I recently moved to an owner occupied apartment with a large shared garden - there are six family groups. One of the neighbours, who is “in charge” of the gardens, uses broken polystyrene drainage at the bottom of pots. I have asked her to refrain but she refuses. Yesterday I discovered that she puts bits of polystyrene in the Niger feeder. She is away at present so I cannot ask her why.
What can be done?
With all the hype on plastics and the harmful effects on the environment, I too was surprised how little there was from bonafide and respectable websites and organisations about the harm it is doing to the environment.
The first and hopefully most productive start is to have a polite conversation and get to understand why she does add polystyrene to the niger feeder.
You say: "I have asked her to refrain but she refuses" so it may be hard to start, because the wall has already been erected, but if you can, then perhaps a gentle friendly approach might help kickstart a fruitful conversation. I am aware some people will not engage in any conversation for a variety of reasons, I once had a neighbour who no matter what, she was always right.
Thankfully, she moved, not just to my relief, but many of the immediate neighbours as well.
There is a good chance it is genuine ignorance and possibly something something that has been passed down over the generations, when many didn't know any better.
I think a good start would be the likes of David Attenborough, and irrespective of what anyone thinks about him, he is a key player in plastic use reduction, having produced many TV documentaries.
Mike
Flickr: Peak Rambler