A modular bird cage includes a plurality of support posts located at the corners of the cage. The support posts are made up of an internal column and an external post surrounding the internal column. The internal column is internally threaded to rigidly connect a base portion and an upper portion of the bird cage. The internally threaded column engages a vertically extending threaded stud extending from the base portion. Two perpendicular, radially extending lugs are mounted on the base portion spaced from the stud. The internally threaded column, when fully engaged with the externally threaded stud, abuts against the two radially projecting lugs, filling the space between the stud and the lugs. A hollow external post is passed over the column and includes two perpendicularly located arched openings which engage the two lugs mounted on the base portion.