The thickness of the bars will also play an important role when choosing the right iron bird cages. If the bars are not thick enough, your bird may be strong enough to cause broken welds, bent bars, and other damages.
For small-sized birds, the ideal bar gauge is 2 mm.
For medium-sized birds, the ideal bar gauge is 2.5 mm.
For large-sized birds, the ideal bar gauge is 3.5 mm.
Keep in mind that there are pet birds that are considered as extra large. For such pets, a gauge size of 5 mm or more is ideal.