The nests are built largely with strands from spider webs, which stretch. The Hummingbirds avoid getting it stuck all over themselves by selecting only certain strands. Specific strands of the web, those that are structural, are non-sticky (unlike most of the web). Hummingbirds know which is which.
They do use the sticky strands for the outside of the nest. To this they can stick tiny bits of lichen or bark to camouflage the nest.
Unwanted animals, including neighborhood dogs, often get into storage bins, bird nests, trash cans and so on. A low-cost remedy is plain old household ammonia. Inexpensive!
Just soak a rag in some ordinary ammonia and fasten it nearby. Raccoons, dogs, squirrels, cats, rats etc. hate the smell and won't stick around. Birds, which have a very, very poor sense of smell, have no idea it's there.