Pandion haliaetus

The Osprey (Pandion haliaetus) is a fish-eating hawk found along coastlines and around marshes, lakes, and rivers almost worldwide. Ospreys are often seen flying over water searching for prey, then hovering and plunging feet first to capture a fish in their talons (fish are normally carried head first and belly down). Bald Eagles may sometimes chase them and force them to drop their catch. During migration, Ospreys may be seen far from water, even over deserts. Migrants travel singly, not in flocks.

The Osprey's diet consists almost entirely of fish, generally in the range of 10 to 30 cm in length. Rarely, small mammals, birds, or reptiles may be eaten.

Ospreys breed in the New World over most of North America south to Guatemala; in the Old World, they breed from the British Isles, Scandinavia, northern Russia, and northern Siberia south (at least locally) through much of Eurasia and most of Africa and Australia to South Africa, the Himalayas, Tasmania, New Caledonia, and the Solomon Islands. They winter from the southern United States south through Middle America, the West Indies, and South America (including the Galapagos Islands) to southern Chile, northern Argentina, and Uruguay; in the Old World, Ospreys winter from the Mediterranean, Black, and Caspian Seas, India, and eastern China south through the remainder of the breeding range.

The Osprey's courtship display includes the pair circling high together; the male may fly high and then dive repeatedly in the vicinity of the nest site, often carrying a fish or stick. The nest is usually constructed at the top of a large tree (often with a dead or broken top) not far from water. Utility poles or other structures, including nesting platforms erected by humans expressly for Ospreys, may also be used. They may nest on the ground on small islands and on cliffs or giant cacti in western Mexico. The nest site is typically very open to the sky. The bulky nest, built by both sexes, is made of sticks and lined with smaller materials. Nests may be reused for many years, with material added each year. Typical clutch size is 3 (range 2 to 4). The eggs, which are creamy white with brown blotches, are incubated by both parents (but mainly the female) for around 38 days. When the young first hatch, the female remains with them most of the time, sheltering them from sun and rain, and the male brings fish back to the nest, which the female feeds the young. Age at first flight is around 51 to 54 days.

In the mid-20th century, Osprey populations in the United States and elsewhere plummeted as a result of accumulations of the pesticide DDT in the food chain, which prevented the formation of normal eggshells (DDT can interfere with normal calcium absorption, resulting in thin eggshells). With the reduction in use of DDT and other conservation efforts, populations of Ospreys and some other affected species have rebounded.

(Kaufman 1996; AOU 1998; Dunn and Alderfer 2011)

Ospreys have a worldwide distribution, wintering or breeding on every continent except Antarctica. Ospreys are not known to breed in South America or Indo-Malasia, but are sometimes found there in the winter. Ospreys are winter breeders in Egypt and some Red Sea islands. Regions where ospreys are particularly abundant include Scandinavia and the Chesapeake Bay region of the United States.

There are four subspecies of ospreys, which are separated by geographic region. Pandion haliaetus carolinensis breeds in North America and the Caribbean, and winters in South America. P. h. haliaetus breeds in the Palearctic region (Europe, north Africa and in Asia, north of the Himalayas) and winters in south Africa, India and the East Indies. P. h. ridgwayi is a non-migratory subspecies. It resides in the Caribbean, with a range that extends from the Bahamas and Cuba to southeast Mexico and Belize. The final subspecies, P. h. leucocephalus is also a non-migratory subspecies. Its range includes Australia and the southwest Pacific.

Biogeographic Regions: nearctic (Native ); palearctic (Native ); oriental (Native ); ethiopian (Native ); neotropical (Native ); australian (Native ); oceanic islands (Native )

Other Geographic Terms: holarctic ; cosmopolitan

Ospreys have a worldwide distribution. They live on every continent except Antarctica. Ospreys do not breed in South America or Indo-Malasia, but they sometimes live there in the winter. Large populations of ospreys are found in Scandinavia and the Chesapeake Bay region of the United States. There are four subspecies of ospreys, which are found in different regions of the world.

Biogeographic Regions: nearctic (Native ); palearctic (Native ); oriental (Native ); ethiopian (Native ); neotropical (Native ); australian (Native ); oceanic islands (Native )

Other Geographic Terms: holarctic ; cosmopolitan

The osprey is nearly worldwide in distribution. It breeds in temperate
and tropical regions of all continents except South America. In North
America the subspecies carolinensis breeds from northwest Alaska and
northern Yukon to central Labrador and Newfoundland and south to Baja
California, central Arizona, southern Texas, the Gulf Coast, and
southern Florida [5,28]. They are migratory throughout most of their
range, wintering in Central and South America as far south as Argentina
and Chile [4,25]. Populations in southern Florida, Baja California, and
the Pacific coast of Mexico are year-round residents [25]. The
distributions of the other three subspecies are as follows [4]:

P. h. haliaetus - occurs from the Palearctic (Europe, the northwest
coast of Africa, and Asia north of the Himalayas).
P. h. ridgwayii - occurs in the Caribbean
P. h. cristatus - occurs in Australia, New Guinea, and nearby South
Pacific islands.

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This species can be found in the following regions of the western United States (according to the Bureau of Land Management classification of Physiographic Regions of the western United States):

1 Northern Pacific Border
2 Cascade Mountains
3 Southern Pacific Border
4 Sierra Mountains
5 Columbia Plateau
6 Upper Basin and Range
7 Lower Basin and Range
8 Northern Rocky Mountains
9 Middle Rocky Mountains
10 Wyoming Basin
11 Southern Rocky Mountains
12 Colorado Plateau
13 Rocky Mountain Piedmont
16 Upper Missouri Basin and Broken Lands

AL AK AZ AR CA CO CT DE FL GA ID LA ME MD MA MI MN MS MO MT NV NH NJ NM NY NC OH OK OR PA RI SC SD TN TX UT VT VA WA WI WY

AB BC MB NB NF NT NS ON PE PQ SK YT

occurs (regularly, as a native taxon) in multiple nations

Canada

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Breeding

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

Global Range: (>2,500,000 square km (greater than 1,000,000 square miles)) Ospreys breed throughout much of the world (not in South America). In the New World, they nest from northwestern Alaska across boreal Canada to Labrador and Newfoundland, and south to Baja California, northwestern mainland Mexico, Yucatan Peninsula, Belize, U.S. Gulf Coast, Florida, and the West Indies. During the northern winter, ospreys in the New World range from California, the U.S. Gulf Coast, and Bermuda south through Central America to South America. In the U.S., primary wintering areas include central California, southern Texas, the Gulf coast, and southern Florida, though the winter range also includes other areas in the southern and southeastern U.S. and various inland sites (Root 1988). The species is also widespread in the Old World (AOU 1998).

Ospreys are large birds of prey (55 to 58 cm long), with a wingspan from 145 to 170 cm. Their long wings have are bent at the carpal ("wrist") joints. They are bright white underneath, with dark brown patches at the carpal joints and a speckled dark brown necklace. They have a dark stripe through each eye, and a dark brown back. Ospreys have light blue-gray feet, yellow eyes and a black beak. Juvenile ospreys look a lot like adults, but their dark feathers have light colored tips that make them look speckled on their backs and wings. They also have orange eyes. Ospreys begin to look like adults when they are about 18 months old.

Female ospreys are usually bigger than males. They have a bigger wingspan (5 to 10% longer than males) and are heavier. In North America, male ospreys weigh 1200 to 1600 g and females weigh 1600 to 2000 g. Female also usually have darker feathers than males.

Ospreys in different regions of the world look a little different from one another. For example, ospreys that live in tropical regions are smaller than ospreys that breed farther north or south from the equator. There are four subspecies of ospreys. Each of these lives in a different region of the world and looks a little different.

Ospreys have several adaptations for hunting fish. They have long legs for reaching into the water and dense, oily plumage that keeps them from getting waterlogged. They also have special valves that keep water out of their nostrils when they dive for fish. Osprey feet are specially adapted for holding on to slippery fish. They have spiny footpads called spicules, long, sharp claws, and a toe that can be turned backward to keep fish from escaping..

Range mass: 1200 to 2000 g.

Range length: 55 to 58 cm.

Range wingspan: 145 to 170 cm.

Other Physical Features: endothermic ; homoiothermic; bilateral symmetry

Sexual Dimorphism: female larger; sexes colored or patterned differently

Ospreys are large birds of prey (55 to 58 cm long), with a wingspan ranging from 145 to 170 cm. Their long wings have a characteristic bend at the carpal ("wrist") joints. They are bright white underneath, with dark brown patches at the carpal joints and a mottled dark brown necklace. Other identifying markings include a dark stripe through each eye, and a dark brown back. The feet of this species are pale blue-gray, and the beak is black. Juvenile ospreys resemble adults, but have a somewhat speckled appearance due to buff-colored tips on their dark brown upper-wing and back coverts and a less well-defined necklace. Juveniles also have an orange-red iris, rather than the yellow iris that is typical of adults. Juvenile plumage is replaced by adult plumage by 18 months of age.

On average, while not necessarily longer, female ospreys are 20% heavier than males and have a wingspan that is 5 to 10% greater. In North America, for example, male ospreys range in mass from 1200 to 1600 g, whereas females range from 1600 to 2000 g. Female ospreys also often have darker plumage and a more defined necklace than their male counterparts.

Ospreys display morphological variation by region. Tropical and subtropical individuals tend to be smaller than individuals that breed at higher latitudes. The four subspecies of ospreys show some variation in size and color. Pandion haliaetis haliaetus and P.h. carolinensis are the largest and darkest subspecies. P.h.ridgwayi is approximately the same size as carolinensis, but is paler on the head and breast. P.h. cristatus is the smallest subspecies, with a dark necklace and pale crown.

Ospreys have several morphological adaptations to their unique fish-eating lifestyle. These adaptations include relatively long legs for a raptor, spiny footpads called spicules, long, sharp, curved claws, and a reversible outer toe to aid in gripping slippery fish. In addition, ospreys have dense oily plumage and efficient nasal valves that prevent water from entering the nostrils when the bird dives to catch a fish.

Range mass: 1200 to 2000 g.

Range length: 55 to 58 cm.

Range wingspan: 145 to 170 cm.

Other Physical Features: endothermic ; homoiothermic; bilateral symmetry

Sexual Dimorphism: female larger; sexes colored or patterned differently

Length: 64 cm

Weight: 1568 grams

Differs from other hawks in having all of the following characteristics: white belly, dark wrist patches, and a white head with a prominent dark eye streak. Other hawks do not habitually plunge feet-first into water to obtain prey.

Ospreys have a wide distribution because they are able to live almost anywhere that has safe nest sites and shallow water with lots of fish. Nests are usually found within 3 to 5 km of a water body such as a salt marsh, mangrove (Rhizophora) swamp, cypress (Taxodium) swamp, lake, bog, reservoir or river.

Ospreys need structures that can support their big nests, and that are safe from climbing predators, like Procyon lotor. In order to be safe from predators, ospreys usually build their nests in places that are difficult for predators to reach, like on the side of a cliff, or over water or on a small island. Over-water nests are built on structures like buoys, channel markers, dead trees and special platforms that people build for ospreys. Ospreys also nest on other man-made structures that are very high, like power poles, radio and TV towers, buildings and even billboards.

Habitat Regions: temperate ; tropical ; terrestrial ; saltwater or marine ; freshwater

Terrestrial Biomes: forest ; rainforest ; mountains

Aquatic Biomes: lakes and ponds; rivers and streams; coastal ; brackish water

Wetlands: marsh ; swamp

Other Habitat Features: suburban ; riparian ; estuarine

More info for the term: association

Ospreys occur in a variety of plant communities in association with
riparian habitat including shrublands, grasslands, swamps, and
coniferous and deciduous forests [14,24,30]. In Minnesota, ospreys nest
most frequently in lowland communities such as those dominated by black
spruce (Picea mariana) and tamarack (Larix laricina) [17]. In
California, ospreys are primarily associated with ponderosa pine (Pinus
ponderosa) and mixed-conifer types [30].

REFERENCES :
NO-ENTRY

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This species is known to occur in association with the following cover types (as classified by the Society of American Foresters):

More info for the terms: hardwood, swamp

1 Jack pine
5 Balsam fir
12 Black spruce
13 Black spruce - tamarack
15 Red pine
16 Aspen
17 Pin cherry
18 Paper birch
19 Gray birch - red maple
20 White pine - northern red oak - red maple
21 Eastern white pine
22 White pine - hemlock
23 Eastern hemlock
24 Hemlock - yellow birch
25 Sugar maple - beech - yellow birch
26 Sugar maple - basswood
27 Sugar maple
28 Black cherry - maple
35 Paper birch - red spruce - balsam fir
37 Northern white-cedar
38 Tamarack
39 Black ash - American elm - red maple
40 Post oak - blackjack oak
42 Bur oak
43 Bear oak
44 Chestnut oak
45 Pitch pine
46 Eastern redcedar
50 Black locust
51 White pine - chestnut oak
52 White oak - black oak - northern red oak
53 White oak
55 Northern red oak
57 Yellow-poplar
58 Yellow-poplar - eastern hemlock
59 Yellow-poplar - white oak - northern red oak
60 Beech - sugar maple
61 River birch - sycamore
62 Silver maple - American elm
63 Cottonwood
64 Sassafras - persimmon
65 Pin oak - sweetgum
69 Sand pine
70 Longleaf pine
71 Longleaf pine - scrub oak
73 Southern redcedar
75 Shortleaf pine
76 Shortleaf pine - oak
78 Virginia pine - oak
79 Virginia pine
80 Loblolly pine - shortleaf pine
81 Loblolly pine
83 Longleaf pine - slash pine
84 Slash pine
85 Slash pine - hardwood
88 Willow oak - water oak - diamondleaf oak
89 Live oak
91 Swamp chestnut oak - cherrybark oak
92 Sweetgum - willow oak
93 Sugarberry - American elm - green ash
94 Sycamore - sweetgum - American elm
95 Black willow
107 White spruce
108 Red maple
98 Pond pine
96 Overcup oak - water hickory
101 Baldcypress
111 South Florida slash pine
109 Hawthorn
110 Black oak
201 White spruce
202 White spruce - paper birch
203 Balsam poplar
204 Black spruce
208 Whitebark pine
209 Bristlecone pine
210 Interior Douglas-fir
211 White fir
212 Western larch
213 Grand fir
215 Western white pine
216 Blue spruce
217 Aspen
218 Lodgepole pine
219 Limber pine
221 Red alder
222 Black cottonwood - willow
223 Sitka spruce
224 Western hemlock
225 Western hemlock - Sitka spruce
226 Coastal true fir - hemlock
227 Western redcedar - western hemlock
228 Western redcedar

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This species is known to occur in association with the following plant community types (as classified by Küchler 1964):

More info for the terms: bog, shrub

K001 Spruce - cedar - hemlock forest
K002 Cedar - hemlock - Douglas-fir forest
K003 Silver fir - Douglas-fir forest
K004 Fir - hemlock forest
K005 Mixed conifer forest
K008 Lodgepole pine - subalpine forest
K009 Pine - cypress forest
K010 Ponderosa shrub forest
K011 Western ponderosa pine
K012 Douglas-fir forest
K013 Cedar - hemlock - pine forest
K014 Grand fir - Douglas-fir forest
K015 Western spruce - fir forest
K016 Eastern ponderosa forest
K018 Pine - Douglas-fir forest
K019 Arizona pine forest
K020 Spruce - fir - Douglas-fir forest
K021 Southwestern spruce - fir forest
K022 Great Basin pine forest
K023 Juniper - pinyon woodland
K025 Alder - ash forest
K026 Oregon oakwoods
K029 California mixed evergreen forest
K030 California oakwoods
K031 Oak - juniper woodlands
K032 Transition between K031 and K037
K047 Fescue - oatgrass
K049 Tule marshes
K050 Fescue - wheatgrass
K051 Wheatgrass - bluegrass
K053 Grama - galleta steppe
K054 Grama - tobosa prairie
K063 Foothills prairie
K064 Grama - needlegrass - wheatgrass
K065 Grama - buffalograss
K066 Wheatgrass - needlegrass
K067 Wheatgrass - bluestem - needlegrass
K068 Wheatgrass - grama - buffalograss
K069 Bluestem - grama prairie
K070 Sandsage - bluestem prairie
K071 Shinnery
K072 Sea oats prairie
K073 Northern cordgrass prairie
K074 Bluestem prairie
K075 Nebraska Sandhills prairie
K076 Blackland prairie
K077 Bluestem - sacahuista prairie
K078 Southern cordgrass prairie
K079 Palmetto prairie
K080 Marl - everglades
K081 Oak savanna
K082 Mosaic of K074 and K100
K083 Cedar glades
K084 Cross Timbers
K085 Mesquite - buffalograss
K086 Juniper - oak savanna
K087 Mesquite - oak savanna
K088 Fayette prairie
K089 Black Belt
K090 Live oak - sea oats
K091 Cypress savanna
K092 Everglades
K093 Great Lakes spruce - fir forest
K094 Conifer bog
K096 Northeastern spruce - fir forest
K097 Southeastern spruce - fir forest
K098 Northern floodplain forest
K099 Maple - basswood forest
K100 Oak - hickory forest
K101 Elm - ash forest
K102 Beech - maple forest
K103 Mixed mesophytic forest
K104 Appalachian oak forest
K105 Mangrove
K106 Northern hardwoods
K107 Northern hardwoods - fir forest
K108 Northern hardwoods - spruce forest
K109 Transition between K104 and K106
K110 Northeastern oak - pine forest
K111 Oak - hickory - pine forest
K112 Southern mixed forest
K113 Southern floodplain forest
K116 Subtropical pine forest

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This species is known to occur in the following ecosystem types (as named by the U.S. Forest Service in their Forest and Range Ecosystem [FRES] Type classification):

FRES10 White-red-jack pine
FRES11 Spruce-fir
FRES12 Longleaf-slash pine
FRES13 Loblolly-shortleaf pine
FRES14 Oak-pine
FRES15 Oak-hickory
FRES16 Oak-gum-cypress
FRES17 Elm-ash-cottonwood
FRES18 Maple-beech-birch
FRES19 Aspen-birch
FRES20 Douglas-fir
FRES21 Ponderosa pine
FRES22 Western white pine
FRES23 Fir-spruce
FRES24 Hemlock-Sitka spruce
FRES25 Larch
FRES26 Lodgepole pine
FRES35 Pinyon-juniper
FRES36 Mountain grasslands
FRES37 Mountain meadows
FRES39 Prairie
FRES41 Wet grasslands
FRES42 Annual grasslands

Systems

• Terrestrial
• Freshwater
• Marine

Ospreys have a wide distribution because they are able to live almost anywhere where there are safe nest sites and shallow water with abundant fish. Nests are generally found within 3 to 5 km of a water body such as a salt marsh, mangrove (Rhizophora) swamp, cypress (Taxodium) swamp, lake, bog, reservoir or river. The frequency with which each of these habitat types is used varies by geographic region.

Ospreys choose structures that can support a bulky nest, and that are safe from ground-based predators. Nest sites can be safe from predators either by being difficult for a predator to climb (e.g. on a cliff) or by being over water or on a small island. Over-water nest sites that are often used by ospreys include buoys and channel markers, dead trees and artificial nest platforms. Ospreys have also been known to nest on various man-made structures, such as power poles, duck blinds, communication towers, buildings and even billboards. In many cases, nests that are built on artificial structures such as nest platforms and power poles are more stable and fledge more chicks per breeding season than nests on naturally-occuring structures.

Habitat Regions: temperate ; tropical ; terrestrial ; saltwater or marine ; freshwater

Terrestrial Biomes: forest ; rainforest ; mountains

Aquatic Biomes: lakes and ponds; rivers and streams; coastal ; brackish water

Wetlands: marsh ; swamp

Other Habitat Features: suburban ; riparian ; estuarine

Depth range based on 14 specimens in 1 taxon.
Water temperature and chemistry ranges based on 1 sample.

Environmental ranges
  Depth range (m): 0 - 0
  Temperature range (°C): 12.466 - 12.466
  Nitrate (umol/L): 3.089 - 3.089
  Salinity (PPS): 31.538 - 31.538
  Oxygen (ml/l): 6.346 - 6.346
  Phosphate (umol/l): 0.565 - 0.565
  Silicate (umol/l): 9.560 - 9.560
 
Note: this information has not been validated. Check this *note*. Your feedback is most welcome.

Comments: Ospreys occur primarily along rivers, lakes, reservoirs, and seacoasts. They often cross land between bodies of water. They typically build large stick nests on living or dead trees and also use numerous man-made structures such as utility poles, wharf pilings, windmills, microwave towers, chimneys, and channel markers (Henny, in Palmer 1988, Campbell et al. 1990). Nests are usually near or above water.

Non-Migrant: Yes. At least some populations of this species do not make significant seasonal migrations. Juvenile dispersal is not considered a migration.

Locally Migrant: Yes. At least some populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).

Locally Migrant: Yes. At least some populations of this species make annual migrations of over 200 km.

Breeding populations in northern North America are migratory. They arrive in northern breeding areas March-May, begin southward migration in August, and are generally gone from the north by September-November

In Costa Rica, migration occurs mainly September-October and March-April (Stiles and Skutch 1989). Eastern and midwestern populations winter in northern South America, Caribbean, Central America, U.S.; western populations winter in Mexico, Central America, and northwestern South America (Ewins and Houston 1992).

Ospreys are unusual among raptors for being piscivores. Their diet consists almost entirely of fish (≥99% of prey items). They are opportunistic, and will eat whatever fish species they can catch – either in shallow waters, or near the surface of deeper waters. North American ospreys are known to eat more than 80 different species of fish.

Ospreys hunt for fish while flapping and gliding 10 to 40 meters above the water. When an osprey spots a fish, it hovers briefly, then dives toward the water. Just before hitting the water, the osprey swings its legs forward and bends its wings back, plunging feet-first into the water. The osprey uses strong wing beats to lift itself and the fish out of the water. Once airborne again, the osprey rearranges the fish in its feet, carrying it with one foot in front of the other so that the fish is facing forward. This position probably makes the fish easier to fly with. The osprey then takes the fish to a perch to eat.

Ospreys generally eat fish starting at the head and working toward the tail. A male who is also hunting food for a mate and chicks during the breeding season will usually eat at least part of the fish before delivering the rest to the female. Ospreys do not usually need to drink water. They get enough water from the fish that they eat.

Ospreys successfully catch fish on 24 to 74% of their dives. Ospreys are usually more successful at mid-tide and when the weather is calm.

Though ospreys eat mostly fish, they have occasionally been seen eating other things, including Aves, Serpentes, voles, Sciuridae, muskrats (Ondatra zibethicus), salamanders, Strombus, and even a small alligator (Alligator mississippiensis). Reports of ospreys feeding on carrion are rare. However, they have been observed eating dead white-tailed deer (Odocoileus virginianus) and opossum (Didelphis virginiana).

Animal Foods: birds; mammals; amphibians; reptiles; fish; carrion ; mollusks

The osprey diet consists almost entirely of fish, but they will
occasionally eat frogs, snakes, ducks, crows, and small mammals
[5,6,28,29]. Ospreys can penetrate only about 3 feet (1 m) below the
water surface. Therefore, they generally catch only surface fish or
those that frequent shallow flats and shorelines. Ospreys are
opportunists. If fish are abundant, accessible, and the right size they
seldom go unconsumed [24]. Poole [24] found that along the southern
coast of New England, about one-half of the fish ospreys eat during the
breeding season are winter flounder (Pseudopleuonectes americanus).
White herring (Alosa spp.) and Menhaden (Brevoortia tyrannus) each
supply another 20 percent of the diet. Inland ospreys are likely to eat
the same species of fish throughout the breeding season, but coastal
populations change prey regularly in response to the seasonal migration
of marine fish [24]. Ospreys in western North America often eat
suckers, carp, bullhead (Ictalurus spp.), and perch (Perca flavescens)
when nesting near warm shallow lakes or reservoirs but eat trout when
nesting near deeper, colder waters [24,29].

Ospreys are unusual among raptors for being piscivores. Their diet consists almost exclusively of fish (≥99% of prey items). They are generally opportunistic, and will eat whatever fish species are accessible to them – either in shallow waters, or near the surface of deeper waters. Studies in North America have documented more than 80 different prey species of ospreys. However, 2 or 3 common species may dominate the diet of local ospreys in a given area.

Ospreys hunt for fish on the wing (less often from a perch), flapping and gliding 10 to 40 meters above the water. When an osprey spots a fish, it hovers briefly, then dives toward the surface of the water. Just before hitting the water, the osprey swings its legs forward and bends its wings back, plunging feet-first into the water. The osprey uses strong, almost horizontal wing beats to lift itself and its prey from the water. Once airborne, the osprey rearranges the fish in its feet, carrying it with one foot in front of the other so that the fish is facing forward. This position presumably makes the fish more aerodynamic, and easier to carry. The osprey then takes the fish to a perch, often near the nest, to eat. Osprey generally eat fish beginning with the head and working toward the tail. A male who is also providing food for a mate and offspring during the breeding season will typically consume at least part of the fish before delivering the remainder to the female. Ospreys do not cache fish. If a fish is larger than an osprey (and his mate and offspring if breeding) can consume, the fish is discarded, carried around with the osprey, or left in the nest. Ospreys do not generally need to drink water. Fish flesh supplies sufficient amounts of water to meet their requirements.

Ospreys catch fish on 24 to 74% of their dives. This success rate is affected by individual ability, weather and tide. Some studies have shown that ospreys are most successful hunting at midtide and when the weather is calm.

Though the vast majority of osprey prey items are live fish, ospreys have been observed to eat other foods on occasion. These include birds, snakes, voles, squirrels, muskrats (Ondatra zibethicus), salamanders, conchs, and even a small alligator (Alligator mississippiensis). Reports of ospreys feeding on carrion are rare. However, they have been observed eating dead white-tailed deer (Odocoileus virginianus) and opossum (Didelphis virginiana).

Animal Foods: birds; mammals; amphibians; reptiles; fish; carrion ; mollusks

Primary Diet: carnivore (Piscivore )

Comments: Ospreys eat almost exclusively fishes (see Palmer 1988 for detailed account of food). Species composition of diet may vary greatly from one area to another. Sometimes ospreys eat rodents, birds, other small vertebrates, or crustaceans.

Ospreys capture prey with a feet-first plunge into shallow water, usually by flight hunting, sometimes from perch. Rarely they have been photographed capturing two fishes at once, one in each foot.

While ospreys provide food for some species, they are probably not the main food source for any species. Because ospreys prey on fish, they probably have a small effect on local fish populations. Like most predators, ospreys are host to many different species of parasites, including feather mites.

Ospreys nests are used by many other species of birds. Smaller cavity-nesting species, such as Quiscalus quiscula, Tachycineta bicolor, Hirundo rustica, sturnus vulgaris and Passer domesticus build nests inside osprey nests. Other larger species take over osprey nests for their own use in the spring before the resident ospreys return. In North America, these species include Ardea herodias, Branta canadensis, Haliaeetus leucocephalus, Buteo jamaicensis, Bubo virginianus, Larus argentatus and Corvus corax.

Ospreys in some areas, especially northern forested regions, may have historically depended on beavers to create habitat for them. Beavers create osprey habitat by building dams, which create shallow ponds for fishing and dead trees for building nests.

Ospreys are vulnerable to predation from aerial predators, such as owls and eagles . In North America, Bald eagles and great horned owls are known predators of osprey nestlings and (occasionally) adults. The speckled appearance of osprey chicks camouflages them in the nest and may be an adaptation to minimize predation by diurnal avian predators like the bald eagle.

Raccoons, snakes and other climbing animals are probably predators of osprey eggs and nestlings. This is probably why ospreys in many areas build their nests over water. Crocodiles may also prey on wintering ospreys. Crocodylus niloticus sometimes kill ospreys bathing and roosting near water in Africa.

Known Predators:

• great horned owls (Bubo_virginianus)
• raccoons (Procyon_lotor)
• Nile crocodiles (Crocodylus_niloticus)
• bald eagles (Haliaeetus_leucocephalus)

Anti-predator Adaptations: cryptic

Crocodiles (Crocodylus spp.) have been known to eat ospreys roosting on
mudbanks, but only owls (mostly great horned owls [Bubo virginianus])
kill adult ospreys with any regularity. Raccoons (Procyon lotor) will
eat osprey eggs and chicks. Predators exert a major impact on the nest
sites ospreys choose. Most climbing predators like raccoons seem
reluctant to swim far, so only aerial predators such as owls reach
overwater nests easily [24].

While ospreys provide food for some species (see Predation), it is unlikely that they represent a significant portion of the diet of any species. Ospreys do prey on fish, and are likely have some effect on local fish populations. Like most predators, ospreys are host to many different species of parasites, including feather mites. They are not parasitic or mutualistic with any other species.

Ospreys nests are used by many species of birds other than ospreys. Smaller cavity-nesting species, such as common grackles, tree swallows, barn swallows, European starlings and house sparrows build nests within osprey nests. Other larger species will usurp osprey nests for their own use in the spring before the resident ospreys return. In North America, these species include great blue herons, Canada geese, bald eagles, Red-tailed hawks, Great horned owls, herring gulls and common ravens.

Ospreys in some areas, particularly boreal and other northern forested regions, may have historically been dependant on beavers for creation of habitat. Beavers create osprey habitat by building dams, which create shallow ponds for fishing and dead trees appropriate for building nests.

Ospreys are vulnerable to predation from aerial predators, such as owls and eagles . In North America, Bald eagles and great horned owls are known predators of osprey nestlings and (occasionally) adults. The speckled appearance of osprey chicks camouflages them in the nest and may be an adaptation to minimize predation by diurnal avian predators like the bald eagle.

Raccoons, snakes and other climbing animals are suspected predators of osprey eggs and nestlings. Selection by such terrestrial predators may explain why the majority of osprey nests in many area, for example in the Chesapeake Bay region of the U.S., are built over water. Crocodilians may prey on wintering ospreys. Nile crocodiles (Crocodylus niloticus) sometimes kill ospreys bathing and roosting near water in Africa.

Known Predators:

• great horned owls (Bubo virginianus)
• raccoons (Procyon lotor)
• Nile crocodiles (Crocodylus niloticus)
• bald eagles (Haliaeetus leucocephalus)

Anti-predator Adaptations: cryptic

Pandion haliaetus is prey of:
Haliaeetus leucocephalus
Bubo virginianus
Procyon lotor
Crocodylus niloticus

This list may not be complete but is based on published studies.

Pandion haliaetus preys on:
Istiophoridae
Anguilliformes
Tetraodontidae
Austromenidia
Umbrina
Sciaena
Polynemus
Actinopterygii
Mollusca
Amphibia
Reptilia
Aves
Mammalia
Fulica americana

Based on studies in:
USA: New York, Long Island (Marine)
Peru (Coastal)

This list may not be complete but is based on published studies.

Note: For many non-migratory species, occurrences are roughly equivalent to populations.

Estimated Number of Occurrences: 81 to >300

10,000 to >1,000,000 individuals

Comments: Global population unknown. Nesting numbers in the conterminous U.S. have been estimated at 8,000 pairs (Henny 1983). Estimated number of breeding pairs in Canada in the early 1990s was estimated at 10,000-12,000 (Kirk et al. 1995).

Courtship - Ospreys generally arrive on their breeding grounds in late
March or early April. Pair bonding persists from one year to the next,
and the same nest site may be used for many years [26]. Most ospreys
are monogamous; occasionally they breed as a polygynous trio (one male
breeding concurrently with two females) [24].

Age at first reproduction - Ospreys generally first breed when they are
between 3 and 4 years old [24,28]. Juveniles spend about 17 months on
the wintering gounds. At around 2 years of age they return to the
nesting grounds but do not breed until the following year [28]. Age at
first reproduction varies not only among individual ospreys but among
populations, apparently in relation to the availability of nest sites
and other resources. For example, birds along the eastern shore of
Chesapeake Bay do not start breeding until they are 5 to 7 years old due
to the lack of nest sites [24].

Clutch/incubation/fledging - Most migratory ospreys lay two to four eggs
from late April to early May and incubate them for 5 to 6 weeks [24,28].
An average of 1.1 to 1.3 young per active nest are fledged per year
[28]. Young fledge when they are about 2 months old [4,28]. They
return to the nest for feeding and roosting for another week, and can be
found nearby for sometime after that [4]. Most resident ospreys lay
their clutch in winter. In southern Florida, for example, ospreys lay
from early December until late February [24].

Life span - On average, out of 100 fledged young, 37 will be alive 4
years after fledging, 17 will be alive 8 years after fledging, and only
six to eight will be alive 12 years after fledging. The greatest
longevity recorded is 25 years [24].

Raccoons can be a major source of nesting failure in some areas.

Ospreys use up to five different calls to communicate with each other. They also use visual displays, like special flight displays or specific body positions to communicate. Often calls and visual displays are used together. Calls are used to for begging, alarm, courtship, and nest defense. Alarm calls are often given when a potential predator or disturbance such as a boat or human approaches the nest. Ospreys giving alarm calls usually stand very erect on the nest, or dive at the disturbance.

Communication Channels: visual ; tactile ; acoustic

Ospreys use several different vocalizations to communicate with one another. Up to five different calls have been recognized by researchers. These calls are nearly always associated with a visual display, such as a characteristic flight or posture. Vocalizations are used for begging, alarm, courtship, and nest defense. One notable display is the “sky-dance,” which is an elaborate aerial display performed by males during courtship and early incubation. During this display, a male carrying a fish or nest material gives a screaming call while simultaneously performing short undulating flights separated by periods of hovering. Alarm calls are often given when a potential predator or disturbance such as a boat or human approaches the nest. These calls are usually accompanied by erect posturing and diving flight.

Communication Channels: visual ; tactile ; acoustic

Ospreys are a relatively long-lived bird species. The oldest known osprey in North America was a 25-year old male. The oldest known female was 23 years old. However, very few individuals live to this age. Chance of survival from one year to the next varies between populations, but is estimated to be approximately 60% for young ospreys (less than 2 years old) and 80 to 90% for adult ospreys.

Range lifespan
Status: wild: 25 (high) years.

Average lifespan
Status: wild: 314 months.

Ospreys are a relatively long-lived bird species. The oldest known osprey in North America was a 25-year old male. The oldest known female was 23 years old. However, very few individuals live to this age. Chance of survival from one year to the next varies between populations, but is estimated to be approximately 60% for young ospreys (less than 2 years old) and 80 to 90% for adult ospreys.

Range lifespan
Status: wild: 25 (high) years.

Average lifespan
Status: wild: 314 months.

Maximum longevity: 32 years (wild) Observations: IMR was estimated based on data from the wild (http://www.fs.fed.us/database/feis/).

Some ospreys live in the same place all year. These ospreys are called “residents” or “sedentary.” Resident ospreys usually start breeding between December and March. Other ospreys migrate between their breeding grounds and wintering grounds. These ospreys breed in areas where it is too cold to spend the winter. Migratory ospreys breed later during the year than residents. They start breeding in April or May.

In migratory osprey populations, the male usually arrives at the nest site a few days before the female. When the male has chosen a nest site, he often performs a flashy aerial flight display near the nest site. Males probably perform this display to attract females and to scare off other males. The male and female build the nest together, using sticks for the outside and softer materials like seaweed, kelp, grasses or cardboard for the lining. They often also include trash that they find laying around, including fishing line, plastic bags and soda cans and bottles. Osprey pairs use the same nest year after year, so returning pairs do not need to build a nest. However, each spring they must spend some time repairing their nest and adding materials before they can lay eggs.

Once a pair has built their nest, the male begins to deliver fish to the female. The male brings food to the female so that she will mate with him. The male continues to hunt all of the fish for the female and the chicks until the chicks have fledged. Once the chicks start flying, the female begins hunting too.

Ospreys are normally monogamous. One male mates with one female, and mating pairs stay together until one of them dies. However, males occasionally have more than one mate. This is called polygyny. When this happens, it is usually in areas where nests are very close together, so that the male can defend and bring food to both nests.

Mating System: monogamous ; polygynous

Ospreys are able to breed when they are three years old. However, in areas where there are not enough nest sites, ospreys may not breed until they are five years old. Once they have begun breeding, ospreys breed once per year.

Non-migratory ospreys breed in the winter and spring and lay their eggs between December and March. Migratory ospreys breed in the spring and summer and lay their eggs in April and May. The female lays one egg every day or every other day until she has laid two to four eggs. The male and female both incubate the eggs, which hatch after about 40 days. Because the eggs are laid one or two days apart, they also hatch one or two days apart. Chicks that hatch first are bigger than the other chicks and are usually dominant over the smaller chicks. If the parents cannot provide enough food for all of the chicks in the nest, the smallest chicks do not get enough food and sometimes die. This is called brood reduction.

When osprey chicks hatch, they are covered in white down with brown streaks on the face, back, and wings. When the chicks are 10 days old, the white down is replaced by charcoal-colored down. Chicks begin to grow feathers when they are two weeks old. Osprey chicks begin to fly when they are 48 to 76 days old. Once they can fly, osprey chicks begin to hunt for themselves, though they usually also take food from their parents until they can catch enough fish to feed themselves.

Breeding interval: Ospreys breed once yearly.

Breeding season: The breeding season lasts for approximately 2.5 to 4 months. Breeding begins between December and March in non-migratory populations. In migratory populations, breeding begins in April or May.

Range eggs per season: 1 to 7.

Average eggs per season: 3.

Range time to hatching: 32 to 43 days.

Range fledging age: 48 to 59 days.

Range time to independence: 7 to 17 weeks.

Average age at sexual or reproductive maturity (female): 3 years.

Average age at sexual or reproductive maturity (male): 3 years.

Key Reproductive Features: seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); fertilization

Average eggs per season: 3.

Average age at sexual or reproductive maturity (male)
Sex: male: 1095 days.

Average age at sexual or reproductive maturity (female)
Sex: female: 1095 days.

Male and female ospreys both care for their young. They feed the chicks and protect them from predators and cool, wet weather. The male provides all of the fish for the chicks before they can fly. This means that males have to catch up 10 fish each day for the female and the chicks. The parents tear the fish into small pieces for the chicks to eat. Osprey parents hunt fish for their chicks until the chicks can hunt enough fish to feed themselves. Chicks can usually feed themselves two to eight weeks after they begin flying.

During the first few weeks after hatching, osprey chicks cannot control their body temperature very well. The female parent broods the chicks frequently for the first two weeks and during very hot or cool weather until they are about four weeks old. Both parents spend a lot of time protecting the nest from other ospreys and potential predators.

Parental Investment: no parental involvement; altricial ; pre-hatching/birth (Provisioning: Male, Protecting: Male, Female); pre-weaning/fledging (Provisioning: Male, Female, Protecting: Male, Female); pre-independence (Provisioning: Male, Female, Protecting: Male, Female)

Some ospreys migrate seasonally, but not all. Non-migratory populations breed and winter in the same location, though they may wander several hours from their nest during the non-breeding season. These populations begin breeding between December and March. Migratory populations generally breed where winters are cold enough to drive fish into deep water where they are inaccessible. These populations begin breeding in April or May.

Courtship in ospreys centers on food and nest sites. In migratory osprey populations, males and females arrive at the nest site separately, the male often arriving several days earlier than the female. Male ospreys sometimes perform a conspicuous aerial display near the nest site. This display usually occurs during early courtship, and may serve to attract potential mates or to threaten an intruder. Both sexes collect materials for the nest, but the female does most of the arranging of materials at the nest. Osprey nests are typically constructed of sticks, and lined with softer materials such as seaweed, kelp, grasses or cardboard. A wide variety of flotsam and jetsam may also be incorporated into osprey nests, including fishing line, plastic bags and nearly anything else that an osprey might find and can lift. Osprey pairs use the same nest year after year, but must spend some time each year repairing it and adding materials before eggs can be laid.

Once a pair has established a nest, the male begins to deliver food to the female. This feeding continues until the young fledge or the nest fails. Generally, females that receive more food are more receptive to mating attempts by the male, and are less likely to copulate with other males. Females beg for food from their mates, and occasionally from neighboring males if they are not well fed by their mate. Males may protect their paternity by feeding their mate. They may also protect their paternity by guarding their mate from other males and copulating frequently when she is most fertile (several days before egg laying).

Ospreys are generally monogamous. However, polygyny can occur in rare instances where nest sites are close enough together that a male can defend two nests. When this occurs, the first nest usually experiences higher reproductive success than the second because the male devotes more resources to that nest.

Mating System: monogamous ; polygynous

The breeding season of ospreys differs between populations. Non-migratory populations breed in the winter and spring, laying eggs between December and March. The breeding season of migratory populations occurs in the spring and summer, with egg laying in April and May. Two to four eggs are laid over a period of several days, each 1 to 2 days apart. Both the male and female incubate the eggs, which hatch after approximately 40 days. Because incubation starts when the first egg is laid, the eggs hatch asynchronously in the order in which they were laid. Chicks that hatch first are larger and have a competitive advantage over those that are hatch later. If food becomes scarce, the smaller chicks are less successful in competing for food, and often die. This decrease in the number of chicks in the nest makes food more available to the surviving chicks, and increases their likelihood of survival. This process, common in raptors, is called brood reduction.

When osprey chicks hatch, they are covered in white down with brown streaks on the face, back, and wings. This is replaced by charcoal-colored down after approximately 10 days. Feathers begin to replace the down at approximately two weeks. By one month after hatching, chicks have reached 70 to 80% of the adult size. Osprey chicks fledge between 48 and 76 days old. Generally, chicks in migratory populations fledge sooner than those in non-migratory populations. After fledging, young ospreys begin to hunt on their own. However, they often continue to return to the nest to receive food from their parents for two to eight weeks after fledging. Because ospreys migrate individually, juvenile ospreys must be fully independent of their parents by the time the southward migration begins.

Ospreys are sexually mature at approximately 3 years old, but may not breed until age 5 in areas where nest sites are scarce. Migratory ospreys in both Europe and the U.S. exhibit a pattern of behavior that is unusual in raptors. Rather than returning to the breeding grounds in their first summer, yearling ospreys almost always remain on the wintering grounds throughout the year. They then return to the breeding grounds the following summer when they are more likely to be able to breed successfully. This strategy allows young ospreys that are too physically immature to breed to avoid an unnecessary migration.

Breeding interval: Ospreys breed once yearly.

Breeding season: The breeding season lasts for approximately 2.5 to 4 months. Breeding begins between December and March in non-migratory populations. In migratory populations, breeding begins in April or May.

Range eggs per season: 1 to 7.

Average eggs per season: 3.

Range time to hatching: 32 to 43 days.

Range fledging age: 48 to 59 days.

Range time to independence: 7 to 17 weeks.

Average age at sexual or reproductive maturity (female): 3 years.

Average age at sexual or reproductive maturity (male): 3 years.

Key Reproductive Features: seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); fertilization

Average eggs per season: 3.

Average age at sexual or reproductive maturity (male)
Sex: male: 1095 days.

Average age at sexual or reproductive maturity (female)
Sex: female: 1095 days.

Both male and female ospreys care for their young. Ospreys provide parental care by protecting their young from from predators and weather, and by feeding them. During incubation and the nestling stage, the male osprey provides food to the female and the chicks. This entails delivering 60 to 100 g of fish to the nest per daylight hour (3 to 10 fish per day) during the nestling and fledgling stages. When a fish is delivered to the nest, one of the adults rips pieces of flesh from the fish and feeds them to the chicks. Parents continue to feed the young until two to eight weeks after they fledge.

During the first weeks after hatching, osprey chicks are not able to control their body temperature well. The female parent broods the chicks almost constantly for the first two weeks. She continues to brood them intermittently during very hot or cool weather until they are approximately four weeks old. Both parents expend considerable effort protecting the nest from intruders, including other ospreys and potential predators.

Parental Investment: no parental involvement; altricial ; pre-hatching/birth (Provisioning: Male, Protecting: Male, Female); pre-weaning/fledging (Provisioning: Male, Female, Protecting: Male, Female); pre-independence (Provisioning: Male, Female, Protecting: Male, Female)

Nesting phenology varies throughout the range. For example, in Florida, eggs are laid from late November to early March, with a peak from December to mid-January. In the Chesapeake Bay region, ospreys first arrive at nests early to mid-March, lay eggs from late March to mid-May, with a peak in April. In southern New England, ospreys arrive beginning in mid- to late March, and eggs are laid between early April to early June, with a peak in mid- to late April. In east-central Labrador, ospreys arrive around early May, and eggs are laid from mid-May to mid-June.In southeastern British Columbia, ospreys arrive in mid- to late April, with egg laying from early May (peak) to late May.

Clutch size is 1-4 (most often 3). Incubation, usually mainly by the female (male provides food), lasts 5-6 weeks. Young fledge in around 50-60 days and thereafter are dependent on their parents for up to several additional weeks. Individuals first breed usually at 3 years, sometimes at 4-5 years.

Delays in clutch initiation, such as caused when Canada geese occupy nest sites, may cause a reduction in reproductive output (Steeger and Ydenberg, 1993, Can. J. Zool. 71:2141-2146). Number of young fledged increases with increased abundance of food resources. Large numbers may nest in a relatively small area when food resources are adequate and nesting sites are plentiful.

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 13
Specimens with Barcodes: 21
Species With Barcodes: 1

Ospreys are not listed under the Endangered Species Act. However, this species is listed as threatened, endangered or a species of special concern in several U.S. states, including Michigan. Ospreys are also protected under the U.S. Migratory Bird Act and CITES Appendix II. They are not listed on the IUCN Red List.

In the late 19th and early 20th centuries, the main threats to osprey populations were egg collectors and shootings. Shooting an egg-collection became less common by about 1950, though ospreys are still shot occasionally. Osprey populations in many areas were accidentally poisoned by the pesticide DDT (dichloro-diphenyl-trichloroethane), and many populations shrunk from the 1950’s through the 1970’s. DDT was banned in the U.S. around 1970, but is still used in some countries where ospreys spend the winter. Populations of ospreys grew again after DDT was banned. Ospreys are now almost as abundant as they have ever been. Ospreys have been helped by people constructing artificial nest structures for them, hacking projects and new habitat that has been created by man-made reservoirs.

IUCN Red List of Threatened Species: least concern

US Migratory Bird Act: protected

US Federal List: no special status

CITES: appendix ii

State of Michigan List: threatened

The National Audubon Society publishes periodic Blue Lists that
indentify population problems in bird species. As of 1982, three
categories were reported: Blue-listed species--those with populations
that are clearly declining; Species of Special Concern--previously
blue-listed species with populations that may be recovering; and Species
of Local Concern--species with presumed population declines that are
unconfirmed or of a local nature. The osprey was blue-listed from 1972
to 1981, of Special Concern in 1982, and of local concern throughout its
range in 1986 [34]. It is state-listed as threatened in South Dakota
[33] and Washington [35], and is currently listed as a sensitive species
in Region 3 by the U.S. Froest Service [8].

Year Assessed

Assessor/s

Reviewer/s

Contributor/s

Justification

History

• 2008
  Least Concern
• 2004
  Least Concern

Ospreys are not listed under the Endangered Species Act. However, this species is listed as threatened, endangered or a species of special concern in several U.S. states, including Michigan. Ospreys are also protected under the U.S. Migratory Bird Act and CITES Appendix II. They are not listed on the IUCN Red List.

In the late 19th and early 20th centuries, the main threats to osprey populations were egg collectors and shootings. These declined by the mid-twentieth century, though some shootings still occur. With the introduction and widespread use of the pesticide DDT (dichloro-diphenyl-trichloroethane), osprey populations in many areas declined sharply from the 1950’s through the 1970’s. During this period, 90% of breeding pairs disappeared from the Atlantic coast between New York City and Boston. DDT was banned in the U.S. around 1970, but continues to be used in some countries that serve as wintering grounds for ospreys. Populations of ospreys largely rebounded after the banning of DDT and are now reaching historic levels. Installation of artificial nest structures, hacking projects and new habitat created by reservoirs have allowed osprey populations to increase and expand their range.

US Migratory Bird Act: protected

US Federal List: no special status

CITES: appendix ii

State of Michigan List: threatened

IUCN Red List of Threatened Species: least concern

Resident breeder.

Canada

Rounded National Status Rank: N5B - Secure

United States

Rounded National Status Rank: N5B,N4N : N5B: Secure - Breeding, N4N: Apparently Secure - Nonbreeding

Rounded Global Status Rank: G5 - Secure

Reasons: Very large range; increasing population trend in many areas where formerly depleted by effects of pesticides; benefiting from active management in many areas; pesticide-related problems still exist in some areas.

Global Short Term Trend: Increase of 10 to >25%

Comments: Population increases and range expansions have been documented for many areas in the United States (Henny and Anthony 1989). These increases are believed to be due, at least in part, to reduced use of pesticides that apparently caused population declines in the 1960s and 1970s. Osprey populations now appear to be reoccupying their historical habitat and, in some areas, have expanded their range to include habitats around new reservoirs. Some other areas have experienced local declines where nesting habitat has been lost or fish populations have declined (Henny and Anthony 1989). A significant increase was recorded in migration counts in northeastern North America, 1972-1987 (Titus and Fuller 1990). See Henny (1986) for regional status in North America; Vahle et al. (1988) for status in the southwestern U.S. Increased in Canada in the 1980s and early 1990s (Kirk et al. 1995, Ewins 1995). Increasing in Utah (Monson 1996, Great Basin Naturalist 56:150-156).

Degree of Threat: C : Not very threatened throughout its range, communities often provide natural resources that when exploited alter the composition and structure over the short-term, or communities are self-protecting because they are unsuitable for other uses

Comments: Now recovering in many areas following severe declines resulting from organochlorine biocide use. A primary threat is the continued use of organochlorines in Central and South America (Henny and Anthony 1989, Evans 1982). Also, organochlorines and other contaminants still are contributing to eggshell thinning and low hatching success in populations nesting around Delaware Bay (Steidl et al. 1991). Other human-related causes of death in the eastern United States include included gunshots, steel traps, impact with or electrocution by high-tension wires, and being caught or drowned in nets (Wiemeyer et al. 1980, cited in Henny and Anthony 1989).

Management Requirements: Management mainly involves erection of nesting platforms, creation of osprey management areas, and/or reintroduction via hacking (reviewed in Henny 1986); also protection of nesting sites in areas subject to logging (see Palmer 1988). See Vahle et al. (1988) and Lefranc and Glinski (1988) for information on research and management needs in the southwestern U.S. See Martin et al. (1986) for specifications for the construction and placement of nesting platforms.

There are no known negative impacts of ospreys on humans. In the past, some fishermen have believed that ospreys competed with them for fish. However, studies have shown that ospreys take a much smaller amount of fish than the fishermen, and do not compete with fishermen for fish.

Ospreys help attract ecotourism to areas. They may also be a valuable indicator species for monitoring the health of large rivers, bays and estuaries. If water is polluted, the pollutants will be found in the fish that the ospreys eat. Since ospreys are sensitive to many of these pollutants, the health of the ospreys can tell us about the health of the aquatic ecosystem where they live.

Positive Impacts: ecotourism

There are no known negative impacts of ospreys on humans. In the past, some fishermen have believed that ospreys competed with them for fish. However, studies have demonstrated that ospreys take a very small portion of all fish harvested and are not serious competition for commercial and recreational fishing.

Ospreys may be a valuable indicator species for monitoring the long-term health of large rivers, bays and estuaries. Ospreys are well-suited to this role because of their piscivorous lifestyle and their known sensitivity to many contaminants. They are also relatively easily studied because they have conspicuous nests and are tolerant of short-term disturbance such as nest observations by researchers. The presence of ospreys may also benefit local economies by boosting ecotourism.

Positive Impacts: ecotourism