Wild Bird Feeding Industry
Aflatoxin in Bird Seed Mixes
Aflatoxin in Bird Seed Mixes
The following information was prepared for the Wild Bird Feeding Industry by Dr. David Bonter, Project Feeder Watch, Cornell University Laboratory of Ornithology. It is reprinted here with Dr. Bonter's permission.

Recent posts to birding listserves across North America have raised concerns about the potential harmful effects of feeding birds seeds and grains that may be contaminated with aflatoxin. In response to numerous requests, following are some comments on the issue from the Cornell Lab of Ornithology.

- Aflatoxins are produced by fungi that are common and widespread in nature, Aspergillus parasiticus and A. flavus.

-The fungi grow most rapidly in humid environments and can grow on foods stored in damp conditions.

-Corn and peanuts are more likely affected than other foods commonly provided at feeders.

-Research conducted by Dr. Scott Henke of Texas A&M University Kingsville found that 17% of the birdseed samples tested in Texas contained relatively large amounts of the toxin. His research further suggests that feeding wild birds foods contaminated with aflatoxin can be harmful.

-While research studying the effects of aflatoxin on free-living birds is scant, evidence suggests that it is not necessary to abandon bird feeding altogether. Data from Breeding Bird Surveys, Christmas Bird Counts, and Project FeederWatch show that populations of most species that use feeders are stable or increasing. In fact, a number of common feeder species have expanded their geographic range in recent years. An estimated 40-60 million Americans feed birds and have been doing so for decades. If aflatoxin-contaminated seeds were negatively affecting bird populations, we'd see downward trends in counts of our most common feeder visitors.

-Providing supplemental food at feeders likely has little effect on bird populations (positive or negative), but the benefits to humans are immeasurable. Feeding birds has enormous educational value, providing humans with a window on the natural world that is important for encouraging people to protect the environment.

The aflatoxin issue raises the importance of providing a safe environment for birds. You may follow several strategies to improve the safety and health of birds at your feeders:

-Clean your feeders regularly with a 10% bleach, 90% water solution. Allow feeders to dry completely before filling with fresh seed.

-Only provide a limited supply of food at a time (as much as can be consumed in a few days).

-Store seed in a dry place to discourage growth of mold and fungus.

-Discard any seed that has become wet.

-Routinely rake the ground beneath feeders to prevent the build-up of seed hulls and fecal material that could promote growth of bacteria and mold.

- Keep your cats indoors! House cats kill millions of birds each year.

- Avoid window collisions (another source of mortality for millions of birds in the U.S. each year). While data are lacking about which approach is best, streamers and silhouettes likely do not significantly reduce window collisions. We suggest keeping feeders greater than 30 feet from windows (so birds are less likely to see the window as a route through your home). Alternatively, place feeders less than 3 feet from windows so that birds leaving the feeders cannot gain enough momentum to do harm if they hit the window. Consider placing deer netting over particularly problematic windows.

-Provide cover near your feeders so that birds can escape from predators.

If you are concerned about the risks aflatoxin may pose to birds, consider avoiding seed mixes containing corn and peanuts, as the Aspergillus fungi are most likely to grow on these food items.

Additional Information from WBFI Headquarters
Websites for More Information on Aflatoxin and Mycotoxins

Link to Cornell University information on Aflatoxin and Health Risks:

Link to Council for Agricultural Science and Technology Interpretive Summary on Aflatoxin and Mycogens.
CAST has the full 199 page task force report available for purchase on its website www.cast-science.org.