Ruddies (unlike most finchbreeders) love the tiny weevils that can infest seed. So if you know someone with weevils in their seed, be kind and take it off their hands. Your Ruddies will thrive on it. (as a suplimentary live food)
LML
All this information is very good but as spoton said.Leave then alone,every time you disturb them it is a reason for them to dump the nest.
I know it is hard not having a sneaky look or feel but by doing that you are courting disaster.
By giving them a reasonable diet, peace and quiet they are a very easy bird to breed.
We've had lots of success with our Ruddies - I never look in their nests. They do tend to go for the nesting sites that are exposed rather than the more hidden spots though. Ours favour ones we get from Bunnings that I think are meant as ornamentals but quite a lot of our birds choose them over pet shop ones. They also love emu feathers but they also drag in greens that we feed them.
I just tried to upload a photo of one of the Bunnings nests - an error keeps coming up when I try to resize it. I will try again tomorrow night when there is someone around who has better computer skills. In the meantime they are in the indoor gardening section and cost around $10 - where the birdfeeders etc are.