Read this sentence from the article:
you may be thinking that looking at birds is silly, but just think about the numbers of the recent record holders and the commitment it takes to get these numbers.
why would the author suggest that looking at birds is silly?
to create a sense of doubt in the reader
to distance himself from what seem to be rather strange people
to show readers that some people do not think birding is interesting
to suggest he has never birded himself but might someday