There is no public database of all FWS/CWS bands for any species of birds that are banded. The reason for this is that the information is scientific and therefore available only by special permission for scientific purposes. Heck, I as a project coordinator haven't been able to get access to data that I would like to see, but I am working on it. When birds are observed, the bander is the person notified. If the bander shares the information for example with our Project, that's great but they don't have to do it.
However there are some databases online that are managed by other organizations/agencies like the Midwest database - but those are voluntary and they rely on the individual banders to keep the records updated which is alot of effort so there is data missing and out-of-date even there.
As for the band colours - when the reintroduction programs began in the 1980s, everyone in North America used black bands for wild hatched birds and red bands for captive-bred birds released into the wild. As more and more birds were produced, some multi-coloured bands (black over green and black over red) were used so that it increases the numbering options - keep in mind that reading a band the size of the tip of your little finger, you really can't have more than 2 digits top or bottom, its just too hard to read them. So with the additional colour combinations, you have more the ability to repeat digit combinations and that helps when you have lots of birds - like the Midwest.
As for only using one band (the aluminium FWS/CWS band) it technically is the only band that has to be put on - adding the ID band is the norm because there is an interest in identifying the birds, however, its not really necessary. Just because you know who a bird is, doesn't change what they do. If you have a peregrine nesting, you have a peregrine nesting regardless of who or where it came from. And there are lots of unbanded birds out there - either because the nest couldn't be accessed at banding time or because they come from a nest we know nothing about. We don't try to catch unbanded birds to put bands on them, that would be unnecessary stress and danger for the birds - and we don't need to know who they are, just that they are. I don't know where Jules came from but that doesn't diminsh her value or her value to the species recovery.
As for which leg, the US likes to be consistent, but that's because most of the banding is done by a few individuals so they have a preference. We try to band consistently but sometimes we get it wrong by which time its too late to take them off - and sometimes we do it on purpose so that we have a quick way to identify between individuals - for example with lots of chicks in Winnipeg, its easy to identify chicks from one nest based on which leg we have put their coloured bands on. In addition we put coloured tape on the aluminium band to help with quick identification in the first few months - and that's not something that's done by everyone but it is done by some.
Hope that helps get you started.
