Volunteer surveys as a means of inferring trends in garden mammal populations

• 1 Habitats associated with humans, and gardens in particular, may prove to be important for populations of certain mammal species. However, means for measuring change in these populations are lacking.
• 2 This paper uses power analyses to examine the potential for mammal observation data, gathered through an extensive volunteer‐based survey of garden birds, to provide measures of population change within garden habitats at both national and regional levels.
• 3 Analyses show that this survey protocol has sufficient power to detect a decline in presence of between 5% and 40% at the national level for 20 of the 24 species included in this study. These results demonstrate that data from volunteer surveys allow the annual monitoring of garden use by a range of mammal species within Britain, and highlight the wider potential of such schemes worldwide.