TRADITIONAL CANARYSEED: SAFE FOR BIRDS, RISKY FOR HUMANS
We can’t say definitively why traditional canaryseed (with silica fibers) is safe for birds and not humans; to our knowledge this has not been studied. Birds do, however, have different physiologies and adaptations for foods they consume.
For example, birds that eat canaryseed crack open the hull—which contain the silica hairs—and eat only the grain inside, just like they would with a sunflower seed. This would reduce their internal exposure to the silica fibers.
Birds' hard beaks may also provide some protection. A study of mice fed traditional varieties of canaryseed found they developed tumors around their mouths and noses, the soft tissue areas that most frequently came into contact with the silica fibers.
Learn about Silica Fiber Free™ canaryseed, which does't have the same risks for humans that traditional canaryseed does.