Pickles, kefir, vinegar, yogurt, sourdough, soy sauce, sauerkraut, cheese and many other products are fermented and don't have alcohol in the end product. For the case of the ff its more like the yogurt and vinegar. Note that to actually make vinegar you first need to make alcohol then bacteria...
One other thing to check is make sure that the birds are actually eating all of that food. Mice and rats can sneak in and eat a bunch without being obvious. Out in the country they come in from the fields/woods so even if you keep it clean some will eventually show up. Here I have neighbors with...