Insect pests, a constant battle for many (Japanese beetles are mine). However, my constantly torn leaves (with/tiny leaf pieces hanging) of late spring spinach, swiss chard & some lettuces were driving me crazy in my careful search of insects. No excrement & nothing described w/ the insects shown in article above. Took me 2 yrs. to find the culprits. Nestling down against a warm stone wall that backs my 6 raised beds, w/butt on also warm stone paths between them, I was reading a book on a cloudy, cold day. (Great place to observe hummers ~ what-in-general is going on in your garden.) Bird 'burble', flashing yellow, rustle in my greens. Huh? It was a small group of Gold Finches - flying in, one after the other to hit my 'salad bar' with large tears, one after the other or 3 at a time of about 9. (Our summer camp has so many birdfeeders, all with sunflower hearts that all birds love ~ ~ ~ what was their problem??) This also occurred during the summer before they nest in Aug. Answ. was lightly laid remy cover the hottest part of the day. So, don't just think of birds just going after fruited trees and shrubs, but may be playing 'sneaky' in other parts of your garden.