I just this web page and found towards the bottom a claim about ambiguous sentences, which doesn't seem right to me.
According to the website:
"Sitting by the fence, the dog growled at the cat" is an example of when zeugma goes wrong. [...] Due to the placement of the word "sitting," it is unclear as to whether the dog, the cat or both of the animals are sitting near the fence.
Another example of such a construction is as follows: "Walking by the tree, the child waved to her friend." Again, who is walking by the tree? One child or both of the children?
So as far as I'm concerned, I think in this case, "the dog" would do the "sitting" and "the child" would do the "walking" (according to what I was taught in school. When the subject "dog" did both the action "sit" and "growl", you can cut it down and make it a Gerund-thing =)) sorry I'm not a native speaker)
Is the website right that these phrases are ambiguous?