How deep a cage is functional?

[Stine]

Hi all!
I hope to find someone on here who has experience with very deep cages - 80 cm or around 31½ inches.
I work in a pet shop that is just about to purchase cages for a bird room and as I'm the only one in the company that is genuinely interested in birds, they pretty much left the cage design to me ^^
In just about every pet shop I see, the birds are in small cages of maybe 60 cm by 40 cm (~24x16 inches) - I don't like to see that. I want to give them room to fly. So currently the plan is to have cages of 3 different lengths: 80 cm, 100 cm and 120 cm. They'll all be around 31 inches high.
What I want to know is - is 31½ inches too deep to be functional? Can you catch the birds in a cage that deep? I know I can in my own 120x60 cm (48x24 inches) cage, but is 31 inches too much? Will I end up stressing the birds unnecessarily by chasing them around to catch them (I will be using a net of cause)? Would it be better to give them a little less room and go with the 24 inches I know will work?
Be aware that when purchasing birds we usually have to buy relatively large numbers (could be 10-20 birds of a species), so the cages will have to fit quite a few birds for a while, until we start getting them sold. We are mainly talking small species though - I don't expect to get anything larger than cockatiels and I really hope we won't ever have more than 10 of those at the same time.
I've seen a few pictures of cages that look like they might be as deep as I'm considering, but no description of how well these cages work for their owners. I hope you can help me with that.

[Sheather]

With a net, a little bigger is actually easier to navigate than too small, so go for it, sounds great for them.

[Dave]

Well, a net is a tough proposition in a cage that size, unless you don't have any perches. Also, if there are two or more birds in that cage, you'll be inducing a lot of terror.

I think, from experience, that a good cage size for finches is 18" deep, 18" tall and 36" long (end to end). (45 cm tall, 45 cm deep, 91 cm long). My own cages have a longer length, but I don't have to catch my birds very often.

If you have a cage where you can slide a divider into it, so you end up with two smaller cages, that would help a lot when it comes time to catch a bird.

[Ricardo Ronsini]

You might have to set bird traps to catch them

[Sheather]

Set the cage up with two or three perches that easily drop down for catching - it's what my store does.

[Stine]

Thank you for your thoughts and ideas. Removable perches is definitely doable. The divider would probably add quite a bit to the price so I doubt we'll do that. Would have been a nice way to reduce the stress for some of the birds that are not being caught though.