The Mockingbird and the Bulbine

Animals have opinions of things just like people do. Evidently we have a Northern Mockingbird that has it in for some plants we grow called Bulbine mesembryanthemoides. Bulbines are succulent lily relatives, with most of the ones we grow coming from the Winter rainfall regions of South Africa. They die back to the ground when the weather gets hot and dry. The ones we like a lot are also "picture leaf" succulents, with leaves that push their transparent tips above the sand and gravel, then most of the leaf is hidden in the ground, yet photosynthesis happens largely underground in the burried green part of the leaf. This is what they look like in cultivation with a bit more of the leaf exposed than is always the case in habitat:

However, the Mockingbird has reduced this to a "hopefully it will live" condition:

Another species is Bulbine haworthioides, which looks like this in cultivation for us:

It hasn't been pecked with the exuberance of some of the other species, yet has taken damage from our Mockingbrid:

Yet another species under attack is Bulbine bruynsi, this one shows light damage and is the least damaged photo I have from this year:

B. bryunsii after Mockingbird attack is a lot less photogenic, and I worry whether it will be able to set seeds:

Birds do not sit still and pose for my photography the way plants do, so the image quality of my photo of the culprit is a wee bit "Loch Ness Monster" quality:

I have questions: This bird and this plant have no natural range overlap - what is the bird getting from the plant? Is this medicine, or a treat, or something it feels some way about? Mockingbirds drink dewdrops, and one idea is that the plants with their crystalline looking leaves appear to be constantly covered in dewdrops. Once pecked, the leaves are clear gel much like from an Aloe vera leaf, so the bird gets a drink as it expects. Now to practical matters: Defense of the plants. I purchased a fistful of 3/16" diameter 3' long dowel rods. I cut them into bits that fit the tray length, and used the remainder of the 4 dowels as verticals. I cut four crosspieces from two more dowels (each about 12" long). I also bought a bag of wooden beads from a craft shop and used a drill press to turn them into vertices of the structure (3 holes at 90 degrees to each other). I assembled this into a rectangular frame that I could fit over the plants, and draped mesh over it. So far, it is working.

I'll update if this continues to work to protect these plants. With luck, they can set seeds successfully in here as well.