Animal Diversity Web

Ge­o­graphic Range

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. (Bruun and Baha el Din, 1999; Poole, 1989; Poole, 1994; Poole, et al., 2002; Porter and Cot­tridge, 2001; Steidl, 1991)

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

Habi­tat

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. (Poole, 1989; Poole, 1994)

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. (Ewins, 1996; Henny and Kaiser, 1996; Poole, 1989; Poole, 1994)

• 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

Phys­i­cal De­scrip­tion

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. (Poole, 1989; Poole, 1994; Sny­der and Sny­der, 1991)

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. (Poole, 1994)

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. (Poole, 1994)

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. (Poole, 1994; Sny­der and Sny­der, 1991)

• Other Physical Features
• endothermic
• homoiothermic
• bilateral symmetry

• Sexual Dimorphism
• female larger
• sexes colored or patterned differently

• Range mass

  1200 to 2000 g

  42.29 to 70.48 oz

• Range length

  55 to 58 cm

  21.65 to 22.83 in

• Range wingspan

  145 to 170 cm

  57.09 to 66.93 in

Re­pro­duc­tion

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. (Poole, 1989)

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. (Poole, 1989; Poole, 1994)

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). (Poole, 1989; Poole, 1994)

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. (Poole, 1994)

• 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. (Ehrlich, et al., 1988; Poole, 1989; Poole, 1994; Sny­der and Sny­der, 1991)

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. (Poole, 1989; Poole, 1994)

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. (Poole, 1989; Poole, 1994)

• Key Reproductive Features
• iteroparous
• seasonal breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual
• fertilization
• oviparous

• 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

• Average eggs per season

  3

  AnAge

• 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 (female)
  Sex: female

  1095 days

  AnAge

• Average age at sexual or reproductive maturity (male)

  3 years

• Average age at sexual or reproductive maturity (male)
  Sex: male

  1095 days

  AnAge

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. (Poole, 1989; Poole, 1994)

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. (Poole, 1989; Poole, 1994; Poole, et al., 2002)

• 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

Lifes­pan/Longevity

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. (Poole, et al., 2002)

• Range lifespan
  Status: wild

  25 (high) years

• Average lifespan
  Status: wild

  314 months

  Bird Banding Laboratory

Be­hav­ior

Os­preys can be mi­gra­tory or seden­tary (non-mi­gra­tory). Non-mi­gra­tory pop­u­la­tions breed and win­ter in the same lo­ca­tion. Mi­gra­tory os­prey pop­u­la­tions gen­er­ally breed north of the non-mi­gra­tory pop­u­la­tions and win­ter south of them, with very lit­tle over­lap be­tween the two groups. The ge­o­graphic di­vi­sion be­tween mi­gra­tory and non-mi­gra­tory pop­u­la­tions is roughly 30 de­grees N lat­i­tude in North Amer­ica and 38 to 40 de­grees N lat­i­tude in Eu­rope. (Fer­nan­dez and Fer­nan­dez, 1977; Poole, 1989; Poole, 1994)

Os­preys nest at a range of den­si­ties, from very soli­tary (many kilo­me­ters from the near­est neigh­bor­ing nest) to loose colonies, with nests less than 100 m apart. Colonies may form be­cause the pres­ence of es­tab­lished nests is a sig­nal of suit­able habi­tat to ar­riv­ing in­di­vid­u­als, or be­cause good nest sites are often clus­tered to­gether, such as on an is­land or along a power line. Group­ing of nests is un­com­mon in rap­tor species be­cause most rap­tors de­fend a feed­ing ter­ri­tory around their nest. Os­preys de­fend their nest or nest site, but do not de­fend a ter­ri­tory around the nest. It is not prof­itable for an os­prey pair to de­fend a ter­ri­tory around the nest be­cause their prey are patchily dis­trib­uted, mo­bile, and often lo­cated sev­eral kilo­me­ters away from the nest. In­deed, os­preys are often ob­served hunt­ing in groups, and may be able to hunt more ef­fi­ciently by doing so. (Poole, 1989; Poole, 1994; Poole, et al., 2002)

Os­preys do vig­or­ously de­fend their ac­tual nests or nest sites from in­trud­ers. This is most likely be­cause nests are used by the same pair for many years, and rep­re­sent a sig­nif­i­cant in­vest­ment of time and en­ergy by that pair. (Poole, 1989)

• Key Behaviors
• flies
• diurnal
• motile
• migratory
• sedentary
• solitary
• colonial

Home Range

Breed­ing os­preys are known to travel as far as 14 km from their nest dur­ing hunt­ing for­ays. Non-breed­ing in­di­vid­u­als are known to travel as far as 10 km be­tween their day­time feed­ing grounds and their roosts. (Poole, et al., 2002)

Com­mu­ni­ca­tion and Per­cep­tion

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. (Poole, 1989; Poole, 1994; Poole, et al., 2002)

• Communication Channels
• visual
• tactile
• acoustic

• Perception Channels
• visual
• tactile
• acoustic
• chemical

Food Habits

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. (Poole, 1989; Poole, et al., 2002)

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. (Poole, 1989; Poole, 1994; Poole, et al., 2002)

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. (Poole, et al., 2002)

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). (Poole, et al., 2002)

• Primary Diet
• carnivore
  • piscivore

• Animal Foods
• birds
• mammals
• amphibians
• reptiles
• fish
• carrion
• mollusks

Pre­da­tion

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. (Poole, 1989; Poole, et al., 2002)

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. (Poole, 1989; Poole, et al., 2002)

• Anti-predator Adaptations
• cryptic

• Known Predators

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

Ecosys­tem Roles

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. (Poole, et al., 2002)

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. (Poole, et al., 2002)

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. (Poole, et al., 2002)

Eco­nomic Im­por­tance for Hu­mans: Pos­i­tive

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. (Poole, 1989; Poole, et al., 2002)

• Positive Impacts
• ecotourism

Eco­nomic Im­por­tance for Hu­mans: Neg­a­tive

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. (Poole, 1989)

Con­ser­va­tion Sta­tus

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. (LaPierre, 1991; Poole, 1989; Poole, et al., 2002)

• IUCN Red List

  Least Concern
  More information

• IUCN Red List

  Least Concern
  More information

• US Migratory Bird Act

  Protected

• US Federal List

  No special status

• CITES

  Appendix II

• State of Michigan List

  Threatened

Other Com­ments

Bones be­long­ing to ear­lier Pan­dion species from the mid- to late-Miocene (ap­prox. 13 mil­lion years ago) were found in Cal­i­for­nia and Florida. These pre­his­toric os­prey species were slightly less ro­bust than mod­ern os­preys, but oth­er­wise very sim­i­lar. (Poole, et al., 2002)

Con­trib­u­tors

Kari Kirschbaum (au­thor), An­i­mal Di­ver­sity Web, George Ham­mond (ed­i­tor), An­i­mal Di­ver­sity Web.

Pa­tri­cia Sharpe Watkins (ear­lier au­thor), Uni­ver­sity of Michi­gan-Ann Arbor.

Ref­er­ences

Bruun, B., S. Baha el Din. 1999. Com­mon Birds of Egypt. Cairo, Egypt: The Amer­i­can Uni­ver­sity in Cairo Press.

Ehrlich, P., D. Dobkin, D. Wheye. 1988. The Birder's Hand­book. New York: Simon & Shus­ter Inc..

Ewins, P. 1996. The use of ar­ti­fi­cial nest sites by an in­creas­ing pop­u­la­tion of os­preys in the Cana­dian Great Lakes Basin. Pp. 109-124 in D Bird, D Var­land, J Negro, eds. Rap­tors in Human Land­scapes. Sand Diego: Aca­d­e­mic Press Lim­ited.

Fer­nan­dez, G., J. Fer­nan­dez. 1977. Some in­stant ben­e­fits and long range hopes of color band­ing os­preys. Trans­ac­tions of the North Amer­i­can Os­prey Re­search Con­fer­ence: 89-94.

Henny, C., J. Kaiser. 1996. Os­prey pop­u­la­tion in­crease along the Willamette River, Ore­gon, and the Role of Util­ity Struc­tures, 1976-93. Pp. 97-108 in D Bird, D Var­land, J Negro, eds. Rap­tors in Human Land­scapes. San Diego: Aca­d­e­mic Press Lim­ited.

In­ter­na­tional Sym­po­sium on Bald Ea­gles and Os­preys, 1983. Bi­ol­ogy and Man­age­ment of Bald Ea­gles and Os­preys. Que­bec: Mac­Don­ald Rap­tor Re­search Cen­tre of McGill Uni­ver­sity.

LaPierre, Y. 1991. Di­vided over voyageurs. Na­tional Parks, 70: 36-40.

Poole, A. 1989. Os­preys: A Nat­ural and Un­nat­ural His­tory. New York: Cam­bridge Uni­ver­sity Press.

Poole, A. 1994. Fam­ily Pan­dion­idae (Os­prey). Pp. 42-50 in J Del Hoyo, A El­liott, J Sar­gatal, eds. Hand­book of the Birds of the World, Vol. 2. Barcelona: Lynx Edi­cions.

Poole, A., R. Bier­re­gaard, M. Martell. 2002. Os­prey (Pan­dion hali­ae­tus). A Poole, F Gill, eds. The Birds of North Amer­ica, Vol. 683. Philadel­phia, PA: The Birds of North Amer­ica, Inc..

Porter, R., D. Cot­tridge. 2001. A pho­to­graphic guide to birds of Egypt and the Mid­dle East. Cairo, Egypt: The Amer­i­can Uni­ver­sity in Cairo Press.

Sny­der, N., H. Sny­der. 1991. Birds of Prey: Nat­ural His­tory and Con­ser­va­tion of North Amer­i­can Rap­tors. Still­wa­ter, MN: Voyageur Press, Inc..

Steidl, R. 1991. Dif­fer­en­tial re­pro­duc­tive suc­cess of os­preys in New Jer­sey. The Jour­nal of Wildlife Man­age­ment, 55: 266-271.