This birdwatcher appears to be time travelling, or they have been backfilling sightings of specific birds.
It's one clerk, in (in my imagination) the cold and damp basement of the British Museum, in 1886, filling in details of birds whose skins have been sent in by many collectors spread out over the Far East, possibly via the vast collection of Allan Octavian Hume. This post gives some more detail, and this one has a link to the collectors' journal that Hume edited in addition to his many other responsibilities.
Once you figure out that the 1886-ish ledger is written mostly by one guy with an achy hand and a huge pile of bird skins, you realise that he arranged his work so that he could do as much writing of "ditto" as possible. We can do the same by using a clipboard management tool like ClipX, which makes transcribing these pages much faster.