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Osprey Info
 Also known as fish hawks, Osprey are found
almost world-wide, along coastlines, lakes and rivers. They occur in tropical
and temperate parts of all continents, breeding from north-western Alaska and
central Canada south to Bahamas and Mexico (Campbell, 1990). They are a
migratory species and, in the western hemisphere, winters from southern United
States south to Chile and Argentina (Campbell, 1990). Osprey are often seen
flying over the water, hovering and perching in trees beside water
courses.
Breeding
"The Osprey breeds from near sea level to at least 1,070 meters
elevation in close proximity to permanent water. Occasionally, nest may be
located up to 4 km from a source of water. Most nests (87%; n=361) were closely
associated with permanent water.” (Campbell,
1990)
Nests: "Nests were situated in trees
(56%; n=395) and on man-made structures (44%). 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
meters, 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, 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.” (Campbell, 1990)
Eggs: For 46 clutches the average
(51%) dates were between May 15 and May 22.
Sizes for 39 clutches averaged (54%) 3 eggs. Incubation period is
about 38 days. (Campbell, 1990).
| Young:
For 419 broods the average (52%) dates were between June 27 and July 20.
Sizes for 412 broods averaged (54%) 2 young. Fledging period is 44 to 59 days.
(Campbell, 1990) |
Osprey chick
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CONSERVATION OF OSPREYS
Their population crashed during the 1950s to 1970s from exposure to
DDT, encroachment onto breeding grounds and shooting. According to the Birders
Handbook it was on the Blue List in the United States from 1972 to 1981.
Conservation programs, including successful use of artificial nesting
platforms, and the banning of DDT have allowed populations to
recover.
LOCAL KNOWLEDGE
OF OSPREYS
According to Volume II of the Birds of BC, “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.” (Campbell,
1990)
One noteworthy record reported a single Osprey in Trail, BC, February
22, 1972. This is an
unusual siting of a bird that by all usual reports migrates south in the
winter!
REFERENCE:
Campbell, R.W., N.K. Dawe, I. McTaggart-Cowan, J.M. Cooper, G.W.
Kaiser, M.C.E. McNall, 1990, The Birds of British Columbia, Volume II,
Nonpasserines, Diurnal Birds of Prey through Woodpeckers.
Prepared by
Nelson
Naturalists:
Emilee
Fanjoy
Elaine Moore
Rita Wege
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