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Range
Cosmopolitan
Occurs in tropical and temperate parts of all continents. In the
Western Hemisphere, breeds from northwestern Alaska and central
Canada south to the Bahamas and from the southern United States
south to Chile and Argentina.
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Status
Uncommon to fairly common migrant and
summer visitant across the southern third of the province, rare
north of latitude 56°N very rare on the Queen Charlotte islands.
In winter, very rare on the south coast, casual in the interior.
Widespread breeder south of latitude 56°N, except the Queen
Charlotte Islands. |
Status
Change
No change. |
Nonbreeding
The Osprey is widely distributed throughout
the province, occuring chiefly near lakes, rivers, sloughs, and
protected coastal waters including lagoons, bays, and inlets it
is reported infrequently on the Queen Charlotte islands and in far
northern mainland areas
On the coast, the first spring migrants
may be seen in late February, but most arrive during the first 2
weeks of April in autumn, the southward movement begins in September,
and by mid-October most have departed. In the southern interior,
early spring migrants appear during the second and third weeks of
February, but the main influx occurs during the second and third
week of April. Migrants arrive in the Chilcotin-Cariboo region during
the first week of April. Autumn departure occurs during late August
and through September. The main exodus in southern areas occurs
during the last 2 weeks of September; most birds have departed by
early October Migrating Ospreys do not regularly aggregate in large
flocks in British Columbia as they do in some other areas in North
America (see Bull 1974); the largest group reported in the province
is 16 birds. |
Breeding
The Osprey breeds throughout the province,
except on the Queen Charlotte islands, generally south of latitude
56°N. Although Cumming (1931) indicates that it "... formerly
nested at Tow Hill .. and is now absent from the north end of Graham
Island [Queen Charlotte Islands]..." there is no conclusive
evidence that it ever bred there. The centre of abundance appears
to be in the vicinity of Creston and Nelson where approximately
140 pairs nest, making this area one of the most concentrated in
the world (Anonymous 1988) The most northern record is from Atlin
Lake (3 young in tree nest, 16 July 1980).
The Osprey breeds from near sea level
to at least 1,070 m elevation in close proximity to permanent water.
Occasionally, nests may be located up to 4 km from a source of water.
Most nests (87%; n=361) were closely associated with permanent water.
Nests close to water were found in the vicinity of lakes (65%),
rivers (25%), or marine shores (9%). Three nests were located near
drying sloughs. Lake nests were either situated on a man-made structure
in the lake (52%), in trees along the shore (39%), or on wooded
islands (9%). River nests were situated either along shores (67%)
or me man-made structures in the river (23%). Nests on dry land
(13%) were located on forested sides of mountains, lightly forested
range land, along highways, roads and railway tracks, or on prominent,
wooded hills. L S. Forbes (pers comm ) found that Ospreys at Creston
sometimes nested be Great Blue Heron colonies. He also notes that
Ospreys there give nesting Bald Eagles a wide berth and that a relocation
of eagle nests caused a redistribution of nesting Ospreys |
| Nests: 
Nests were situated in trees (56%; n
= 395) and on manmade structures (44%). Most tree nests (64%) were
in dead trees, including black cottonwood and 5 species of conifers.
Living trees (36%) included 2 deciduous and 7 conifers us species
Most nests were located at or near the top of the tree. Man-made
structures supporting nests included wooden pilings (53%), cross
members of wooden power poles (32%), navigation lights in lakes
(8%), as well as cranes, artificial nest platforms, gas pylons,
microwave dishes, a cable across a river, a wharf, and a chimney.
Heights of 381 nests above ground or water ranged from 1 to 61 m,
with 59% recorded between 9 and 18 m.
Nests ranged from compact to large, bulky
structures of sticks, branches, and twigs. They were usually lined
with a variety of material, including twigs, grasses, bark (black
cottonwood and ponderosa pine), mosses, weeds, fish bones, twine,
and down. Measurements for 8 nests ranged from 0.6 to 2.3 m for
outside diameter, and 0.3 to 1.7 m in height.
One nest in the east Kootenay was used
for 11 consecutive years. Two active Osprey nests built on a wharf
were only 6 m from each other. Ospreys have been recorded displacing
Canada Geese and Great Horned Owls from their nests, although at
Creston, geese often prevent Ospreys from using a nest (L. S. Forbes
pers. comm.). Forbes also notes that Ospreys occupying nests from
which geese had fledged young rarely reared young successfully.
Eggs:
Dates for 46 clutches ranged from 30
April to 23 June, with 51% recorded between 15 and 22 May. Calculated
dates indicate that eggs could be found as early as 17 April and
as late as the end of June. Sizes for 39 clutches ranged from 2
to 4 eggs (2E-16,3E-21,4E-2), with 54% having 3 eggs. Incubation
period is about 38 days but may extend to 43 days (Barber and Koplin
1972).
Young:
Dates for 419 broods ranged from 21 May
to 4 September (2 young fledged), with 52% recorded between 27 June
and 20 July. Sizes for 412 broods ranged from 1 to 4 young (1Y-117,
2Y-221,3Y-67,4Y-7), with 54% having 2 young. Fledging period is
44 to 59 days (Stotts and Henny 1975). |
Remarks
In the Creston area, numbers of breeding
Ospreys increased between 1968 and 1981. This increase was attributed,
in part, to the installation of a water management system which
increased the abundance of prey fish available to the birds (Flook
and Forbes 1983). In 1981, a mean of 1.5 young was fledged from
27 occupied nests in the Creston area. This mean is above the rate
necessary to maintain a stable Osprey population (Henny 1983,1986;
Henny and Wight 1969; Spitzer et al. 1983). |
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