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Range
 Breeds
from central Alaska and Yukon, southwestern Mackenzie,
northern British Columbia, southwestern Alberta, and
Saskatchewan south through the western United States to Baja
California and southern Mexico. Winters from central coastal
California to southern Mexico and northern Central
America.
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Status
Status is complex. On the
coast, common to very abundant spring migrant on
southeastern Vancouver Island and the entire lower Fraser
River valley in the Georgia Depression Ecoprovince. Fairly
common to very common summer visitant and autumn migrant
there; occasionally abundant in autumn and very rare in
early winter. Uncommon to locally common migrant and summer
visitant to Western Vancouver Island and the southern and
northern portions of the Coast and Mountains Ecoprovince;
very rare transient on the Queen Charlotte
Islands.
In the interior, fairly common
to very common (occasionally abundant) spring migrant and
summer visitant to the south-central portions of the
province, including the Southern Interior and Southern
Interior Mountains ecoprovinces; common to abundant
(occasionally very abundant) autumn migrant; casual in
winter there. Northward, throughout the rest of the
province, uncommon to locally common migrant and summer
visitant except in the extreme northeastern corner, where it
is a casual spring transient in the Taiga Plains
Ecoprovince.
Breeds.
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Status
Change
No change.
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Nonbreeding
 The
Violet-green Swallow is widely distributed across southern
British Columbia except for the west coast of Vancouver
Island and the central mainland coast, where it is localized
and scarce in some years. It is less numerous through the
Cariboo and Chilcotin areas, and its distribution is further
reduced in the northern parts of the province. Unlike the
Tree Swallow, the Violet-green Swallow seldom appears on the
Queen Charlotte Islands or in the Taiga Plains, and then
only during migration.
The Violet-green Swallow occurs
from near sea level to 1,400 m elevation. Migrating flocks
closely follow rivers, lakes, and valley bottoms as they
move northward during the spring migration before dispersing
into breeding areas. Both on the coast and in the interior,
it seems to favour lowland areas with open terrain and
concentrations of flying insects, on which it feeds. It is
usually found over freshwater habitats, including large and
small lakes, rivers, marshes, bogs, wet meadows, and beaver
ponds; adjacent forest is also used. This swallow forages
from low over water or ground surfaces to heights of 100 m
or more above a forest canopy. The Violet-green Swallow
occurs less frequently along the coast except over
estuaries, where it can be found in brackish meadows,
mudflats, fields, and grassy beaches. Rural and urban areas
are also used, particularly agricultural pastures and
well-treed suburbs. In the early spring, sunny cliff faces
may also provide important foraging sites.
The timing of the spring
migration varies widely between years. Violet-green Swallows
are among the earliest returning swallows and are
particularly dependent on weather conditions, which
determine the timing of insect hatches. In exceptionally
mild winters, the occasional bird can arrive at the south
coast in early February, and in some years the first flocks
arrive in late February. Normally, however, large numbers of
Violet-green Swallows appear suddenly on the Fraser River
delta and southeastern Vancouver Island in March, and
increase through April. These are birds in passage. Their
numbers decline abruptly in May and drop further in June and
July. A similar trend is evident from other areas along the
coast. The coastal movement peaks about 2 weeks ahead of
migration through the southern interior.
In southern portions of the
interior, birds may arrive in late February and early March;
their numbers peak in April and then decline. Spring
migration through the Southern Interior and Southern
Interior Mountains is smaller and less spectacular than the
coastal movement. In the Cariboo and Chilcotin areas of the
Central Interior, the peak movement occurs in the second and
third weeks of April. Few birds move through the Sub-Boreal
Interior. In the northern interior, early arrivals occur in
mid to late April, becoming most numerous in early
May.
In spring, the Violet-green
Swallow usually migrates in flocks of 20 to 200 birds,
although flocks of thousands can occur. Of 86 aggregations
with more than 200 birds, 84% occurred in the Georgia
Depression, 2% in the Southern Interior, 13% in the Southern
Interior Mountains, and 1% elsewhere. During peak spring
movements, large numbers may accumulate in good foraging
areas. For example, all records of more than 1,000 birds are
from lakes, all in the extreme south. The 5 maximum counts
(2,500 to 9,000 birds) were all recorded in April or the
first week of May, at Beaver and Elk lakes, north of
Victoria. The highest total count of Violet-green Swallows
in the province is 11,000 birds, tallied near Victoria at
Elk, Beaver, and Prospect lakes on 15 April 1970 (Tatum
1971). Southeastern Vancouver Island has the largest spring
movements in the province.
Post-breeding flocks congregate
over larger lakes, rivers, and marshes in July and August
before moving southward. During midsummer, mixed flocks of
swallows, numbering hundreds of birds, are common sights
over interior lakes.
The autumn migration is more
protracted than the spring movement and involves smaller
flocks of Violet-green Swallows. Peaks vary between years,
but generally their movements begin earlier than those of
other swallows. Numbers recorded on the southern migration
also suggest different behaviour than during the spring
movement. On the coast, where there is such a dramatic
northern movement in spring, swallows depart almost
unnoticed in autumn, and most have left by the first week of
October. In the southern portions of the interior, however,
almost the reverse is true. Of 24 autumn flocks of 200 birds
or more, only 12% were from the south coast while 88% were
from the southern portions of the interior.
In the northern and central
regions, migration begins shortly after nesting ends. The
highest numbers occur in July, and most birds have gone by
early to mid-August. In the Okanagan, Kootenay, and Columbia
valleys, the highest numbers occur in August and September,
and most birds have gone by the first week of October. In
the Okanagan valley, the autumn migration peaks in early
September (Cannings et al. 1987). Almost all Violet-green
Swallows have left the province by the end of
September.
The pattern of records suggests
different routes for spring and autumn migration. In spring,
most Violet-green Swallows move northward along the coast,
taking advantage of the milder weather and available food.
The small number of birds that migrate in spring up the
valleys of the southern portions of the interior suggests
that the nesting population in the Central Interior and
beyond is derived from the large coastal concentrations that
move into the interior along major west-east river valleys.
Following the breeding season, coastal birds leave shortly
after their young fledge and no noticeable concentrations
occur. For birds in the interior, there is no advantage in
returning to the coast. Swarms of late-summer chironomids
and other flying insects create an abundant supply of food
over lakes and ponds. Observations of large numbers indicate
that the swallows leave through the Okanagan, Creston, and
other southern valleys. Mountain passes and montane areas
(e.g., Manning Park) may also be important autumn migration
corridors, but their use has not been well
documented.
Although migrating swallows
spend much of their time on the wing, perching and roosting
sites are important habitat components. Frequently, they use
snags, leafless trees or branches, and roots protruding from
eroding river banks. In rural and urban areas, telephone
lines, buildings, wire fences, and bridges also provide
perching sites.
On the coast, the Violet-green
Swallow has been reported every month of the year, although
it occurs in substantial numbers only from late February to
late September. In the interior, it has been reported from
19 February to 8 November.
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Breeding
 The
Violet-green Swallow breeds throughout most of its range in
the province. It is scarce in the Peace Lowland and in the
Northern Boreal Mountains. The northernmost breeding records
are from the Tatshenshini River, Atlin, Fireside, and
Sulphur Creek, along the northern boundary of the province.
There is a vast area west of the Rocky Mountains and north
of the latitude of Fort St. John where there have been few
observers and thus few nest records. For example, although
Swarth (1922) found them abundant at Telegraph Creek, there
are no other nesting records in the Stikine River drainage.
There are just 3 nesting records on the coast north of
Vancouver Island: Owikeno Lake, Kitsumkalum Lake, and Alice
Arm. The centre of breeding abundance for the Violet-green
Swallow is in the Georgia Depression, Southern Interior, and
Southern Interior Mountains, where it has adapted well to
human-influenced habitats. Breeding has not been reported
from the Queen Charlotte Islands or the Taiga
Plains.
This species reaches its
highest numbers on southeastern Vancouver Island and in the
lower Fraser River valley of the Georgia Depression. An
analysis of Breeding Bird Surveys for the period 1968
through 1993 could not detect a net change in numbers on
either coastal or interior routes. Both Robbins et al.
(1986) for North America and Erskine et al. (1992) for
southern British Columbia also note stable Violet-green
Swallow populations.
On the coast, the Violet-green
Swallow has been found breeding from near sea level to 390 m
elevation; in the interior, it breeds from 300 to 1,400 m
elevation. It seems to thrive in close association with
humans (Weber 1972; Allen et al. 1977). Over 75% of 847
nests were from human-associated habitats. Most nests (62%;
n = 805) were found in backyard gardens and residential
buildings, roadside habitats, meadows, or shorelines (lakes,
streams, marshes, seashores). Only 6% were reported from
cliffs, which suggests a bias due to observer distribution.
Other habitats included orchards, pasture and other
farmland, parks, golf courses, and campgrounds.
The Violet-green Swallow has
been recorded breeding in the province from 1 April
(calculated) to 24 August.
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Nests: 
 Although
the Violet-green Swallow nests solitarily, it also nests in
substantial colonies, particularly on cliffs. Colony size
ranged from 3 to 40 pairs (n = 16), with 8 between 5 and 15
pairs. Thirteen of the colonies were found in the
interior.
The Violet-green Swallow has
adapted well to nesting in human-made habitats such as nest
boxes, the crannies of houses, garages, sheds, barns, and
other buildings, and in posts and poles, stone and brick
walls, and bridges. Natural nest sites include rock cliffs,
snags, and cavities in living deciduous and coniferous
trees. Along the Fraser River canyon, near Williams Lake, it
nests all along the cliffs, but has never used any of the
more than 1,000 boxes on the adjacent plateau (A. Roberts
pers. comm.). Violet-green Swallows seem to prefer boxes on
buildings rather than those on poles and posts. In suburban
environments, the House Sparrow frequently displaces the
Violet-green Swallow from nest sites (Erskine
1979).
In the Cariboo and Chilcotin
areas, about half of all nests were found in natural
situations. Further north, in the SubBoreal Interior and
Boreal Plains, natural sites such as crevices in cliff faces
and cavities in a variety of tree species were the preferred
nesting sites.
The adaptability of the
Violet-green Swallow is indicated by the diversity of nest
sites reported; any darkened cavity with an adequate
entrance hole or crevice seems suitable. The species has
been reported nesting inside the walls of buildings and on
fiberglass bats in attics where they have gained access
through knotholes or ventilation louvres, under tiles on the
ridges of house roofs, between logs in log buildings, under
roof shingles and flashing, in chimneys, in a trailer hitch
of a semi-trailer truck, under a plywood sheet in a
lumberyard, in plumbing vent pipes of buildings, and in the
blasting holes of roadside rock-cuts. Sometimes a human-made
site can prove to be a death trap for the birds. In the
mid-1970s, dismantling of a wooden shed on the Alaksen
National Wildlife Area, south of Vancouver, revealed nearly
100 swallow skeletons between the studs of a wall (R.
McKelvey pers. comm.). The knothole through which they had
entered was about 1.2 m up the wall, and the remains filled
the space between the studs to a depth of about 0.8 m. After
having gained access, the swallows, for some reason, could
not return to the hole to exit.
Reported nests were loosely
constructed, the amount of material governed by the size of
the cavity occupied. The nest was usually a collection of
grasses with a small cup formed in the centre or in 1 corner
of the cavity; the cup was formed with finer grasses and
lined generously with feathers. White feathers seemed to be
preferred. Most nests (94%; n = 515) were made of grasses
and were feather-lined (80%). One nest was made entirely of
feathers. Other materials included plant fibres, rootlets or
twigs (6%), mud (5%), hair (3%), conifer needles, wood
chips, plant down, and human-made materials such as
fiberglass insulation, string, rope, and paper. Nest sites
are reused in successive years.
The heights of 460 nests in
nest boxes ranged from 0.3 to 21 m, with 54% between 2.4 and
4.2 m; 344 nests where nest boxes were not used ranged from
ground level to 78 m, with 62% between 2.4 and 6.0 m. Many
of the known cliff sites have not been included in the
samples.
Eggs:
Dates for 302 clutches ranged
from 7 April to 21 July, with 51% between 29 May and 16
June. Calculated dates indicate that eggs can occur as early
as 1 April and as late as 1 August. Clutch size ranged from
1 to 8 eggs (1E-13, 2E-18, 3E-20, 4E-92, 5E-117, 6E-37,
7E-4, 8E-1), with 69% having 4 or 5 eggs. The 8-egg clutch
may have been the product of 2 females. The incubation
period in British Columbia ranged from 14 to 17 days (n =
16), with a median of 15 days, similar to the 14 or 15 days
reported by Turner and Rose (1989) and Brown et al.
(1992).
Nest
Success:
Of 188 nests found with eggs
and followed to a known fate, 139 produced at least 1
fledgling, for a success rate of 74%. Coastal nest success
was 76% (n = 82); interior success was 74% (n = 106).
Weather and parasitism by the larvae of Protocalliphora sp.
can have significant negative impact on the breeding success
of the Violet-green Swallow (see also Tree Swallow and Barn
Swallow). Other causes of egg or young mortality in British
Columbia included predation by House Sparrows, chipmunks,
squirrels, crows, deer mice, Cooper's Hawks, and American
Kestrels; and nest usurpation by European Starlings, Crested
Mynas, and House Sparrows. There are 2 reports of birds
laying second clutches after the first brood was
successfully raised; there are a number of reports of
renesting following the loss of eggs.
Young: Dates for 416 broods
ranged from 15 April to 24 August, with 53% between 20 June
and 9 July. Sizes of 353 broods ranged from 1 to 7 young
(1Y-20, 2Y-50, 3Y-7, 4Y-142, 5Y-105, 6Y-26, 7Y-3), with 59%
having 4 or 5 young and 76% with 3 to 5 young. The nestling
period in British Columbia ranged from 23 to 27 days (n =
14), with a median of 25 days. Edson (1943) found a nestling
period of 23 days.
Brown-headed Cowbird
Parasitism: In British Columbia, cowbird parasitism was not
found in 800 nests recorded with eggs or young; the
Violet-green Swallow has not been found as a cowbird host
elsewhere in North America either (Friedmann et al. 1977;
Friedmann and Kiff 1985).
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Remarks
Godfrey (1986) shows the
breeding distribution of the Violet-green Swallow to include
the Queen Charlotte Islands and the Taiga Plains Ecoprovince
in extreme northeastern British Columbia; however, we could
find no evidence that this swallow breeds in those
areas.
British Columbia is the centre
of Violet-green Swallow breeding abundance in Canada. Yet,
as Brown et al. (1992) note, "Despite an extensive
distribution, less is known about the Violet-green Swallow
than nearly any other North American Swallow." Their review
could find no recent studies of the species' breeding
biology or behaviour and was based primarily on reports from
the 1940s and 1950s. Interested researchers in British
Columbia have the opportunity to add to our knowledge of
this species.
Erskine (1979) notes that the
Violet-green Swallow's ability to nest in remote cliffs and
tree cavities and, at the same time, adapt well to human
habitation may have saved it from harmful human impact. It
readily takes to nest boxes, and once established will
return year after year; an adult female banded at a nest box
on 30 June 1983 at the Qualicum National Wildlife Area,
Vancouver Island, was recaptured in successive years in the
same or a nearby nest box until 18 June 1989.
Since the Violet-green Swallow
is a secondary cavity-nester, its nesting density may be
limited by a scarcity of suitable nest sites in regions
lacking rock cliffs (Brawn and Balda 1988).
See Brown et al. (1992) for a
summary of the life history of the Violet-green Swallow in
North America.
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Located
at:
675 Belleville Street,
Victoria, British Columbia,
CANADA
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Copyright © Royal BC Museum
All rights reserved
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This
information was scanned from The Birds of British Columbia (Campbell et
al.), Volume III, pages 144-151. Volumes I, II and III of The Birds of British
Columbia can be ordered electronically at: 
Nests