I'm convinced that the matron border collie on the farm, Sydney, has Obsessive/Compulsive Disorder. Of course, I think ALL border collies have OCD in varying levels, but Sydney's is definitely the most pronounced.
A couple of years ago, we had pigs on the farm. Sydney was transfixed by these critters. Anytime you couldn't find her up on the porch, she was stalking around the hog lot, staring them down, sizing them up, and basically flaunting her status on the totem pole.
Now that we don't have pigs anymore, Sydney has developed a new obsession. This one is even more weird, 'cause no one has seen the object of her fascination. She'll go out and lay about 25 feet from the mulberry tree and stare up into the branches. And not for just a couple of minutes here and there ... she does this FOR HOURS.

Never breaking her stare, she is absolutely mesmerized by whatever the heck it is up there in the tree. We've all tried to analyze the look that's on her face ... is it malice? Is this an old rivalry? Or maybe it's pleading, as in, 'Come down, let's romp!' The jury is still out. One thing is for certain, though. The girl has dedication. And because of the as-yet 'imaginary friend' status of this obsession, she's also maybe got a little bit of the ol' family crazy.