Two points, from the study itself, 50B is their median estimate but their mean estimate is 428 billion [1]: > We calculate that there are likely to be ∼50 bill

Two points, from the study itself, 50B is their median estimate but their mean estimate is 428 billion [1]: > We calculate that there are likely to be ∼50 billion individual birds in the world at present: about six birds for every human on the planet. This represents the midpoint of our estimates (i.e., the median), albeit with considerable uncertainty (Fig. 2). Compared with the median estimate, the mean estimate of the aggregated distribution for all birds in the world was ∼428 billion individual birds (Fig. 2). While we provide an estimate with a wide highest-density interval, our estimate corresponds well with a previous estimate of the number of individual birds in the world by Gaston and Blackburn (37), who estimated that there were between 200 and 400 billion individual birds in the world. Notably, Gaston and Blackburn (37) did not estimate species separately but rather extrapolated from small-scale density estimates in which all bird species were considered equal. We, however, provide data for nearly all the world’s bird species. This is a massive disparity in their own estimates, and they acknowledge the uncertainty. As others have noted, they are also not including farmed birds, so this is an estimate of birds in nature. 1. https://www.pnas.org/content/118/21/e2023170118 https://www.pnas.org/content/118/21/e2023170118