Hello all
David Geering recently raised the question : "how regularly do, what are
probably best considered vagrant, birds need to
show up to be considered regular migrants?"
Here's what books give as various related definitions. Some define vagrants as
recorded less than 10 or 20 times in
Australia. And an old rarities committee definition indicates about less than
10 records. At the opposite end of the
spectrum, "migrant" comes out with a range of definitions but with various
common factors.
Migrant:
Atlas of Bird Migration: refers to the various types of migration such as
altitudinal etc. but states conventional
migrations are regular, taking place at the same time each year, and fixed in
distance and direction.
Shorebirds of Australia, Lane and Davies: "Strict migrant": most of their
population moves annually between traditional
breeding and non-breeding areas; to a strict schedule
Reader's Digest Complete Book: regular, annual movement of a whole population
or a large part of it between 2 areas, each of
which is occupied for part of the year, usually one for breeding
Atlas of Australian Birds: moves regularly from one area to another, often
from breeding to non-breeding area and back
again.
Pizzey & Knight: regular, usually seasonal, geographical movement and return.
Altitudinal migration being movement of
populations or birds that breed at high altitudes down to lower levels in
autumn-winter and back to higher levels for the
breeding season, usually spring-summer.
Pizzey & Doyle 1980: regular, reciprocal annual pattern of movement. Breed in
one part of their range and regularly go to
another part of their range during non-breeding season.
Sasol Birds of Southern Africa: a species which undertakes (usually) long
distance flights between its breeding and
non-breeding areas.
Newman's Birds of Southern Africa: regular movement between 2 alternative
regions inhabited at different times of year, 1
region in which they breed and the other used when not breeding. Altitudinal
migrant: move seasonally from one altitude to
another
Slater 1986: moves from area to area on a regular basis
Field Guide to NZ Birds, Heather and Robertson: moves annually and seasonally
between breeding and non-breeding areas.
Includes species which reach NZ each year, even if in small numbers.
Simpson & Day 1986: regular geographical movement
Passage Migrant:
World Birds, Brian P Martin: bird that passes through on migration, mostly in
autumn and spring, and does not remain for
most of the winter or summer. Refers to migration as "seasonal".
Roberts' Birds of Southern Africa: birds passing through on migration from one
point to another but not stopping over
Atlas of Australian Birds: migrant observed at a place between its departure
point and its destination
Overwintering:
Sasol Birds of Southern Africa: a bird which remains in the region instead of
migrating to its breeding grounds
Nomad:
Pizzey & Knight: variable, erratic movement - in Australia often related to the
effects of irregular rainfall
Newman's Birds of Southern Africa: species with no fixed territory when not
breeding
Slater 1986: moves from area to area with no seasonal regularity
Simpson & Day 1986: variable, often erratic movement with regard to time and
area
Birds of Tasmania, RH Green: wandering in search of food, remaining in one
locality to breed or while conditions are
favourable
Irruption / Invasion:
Atlas of Bird Migration: in talking about Irruption, refers to one thing in
common about the irruptive bird species, i.e.
they have a relatively restricted diet which is itself subject to wide
fluctuations in abundance.
Pizzey & Knight: irregular movement in which large numbers of birds (of one or
a few related species), move into areas where
they are not usually found in such numbers. Typically a single event, without
a regular, reciprocal movement and thus not a
migration. In Australia, usually caused by inland droung or better than normal
inland rainfall causing improved breeding
success, often followed by an exodus.
World Birds, Brian P Martin: of Invasion: Sudden range expansion into new area
Sasol Birds of Southern Africa: of Irruption: rapid expansion of a species'
normal range
Newman's Birds of Southern Africa: of Range Expansion: process in which a
species increases its breeding range - spread
into regions not previously occupied. of Irruption: irregular migration into
a new area, often brought about by
unfavourable conditions in the normal range of a species, and usually of a
temporary nature. of Aggregation: gathering
brought about by some common interest such as a temporary food availability,
after which individuals disperse separately
Dispersal
Newman's Birds of Southern Africa: more or less random centrifugal movement
away from a locality.
A Guide to Birds, K Hudec (about UK/European birds): birds which outside the
nesting season roam the countryside but usually
not far from the nesting grounds
Vagrant / Accidental:
Christidis and Boles/Australian Taxonomy 1994: of Vagrant: less than 10
records in total. The V* rating indicates more
than 10 records on the mainland but breeds only on island territories within
Australia
Pizzey & Knight: of Vagrant: bird found in area not its usual range or habitat
(found welll out of normal range), having
strayed there by accident or mistake, eg blown by gales. Rare and irregular in
occurrence: a species that has occurred in
the country less than 20 times in total.
Pizzey & Doyle 1980: of Vagrant: birds recorded less than twenty times in
Australia "so far as can be ascertained".
"Clearly this is a most arbitrary grouping. Vagrants in Australia are mostly
migrants at or beyond the periphery of their
normal winter range - but some may be so far from their normal range as to be
apparently lost.
Atlas of Australian Birds: bird wandering outside the normal range of the
species
World Birds, Brian P Martin: A wanderer outside the normal migration range,
usually blown off course by adverse winds.
Sasol Birds of Southern Africa: of Accidental: a vagrant or stray species not
normally found within the region. of
Vagrant: rare and accidental to the region
Field Guide to NZ Birds, Heather and Robertson: of Vagrant: a wanderer, bird
having turned up unexpectedly in an unusual
direction, having been caught up in a severe storm, is blown well of course,
whereas a straggler is in about the right
direction but has gone further than usual
Simpson & Day 1986: of Vagrant: bird found in an area which is not its usual
habitat, having strayed there due to
disorientation, adverse winds etc.
Straggler:
Field Guide to NZ Birds, Heather and Robertson: bird that follows its normal
migratory path but goes too far or strays off
course
Casual:
Pizzey & Knight: species outside its normal range, though not necessarily
outside its normal habitat. Reported more
frequently than accidentals or vagrants.
Endemic: / Indigenous
Pizzey & Knight: confined to a region or country.
Roberts' Birds of Southern Africa: of Endemic: living in, and usually
originating in, one geographical area only, and found
nowhere else. of Indigenous: native to a geographical area, ie not exotic or
introduced
Sasol Birds of Southern Africa: of Endemic: species whose breeding and
non-breeding ranges are confined to a particular
region
Newman's Birds of Southern Africa: found only in a specific region or country
Field Guide to NZ Birds, Heather and Robertson: natural range is in a certain
country and nowhere else
Simpson & Day 1986: native to a particular area
Near Endemic:
Sasol Birds of Southern Africa: species whose range is largely restricted to a
region, but extends slightly outside the
region's borders.
Breeding Endemic:
Sasol Birds of Southern Africa: breeds only in a particular region but
undertakes movements or migrations during the
non-breeding season such that a measurable proportion of the population leaves
the region.
Resident / Sedentary:
Pizzey & Knight: remaining in one place all year, non-migratory.
World Birds, Brian P Martin: of Resident: Species remaining throughout the
year in a specified area. Of Sedentary: a
species which is non-migratory.
Slater 1986: lives in the area all year
Simpson & Day 1986: of Sedentary: locally living, not travelling far
Birds of Tasmania, RH Green: of Sedentary: remaining in the same locality for
whole of life
Feral / Exotic:
Pizzey & Knight: of Feral: domesticated species escaped or released and living
wild
Roberts' Birds of Southern Africa: of Exotic: introduced from another part of
the world, i.e. not indigenous
Sasol Birds of Southern Africa: of Feral: species which have escaped from
captivity and now live in the wild
Field Guide to NZ Birds, Heather and Robertson: of Feral: living wild after
domestication. of Introduced: bird brought to
NZ by people, not by its own efforts
Simpson & Day 1986: of Feral: returned to the wild after domestication
And for additional interest:
Handlist of Birds in NSW, Morris, McGill and Holmes 1981:
Regarding the handlist's estimates of abundance for species considered to occur
regularly, these descriptions for maximum
population size in any given year:
Rare < 100
Scarce 100 - 1000
Uncommon 1000 - 10,000
Moderately common 10,000 - 100,000
Common 100,000 - 1,000,000
Abundant > 1,000,000
RH Green for his Birds of Tasmania book described his abundance notes as
follows:
Rare: rarely recorded
Uncommon: seen only occasionally
Common: regularly seen as odd pairs and individuals
Numerous: regularly seen, sometimes in dozens per day
Very numerous: regularly seen, sometimes in hundreds per day
In loose keeping with the Handlist of Birds above, Green states that the
average number in one of his categories differs by
about tenfold from the next.
And finally: an RAOU 1991 report on Records Appraisal Committee opinions
defined "rarities" as having reporting rates over a
10 year period to a maximum average of 1.5 records per year. Species are
removed from the review list if they've had a
greater average than 1.5 records per year AND sightings in at least 7 of the
preceding 10 years. That was 1991 - not sure
what it is now - someone from BARC or Birds Australia could update this
information.
Irene Denton
Concord West, 12 km from Sydney city, NSW Australia
33 50 17 S 151 05 25 E
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