BRANTA — Melanie Orros
Characterisation and ecological effects of garden bird feeding
Institution: University of Reading, UK
Supervisor: Mark Fellowes
Details: PhD 2013 (Completed)
Subject Keywords: supplementary feeding; urban ecology; bird feeding; gardens; citizen science; raptors; Red Kite
Species Keywords: multiple garden-feeding species; Red Kite, Milvus milvus
Garden bird feeding is amongst the most widespread of humanÔêÆwildlife interactions worldwide, particularly in urban areas. Despite the evident scale of energy input and subsequent likely ecosystem perturbation however, surprisingly little research has investigated this activity. Most previous work has focussed on direct influences on provisioned birds and has taken place outside gardens. Effects seen in other locations and under experimental feeding regimes may differ in nature and extent from those within the highly anthropogenically modified and diverse habitats of gardens and under householders' usual provisioning patterns. My research focussed on garden bird feeding in a large UK urban area centred around the town of Reading. Questionnaires revealed that over half of households feed birds, predominantly year-round. A longitudinal study indicated that a median of 628 kilocalories/garden/day is given. UK-wide this could support c. 200 million individuals of an average garden-feeding bird (based on 10 common species) assuming 100% uptake. Reading is unusual amongst UK urban areas in that reintroduced red kites (Milvus milvus) are now common day-time visitors. The combined results of several studies suggested that garden feeding is key to this urban presence. Surveys of kite feeders indicated that median provisioning levels could support c. 160ÔêÆ355 kites/day across the Reading urban area and further that most feeding meets recommended guidelines. Garden bird feeding can also indirectly influence co-existing taxa. Comparisons of aphid colonies exposed to and protected from birds in both feeding and non-feeding gardens found significant reductions in size and survival time of exposed relative to protected colonies only in feeding gardens. Further work revealed reduced numbers of Carabidae around bird feeders compared with control areas under householders' usual provisioning patterns. These depletory effects are attributed to increased avian predation around bird feeders. Overall, my research demonstrates that a common domestic activity has a diverse range of influences both on targeted species and indirectly on others. Further research is required to investigate the significance of these worldwide.
Orros M.E. & Fellowes M.D.E. 2012. Supplementary feeding of wild birds indirectly affects the local abundance of arthropod prey. Basic and Applied Ecology 13 (3):286-293
Orros M.E. & Fellowes M.D.E. 2014. Supplementary feeding of the reintroduced Red Kite Milvus milvus in UK gardens. Bird Study 61: 260-263.
Orros M.E., Thomas R.L., Holloway G.J. & Fellowes M.D.E. (in press). Supplementary feeding of wild birds indirectly affects ground beetle populations in suburban gardens. Urban Ecosystems, In press.