent trends derived from equivalent national recording schemes (Breeding Bird Survey (BBS) for birds, Wider Countryside Butterfly Monitoring Scheme (WCBMS) for butterflies). The data thus relate only to transects which were recorded consistently (nine for birds, seven for butterflies), and to species that were present on the majority of transects. This dataset thus represents a subset from the whole Hillesden biological survey dataset for these two groups, and contains maximum annual counts per transect, across monthly visits (April-August) within the permitted time frame from equivalent national recording schemes (BBS for birds, WCBMS for butterflies). Data were collected as part of a project led by the UK Centre for Ecology and Hydrology, funded by Defra, with analytical work funded by the Natural Environment Research Council (NERC) under research programme NE/N018125/1 ASSIST. ASSIST is an initiative jointly supported by NERC and the Biotechnology and Biological Sciences Research Council (BBSRC). Full details about this dataset can be found at https://doi.org/10.5285/c8d0ac67-6d47-42b1-af29-2339be8a5d82
