Mortality of Wintering Ospreys and Other Birds at Aquaculture Facilities in Colombia

j RaptorRes. 37(4):292-298 ¸ 2003 The Raptor ResearchFoundation, Inc.

MORTALITY OF WINTERING OSPREYS AND OTHER BIRDS AT AQUACULTURE FACILITIES IN COLOMBIA

M•tc j. BECHARD1 Departmentof Biology,Boise State University, Boise, ID 83725 U.S.A.

CgsA• MARO•t:Ez-R•YEs2 Alexandervon HumboldtInstitute, Carrera 7, No. 35-20, Bogotd,Colombia

A•ST•CT.--Ospreys (Pandionhaliaetus) winter throughoutthe countryof Colombia.Recoveries of banded Ospreysindicate that many are shot in the countrywith the number increasingsince the 1970s.The increasedincidence of shootinghas coincidedwith the developmentof aquaculturefacilities in Colom- bia that raise tilapia (Oreochromisspp.). Becausethese facilities typically lose production to birds suchas Ospreysthat depredate fish, we conducteda surveyof 83 facilitiesin three statesor departmentsin Colombia in 2001 to determine the speciesof birds that take fish at aquaculture facilities and the numbers that are killed each year. Our resultsshowed that bird depredation occursat aquaculture facilitiesthroughout the country,but mostlyin the southernportion of the country in the department of Huila. Facility managers reported shooting Ospreysin all three departments with as few as five individualsshot annuallyin Antioquia in northern Colombiato as many as 270 shot annuallyin Huila. In addition, facilitymanagers reported shootingnine other speciesof birds includingGreen Kingfishers ( Chloroceryleamericana), Great Kiskadees(Pitangus sulphuratus), Snowy Egrets (Egretta thula), Great Egrets ( Casmerodiusallms), Olivaceous Cormorants (Phalacrocoraxolivaceus), Black-crowned Night-Herons (Nyc- ticoraxnycticorax), White-necked Herons (Ardeacocoi), Cattle Egrets (Bubulcusibis), and StriatedHerons (Butoridesstriatus), for a total estimateof >9000 birds shot in the three departmentsannually. A number of alternative methodsto shootinghad been used to reduce lossesto birds including the installationof netting, overheadwires, scarecrows, and noisemaking devices,but, neither thesemethods nor shooting, were effectivein deterring avianpredators. KEYWORDS: Osprey;Pandion haliaetus; aquaculture facilities; mortality; Oreochromis spp.; shooting, tilapia.

MORTALIDAD DE AGUILAS PESCADORAS (PANDION HALIAETUS) INVERNANTES Y OTRAS AVES EN INFRAESTRUCTIRA PISCICOLA EN COLOMBIA

RESUMEN.--E1figuila pescadora(Pandion haliaetus) pasa el invierno en todo el territorio colombiano. La recaptura de •tguilaspescadoras anilladas indican que muchasson cazadasen este pais con cifrasen aumento desde 1970. La incidencia del numero de •tguilasmuertas coincide con el desarrollode la acuiculturaen Colombiay la cria de tilapia roja (Oreochromisspp.). Estaindustria tradicionalmente ha tenido problemascon avesdepredadoras de pecespor lo cual realizamosuna encuestaen 83 granjas piscicolasen tres departamentosde Colombia en el 2001 para determinar las especiesque consumen pecesy el numero de aveseliminadas anuahnente. Nuestros resultados mostraron que la depredaci6n por avesen la infraestructurapiscicola ocurre en todo el territorio pero el problema es mas severoen la porci6n sur del pals en el departamentodel Huila. Los propietariosde las granjasreportaron que eliminan figuilaspescadoras en los tres departamentos,con pocosindividuos en Antioquia (al norte de Colombia)equivalente a 5 individuos,y un numerom•tximo en el Huila de 270 individuos.Adicional- mente los propietariosreportaron que cazanotras nueve especies de aveslas cuales incluyen a Chloloceryle americana,Pitangus sulphuratus, Egretta thula, Casmerodius allms, Phalacrocorax olivaceus, Nycticorax nycticorax, Ardeacocoi, Bulmlcus ibis, Butorides striatus, para un total estimadode >9000 aveseliminadas anuahnente en los tres departamentos.Los propietariosde las granjasreportaron que han probado otrosm6todos de control aparte de las armas de fuego, para reducir las perdidastales como la instalaci6nde redes

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292 DECEMBER 2003 OSPREY MORTALITY IN COLOMBIA 293

protectoras,cuerdas de alambre, espantap•jaros,aparatos con sonidos,pero ninguno ha resultado eft- cientein incluyendoel usode lasarmas de fuegopara la reducci6nde lasperdidas econ6micas causadas por aves. [Traducci6n de los autores]

Ospreys (Pandion haliaetus)breed throughout Therefore, shooting may selectively eliminate North America (Palmer 1988, Poole 1989, Johns- younger individuals and possiblydecrease recruit- gard 1990, Poole et al. 2002). During the 1950s ment of new breeders into populations.Currently, and 1960s, pesticide contamination threatened there is insufficient information to judge the ex- many populations and declines were widespread tent and severityof the South American shooting across the breeding range (Poole 1989). Since threat, despite the fact that it may have increased then, populationshave rebounded and, today,the sincethe 1970s (Poole and Agler 1987, Ewinsand Ospreyis again a common speciesin coastal,lake, Houston 1992). and riverine habitats.The Ospreyis migratory with Sincethe 1970s,fish farming or aquaculturehas populationsfrom locationsin the westernU.S. win- become a new and thriving businessin Latin Amer- tering in Mexico and Central America (Henny and ica. Production systems consisting of extensive Van Velzen 1972,Melquist et al. 1978,Johnsonand ranching operations where fry are released into Melquist1991, Martell et al. 2001) and populations reservoirs and later harvested as adults have been from coastal areas of the eastern U.S. and Canada built in Mexico, Central and South America (Fitz- and the Great Lakes region of the Midwestwinter- simmons 2000). Many aquaculture facilities spe- lng in South America (Martell et al. 2001, Poole et cialize in the production of tilapia (Oreochrom•s al. 2002). Ospreysbanded asnestlings in Maryland, spp.), which are now produced in virtually every Virginia, New York, NewJersey, Michigan, and Wis- country of the Americas. By 1998, the annual pro- consin have mainly been recovered in Colombia, duction of tilapia had grown to 201 067 mt (metric Venezuela, Equador, and Brazil indicating that tons) in Latin America and the U.S. imported northern South America is a primary wintering 72 428 mt of live weight fish in 2000 (Fitzsimmons area for eastern and Midwestern populations 2000). Aquaculture facilities typicallyraise tilapia (Henny and Van Velzen 1972, Poole and Agler in shallowponds that are • 1 ha in size, but, with 1987, Niemuth 1991). facilities consistingof •30 ponds, they can have The Osprey is unusual becauseit is exclusively large areas of impounded water. Tilapia are sur- piscivorouseating a wide variety of fresh and salt- face-feedersand, when thousandsof these bright water fish species(Poole 1989, Poole et al. 2002). red fish come to the surfaceto feed, they become It has traditionally been called the "fish hawk" in easyprey for piscivorousbirds. North America and "aguila pescadora" in South With its tremendous warm water resources, Co- America and it has been shot, had its nests robbed lombia hasbecome one of the leadingaquaculture or torn down, and otherwise been persecuted in fish producers in South America (Fitzsimmons areaswhere people believe it competeswith them 2000). Commercial fish production began in the for sport or commercial fisheries. The Osprey is 1980s and by 1996, 22 statesor departmentswere protected from shooting and other forms of hu- producing a mean of 25 063 mt of fish a year (Ins- man-causedmortality in North America but, on its tituto Nacional de Pescay Aquicultura de Colom- Caribbean and Central and South American win- bia [INPA] unpubl. data). Some commercial facil- tering grounds, there are few laws restricting the ities raise rainbow trout (Oncorhynchusmykiss), but killing of birds. Band recoveriesof dead Ospreys most are dedicatedto the production of tilapia and indicate that shooting and trapping continue to Colombia producesa mean of 15 000 mt of tilapia threaten the species on its wintering grounds each year (Fitzsimmons2000). There is an obvious (Pooleand Agler 1987,Santana and Temple 1987, potential for large numbersof piscivorousbirds to Ewins and Houston 1992). The Osprey is also un- be killed at these aquaculture facilities and, as usual becauseit does not breed until three years such, these facilitiesmay have some effect in redls- of age and immatures remain on the wintering tributing populations of resident and wintering pi- grounds continuouslyuntil they become sexually scivorousbirds in the country. Becauseof the es- mature (Henny and Van Velzen 1972, Poole 1989). calating numbers of Ospreys that are shot at 294 BECHARDAND M•RQUEZ-REYES VOL. 37, NO. 4 aquaculture facilities and brought to rehabilitation Table 1. Questionnaireadministered to aquaculturefa- facilities in Golombia (pets. observ.) and increas- cility ownersand managers to estimate bird depredation ing concern from the birding community about and mortality at aquaculture facilities in the departments the numbers of Ospreys being killed each year of Antioquia, Valle del Gauca, and Huila in Golombia. (Nielson 1998), we undertooka surveyto assessthe extent of the threat to North American Ospreys Facility name w•ntering in Golombia from shooting, trapping, Permit number Location and other human-causedmortality at aquaculture Name of water source facilities throughout the country. Water temperature (øG) STUDY AREAS AND METHODS Number of ponds Area of impounded water (ha) We chose three departments, Anfioquia in northern Fish speciescultivated Colombia, Valle del Cauca in west-central Colombia, and Annual fish production (mr) Huila in southern Colombia, to conduct our survey.We Annual income (pesos) chose these departments because they provided a good representation of the variation in the sizesand produc- Do you have problemswith bird depredation? uon of aquaculturethcilities in the country,and each de- How much do you estimateyou lose annually to bird partment had ca. 30 commercial aquaculture facilities depredation? (pesos) that were either licensed by the Corporacion de Valle del Which speciesof birds are a problem and rank each Cauca or by INPA. Antioquia (05ø26'-08ø52'N,73ø53 '- speciesin terms of the seriousnessof the problem (1 77ø07'W) has a total of 28 licensedaquaculture facilities = none or little problem, 2 = slight problem, 3 = and was the largest of the three departments surveyed moderate problem, 4 = seriousproblem, 5 = severe coveringan area of 63 612 km2. The departmentof Valle problem with fish taken daily). del Cauca (03ø04'-05ø02'N,72ø42'-74ø27'W) encompass- es a 22 140 km 2 area of west-central Golombia and has Do you shoot problem birds?If yes, estimate the num- 32 licensed aquaculture facilities. The department of bers of each speciesthat are shot annually (1-10, 11- Huila in the southern portion of Colombia (01ø33'- 20, 21-50, 51-75, 76-100, 101-200, >200). 03ø47'N, 74ø28'-76ø36'W) is the smallestof the three de- Have you used other methods of deterring birds from partmentscovering an area of 19 890 km2 and it has 27 taking fish at your thcility?If yes, please describeeach licensed aquaculture facilities. method and rate its efibctiveness. Of the 87 licensed aquaculturefacilities in the three departments,we visited all except four to interview facil- xtyowners and managerswho were familiar with the daily operations of the facilities. The four facilities not visited problem (Table 1). Most of the intervieweesknew the were in the department of Valle del Cauca, and they were local common names tbr the speciesof birds that caused not surveyedeither becausethe ownersdeclined to par- depredation lossesat their farms. When there was any ticipate or because they were in locations where condi- question about the identity of a speciesof bird, we used tions made them too dangerous to visit. During each visit, color photographsand color plates in Hilty and Brown we administereda standardquestionnaire to ownersor (1986) to help intervieweesidentify the species.To esti- managerswho were familiar with the daily operations of mate the numbers of each speciesshot annually at each facilities. Before administering the questionnaire,a state- facility, we used the midpoints of the rangesgiven by in- mcnt signed by officials of INPA and the Ministry of the tervieweesfor the numbers of birds they shot each yem: Environment was read stating that all answerswould be To rank speciesin terms of the seriousnessof the threat kept confidential and that no legal proceedingswould they posed to the production of fish, we averaged the result from any answersgiven to the questioner. The rankingsgiven by the facility ownersin each department. questionnaire was administered verbally, and we com- pleted the answerson the questionnaire forms as the in- RESULTS tervieweesresponded to them. The questionsasked for information on the size of the facility (number of ponds A total of 82 of the 83 aquaculture facilities sur- and ha of impounded water), its annual fish production veyed reported experiencing depredation lossesto (mt), if birds were a problem becausethey impacted an- the following 10 speciesof birds: Green Kingfisher nual fish production, the speciesof birds depredating (Chloroc•yleamericana), Great Kiskadee (Pitangus fish, the seriousnessof the impact by each species(on a scale from 1-5 with 1 being a specieswith one or a few sulphuratus),Snowy Egret (Egretta thula), Great individuals infrequently depredating ponds and 5 being Egret (Casmerodiusalbus), Olivaceous Cormorant a specieswith several individuals depredating ponds on ( Phalacrocoraxolivaceus) , Black-crowned Night-Her- a daily basis), if birds were shot, which speciesof birds on ( Nycticoraxnycticorax) , White-necked Heron ( Ar- were shot, estimated number of each speciesshot each year (1-10, 11-20, 21-50, 51-75, 76-100, 101-200, or deacocoi), Cattle Egret ( Bubulcusibis), Striated Her- >200 shot annually), and alternative methods to shoot- on (Butoridesstriatus), and Osprey (Table 2). Of the xng that had been used to decrease the depredation 82 facilities with depredation losses,35 reported DECEMBER 2003 OSPREY MORTALITY IN COLOMBIA 295

Table 2. Mean ranking of birds that pose depredation problems at aquacnlturefacilities in the departmentsof Antioquia, Valle del Cauca, and Huila in Colombia and estimatesof the number of each speciesshot annually.

ANTIOQUIA VALLE DEL CAUCA HUILA

SPECIES RANKING 1 NO. SHOT RANKING 1 NO. SHOT RANK1NG1 NO. SHOT TOTAL SHOT

Green Kingfisher 2.6 44 2.5 65 3.5 1836 1945 Great Kiskadee 1.7 0 1.7 0 2.5 1692 1692

-- SnowyEgret 1.1 0 1.1 0 2.9 1621 1621 Great Egret 1.8 45 2.25 65 2.75 931 1041 Olivaceous Cormorant 1.8 230 1.4 19 1.0 288 537 Black-crownedNight-Heron 1.0 0 2.6 105 2.0 318 423 White-necked Heron 1.6 5 2.0 13 1.4 403 421 Cattle Egret 1.0 15 1.0 0 1.7 400 415 Striated Heron 1.3 0 2.5 35 1.1 364 399 Osprey 1.5 5 2.6 40 2.8 270 315 Total shot 356 342 8323 9021

• 1 = none or little problem, 2 = slight problem, 3 = moderate problem, 4 = seriousproblem, 5 = severeproblem with fish taken daily. shooting birds killing a co•nbined estimate of duction to bird depredation. At 23 facilities, birds >9000 birds per year. Facilitiesin all three depart- ranked as causing the most serious depredation ments reported Green Kingfishersas causing the losseswere Green Kingfishers, Great Egrets, Oli- most seriouslosses and managersat these facilities vaceous Cormorants, Great Kiskadees, and White- reported killing more kingfishers (ca. 2000/yr) necked Herons that took fish either while perching than any other species.Facilities also experienced on overhead wires or while wading along the edges depredation lossesto Great Kiskadees,which took of ponds (Table 2). Only four facilities in Antio- pelletized fish food and fingerlings,and managers quia ranked Ospreysas causingthe most serious at these facilities shot an estimated 1700 kiskadees production losses,and all of these facilities spe- per year. As a group, ciconiiformswere viewed as cialized in tilapia production. Eight facility man- causingthe most seriousdepredation lossesat fish agers said they shot an estimated 230 Olivaceous farms with SnowyEgrets, Great Egrets, and Black- Cormorants, 45 Great Egrets, 44 Green Kingfish- crowned Night-Herons generally consideredto be ers, 15 Cattle Egrets, and 5 White-necked Herons the biggestthreats to facility production. Managers annually,but only 5 Ospreysper year. of facilities shot an estimated total of >3000 egrets Valle del Cauca, the second-largest,fish-produc- and night-herons.An estimated315 Ospreyswere ing department in Colombia, had a mean annual shot each year at facilities. Ospreyswere consid- fish production of 4560 mt, most of which was ti- ered to cause the most seriousdepredation losses lapia. The aquaculture facilities consistedof fewer in southern Colombia in the department of Huila. ponds (œ= 13.1 ___13.3 ponds,range = 1-56, N = The one facility that did not experiencebird dep- 28) but they were much larger in size (• = 5.5 +- redation problems waslocated in Antioquia and it 5.8 ha of impounded water, range = 0.4-18.2, N = raised primarily rainbow trout that were grown in 28), than in Antioquia. Twenty of the facilities completely-coveredraceways and protected from raiseda mean of 67.6 - 90.6 mt (range = 5-240) birds. of tilapia each year. All 28 of the facilities surveyed Aquaculture facilitiesin Antioquia ranged in size in Valle del Cauca reported lossesin fish produc- from 1-400 ponds(• = 36.8 + 74.8,N = 28, +SD) tion to bird depredation. Black-crowned Night- with 0.01-26.0 ha of impounded water (• = 1.8 _+ Herons, Ospreys,Green Kingfishers,Striated Her- 5.1, N = 28) raising a mean of 79.02 - 155.9 mt ons, and Great Egrets were considered to be of fish per year (range = 1.5-600, N = 28). Twenty- problem specieswith mean rankings >2 (Table 2). two of the facilitiesraised mostly rainbow trout and Fourteen facility managersreported Ospreysto be the remaining six raised mainly tilapia. A total of a seriousproblem species.Only four facility man- 27 facilitiesin Antioquiaexperienced losses in pro- agers in Valle del Cauca said they shot birds and 296 BECHARD^•D M•QU•Z-R•ws VOL. 37, NO. 4 estimatedkilling 105 Black-crownedNight-Herons, cause these facilities are relatively small and trout 65 Great Egrets, 50 Striated Herons, 40 Ospreys, are mainlyraised in coveredraceways that are pro- and 20 White-necked Herons each year. tected from birds. The departmentsof Antioquia, The department of Huila was the smallestfish Cordoba, Huila, Meta, Tolima, and Valle del Cauca producer of the three departmentssurveyed, pro- each average >2000 mt of fish production annu- ducing a mean of 2132 mt of fish per year, nearly ally, ranging from a low of 2100 mt in Cordoba to 94% of which wastilapia. Aquaculture facilities in a high of 6589 mt in Meta. These departments Huila had more pondsthan in either Antioquia or have the largest aquaculture facilities and raise Valle del Cauca (• = 62.1 -+ 139.7 ponds,range = mainly tilapia in large, shallow ponds that are 3-650, N = 27), but they were smallerin sizeand prone to bird depredation. Therefore, these de- covered a mean of 4.1 ___6.1 ha (range = 0.2-25, partments have the greatestpotential for develop- N = 27). Nevertheless,five of the facilities in Huila ing bird depredation problems and the shooting were very large consistingof >20 ponds and >15 of birds at aquaculture facilities. ha of impounded water. Facilitiesin Huila were The results of our survey showed that several very productive, producing a mean of 99.08 _+ speciesof birds depredate aquaculturefacilities in 132.42 mt of tilapia (range = 2.5-840, N = 27) Colombia with the depredation problem apparent- annually.In Huila, all 27 aquaculturefacilities sur- ly increasingfrom north to south in the country. veyed reported lossesin fish production to bird The most common solution to the problem that depredation. Green Kingfishers,Great Egrets, and has been usedby facility managersis shooting,and Great Kiskadeeswere again ranked as causing se- shooting appears to increase from as few as 100 rious depredation problems (Table 2). Twenty-two birds shot in Antioquia in northern Colombia to facility managersreported Ospreysto be a serious as many as 8000 shot annually in Huila in southern depredation problem and 11 of thesereported Os- Colombia. This increase appears to be due to a preysto be their most seriousproblem species.Un- shift in the emphasisof fish production at aqua- like the other departments, aquaculture facilities culture facilitiesin the country from mostlytrout in Huila experiencedserious depredation losses to production at facilities in northern Colombia to Snowyand Catde Egrets. Birds were shot at 23 fa- mosdytilapia productionin southernColombia. In cilitieswith an estimated8323 birds killed annually northern Colombia, most facility managersdo not •ncluding 1836 Green Kingfishers,1692 Great Kis- consider the bird depredation problem to be se- kadees, 1621 SnowyEgrets, 931 Great Egrets, 403 vere enoughto warrant killing birds and only eight White-necked Herons, 400 Cattle Egrets, 364 Stri- of them said they shot kingfishers,herons, egrets, ated Herons, 318 Black-crowned Night-Herons, and Ospreys.In Huila, facility managersappear to and 270 Ospreys.One facilitymanager reported see bird depredation as a more seriousproblem. shooting >100 Ospreysat a communal roost tree This attitude was reflected in the numbers and va- located on the Magdalena River, where as many as riety of birds they shot. All of the fish farm man- 50 Ospreyswould roost each night. The number agers who shot birds, also said that shootingwas he shot did not reduce the depredation problem not an effectivemethod of decreasingtheir losses at his facility becauseas many as 20 Ospreysfed becausenew birds simplyreplaced birds that were there daily. The day we visited the facility,we ob- shot. served 10 Ospreystaking fish from his ponds. The numbersof Ospreysreported shot eachyear also increasedfrom five in Antioquia to over 270 DISCUSSION in the southerndepartment of Huila. Ospreyswere Of the 22 departmentsin Colombia that have consideredto be only a minor problem in Antio- INPA-licensed commercial aquaculture facilities, quia causingproduction lossesat only thosefacil- annual fish production averages<100 mt in the ities that emphasized tilapia production. The departments of Arauca, Adantico, Gasanare, Cau- shooting in Huila increased correspondinglywith ca, Cesar, Choco, Guaviare, and Vichada, and an increasein the productivityof tilapia in this de- <1500 mt in the departments of Boyaca, Cundi- partment. Warmer water temperaturesin this de- namarca, Risaralda, Putumayo, and Santander. partment are more conduciveto the productionof Most of this fish production is rainbow trout so we tilapia. Tilapia are raised in large, shallow im- d•d not consider facilities in any of these depart- poundmentsaveraging nearly 5 ha in size.At any ments to pose seriousshooting threats to birds be- time, aquaculture facilities in Huila have as many DECEMBER 2003 OSPREYMORTALITY IN COLOMBIA 297

as 1 million tilapia in variousstages of growth. The any laws that prevent shooting and those that do combination of the large amount of impounded frequently lack enforcement. Shooting is an easy water and the multitude of easily-capturedfish prey method of eliminating problem birds and band re- are natural lures for Ospreys. covery data from Central and South America sup- Of the speciesthat were shot, only Great Egrets, port that this is the usual method of reducing the SnowyEgrets, Cattle Egrets, Black-crownedNight- avian depredation problem. Of the Ospreysband- Herons, and Ospreysare consideredto be boreal ed in Canada, 39% have been recovered shot and migrants in northern South America (Davis 1993, the number shot appears to have increased since Parsons amd Master 2000, McCrimmon et al. 2001, the 1970s,which coincideswith the timing of the Ridgley and Greenfield 2001). All, excluding the first construction of aquaculture facilities in Latin Osprey,are also resident speciesthat breed aswell America (Poole and Agler 1987, Poole 1989, Ewins as winter in Colombia (Hilty and Brown 1986); and Houston 1992). Populationsof Ospreyscon- therefore, it was impossibleto assessthe overall tinue to increase throughout North America threat of Colombian aquaculture facilities to bo- (Poole et al. 2002) indicating that the mortality at real migrants. We recovered a total of six USGS aquaculturefacilities has probablynot yet reached bands that owners had removed from dead birds, numbers great enough to impact populations of but had not reported to the Bird Banding Labo- North American Ospreys.Nevertheless, in view of ratory. All were from dead Ospreys.Two were from the current growing global trend in fish farming, Ospreys that had been banded as nestlingsin mortality from shootingwill only increasein years Maine and one each came from Wisconsin,Virgin- to come, perhaps developing into a seriousprob- •a, New York, and Connecticut,further supporting lem for Osprey populations in the eastern and the view that Colombia is an important wintering Midwestern U.S. area for Ospreysfrom the easternand Midwestern Our survey showed that fish farm owners had U.S. tried a variety of nonlethal bird deterrents to re- Aquaculture of tilapia first began in the Ameri- duce their annual lossesto birds.The mostwidely- cas in the 1960s and 1970s.Currently, Mexico is used alternatives to shooting were noise-making the biggest producer of tilapia but the industry is devices,such as guns, cannons, and fireworks, and rapidly growingin Honduras,Costa Rica, Cuba,Ja- patrolsby people who flushedbirds from the edges maica, Colombia, Ecuador, Peru, Venezuela, and of ponds. None of these methods had proven ef- Brazil (Fitzsimmons 2000). Future production fectivebecause problem birds apparentlyeither be- trends include further intensification of produc- came habituated to the noise makers or simply tion in every country with Brazil expected to become the biggest producer of tilapia in the next learned to ignore people patrolling ponds. A few facility managers had tried using scarecrowsand 20 yr (Fitzsimmons2000). Ospreyswinter in all of these countries, therefore, if this trend continues, dogsto frighten birds away.Neither of thesemeth- we could expect an increase in the shooting of Os- ods was effective after problem birds became ac- preys on their wintering grounds. In North Amer- customedto them. Another widely-useddeterrent ica, the construction of reservoirs for irrigation was the installation of netting around ponds. Nets and flood control have had a substantial effect on were frequently used to reduce losesto birds such the redistributionof breeding Ospreys,particularly as herons and egrets that hunt along the edges of in the western U.S. (Henny et al. 1978a, 1978b, ponds. Owners reported that the deviceswere rel- Swenson 1981, Poole 1989). A similar phenome- atively effective provided the netting was main- non may be currently underway in Latin America. tained along the edges of ponds. Such mainte- Aquaculture facilities may redistribute wintering nance was labor intensive and it was difficult to populationsof Ospreysaway from natural habitats make certain that the netting was in place at all such as coastal, lake, and river areas to man-made times. Only five fish farms reported having tried reservoirs,where they are lured by the abundance using overheadlines to deter depredation from ae- of easily-capturedfish prey.Unlike North America, rial foragerssuch as Ospreys(Salomon and Conte where legislativecontrols and public education has 1981). The five that tried this method found it to reduced the risk of Ospreysbeing shot (Poole and be relatively inexpensive and potentially effective Agler 1987), in Latin America shootingcontinues in reducing lossesto large aerial-hunting birds like to be a very real threat. Many of the countrieslack Ospreys. 298 B•.CH•d) AND •M2gtRQUEZ-REYES VOL. 37, NO. 4

ACKNOWLEDGMENTS sitesof North American Ospreysas determined by sat- We thank F. Ramirez, E Estela,andJJ. Orozco for help ellite telemetry.Condor 103:715-724. with surveysof fish farms. W. Weber, SAO, P. Montoya, MCCmMMON,D.A., JR.,j.c. OGDEN,AND G.T. BANCROFT. Corporacion de Valle del Cauca, and M.L. Vidal, Cor- 2001. Great Egret (Casmer0diusallms). In A. Poole and poracion de Huila alsoprovided support for the project. F. Gill [EDs.], The birds of North America, No. 570. This studywas funded by the Western Hemisphere Pro- The Academyof Natural Sciences,Philadelphia, PA, gram, USFWS, Washington, DC, Agreement Number 14- and The American Ornithologists' Union, Washing- 48-98210-99-G416. ton, DC U.S.A.

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