Blue tit outside my window

I now see that there are more varied visitors to my bird feeder than I realised. I thought they were all sparrows or coal tits, but now I see we have chaffinches, blue tits and a solitary robin as well. So due to demand in these chilly times I've topped up the bloomin' thing up yet again with tasty treats.They all seem to like the black seeds. In the meantime I'm wondering why certain people have not been in touch with me, so I've tried to reach out. What else can you do?