Bird feeding is a popular hobby around the world, with millions of people putting up bird feeders in their yards or gardens to attract feathered visitors. But does feeding birds actually help support biodiversity? Here’s a look at what the research says.
What is biodiversity?
Biodiversity refers to the variety of life in a given area. It encompasses genetic diversity, species diversity, and ecosystem diversity. Greater biodiversity is generally seen as beneficial, providing more ecological niches and making ecosystems more resilient. Threats to biodiversity include habitat loss, pollution, climate change, and invasive species.
How could bird feeders help biodiversity?
There are a few ways that bird feeders could potentially help support biodiversity:
- Providing supplemental food resources allows more individual birds to survive, especially over winter when natural food is scarce.
- Feeders may help some species expand their range into new areas.
- The presence of feeders may increase overall bird abundances and densities.
- Providing food resources may help migratory birds successfully refuel during their journeys.
In theory, if feeders allow more birds to thrive, they could support a greater diversity of species in an area and provide more opportunities for ecological interactions and niches.
Do bird feeders actually increase biodiversity?
While the points above make logical sense, the actual research on whether bird feeders increase biodiversity shows mixed results:
- Several studies have found higher species richness and diversity in areas with bird feeders compared to unused control sites.
- However, other studies have found no effect of bird feeding on species diversity at a local scale.
- Feeders may disproportionately benefit certain common urban adapted birds over rarer and more specialist species.
- Abundance and community composition may change with feeding, but species richness does not.
- Effects likely depend on geography, habitat, season, and other local factors.
Overall the research remains equivocal. Here is a more detailed look at some key studies on the biodiversity impacts of feeders:
Studies finding increased diversity at feeders
Davies et al 2009 – In this study in southeast Australia, properties with bird feeders had higher bird species richness and diversity than properties without feeders. Totals of 55 species were recorded at feeding sites compared to 32 species at control sites.
Galbraith et al 2015 – A UK study that compared neighborhoods with and without feeding stations. Bird species richness and diversity was higher in neighborhoods with supplementary feeding.
Belaire et al 2014 – An American study finding higher native bird richness and diversity in yards with bird feeders compared to those without feeders.
Studies finding minimal or no diversity effects
Jones and Reynolds 2008 – Feeders increased bird abundance but did not alter native bird species richness in Arizona desert suburban areas.
Or?os-Kohalmi et al 2013 – In Hungary, richness and diversity did not significantly differ between villages with and without bird feeding.
Anderson et al 2014 – No detectable difference in native bird communities between properties with and without bird feeders in Canberra, Australia after controlling for habitat variables.
Why the mixed results?
There are several potential reasons why the effect of bird feeders on biodiversity remains unclear:
- Site specific factors like habitat type and existing species influence results.
- Low statistical power in some studies due to small sample sizes.
- Biodiversity metrics are variable and complex to measure accurately.
- Indirect ecosystem effects are unknown – e.g. could feeders facilitate some species at the expense of others?
- Backyard feeders may benefit urban-adapted generalists over specialists.
- Feeders alone may not provide resources to meaningfully influence diversity at a landscape scale.
Best practices for promoting biodiversity at feeders
While the effect of bird feeding on biodiversity remains equivocal, some best practices can help make feeders more beneficial:
- Use diverse food types, including suet, nuts, and fruit, to attract more species.
- Avoid cheap mixed seed, which favors aggressive species.
- Position feeders near native plants to provide shelter and nesting sites.
- Limit feeder dominance by aggressive species like doves and grackles.
- Clean feeders regularly to avoid disease spread.
- Prevent window collisions with UV-reflective decals.
Following these tips can help make feeders welcoming for more species while minimizing potential downsides.
Conclusion
The question of whether bird feeders increase biodiversity does not have a clear scientific consensus yet. While some studies have found positive effects, others show neutral or mixed impacts. The effects likely depend on the specific context and habitat. Well-managed feeders may provide small local biodiversity benefits, but are unlikely to meaningfully influence diversity at a landscape scale. Following best practices can enhance potential upsides for birds while minimizing risks. More large-scale, long-term research is needed to better understand the complex relationship between supplemental feeding and biodiversity.