Twitchers' vocabulary is the set of jargon

Jargon

Jargon is terminology which is especially defined in relationship to a specific activity, profession, group, or event. The philosophe Condillac observed in 1782 that "Every science requires a special language because every science has its own ideas." As a rationalist member of the Enlightenment he...

 words used by twitchers. Twitchers are committed bird-watchers who travel long distances to see a new species just to add a species their "lifelist

Lifelist

A lifelist, or life-list, is a list of all biological species seen by a person. The phrase is particularly common among bird watchers, some of who compete with each other to have the most complete list....

", "year list" or other lists. Some terms may be specific to regional birding communities, and not all are used due to dialectic and cultural differences.

Terms

• 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.
• Mega or Megatick: A very rare bird
• Chooks: already seen or common birds (used in Australia).
• Crippler: A rare and spectacular bird that shows brilliantly, perhaps an allusion towards its preventing people from moving on.
• To dip out (or dip): To miss seeing a bird which you were looking for.
• Dude: "A posh bird-watcher who doesn't really know all that much about birds." A novice birdwatcher; slightly pejorative term. Also used to refer to someone who primarily seeks out birds for photography rather than study.
• First: A first record of a species (in a defined area, such as a county
  County
  A county is a jurisdiction of local government in certain modern nations. Historically in mainland Europe, the original French term, comté, and its equivalents in other languages denoted a jurisdiction under the sovereignty of a count A county is a jurisdiction of local government in certain...
  
   first).
• To grip off (or grip): To see a bird which another birder missed and to tell them you've seen it.
• Jizz
  Jizz (birding)
  Jizz is a term used by birders to describe the overall impression or appearance of a bird garnered from such features as shape, posture, flying style or other habitual movements, size and colouration combined with voice, habitat and location....
  
  : the overall impression given by the general shape, movement, behaviour, etc., of a species rather than any particular feature. Experienced birders can often identify species, even with only fleeting or distant views, on jizz alone.
• Lifer: A first-ever sighting of a bird species by an observer; an addition to one's life list.
• List:
  • Noun: a list of all species seen by a particular observer (often qualified, e.g. life list, county list, year list, etc.). Keen twitchers may keep several lists, and some listers compete to amass longer lists than their rivals.
  • Verb: to keep or compile a bird list (lister is close in meaning to twitcher).
• Plastic: Adjective used to indicate a bird which has escaped from captivity, rather than a genuinely wild bird.
• Sibe: A bird from Siberia
  Siberia
  Siberia is an extensive region constituting almost all of Northern Asia. Comprising the central and eastern portion of the Russian Federation, it was part of the Soviet Union from its beginning, as its predecessor states, the Tsardom of Russia and the Russian Empire, conquered it during the 16th...
  
   (usually applied to rare migrants).
• String:
  • Noun: A dubious, "ropy" record.
  • Adjective: Stringy
  • Verb: to claim such a record.
• Tick: An addition to a personal list (sometimes qualified as year tick, county tick, etc.). Life tick and lifer are synonymous. A tart's tick is a relatively common species added to one's list later than might be expected.
• Yank: A bird from North America
  North America
  North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
  
   (usually applied to rare migrants).

Some species have nicknames, for example: "RB Flicker" for Red-breasted Flycatcher

Red-breasted Flycatcher

The Red-breasted Flycatcher is a small passerine bird in the Old World flycatcher family. It breeds in eastern Europe and across central Asia and is migratory, wintering in south Asia. It is a regular passage migrant in western Europe, whereas the Collared Flycatcher which breeds further west is...

, "Gropper" for Grasshopper Warbler

Grasshopper Warbler

The Grasshopper Warbler, Locustella naevia, is an Old World warbler in the grass warbler genus Locustella. It breeds across much of temperate Europe and Asia. It is migratory, wintering from northwest Africa to India....

, "PG Tips

PG Tips

PG Tips is a brand of tea in the United Kingdom, manufactured by Unilever UK. It is claimed that Britons drink 35 million cups of the tea every day.-Brand name:...

" for Pallas's Grasshopper Warbler

Pallas's Grasshopper Warbler

The Pallas's Grasshopper Warbler, Locustella certhiola, is an Old World warbler in the grass warbler genus Locustella. It breeds in east Asia. It is migratory, wintering from India east to Indonesia....

. Twitchers (and birders in general) will also use a mixture of scientific and slang terms for feather tracts and so on.