Bird Cage Bar Spacing Guide: The Right Gap for Every Species, and Why

The figures by species

Bird	Merck Veterinary Manual	Other veterinary sources	Retail charts (not veterinary; for comparison)
Finch, canary	Not listed	PetMD (Dr. Latas): small birds no more than 1/2 in	Exotic Wings: 1/4 to 3/8 in
Budgie, parrotlet	0.5 in	PetMD: no more than 1/2 in	Exotic Wings: 3/8 to 1/2 in
Lovebird	0.5 in		Exotic Wings: 3/8 to 1/2 in
Cockatiel	0.5 in		Exotic Wings: 1/2 to 5/8 in
Conure, caique, Poicephalus, mini macaw	0.75 in		Exotic Wings: 1/2 to 5/8 (small conures), 5/8 to 3/4 (large conures, caiques, Poicephalus, Pionus, mini macaws)
African grey, Amazon, small cockatoo	0.75 in (printed "0.751")		Exotic Wings: 3/4 to 1 in
Macaw, large cockatoo	1.5 in		Exotic Wings: 1 to 1.5 in

The retail chart is from a bird store and is shown because it is what most listings follow; where it is narrower than Merck (finches), the narrower figure is the cautious one. Where it allows wider than Merck (5/8 for cockatiels), Merck's 0.5 is the veterinary figure.

Why the gap matters

VCA's housing pages put it in one sentence: bars must be close enough together that the bird cannot get its head or legs stuck between them. A bird that pushes its head through and panics cannot pull back; the cockatiel and lovebird cases in retail warnings are head entrapment at 3/4 and 1 inch. A gap that is too narrow does not trap a head but can trap a toe or a band, which is the reason the ranges have a lower bound too.

The finger test

MSPCA-Angell, citing the AAV: pick a finger or fingers about as thick as the bird's wing; if it fits between the bars, the spacing is not right for that bird. It is a test of the actual bird, which a table cannot be, and it works in a store.

Gauge matters as much as gap for big birds

Dr. Latas (PetMD): with larger birds the bars must be strong enough that they cannot bend them with their beaks, and bars should not converge as they do in domed cages. Prevue states its gauges: 12 and 16 on the F040 (small birds), 8 and 12 on the F050, 9 and 12 on the 3151 and 3152, 9 on the 3154 and the macaw cages, 8 on the stainless Imperial. Lower is thicker. A listing that states spacing but not gauge has told you half the story; for a macaw, Prevue's 9-gauge macaw cages and the 5 mm bars retailers quote for A&E's walk-in aviary are the kind of figure to look for.

Horizontal bars

Climbing birds use horizontal bars; a cage with horizontal bars on at least two sides gives a budgie or cockatiel something to climb. It does not change the spacing rule.

Doors, feeder holes and the top

Spacing is measured between the vertical bars, but the gaps that catch birds are often elsewhere: around swing-out feeder doors, at the top of a dome where bars converge (Dr. Latas), at the seed skirt, and at the grille. Check every opening with the same finger.

Cages at each spacing

Spacing	Cage	Gauge	Birds (by the Merck table)
3/8 in	Prevue Parakeet Manor 98012; Prevue SPF0610 stackable flight cage	14 and 16 (Manor, Prevue)	Finches, canaries, budgies (travel or small flight)
0.4 in	Yaheetech 39-inch, 54-inch and 69-inch; VEVOR 30-inch and 843; YITAHOME 62-inch	Not stated (VEVOR 41-inch: 2.6 mm wire)	Budgies, lovebirds, cockatiels, parrotlets
1/2 in	Prevue F040, F041, F050; Prevue Square Roof 31991; PawHut hexagon aviary	12 and 16; 8 and 12; not stated	Budgies through cockatiels
5/8 in	Yaheetech 52-inch, 60.5-inch, 68-inch play top; Flyline corner (small)	Not stated	Cockatiels and small conures by the listings; over Merck's 0.5 for budgies
3/4 in	Prevue 3151, 3152, 3154; Flyline corner (X-Large); Prevue travel cage 1305	9 and 12; 1/8 in; 9 and 11	Conures, caiques, Poicephalus, greys, Amazons
1 in	Prevue Imperial 3457; Flyline XXL flight; Seny double; Mcage XX-Large; A&E walk-in aviary	8; not stated; not stated; not stated; 5 mm (retailer)	Greys and Amazons at the retail upper figure; mini macaws
1 3/8 in	Prevue Empire 3157 and Silverado 3155S	9	Macaws and large cockatoos (under Merck's 1.5)

What to skip

Skip any listing that gives no spacing at all. Skip 3/4-inch cages for budgies and lovebirds however the title reads. Skip domed cages for large birds (converging bars, Dr. Latas). And skip trusting the title's species list: the Yaheetech 60.5-inch names budgies at 5/8 inch, and Prevue's Imperial names cockatiels at 1 inch, against the Merck figures.