I was always led to believe it was mercury-based and therefore poisonous? Even if it doesn?t harm the bird, surely the meat must be tainted in some way?
I may be wrong, but I think mercury based seed dressing has been banned for some years now, but even so, when it was used, it never seemed to harm pigeons.
As I understand it, the dressing was not designed to deter avian pests, but to minimise diseases such as mildew.
Pigeons only had access to the seed for a relatively short period of time, so they were immune to any long-term effects.