From a hundred feet in the air, the hovering
angler folded its wings, silently slipping like lightening from the sky.
Suddenly a four-foot portion of the lake thundered into prisomed plumes of
diamondized droplets. Completely immersed, the feathered predator floated to
the surface, struggling to emerge with a fish in its talons. A third, then
fourth, labored wing-beat increased the height from the lake's surface. In a
remarkable finale, the fishing raptor shook off excess water, gliding ever so
closely to the pool's shimmering surface again. While positioning the fish
straight ahead, torpedo-style in its talons, the Osprey began stroking upward,
its wriggling prey secured. With most efficient style, this lean, flying
machine had spied its quarry and with amazing desire, just took it. You thought
your tackle box contained everything you needed to catch a fish, but this was
truly an incredible display of "fishing perfection!"
Ospreys are well equipped for obtaining a meal.
They can see five times more clearly than people, so they easily spot their
prey. As bow-hunters realize when spear-fishing, underwater targets are not
where they appear, due to water's refraction of sunlight rays. In flight
Ospreys close the nictitating membrane, a thin layer of clear tissue like an
inner eyelid, over their eyes to keep the eye moist. During a dive the membrane
protects the eye when Ospreys hit the water. They are the only raptor with nose
flaps that close, so they can go completely under the surface. Also, Ospreys'
pale-bluish toes are tipped with nature's finest fishhooks: talons, sharp as
needles. Toes have roughened protuberances or "spicules" to hold slippery fish,
and outside toes are capable of swiveling backward to join the rear toe or
"hallux" (two toes clamping with two toes versus the standard three toes and
hallux). This allows grasping fish torpedo style, which reduces wind resistance
while in flight. Ospreys also have the ability to lift from water, vertically,
using specialized joints at wing wrists or "carpals". These anatomical tools
distinguish ospreys as unique in the raptor kingdom. No other birds of prey
combine all of these capabilities into one species.
The Osprey’s scientific name (Pandion haliaetus)
comes from the mythical king of Athens, Pandion, whose daughters were turned
into birds, and by the Greek words halos, referring to the sea, and aetos, or
eagle. Ospreys, commonly called fish hawks or fish eagles, are neither a true
hawk nor eagle. The species is of ancient lineage and is presently classified
near the, hawk-like, kite family. It has a worldwide range and some
ornithologists call the Osprey “The Natural Citizen of the World.” Four
subspecies are presently recognized, two of which occur in North America; P.h.
carolinensus in temperate North America (including Iowa) and P.h. ridgwayi in
the Caribbean. The common name Osprey is from ossifragus, a Latin word meaning
“bone breaker,” referring to the strong grip of its talons.
Osprey fossils, the bones and other remains of
ancient animal life, show that Ospreys have been on earth for 13 million years.
An Osprey from the past was smaller, but had a range similar to today’s
Ospreys.
People have long admired the Osprey’s fishing
skills and strength, incorporating Ospreys into their cultures. Ancient Greeks
thought Ospreys could predict lightning. Asian emperors had Osprey pictures
woven into palace tapestries. In South America, native people used Osprey
feathers and bones in ceremonies to guarantee fishing success. In Canada, a
Northwest Coast First Nation legend tells of a marriage between an Osprey and a
whale that created the Orca whale. An Orca is actually a large and
black-and-white dolphin that jumps out of the water like a bird in flight and
has a cry that sounds like an Osprey’s. Osprey calls consist of a series of
shrill, staccato whistles, gradually rising in pitch, tewp, tewp, teelee,
teelee, tewp.
Ospreys are large narrow-winged, fishing
raptors, weighing between 2.5 and 4.5 pounds. An Osprey’s six-foot wingspan is
so large it is sometimes mistaken for an eagle, but an Osprey’s wing is narrower
and curves backward at its wrist, like the wing of a gull. Unlike an eagle’s
wing-plane, which is straight, the Osprey needs to rise out of water with a
large fish and has a special joint allowing this maneuver. In contrast to the
eagle an Osprey’s forehead is smooth. Ospreys don’t fly through trees or tall
grass to catch their prey, so they don’t need the bony ridge above their eyes
that other raptors have for protection.
Ospreys’ field marks are dark carpal, or wrist,
patches on the underside of each wing. The dark spots come in handy when the
bird is hunting. From a distance the dark spots look like two small gulls
dipping and soaring rather than one large bird about to
strike.
An Osprey wears light feathers on the underside
of its body and dark feathers on top. The white feathers on its chest look like
the light colors of the sky to its prey - any fish swimming below. The dark
colors camouflage, or hide, the Osprey from its predators, large owls that
attack from above, particularly when they’re on the nest. The brown and white
barred, or evenly striped, feathers on the underside of an Osprey’s wings and
tail help hide its shape in flight. To camouflage its head, an Osprey wears
dark spots on top, and a dark stripe through its eye area, like wraparound
sunglasses. This eye stripe, called a malar (MAY-ler) stripe, may reduce sun
glare, like the black grease used under the eyes of athletes. An adult Osprey’s
eyes are yellow. Its brown hooked beak, its gray legs and feet, and its black
talons don’t reflect sunlight, so there’s no glare to give away its position.
An Osprey’s talons are made of keratin, the same substance as our fingernails.
If part of a talon breaks off it will slowly grow back.
Unlike many raptors, male and female Ospreys are
very similar. A female Osprey is slightly larger, and usually wears a darker
necklace, or band of speckles, across her white chest that helps her hide while
nesting.
While hunting, Ospreys can spot a fish two hundred feet away. An
Osprey is a strong flyer, flying with a slightly circular motion at about 25
mph. When diving for its prey, an Osprey enters the water at about 40mph and can
catch a fish up to three feet underwater. Studies report a family with two
young needs four to five fish per day. Fish like bullheads and carp forage
about the bottom and lakesides. With their interests directed downward, they
become vulnerable for Ospreys from above. Fish taken are generally in the range
of 5 – 12 inches in length. A fish is usually successfully snagged in one out
of three tries. Ospreys are known to carry fish upwards of five miles to remote
nests.
An Osprey bathes often by wading breast-deep into shallow water,
putting its heads underwater, and beating its wings. Excess water is shaken
from wings and the bird flies to a sunny perch, where it holds its wings out to
dry like laundry hanging on a clothesline. After feeding, an Osprey may wipe
its beak on a branch, or flick away fish scales by shaking its head back and
forth. To clean its feet it flies low over the surface of the water and drags
them through the water. It may also do this to cool itself on a hot
day.
Nests may be built at varying heights upon any
structure, natural or man-made, that provides a platform. Ospreys occasionally
nest on or near the ground or upon buoys over water. Nests are usually one foot
deep, four to five feet wide, made of sticks and lined with grass. Apparently,
visibility is important in nest-site selection; osprey nests provide a
commanding view of surroundings. They are usually located on prominent
landforms, peninsulas or islands with few, or preferably no, tree branches
higher than the nest.
Osprey clutches consist of three or four eggs
that are creamy white and heavily spotted brown. Eggs are laid at
two-to-three-day intervals in late May. After the first egg is laid,
incubation proceeds for 38 days and is dominated by the female. Both parents
have “brood patches” to aid incubating eggs. Brood patches are featherless
areas on raptors’ abdomens where eggs receive warmth for necessary incubation.
The male provides food for the female and brood after hatching. The female
remains in constant attendance the first 30 days, providing protection from
predators and the elements. Predators include raccoons, gulls, crows and owls.
When predators are near, camouflaged nestlings lie outstretched and motionless
as a natural defense.
At 42 days, young can tear apart fish provided
by parents and around 53 days, first flight occurs. Young of the year quickly
acquire fishing skills and gradually expand their range until dispersal in late
August. Immature Ospreys spend up to 20 months at their over-wintering areas in
Central and South America. Some Ospreys migrate 4,000 miles from the Northern
Hemisphere to the Southern Hemisphere. Adults attain sexual maturity when three
to four years of age. Researchers estimate first-year bird mortality at 51 -
57% with adult mortality at 16 - 20% annually. Average life expectancy can be
fifteen years. So an Osprey may migrate over 62,000 miles in a lifetime. That
is about as far as 2 ½ times around the world!
Ospreys were heavily affected by the biocide
crash of the 1950s, which was caused by organo-chlorines like DDT.
Organo-chlorines caused eggshell thinning which led to fewer and fewer young to
replenish the population. Numbers were severely reduced throughout their range,
but were hardest hit in Great Lakes and Atlantic coast areas. Osprey
populations have shown a gradual increase since DDT and similar substances were
banned in the United States in 1972. By 1981, 8,000 osprey pairs existed in the
continental 48 states, and by 1994 a national survey tallied 14,109
pairs.
According to tribal elders of the Omaha nation,
accounts of Ospreys nesting along Iowa waterways are included in their oral
traditional stories. These indigenous people have lived throughout northwestern
Iowa for thousands of years. However, no successful Osprey nesting had been
documented in Iowa since European settlement. A report in 1892 indicated a
nesting might have occurred along the Cedar River, but the addled Osprey egg was
not recognized by the Iowa Ornithologists' Union of that time as positive proof
of nesting. In the year 2000, an osprey nesting attempt occurred in
northwestern Iowa. It was believed the pair was the result of Ospreys released
by Minnesota DNR in mid 1990s at Heron Lake in southwestern Minnesota,
approximately 25 miles north of the nest. No eggs were laid but this pair held
a promise for future nesting successes. (This was the pair that successfully
nested at Spirit Lake Middle School outdoor classroom in 2003.)
Male Ospreys show strong fidelity to ancestral
breeding areas, preferring to nest colonially where adults originated. Female
ospreys may disperse hundreds of miles from their origin, however males will
generally return within about 20 miles of origin. Due to this very low
dispersal tendency by males, young Ospreys are prime candidates for relocation.
Projects are designed to spread young of the population, geographically, to
areas where ospreys do not nest. This strategy will ultimately improve nestling
survival and complete continental population distribution.
With construction of lakes and reservoirs by
Department of Natural Resources, County conservation boards, private industry,
and U.S. Army Corps of Engineers, potential Osprey habitat exists today that was
previously not available. Historically, there were numerous Osprey summer
sightings in Iowa, but apparently these young, non-breeding Ospreys returned to
areas where they were reared for mating and nesting. During the last 20 years,
the number of migrants through Iowa has increased as breeding populations to the
north have grown. Despite this population growth, Ospreys have demonstrated
little breeding range expansion. Minnesota and Wisconsin DNR officials
suggested that Ospreys, in our lifetime, do not readily pioneer new breeding
ranges. Instead, they experience suppressed reproduction as density of nesting
pairs increase. Scientists have determined that a raptor population is in
jeopardy of crashing, when the average fledging success of young per nest
approaches 0.8 chicks/nest. To address this issue, young Ospreys from Wisconsin
and Minnesota began being relocated to areas with suitable habitat in southern
Minnesota, Iowa, Kansas, Missouri and Ohio. Wildlife populations evenly
distributed across suitable habitat will be able to withstand pockets with high
contaminants that stress those populations. As biological indicator species,
raptors reflect the health of our environment. Contaminants like DDT negatively
impact or destroy raptor populations and will ultimately affect humans
negatively.
Dr. Larry Rymon, noted Pennsylvania
ornithologist who initiated Osprey relocations along the eastern seaboard,
observes that 45% of the continental Osprey population nest upon manmade
structures. Therefore nesting platforms have been placed near all release sites
in anticipation of returning Osprey usage. Mr. Bill Fraundorf from ALLETE
Energy of Minnesota and Mr. Mark Martell of Minnesota Audubon and Ms. Pat
Manthey and Mr. Lowell Tesky of Wisconsin DNR, assisted by The Raptor Center of
St. Paul, have provided Ospreys for Iowa releases.
Young Ospreys' availability for potential
relocation is evaluated in early July. Approximately 42-day-old Ospreys from
Minnesota and Wisconsin are located in nests where more than one young exists.
Within hours, The Raptor Center staff members in St. Paul examine the Ospreys
for relocation suitability. When approved, birds are driven to release sites
and placed in carefully constructed release towers or "hack sites." Hack sites
are predator proof 8' x 8' x 8' structures with bars on the front that provide
visibility of surroundings. The bars are opened when ospreys are released.
Trained volunteers feed the young daily in such a manner that the birds do not
imprint on people. By quietly viewing ospreys through one-way mirrored glass or
from monitors, detailed observations of each bird's temperament and condition
are logged daily.
When Ospreys are approximately 53 days of age, they are
full-grown with rapidly developing feathers and are ready to be released. The
birds are actually heavier than they will be as adults, due to built-in fat
reserves until self-sufficiency is achieved. Great care is exercised to ensure
that young are not startled into their first flight - at this stage of the young
Ospreys’ development, the less disturbance or drama, the better. Once Ospreys
have flown, volunteer spotters monitor the birds' movements the best they can,
either from shore or in boats for the first few days. It has been shown that
young Ospreys can fly better, the first time out, than they can land upon a
perch. As with other raptors, returning to a perch near the hack box can become
a fatal learning experience for young flyers. After the Ospreys fledge,
volunteers supplement the birds’ diets with fish at the hack site, until birds
begin fishing on their own and self-sufficiency is achieved.
These combined activities by volunteers provide
tremendous opportunities for outdoor-loving families to connect with a most
dynamic raptor. These duties have become great opportunities to establish
touchstones with our environment and influence our need to be good stewards of
our land and waters. Efforts by these volunteers are moving this project
forward. There is empowerment volunteers can build upon in other wildlife and
habitat enhancement projects.
The Iowa Department of Natural Resources has
assisted conservation partners with technical assistance and providing proper
permits to bring Ospreys to Iowa. Encouragement and fish to successfully
release Ospreys in Iowa have also been included. Ms. Jodeane Cancilla of the
Macbride Raptor Project located near Coralville Reservoir spearheaded this
work. Beginning in 1997, four or five young ospreys were released annually at
their facility from 1997 until 2002. Since that time, Hartman Reserve Nature
Center staff in Cedar Falls released Ospreys at their facility from 1998 -
2005. In succession County Conservation Boards and volunteer groups have placed
Ospreys at Jester Park in Polk Co. from 2000 - 2004, Don Williams Lake in Boone
Co. from 2003 - 2006, Clear Lake in Cerro Gordo Co. from 2004 - 2008, Wickiup
Hill in Linn Co. from 2004 - 2007, Red Rock Reservoir in Marion Co. from 2005 -
2008, White Rock Conservancy by S.O.A.R. from 2006, Spirit Lake in Dickinson Co.
from 2007, Mud Lake in Dubuque Co. from 2008, and Annett Nature Center in Warren
Co. from 2009. The U.S. Army Corps of Engineers has provided distinguished
service for releases at Coralville and Saylorville Reservoir respectively.
Assisted by literally hundreds of volunteers, these conservation organizations
have devoted their efforts to bring Ospreys to Iowa as a nesting species.
Project fundraising is the responsibility of the conservation organizations
doing the releases. Ospreys cost about $525 per bird. In Iowa, Ospreys have
two bands, a silver U.S. Fish and Wildlife Service band and a numbered, lavender
band on separate legs. Wild produced Ospreys from Iowa receive a green USFWS
band on their left leg. In 2010 a green banded, F2 generation Osprey fledged
three young at Polk City Refuge in Polk County. Also, in 2010 natural
reproduction around the state was 21 Ospreys at fourteen successful sites which
equaled the number of birds relocated to Iowa at 21 Ospreys.
We can think of Ospreys as "sentinels of clean
water." Ospreys rely upon fish for food and fish need clean water. Ospreys
also need to be able to see fish in our water, so turbidity and siltation become
critical issues. Fish need clean water, ospreys need clean water; we all need
clean water. But clean water doesn't just happen. It requires standards of
decency that can benefit everyone and everything. Joining Bald Eagles,
Trumpeter Swans, Sand-hill Cranes, wetland mammals and our myriad of waterfowl,
Ospreys can be appreciated in all water quality endeavors and provide a
rewarding environmental connection for all Iowans. Moreover, as a highly
desirable watchable wildlife species, it's great to see "fishing perfection" in
Iowa.
For more information contact: the
Wildlife Diversity Program, 1436 255th St., Boone, IA
50036.As the osprey flew
from sight, we felt privileged to
part the placid pool with our paddles and
proceeded onward.
Story by Pat Schlarbaum and photos
courtesy of Bill Schuerman
