A squirrel deterrer is definitely an asset for any backyard Birder. This Add-A-Cage is designed specifically to prohibit black and grey squirrels from your feeders.

 The most effective way to avoid losing all your bird food to starlings and blackbirds is to physically prevent them from gaining access to the food. These birds are simply too large to fit through the openings of the cages that surround the feeders below, yet smaller birds fly right through the openings in much the same way as they would fly through a fence or navigate in the dense branches of a bush. Even the larger woodpeckers can still feed thanks to their long necks, prying beaks, and agile tongues, which can stretch to obtain food. 
These cages will also stop squirrels and quickly pay for themselves in terms of food saved.

NOTE: Cages should have a diameter of 11” to avoid grackles and starlings eating the food by sticking their necks through the bars of the cage.

With its wide slot at the top, it allows numerous types of hanging feeders. The 1" hole at the bottom gives Birders the option to mount it onto a pole. 

Cage measures 12" in diameter and 16 ½" tall.

1 3/4" is largest space between bars.