The Osprey is a cosmopolitan species, occurring on all
continents except Antarctica. Endangered by DDT, Ospreys have made
a remarkable recovery since that pesticide was banned in the 1970s.
It is now, once again, a fairly common bird of the boreal forest
and foothills region of Alberta, probably absent only from the arid
southeastern part of the province, except during migration. Since
Ospreys catch fish, their only prey, they are always associated
with lakes or streams. At least two dozen pairs nest along the Bow
River, from Banff to Calgary. If not disturbed, they readily nest
within urban areas. In Calgary, at least seven pairs were resident
in 2004. The first birds arrive in mid-April. Most depart for more
tropical areas by the end of September, some going well into South
America. Osprey, usually flying about 30 m (100 feet) up, scan the
water for fish, their only food. They often hover in one spot for a
prolonged period before making a spectacular plunge dive, wings
raised, feet extended out front, to capture their prey. Sharp
talons and spiny soles ensure a good grip. Rising to the surface,
with a few flaps they again become airborne, then shaking to rid
themselves of excess water, continue flying. Shortly after, they
re-position the fish headfirst, to streamline their flight. Bald
Eagles often try to steal their prey. Sometimes they capture a fish
too large to carry. Unable to let go, they flap and drag the prey
to the shore. If it is a really large specimen, it may pull the
Osprey underwater, drowning it. Most of their prey fish are species
of little interest to man. Their nest, re-used year after year, is
a bulky structure. In the past, it usually was sited on a strong
branch or on the top of a broken tree, a cliff pinnacle or even on
the ground. In recent years, Ospreys have taken to using man-made
structures - utility poles, electrical or communication towers,
church steeples and nesting platforms especially erected for them.
The female does most of the incubating of the usually three eggs,
for 32 to 33 days; the male bringing her food at the nest site. She
broods and tends to the young for a further 30 days. They begin to
fly at 51 to 59 days of age, becoming independent within one week,
but remain near the nest for up to eight weeks.