I think this is a reminder from the little blue tit that I must replace the coconut shells that contained suet and seeds. Sorry little bird. I promise I shall buy some again soon.
So do you buy the coconut shells filled? You can't refill them? Never heard of such a bird feeder, but it's so natural looking (despite the wrong tree shape) that I'd love to have one in my backyard, too. Must look them up.
@jyokota yes you can buy them ready filled and you come refill them if you had enough fat to put in them. This one is hanging from some twigs/branches that I have stuck in the ground so that I can photograph them on something other than a feeder