These don’t look like bowling balls. Or maybe that is just because they are in a garden setting. Some people, on being told that this is what they are, have rolled them over and only on seeing the finger holes do they believe that they are, indeed, spheres with a history in fast lanes.
This one got put in the cement bird bath that was never used by the birds because it was too much of a cat height.
Its soft green is the color of sage leaves and it mirrors people walking to and from the house, perhaps keeping record in a friendly gossipy sort of way.
A stand meant to hold a large candle, this fit the silver -streaked bowling ball perfectly. The two birds may be reflecting as well. 
A mirror works its magic and this ball seems to be peeking at itself.