An improved bird cage structure includes a pair of symmetric right and left grid frames, a pair of symmetric front and rear grid frames, a top grid frame and a bottom grid frame. The right and left grid frames have respectively latch elements extended outward to engage with the top grid frame and fastening elements disposed at selected locations for fastening the engaging elements located at the front and rear grid frames to form a sturdy bird cage. The grid frames have respectively a slot opening to hold a slant chute for forming a collection trough. The cage may be detached easily to single pieces and packed to a small size, and can be transported conveniently at a lower cost.