I do not recommend numbered plastic bandettes alone - I lost an entire year of record keeping because they either broke, pulled off, or the numbers rubbed off of them. I tried everything including, but not limited to: bandettes, rigid spiral bands, NPIP bands (which come off if you look at them), rubber bands, zip ties, nail polish (yes, I'm serious), tattooing, and wings bands. Of them all, wing bands are the best I've found for growing birds. I've used them for about 4 years or so and out of hundreds used I've had less than a half dozen come off. The downside is you have to catch the bird and dig through feathers to read them, and for that reason I use aluminum butt-end bands once they are finished growing. It might be worth it for convenience to use bandettes on growing birds for quick ID but I would definitely use a more permanent form of ID in conjunction with them.
I strongly recommend toe punching as well. I do that to track breeding groups, while the bands identify individual birds. All bands fail sometimes, and with the toe punch you may not know which bird it is but you will at least know who it's parents were. The only thing more frustrating than getting a bird with a serious defect and not knowing who produced it is getting a really great bird and having no idea how to do it again.
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