The only birds I raise that I use numbered bandettes on are Black Penedesencas which are the larger of the 4 varieties but still may have a bit smaller legs than marans.
I've translated from Catalonian the sizes needed for cocks and hens and mine can't use bands that large, however I recently discovered those recommendations are for the improved (larger) version. I have the classic.
#9 has been sufficient for all the hens.
What I did, and you may want to do so as well is get #7 and #9.
I used to only use colored zip ties till they were mature. But now I use different colors based on the year they hatch and as soon as they're big enough I use #7 in the appropriate color and when they start getting tight I switch to #9.
I bought 7, 9 and 11. Only mature roosters get 11.
I use the same color code used for queen bees. Queen bees use 5 colors, I do the same for the chickens.
white for years ending in 1 & 6,
yellow - 2, 7
red - 3, 8 ... for chickens I use orange
green - 4, 9
blue - 5, 0
This way I can tell how old a bird is by looking at the color of the leg band. Each year the numbers can them start over.
Even when they fit well, bandettes can be lost so keep an eye on them regularly so missing bands can be replaced before you lose track of the bird.
Wing bands may be better but I'm good with bandettes for now.
Hope this helps.
Edited by ChickenCanoe - 12/1/15 at 1:56am