Squirrels are a widespread, adaptable and extremely resourceful group of mammals that are found on the continents of Europe, North America, South America and Asia. Squirrels feed on the fruits, nuts and seeds of a wide range of plants making bird tables and hanging bird feeders highly attractive sources of food to squirrels living in the vicinity of humans. In fact it is only by an arbitrary selection process by humans that has made the birds the invited guests and the squirrels the gatecrashers of the party; these abundant sources of food could quite as easily be "squirrel tables" and "squirrel seed feeders", and that is exactly how the squirrels see it.
Unfortunately, it often proves that the squirrels are unable to dine politely alongside their avian friends and the result is that the birds are totally ousted and forced to watch from the sidelines whilst the squirrels gorge themselves on the banquet. As a result, bird feeding humans have often resorted to a variety of measures in an attempt to deter the invading squirrels - all too often these measures are in vain and the result is a healthy industry in squirrel proof bird feeders.
Such is the intelligence and persistence of squirrels when raiding bird feeding stations that it stretches human intelligence when designing squirrel proof bird feeders. These squirrel proof bird feeders in turn present new challenges to the squirrels, requiring ever-increasing levels of intelligence to bypass or destroy. However, there are squirrel proof bird feeders now on the market that do actually prevent squirrels from stealing the bird's food.
There are many alternatives to buying squirrel proof bird feeders - Alternatives to Squirrel Proof Bird Feeders - but eventually the squirrels' cunning and intelligence will find a way around virtually anything that can be devised. Take a look at this video clip and you will see what amazing feats the squirrels will perform to raid the bird table.
It should be added that whilst I am a bird lover I have nothing against squirrels, in fact I enjoy watching them as much as the birds, it is just that at the bird table they seem to take more than their fare share whilst the birds struggle to get more than a few seconds at the food.
There are a number of designs that are used in the manufacture of squirrel proof bird feeders: Types of Squirrel Proof Bird Feeders.