Blackbird proof garden mulch

[Grey_Area]

We love our two families of blackbirds; and they are pretty fearless with us. But, I'd rather they left the garden mulch on the garden, and not everywhere else. They love to dry bathe in the composted bark I put down, as well as the usual digging for insects, worms etc.. part of life I guess.

I have in the past used coco shell as this can bind to itself quite well, but it's quite scarce in my local area, so are there any viable alternatives that self bind and will at least for the first few hours remain where it's put.
TIA.