Interesting--that's just how they sound when I go inside the cage, but they don't seem very alarmed--often they just flit to the other side of the tree. Perhaps that call also means, "Here comes our waiter--maybe he's bringing dessert!"
Several forum members have said that mesh is the only way to protect fruit from birds, and I'm convinced they're right. Birds seem to get used to deterrents very quickly, and then ignore them. In this case, I was the victim of my own wishful thinking--I figured that the slightly larger mesh openings would still exclude all, or at least, most, of the verdins, and that a few tiny birds couldn't do that much damage. Ha! I didn't realize there would be so many--the netting actually makes it better for them because they don't have to compete with the big birds, and they seem to be flocking from all over. Even if I was inclined to shoot them, which I'm not, there are simply too many for it to be effective.
So, at some point I'll have to bite the bullet (or the B.B.) and buy the smaller-sized netting. My wife at least supports the idea--after tasting all those peaches along with the first batch of apricots (before the little stinkers figured out how to get in), I think she would do whatever it takes to keep harvesting tree-ripened fruit. In the meantime, I'll be out there with clothespins and newspaper, covering the last of the apricots and the first of the plums--maybe losing a few battles but still confident about eventually winning the war.