Some definitions of and references to 'vagrants' in the books. In summary,
there are 2 kinds of usage -
a) narrow or technical, sometimes depending on precise numbers of
b) a broader usage, sometimes to the point of extreme vagueness, sometimes
relying, not always helpfully, on the concept of a 'usual range' -
Audubon Encyc of NAm Birds:
Term for a bird that has wandered outside its normal migration range; also
a term for those resident birds that migrate irregularly because of food
shortages or for other reasons.
(New) Hbk of WA Birds vol 2:
Rare and irregular in occurrence
Bds Wallacea (Coates):
A bird which is of irregular or accidental occurrence
Bds of SE Asia (Robson)
A status for a species nationally or regionally when it is accidental (rare
and irregular) in occurrence
Christidis & Boles:
V = Vagrant, (less than 10 records in total)
A New Dict of Bds (AL Thomson)
A wanderer outside the normal migration limits of the species or subspecies,
so far as that can be judged
Simpson & Day (early eds):
A bird found in an area which is not its usual habitat (sic), having strayed
there due to disorientation, adverse winds,etc
Spec and Biog of Bds (Newton):
" ... More than half of the 570 or so species on the British list are
vagrants, which appear from time to time but do not regularly breed,
overwinter or migrate through Britain. Some such species occur in numbers
every year, while others appear less often, in extreme cases perhaps only
once in several decades. ..."
Gde to Bds of India (Grimmett etc):
"Abundance is described using mainly the following terminology, which is
based on subjective assessment. Abundance decreases down the list:
Bds of Aust High Country:
Occurring as an infrequent and unpredictable visitor. Vagrant birds may get
mixed up with flocks of related species and be seen in areas outside their
NGS Gde to Bds of North Am:
"Birders call CASUAL the species that turn up irregularly in small numbers
in areas outside their normal range. Casual occurrences are not unexpected
but neither are they annual. A VAGRANT has strayed off its usual migration
route. A VISITOR is making a stopover during migration or has wandered out
of its usual range. Vagrants and visitors are both unexpected. ACCIDENTAL
refers to species that have been seen only a few times in an area that is
far out of their normal range."
Peterson field guides do not use the expression 'vagrant', but other terms
with given definitions eg in the 'Texas' field guide:
"RARE: 1-5 in a year but probably regular.
IRREGULAR: Not every year but may occur in numbers
CASUAL (or OCCASIONAL): On the local level this means only 1 or 2 records
in a decade, but the bird might be expected to reappear. When referring to
the state as a whole it means more than 5 records but less than 15
ACCIDENTAL: On the local level this means 1 record; the bird might not
reasonably be expected again. On the state level, accidental means 5
records or less"
Dir of Aust Bds (Schodde & Mason):
"Vagrants and Introductions
.... Rarely recorded vagrants and visitors that have yet to be shown to be
integral members of this fauna are listed separately in Appendix I; ....
Most are cyclone-blown waifs or overshot palearctic migrants that normally
winter throughout southeast Asia and Indonesia. They only reach Australia
by chance, usually as single birds in one-off events, and, contrary to most
titles advertising their recording in the literature, are hardly new species
Bds of Aust (McDonald):
'... In the arid interior species have a nomadic distribution pattern ...
[They] may be well known in one area for several years then suddenly
disappear, to reappear again later - then go 'flyabout'. In years of great
drought some dry country species invade coastal districts but do not settle
there. Individual birds are known to get 'lost', probably meaning that
whatever instinct holds them to a certain range ceases to function and they
wander long distances. It is not always possible to know which records are
of vagrants and where to draw the distribution limit. ..."
ACT 1992 Atlas:
A species whose normal range does not include the ACT
F Gde to Rare Bds Brit and Europe
"The species covered are -
1. true vagrants, not breeding in Europe and which are only rarely recorded,
2. very rare breeding birds (generally less than 100 pairs), and not seen in
large numbers in migration"
[The 'status code' used has been mentioned previously]
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