A birdcage is a cage

Cage (enclosure)

A cage is an enclosure made of mesh, bars or wires, used to confine, contain or protect something or someone. A cage can serve many purposes, including keeping an animal in captivity, capturing, and being used for display of an animal at a zoo.-History:...

 designed to house bird

Bird

Birds are feathered, winged, bipedal, endothermic , egg-laying, vertebrate animals. Around 10,000 living species and 188 families makes them the most speciose class of tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Extant birds range in size from...

s as pet

Pet

A pet is a household animal kept for companionship and a person's enjoyment, as opposed to wild animals or to livestock, laboratory animals, working animals or sport animals, which are kept for economic or productive reasons. The most popular pets are noted for their loyal or playful...

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Antique (or antique-style) birdcages are often popular as collectors' items or as household decor but most are not suitable for housing live birds, being too small, or of unsafe materials or construction. Good quality cages designed for pet birds are more suitable.

In general, the larger and the more active the bird, the larger the cage one should use.