Garden bird feeding is a key and beloved form of human-wildlife interaction. Although generally positive for the people doing it and perceived to be helpful for bird conservation as part of wildlife gardening, this may not always be the case in reality. Here we will explore research on the impacts, challenges and trade-offs in garden bird feeding as currently carried out in the UK.
Q&A with Dr Hugh Hanmer
Dr Hugh Hanmer is a Senior Research Ecologist for the British Trust for Ornithology (BTO) Terrestrial Ecology team. His research primarily focuses on urban ecology and avian demography using long and short-term citizen science surveys alongside novel field surveys. He has a particular interest in the impacts of and human-wildlife interactions around garden bird supplementary feeding, first started during his PhD at the University of Reading and continued at BTO.
What is the optimal frequency for feeding garden birds?
Every garden is different, so there isn’t an optimal frequency for putting food out. However, if you are going to put out food, what we do recommend is avoiding putting out excess food which will change with the conditions and seasons. For example, finch trichomonosis potentially survives better in damp conditions so if you have lots of food out there in damp feeders, then you could well be having an unintentional negative effect. Putting less food out but topping it up more often could be better. This also makes it easier to clean feeders regularly which we recommend doing as often as practical, with weekly being a good target to aim for, alongside cleaning water baths and disposing of split food.
Does attracting small garden birds also attract predators?
Sparrowhawks are our main native small garden bird predator and may be attracted to bird feeders, although this is difficult to prove in practice. However, in general they are not believed to have a significant impact on small bird populations and if anything, small bird populations numbers are expected to drive Sparrowhawk numbers which have declined in recent years. Domestic cats are another predator that can catch garden birds and those population is not affected by natural prey availability, so it is important to consider the placement of feeding stations out of reach of cats and close to cover to help birds evade predators in general.
Alongside direct predation risk, there is also some evidence that by feeding birds during the breeding season, we attract more potential nest predators into the area and increase the risk of nests being predated.
Will providing food in winter cause garden birds to struggle in spring during breeding when there could be insufficient natural food available?
Again this is hard to test directly but as far as we can tell no, or at least not at a scale that matters, and it’s important to remember that supplementary feed is only generally a relatively small amount of most birds diet under normal conditions. However, competition for suitable breeding territories and sites may be of more concern. For example, the potential impact of more dominant Blue Tits and Great Tits surviving the winter, on more subordinate Marsh Tits and Willow Tits which use feeders less, may have contributed to their population declines.
Should we restrict feeding garden birds to period where food is particularly scarce, such as during freezing weather?
Potentially and this is what was done in the past. That’s probably where you can have the biggest impact, and it may well be better. For example, it may reduce potential disease transmission because it’s not suitable for some pathogens in those conditions either.
Literature References
- Plummer et al (2019): The composition of British bird communities is associated with long-term garden bird feeding: http://dx.doi.org/10.1038/s41467-019-10111-5
- Nillsson et al (2020) Predictability of food supply modulates nocturnal hypothermia in a small passerine: https://doi.org/10.1098/rsbl.2020.0133
- Robb et al (2008) Winter feeding of birds increases productivity in the subsequent breeding season: https://doi.org/10.1098/rsbl.2007.0622
- Harrison et al (2010) Does food supplementation really enhance productivity of breeding birds?: https://link.springer.com/article/10.1007/s00442-010-1645-x
- Plummer et al (2015) Is supplementary feeding in gardens a driver of evolutionary change in a migratory bird species?: https://doi.org/10.1111/gcb.13070
- Robinson et al (2010) Emerging Infectious Disease Leads to Rapid Population Declines of Common British Birds: https://doi.org/10.1371/journal.pone.0012215
- Hanmer et al (2016) Provision of supplementary food for wild birds may increase the risk of local nest predation: https://onlinelibrary.wiley.com/doi/abs/10.1111/ibi.12432
- Hanmer et al (2022) Habitat-use influences severe disease-mediated population declines in two of the most common garden bird species in Great Britain: https://doi.org/10.1038/s41598-022-18880-8
- Lawson et al (2018) Health hazards to wild birds and risk factors associated with anthropogenic food provisioning: https://doi.org/10.1098/rstb.2017.0091
- Shutt and Lees (2021) Killing with kindness: Does widespread generalised provisioning of wildlife help or hinder biodiversity conservation efforts? https://doi.org/10.1016/j.biocon.2021.109295
- Abraham et al (2024) Supplementary bird feeding as an overlooked contribution to local phosphorus cycles: https://doi.org/10.1002/fee.2793
- White et al (2023) The Joy of birds: the effect of rating for joy or counting garden bird species on wellbeing, anxiety, and nature connection: https://doi.org/10.1007/s11252-023-01334-y
Further info and links
- BTO Garden BirdWatch: https://www.bto.org/our-science/projects/gbw
- Feeding Garden Birds Guidance: https://www.bto.org/how-you-can-help/providing-birds/feeding-garden-birds
- Good Hygiene Practice for Feeding Garden Birds: https://www.bto.org/how-you-can-help/providing-birds/feeding-birds/good-hygiene-practice
- Report a sick or dead garden bird to Garden Wildlife Health: https://www.gardenwildlifehealth.org/

























