this is not a bug, but rather a consequence of your relatively low total number of bird observations, even though you have a lot of species. When going to https://www.inaturalist.org/observations?place_id=any&taxon_id=3&view=observers, it shows the top 500 observers by number of observations. When you then order by number of species, it does not actually show the top 500 observers by number of species, but actually just reorders the existing 500 observers by number of observations. So even though your number of species would put you in the top 75 users, your number of raw observations is outside the top 500, thus you won’t appear on the leaderboard