Answer:
A pigeon
Explanation:
The question above is related to the story entitled, "Neverwhere," which was written by Nail Gaiman.
The situation above happened when Door (a young woman from London Below) was in Richard's (a young businessman who recently discovered London Below) apartment. She summoned a pigeon by sprinkling some breadcrumbs on the window. The pigeon came and pecked on the crumbs and Door attached a messaged on its leg while Richard was holding it.
Then, Door took the bird in her hands and faced it. She also made similar burbling sound of pigeons as a way of communicating with it.
So, this explains the answer.
