Q: This task is about reading the given passage and construct a question about the information present in the passage. Construct a question in such a way that (i) it is unambiguous, (ii) it is answerable from the passage, (iii) its answer is unique (iv) its answer is a continuous text span from the paragraph. Avoid creating questions that (i) can be answered correctly without actually understanding the paragraph and (ii) uses same words or phrases given in the passage.
San Diego County has one of the highest counts of animal and plant species that appear on the endangered species list among counties in the United States. Because of its diversity of habitat and its position on the Pacific Flyway, San Diego County has recorded the presence of 492 bird species, more than any other region in the country. San Diego always scores very high in the number of bird species observed in the annual Christmas Bird Count, sponsored by the Audubon Society, and it is known as one of the "birdiest" areas in the United States.
A:
How many bird species have been observed in San Diego?