After I took Geoffrey; the Bus Spotter, I asked him what he does after writing the number of buses in his booklet. He told me twice a month, all of the bus spotters in the region get together in a pub and share their results.

Bus spotting is a pastime in which one seeks to see all buses in a particular fleet or those produced by a particular manufacturer. A person who engages in these activities is known as a bus spotter, bus fan (popular name in Hong Kong), bus nut (term popular in the UK) or bus enthusiast (although this term can also cover preservationists). Within the bus industry bus spotters are known as moquettes, from the material used to make the seat coverings. As with train or aircraft spotters, bus spotters spend much time outdoors with notepads, cameras or camcorders, monitoring bus routes.
Bus spotters are relatively unconcerned by timetables or network quality but they may be interested in new liveries, especially ad-hoc schemes to advertise particular products or events. Some may be so keen that they might track a vehicle through its life, knowing for example which fleet numbers it has carried with different owners and when mechanical parts or interior fittings were renewed. Bus spotting has never had the wide following achieved by train spotting in the UK, even though enthusiasts can share the common term of "gricer", however it has become popular in Hong Kong and bus societies have been formed there.
Bus spotters like to take photographs of buses and ride on them. Since bus spotting involves urban mass transit, it often goes hand in hand with metrophily. In New York, the two are often combined into "transit fan", a person who studies both bus and rail rapid transit, with the same diligence.

en.wikipedia.org/wiki/Bus_spotting