Final answer:
The bird that visited the site and had been disappointed according to the narrator was the heron, a tall, white bird that left due to the commotion caused by other birds.
Step-by-step explanation:
According to the narrator, the bird that had visited the site and had been disappointed was the heron. This is evidenced in the segment that describes the frustration of the heron when a company of shouting cat-birds arrives, causing the solemn heron to depart. The heron is described as a 'queer tall white bird with soft feathers and long thin legs', which distinguishes it from the other birds mentioned in the passages. In the context provided, the heron seems to be seeking a quiet place, and the commotion created by other birds leads to its disappointment.