Don't judge the owner too harshly. If they were really being cruel, they'd have taken the tags off the feet first so they couldn't be identified.

The reality is that low-humidity conditions tend to help stave off mite infestations, and the weather at this time of year is really good for that. The birds are also really adept at fending for themselves, finding shelter and re-nesting.

Mites aren't a death sentence, but they can also be treated with a dip of some kind.

If I saw this, I'd first assume that they're treated and need time away from the main roost for the cure to do its job. Given that the feed was dumped there, maybe it is more insidious. But the tags still being on, it may as well have a driver's license - because everyone in the neighborhood who raises, will know generally where they come from.