When was the last time you cleaned your bird feeder?
Bird feeders are a common sight in the city. For many, they represent a chance to view nature from the comfort of their own home, with little else required but to go out each morning to fill the feeder in their pajamas. This gives city dwellers the chance to interact with birds in a way that would be difficult for them to accomplish otherwise. However, there is more to feeding birds than one might consider at first glance.
While most owners are aware of the need to fill the bird feeders, few of them actually take the effort to clean them their feeders. As birds have no qualms about pooping and eating in the same location, feeders have a high potential to be a reservoir for disease. Even for those who acknowledge the problem, there are no current standards on how frequently to clean feeders, or what the consequences of neglecting to clean them are.
Are bird feeders diners or disease centers?
Recent work, presented at Behaviour 2019 by the McGraw lab at Arizona State, has looked at how bird feeders can act as objects for disease transmission in urban environments, and if cleaning the feeders can affect the disease status of its guests. House finches are one of the most common visitors to bird feeders across the USA and also suffer from a high prevalence of coccidian protozoa infestation, making them an ideal system in which to study this question. As urban finches have higher rates of coccidian infection, the study was repeated in both urban and rural sites to determine if urbanization interacted with the effect of cleaning.
The research team put up feeders in both urban and rural sites, which were either cleaned or left alone. After 5 weeks, the treatment type of each feeder was switched, with the previously clean feeders now being left dirty and the dirty feeders being cleaned and the experiment was repeated. After each 5 week treatment, fecal samples were taken from males and females to determine coccidian prevalence in the population.
Going into the study, the McGraw lab had predicted that there would be an increase in the prevalence of coccidian infection when the feeders were not being cleaned and decrease with cleaning. This effect would be exaggerated in rural areas, as the rural populations would not be as accustomed to the high rates of transmission that occur in high-density sites (bird feeders) compared to their urban counterparts. However, as usual in science, the results were not as clear.
Cleaning helps … sometimes
Male finches in rural settings behaved exactly as expected, with more males being infected when the feeders were dirty than when clean. Females, on the other hand, seemed to unaffected by the state of the feeder, with females being equally likely to be infected at clean or dirty bird feeders. At the urban site, the story got even weirder. Male finches were unaffected by the cleanliness of the feeder while female finches appeared to healthier at the dirty feeders!
More work needs to be done to determine what exactly is happening at these feeders. Until then though, this talk does have some valuable lessons for the city dweller who wants to contribute to their urban wildlife community. Even with the best of intentions, we can have large unintended consequences for the urban wildlife that lives amongst us. Sometimes good and sometimes bad, but quite often hard to predict. Which is all the more reason we should try and understand it.
Featured image “Bird feeder 1” by col.b is licensed under CC BY 2.0.
