humm, if the seeds are treated with chemicals, the plants that grows from them isn't, the chemical treatment is agains...birds who might pick them off the field, against...mold that might grow on them if they are stored in not exactly the right conditions and maybe against worms, plants that grow from them are surelly chemical free.
where to get seeds of sunflowers? i don't know what they sell in the USA as bird food but the most common thing around here is sunflower seeds so..if the birds are still alive...