What feed should not be given

The bird feeding experience is influenced by the quality of the wild bird food presented and the effectiveness with which it is made available to the birds. Foods vary greatly in their attractiveness, as will be discussed later, and some bird feeders have a much higher innate attractiveness than others. For example, "squirrel-proof" feeders tend to have a low innate attractiveness to birds than feeders that are not designed to be squirrel-proof. Therefore their use results in a less satisfactory bird feeding experience than would be the case if an attractive non-squirrel-proof feeder were presented and squirrel-proofed through external means, such as baffles.
It is very important that care should be taken of what to feed wild birds and what not too. Birds are very complex animals that are not domesticated. They require very specific care in order to remain healthy and happy. So some suggestions are given below of what not to feed wild birds.

Wild birds should never be given chocolates even though like humans they love chocolates too. Chocolate is not bad for birds just because it is high in calories and fat but it contains a compound called theobromine. Birds due to their smaller size and more rapid metabolism may be even more susceptible to its toxic effects. Signs of chocolate toxicity include: hyperactivity, vomiting, diarrhea, heart arrhythmias, seizures, dark colored droppings and death.

Salt is important but it should be avoided in large quantities because then it can lead polydipsia, or increased water consumption and subsequent polyuria, or increased fluid (urine) in the droppings. Because excess salt is excreted via the kidneys, a bird with mild to moderate kidney dysfunction may consume toxic doses of salt readily.

Alcohol should not be fed to the wild birds. There is incidence of birds that died by accident while flying under the influence.

Organically grown food should be avoided because sometimes they have pesticide sprayed as well that act like toxins for wild birds.

Avocado causes ingestion, cause irritation and excessive preening, cessation of eating, rapid short breaths and death.

When the fruits are fed remove the pits and seeds of it and the fruits should be given in limited amount because they have high consistency of sugars.

Caffeine should be shunned for e.g. tea and coffee.

Birds are lactose intolerant so avoid giving in a lot of milk products to them because this can make them suffer with severe diarrhea.

Iceberg lettuce has no calories and must not be fed.

Mushrooms have the potential of being toxic.