Answer by Tim Hofstetter:
Sometimes, from heart attack, but not always. I rescued a hummingbird a couple of years ago. It had become entangled in spider web from my barn, and its feet were completely wrapped in web, making it impossible to land and extremely difficult to fly. I captured it as gently as possible, gave it some sugar water (no telling how long it had been there) with an old syringe body, and spent about half an hour untangling the web from its feet. I never got all of the last of it, but I got the feet completely functional again. The bird was frightened, but could tell easily that I meant it no harm and I was actually helping it. By the time I was finished, it had lost nearly all its fear and seemed comfortable perching on my finger. I let it gain strength, protecting it from the cats, until it felt strong enough to fly away. It had some stories to tell when it got home.
If you look closely, you can still see a little webbing on its feet and beak: