Some birdwatchers are keen rarity seekers and will travel long distances to see a new species to add to one of their "lists", e.g., life list, national list, state list, county list, etc. These fanatical birders are commonly known by the light-hearted slang term of twitchers, particularly in the United Kingdom.

Comedian and celebrity birder Bill Oddie introduced many birdwatchers to the distinctive vocabulary that distinguishes such a chaser of rare birds from other varieties of birdwatcher in his Little Black Bird Book (first published in 1980)

Examples of the twitchers' vocabulary

• To dip out (or dip): To miss seeing a bird which you were looking for.
• To grip off (or grip): To see a bird which another birder missed and to tell them you've seen it.
• To burn up or flog: To beat around in the undergrowth hoping to flush a bird. A desperate measure and not a kind way to treat an exhausted migrant.
• Dude: A novice birdwatcher; slightly pejorative term. Not someone who knows their feather tracts!
• String: A dubious, "ropy" record (or, as a verb, to claim such a record).
• Lifer: A first-ever sighting of a bird species by an observer; an addition to one's "life list".
• Year tick: A first sighting of a bird species in a particular year by a particular observer; an addition to one's "year list".
• Crippler: A rare and spectacular bird that shows brilliantly, perhaps an allusion towards its preventing people from moving on.
• Sibe: A bird from Siberia (usually applied to rare migrants).
• First: A first record of a species (in a defined area, often the United Kingdom).

Some species have nicknames: for example "RB Flicker" for Red-breasted Flycatcher, "Gropper" for Grasshopper Warbler, "PG Tips" for Pallas's Grasshopper Warbler etc. etc. Twitchers (and birders in general) will also use a mixture of scientific and slang terms for feather tracts and so on.