Avian pox is a virus affecting several garden bird species, mostly rather mildly, but a much more dangerous variant appeared in 2006, mostly affecting the great tit Parus major. It seems to be mainly confined to the southern and eastern part of England and has caused population declines, although not as marked as for greenfinch6..
Another but lesser concern is Salmonella infection in small songbirds, but this has declined in incidence over the last ten years. Finally, stale birdfood can be toxic through aflatoxin secreted by the moulds Penicillium and Aspergillus especially on peanut. Autopsies of dead house sparrows and greenfinches have detected the toxins, which have also been found at high levels in garden bird feeders6.. It remains unclear what if any effect this is having, but it would be very prudent to ensure only high-quality (human food grade) peanuts or seed are provided.
If you can’t clean your feeders regularly, it’s probably best not to use them. Feeding birds is a good thing to do, but only if it has minimal risk of disease transmission. Put only enough food in the feeder to last a few days and clean it before refilling. Remove any soggy or sprouting grain, then either put the feeder in a hot wash in the dishwasher, or clean it using dilute (1:9) bleach. Dry it before refilling.
[Another protective tip is to hang feeders near (about 1m) from windows rather than further away. This helps reduce the risk of dangerous high-speed window impacts7..]
1. Cox DTC, Gaston KJ. (2018) Human–nature interactions and the consequences and drivers of provisioning wildlife. Phil. Trans. R. Soc. B 373: 20170092. http://dx.doi.org/10.1098/rstb.2017.0092
2. Plummer, K.E., Risely, K., Toms, M.P. et al. The composition of British bird communities is associated with long-term garden bird feeding. Nat Commun 10, 2088 (2019). https://doi.org/10.1038/s41467-019-10111-5
3. Plummer, K.E., Siriwardena, G.M. Conway G.J., Risely K. & Toms P. (2015) Is supplementary feeding in gardens a driver of evolutionary change in a migratory bird species? Glob. Chang. Biol. 21:4353-63.
6. Lawson B, Robinson RA, Toms MP, Risely K, MacDonald S, Cunningham AA. (2018) Health hazards to wild birds and risk factors associated with anthropogenic food provisioning. Phil. Trans. R. Soc. B 373
: 20170091. Available here
Page written by Steve Head: Reviewed by Ken Thompson