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North American Osprey Populations and Contaminants: Historic and Contemporary Perspectives
Abstract and Figures
Osprey (Pandion haliaetus) populations were adversely affected by DDT and perhaps other contaminants in the United States and elsewhere. Reduced productivity, eggshell thinning, and high DDE concentrations in eggs were the signs associated with declining osprey populations in the 1950s, 1960s, and 1970s. The species was one of the first studied on a large scale to bring contaminant issues into focus. Although few quantitative population data were available prior to the 1960s, many osprey populations in North America were studied during the 1960s and 1970s with much learned about basic life history and biology. This article reviews the historical and current effects of contaminants on regional osprey populations. Breeding populations in many regions of North America showed post-DDT-era (1972) population increases of varying magnitudes, with many populations now appearing to stabilize at much higher numbers than initially reported in the 1970s and 1980s. However, the magnitude of regional population increases in the United States between 1981 (first Nationwide Survey, ∼8,000 pairs), when some recovery had already occurred, 1994 (second survey, ∼14,200), and 2001 (third survey, ∼16,000-19,000), or any other years, is likely not a simple response to the release from earlier contaminant effects, but a response to multi-factorial effects. This indirect "contaminant effects" measurement comparing changes (i.e., recovery) in post-DDT-era population numbers over time is probably confounded by changing human attitudes toward birds of prey (shooting, destroying nests, etc.), changing habitats, changing fish populations, and perhaps competition from other species. The species' adaptation to newly created reservoirs and its increasing use of artificial nesting structures (power poles, nesting platforms, cell towers, channel markers, offshore duck blinds, etc.) are two important factors. The timing of the initial use of artificial nesting structures, which replaced declining numbers of suitable trees at many locations, varied regionally (much later in the western United States and Mexico). Because of the increasing use of artificial nesting structures, there may be more ospreys nesting in North America now than ever before. Now, with the impact of most legacy organic contaminants (DDT, other organochlorine [OC] pesticides, polychlorinated biphenyls [PCB], polychlorinated dibenzo-p-dioxins [PCDD], polychlorinated dibenzofurans (PCDF]) greatly reduced or eliminated, and some osprey populations showing evidence of stabilizing, the species was proposed as a Worldwide Sentinel Species for evaluating emerging contaminants. Several emerging contaminants are already being studied, such as polybrominated diphenyl ethers (PBDE) and perfluorinated acids and sulfonate compounds (PFC). The many advantages for continued contaminant investigations using the osprey include a good understanding of its biology and ecology, its known distribution and abundance, and its ability to habituate to humans and their activities, which permits nesting in some of the potentially most contaminated environments. It is a top predator in most ecosystems, and its nests are relatively easy to locate and study with little researcher impact on reproductive success.
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... occurs almost exclusively in osprey [22]; thus, the abundance, infection prevalence and geographic distribution of osprey are important determinants of infections in fish. In North America, osprey numbers declined precipitously in the 1950s and 1960s due to the use of dichlorodiphenyl-trichloroethane (DDT) [73], which caused eggshell thinning, mortality and decreased reproductive success [74]. Osprey numbers have increased substantially since the banning of DDT in 1972, increased federal protection from the Migratory Bird Act and active construction and preservation of breeding habitats (e.g. ...
... nest platforms; [75]). Between 1981 and 2001, for example, the number of breeding osprey pairs in annual USA breeding bird surveys doubled from 8 000 to 16 000 [74], likely facilitating concurrent increases in Scaphanocephalus dispersal and population size. However, this would not explain why infections among archival fishes were rare in the first half of the twentieth century before DDT use was widespread, which is a period for which we know little about osprey population dynamics or their infection with Scaphanocephalus [74]. ...
... Between 1981 and 2001, for example, the number of breeding osprey pairs in annual USA breeding bird surveys doubled from 8 000 to 16 000 [74], likely facilitating concurrent increases in Scaphanocephalus dispersal and population size. However, this would not explain why infections among archival fishes were rare in the first half of the twentieth century before DDT use was widespread, which is a period for which we know little about osprey population dynamics or their infection with Scaphanocephalus [74]. ...
Despite evidence that certain diseases of marine wildlife are increasing, long-term infection data are often lacking. Archived samples of hosts from natural history collections offer a powerful tool for evaluating temporal changes in parasitism. Using vouchered fish collections from the Southern Caribbean, we investigated long-term (1905–2022) shifts in infections by the trematode Scaphanocephalus spp., which causes black spot syndrome (BSS) in reef fishes. Examination of 190 museum-preserved fishes from Curaçao and Bonaire revealed that Scaphanocephalus infections are not new, with histologically confirmed detections from as early as 1948. However, Scaphanocephalus was rare among archival surgeonfish and parrotfishes, with an infection prevalence of <10% and an average abundance of 0.25 metacercariae per fish. Contemporary collections of 258 ocean surgeonfish and parrotfishes (7 species) supported a 7-fold higher prevalence (71%) and a 49-fold higher abundance (12.1). These findings offer evidence that infections by Scaphanocephalus spp. have increased substantially over the past century and underscore the value of biological repositories in the study of emerging parasites within marine ecosystems. We emphasize the need for additional research to evaluate the geographical extent of BSS emergence, test proposed hypotheses related to shifts in host density or environmental characteristics and assess the consequences for affected species.
... Population recovery began following the banning of dichlorodiphenyltrichloroethane (DDT) in 1972 (Spitzer and Poole 1980;Henny 1987;White 1994;Monson 1996;Bierregaard et al. 2016). Increases in population size and geographic range continued in response to reduced human persecution, adoption of human structures as nesting sites, and creation of new aquatic habitat through reservoir construction (Henny et al. 2010). The species remains susceptible to declines in some areas from toxins, reduction in food availability, and drought (Bierregaard et al. 2016). ...
... Monitoring of osprey populations, including apparently healthy ones, has been recommended to serve as a baseline indicator of environmental contamination and health (Henny et al. 2010). The apparent health of the osprey population since the DDT era, however, has reduced research and management attention in many areas, including California. ...
The osprey (Pandion halieatus) declined globally in the mid-late 20th century due primarily to pesticide contamination that reduced reproduction. The species has recovered through much of its range, and its range in California has increased. The species has received limited attention in recent decades, despite recommendations that it be monitored as an environmental indicator. In 2021, we located a sample of 39 osprey occupied nests near the Sacramento River and at reservoirs and small ponds in central interior California and determined habitats used and reproductive success. Nearly one-third of nests were located within 100 m of waterbodies and 88% were within 1000 m. The median distance of nests from roads was 51 m. Thirty-four (87%) of occupied nests were on anthropogenic sites, including utility poles, poles erected for ospreys, transmission towers, light poles, and port structures. Only five nests (13%) were in trees and snags. Nearly half (48%) of nests were on platforms constructed on utility poles and on poles erected for ospreys, both placed to protect electrical systems. Water levels in reservoirs, and some small farm ponds, were lower than average in 2021 due to drought, while the Sacramento River and Port were less selected. Twenty-four (71%) of 34 adequately monitored nests were successful in fledging at least one young. Productivity averaged 1.27 young/occupied nest, suggesting a healthy population. Reproductive success differed significantly among nests at different water body types, with river-port, reservoir, and pond sites exhibiting high, moderate, and low productivity, respectively. Our results document a range expansion into central interior California, presumably in response to reduced pesticide levels, reservoir creation, and availability of anthropogenic nest sites. Results also suggest that drought, and thus predicted warming and drier climate, may disproportionately affect populations nesting at non-riverine habitats by reducing the amount foraging area and increasing the distance from nest sites to foraging areas.
... Our study provides evidence of an overall increase in non-essential metal and As contamination in black kites following the Aznalcóllar mine spill. This result mirrored the progressive increase previously reported for several of their prey taxa, and thus confirm the utility of toppredatory species as sentinels for biomonitoring metal pollution and evaluating ecosystems health (Henny et al., 2010;Rodríguez-Jorquera et al., 2017). ...
... Egg shell thinning (as also indicated by the related parameters desiccation index and shell index) is the classical harmful effect that is mainly linked to DDE exposure of ospreys and other raptors [45,46,76,93]. Studies of Wiemeyer et al. [76] indicated that shell thinning by 10% was associated with DDE concentration of 2000 ng/g ww, 15% with 4200 ng/g ww and 20% with 8700 ng/g ww. ...
Time trends and regional differences of polychlorinated dibenzo-p-dioxins and -furans (PCDD/Fs), polychlorinated biphenyls (PCBs), polychlorinated naphthalenes (PCNs), DDTs, polybrominated biphenyls (PBBs) and polybrominated diphenylethers (BDEs) were studied in unhatched osprey eggs collected by bird ringers in 1972–2017 from four areas in Finland. Two study areas were from Baltic Sea, Northern Quark and Finnish Archipelago Sea, while the two others were inland lake areas, eutrophicated Lake Vanajanselkä affected by industrial emissions, and Pristine SW Lake Area. The highest concentrations of most compound groups were in Lake Vanajanselkä consistent with high emissions, the predominance of bream as a prey, and higher concentrations in bream compared to other prey fish. Concentrations of all chlorinated compounds decreased significantly in all study areas. Average annual decreases were ∑PCDD/F 2.3–4.9%, ∑PCB 2.2–4.2%, ∑PCN 2.6–7.0% and ∑DDT 7.1–9.5%, primarily in line with decreased levels in prey fish. From 1972 PBBs and BDEs increased significantly until 1990s declining rapidly thereafter. PCDD/F congener profile was dominated by 2,3,4,7,8-PeCDF, except in Lake Vanajanselkä by 1,2,3,6,7,8-HxCDD. PCB congener profile was dominated by PCB 153 in all study areas, followed by PCB 180 and PCB 138. Among dioxin-like compounds PCBs contributed 82%, PCDDs 14% and PCDFs 4% to toxic equivalent quantity (∑TEQ). PCB 126 contributed most to ∑TEQ, followed by 1,2,3,7,8-PeCDD. BDE 47 being the dominant BDE congener, followed by BDE 100. ∑DDT concentrations were relatively similar across all study areas, with DDE contributing about 90%. Productivity of chicks per active nest was significantly decreased in Lake Vanajanselkä, and the likely explanation is embryotoxicity of dioxin-like compounds. It is plausible that dioxin-like compounds influenced embryonic survival among highly exposed ospreys prior to 2010, especially in Lake Vanajanselkä and Northern Quark. However, decreased survival due to DDE-induced eggshell thinning seems unlikely after 1985, and BDE levels were below those potentially causing adverse effects.
... The osprey is an obligate piscivore (Poole, 1989;Poole et al., 2002) that is considered to be a sensitive indicator of fish stocks (Grove et al., 2009;Henny et al., 2010). Chesapeake Bay supports one of the largest osprey breeding populations in the world (Henny, 1983). ...
Forage fish support the largest fisheries in the world and play a vital role in marine food webs by transferring energy from plankton to consumers within higher trophic levels. Growing commercial demand for these species and concern for the impact of over harvest on predator populations has driven a paradigm shift in management objectives from maximizing economic return to the establishment of ecosystem-based limits on harvest rates. How well current harvest policy supports noncommercial species like piscivorous birds remains poorly understood. We investigated the relationship between osprey breeding performance within the lower Chesapeake Bay and a menhaden stock index during a period (1974-2021) when the menhaden index fluctuated over 35-fold. Reproductive rate (young/pair/year), brood provisioning (fish/10-h) and the proportion of menhaden in the diet all declined during the study period. Indicators of food stress including brood reduction and nest failure increased during the study period. The population transitioned from reproductive surplus (demographic source) to reproductive deficit (demographic sink). A significant relationship between reproductive rate and the menhaden index suggests that osprey population viability requires that the menhaden stock be restored to 1980s levels. Current ecological reference points based on the food requirements of predatory fish are unlikely to protect the osprey population. We suggest the establishment of menhaden or reproductive thresholds designed to allow osprey to meet demographic targets (1.15 young/pair/year).
... Striped Bass populations have recovered from the historic lows observed in the 1980s (Richards and Rago 1999;Hartman and Margraf 2003). Similarly, avian predator populations, including osprey and double-crested cormorants, were devastated by DDT contamination in the mid-20th century and have experienced a significant rebound during recent decades (Hatch 1995;Henny et al. 2010). ...
Objective
Alewife Alosa pseudoharengus and Blueback Herring A. aestivalis , collectively referred to as river herring, are anadromous clupeids inhabiting the North American Atlantic coast. Although the seasonal patterns of their spawning migration are well studied and predictable, the fine‐scale movements are still poorly resolved.
Methods
This study used high‐resolution acoustic imaging to study the fine‐scale behavior of river herring during their spring spawning migration in two coastal rivers in Massachusetts, United States.
Result
Observations suggest that seasonal patterns of migration appear to be influenced by temperature, while fine‐scale patterns in migration were associated with the time of day, tidal state, and their interaction. River herring were consistently observed during both day and night, with elevated peaks of activity in the early morning and late afternoon. Daytime movement consisted of the intermittent passage of large, dense schools, while nighttime movement consisted of the frequent passage of individuals or small groups. The highest numbers of herring observations were associated with flood and high tides. Additionally, the interactions between time of day and tidal state resulted in synergistic positive effects during crepuscular incoming tides, which were favorable to movement, and synergistic negative effects during midday low tides, which inhibited fish movement.
Conclusion
The changing relationship between the time of day and tidal state within the season manifested in changing periodicity in fish movement to correlate with favorable movement conditions. Since movements may be related to both time of day and tide, previous run size estimates from visual counts made only during the day may be too low. Sampling methodologies that collect information during all 24 h would likely produce the most accurate run size estimates. This study highlights the need to view river herring migration in a holistic context predicated by multiple environmental and biological factors that vary at several temporal scales (i.e., seasonally, daily, and hourly).
... The declines, subsequent conservation actions and recovery for select raptor species affected by DDT have been well documented (Cade 1974, Simons et al. 1988, Bowerman et al. 1995, Cade et al. 1988, U.S. Fish and Wildlife Service 2003, Henny et al. 2010). However, not all raptor species severely affected by DDT have been well studied (Schick et al. 1987). ...
In North America, the population genetic structure of many raptor species has been shaped by patterns of post‐glacial population expansion and anthropogenic forces, such as the widespread use of the organochlorine pesticide DDT during the mid‐20th century. While common themes of post‐glacial avian population expansion have emerged, little is known about the genetic impacts of DDT on raptor species that experienced a population bottleneck but were not the focus of conservation efforts. We investigated how the combination of post‐Pleistocene environmental change and the DDT‐era population bottleneck have influenced the contemporary population structure of Merlins Falco columbarius in North America. We genotyped migrating Merlins across North America (n = 272), at 23 polymorphic microsatellite loci and generated sequence data for a 569‐base pair segment of the mitochondrial control region. We used hierarchical analysis of molecular variance, pairwise Fst/ϕst comparisons, and Bayesian clustering analyses to assess genetic differentiation between individuals from eastern and western North America, distinct migratory flyways, and three recognized North American subspecies. Across all analyses, we found low or no population differentiation, suggesting North American Merlins are largely comprised of one panmictic population showing evidence of a post‐glacial population expansion with little genetic differentiation detected between regions. Furthermore, we did not detect a contemporary signal of a genetic bottleneck that could have resulted from the DDT‐era population decline with the markers used in this study. Consistent with other avian species, we found a correlation between allele length variation at a microsatellite isolated from the 3’ UTR of the ADCYAP1 gene and migratory versus sedentary characteristics in Merlin subspecies. We detected two common mitochondrial control region haplotypes in the geographic regions sampled, a unique pattern among other wide‐spread North American raptor species. This study furthers our understanding of the genetic and demographic history of Merlins in North American and can inform future genomic studies on this species.
... The osprey (Pandion haliaetus) is a large bird of prey belonging to the family Pandionidae (Monti et al. 2015). It is distributed on every continent of the world, except Antarctica (Henny et al. 2010;Canal et al. 2018;Grenier et al. 2020;Monti 2020). Despite its widespread distribution, it breeds in a few geographical areas, such as Australia, Eastern Europe, and the United States (Kjellé et al. 2001;Holmes 2007;Brazil 2009). ...
The first breeding of osprey (Pandion haliaetus) on Jeju Island, South Korea, were observed in 2015, and ospreys bred on three sites. We found a total of three nests and observed that A site nest bred on successfully from 2017 to 2020. The number of eggs per clutch ranged from two to four, with a mean ± SD of 3.16 ± 0.75. The nesting period varied from 71 days to 79 days, with an average duration of 76.2 ± 3.18 days. The incubation period ranged from 34 days to 38 days, averaging 35.8 ± 1.72 days. Fledging dates ranged from July 4th to 13th. The nest tree species was Pinus thunbergii, and the average tree height was 16.2 ± 3.12 m. On average, the nest height from the ground was 14.8 ± 2.57 m. The average diameter at breast height of the nesting trees was 36.1 ± 2.02 cm. Of the total 19 eggs produced, the hatching rate was 91.4% ± 10.2%, fledgling rate was 68.6% ± 26.9%, and breeding success was 65.6% ± 25.1%. Little ecological information is available on osprey living in South Korea; therefore, this study makes a meaningful contribution to provide baseline ecological data from South Korea for this species.
The Morley Nelson Snake River Birds of Prey National Conservation Area (NCA), in southwestern Idaho, USA supports a large population of breeding Prairie Falcons (Falco mexicanus). Abundance of Prairie Falcons in the NCA was previously monitored in 1976–1978 and 1990–1994. That research indicated maximum counts for each period in 1976 and 1992 and a possible population decline across that time span. We assessed the abundance and nesting success of Prairie Falcons in the NCA in 2002–2003 and 2019–2021, and we compared results to data from before 2000 to assess possible population change. Number of nesting pairs increased over 45 years from peak counts of 206, 193, and 217 in the 1970s, 1990s, and early 2000s, respectively, to 257 in 2021. Increases were not concentrated in one region, but widely distributed across the study area. Rates of nesting success in 2002–2003 and 2019–2021 averaged 57 ± 11.8% (SD) at 49.8 ± 3.3 nests observed each year and did not differ from pre-2000 rates. Finally, our analysis showed that in all 10 years in which a full census was conducted, a sampling approach to surveys would have been effective at estimating the number of falcons nesting within the NCA. Prairie Falcons are of conservation concern because of possible population declines in parts of their range. These results illustrate an area with apparently increasing numbers of this important species and highlight the importance of long-term surveys for tracking population fluctuations and the value of a national conservation area for providing raptor breeding habitat.
This note documents changes in both substrate used for nest sites and distribution of nesting Ospreys in the San Francisco Bay area over the last 2 decades. Ospreys shifted from use of natural to artificial structures for nesting, as well as shifting nesting distribution from a fresh-water reservoir to the San Francisco Bay estuary. Changes in predator populations, prey, and availability of nest sites may be influencing these changes. The shift from use of natural to artificial structures for nest sites by Osprey mirrors a pattern observed in other western states.
Ospreys (Pandion haliaetus) once nested throughout most of the U.S. The decline in this population due to biocide use has been well documented, as has its recovery following the U.S. ban on DDT in 1972. A general increase in the nesting distribution and abundance of Ospreys was reported in the U.S. in 1981 but there was limited dispersal into states with low or extirpated populations. We conducted a nationwide nesting survey of nesting Ospreys in 1994, updating the 1981 data. Our data indicate a dramatic increase in die U.S. Osprey population from ∼8000 nesting pairs in 1981 to ∼14 200 in 1994. The most dramatic increases were seen in traditional nesting areas, with some new nesting in the interior U.S. Hacking projects, construction of reservoirs, nest platform management and increased public relations have contributed to the growth of this nesting population.
The major impacts of current biocide uses on birds are in the Third World countries, where restrictions are uneven and where effects are largely undocumented. Since the application of a biocide to the environment inevitably results in the death or organisms, there is also an inevitable disruption of the local food web. Birds are therefore potentially affected in a variety of ways. Mortality may follow the ingestion of a poison; accumulation of persistent chemicals in tissues may result in an impairment of reproduction; and a reduction or modification of the food supply is frequently an immediate effect of biocide application. The increasing use of herbicides in agriculture, silviculture and in land management in general is causing many modifications of the available habitat. -from Author
Ospreys are good indicators of the health of estuarine areas because they feed almost exclusively on fish with the balance on other aquatic biota. Through the 1980s, ospreys nesting on Delaware Bay in New Jersey had reduced reproductive success relative to those nesting on the Atlantic coast and the Maurice River, a tributary of Delaware Bay. Earlier research suggested that elevated levels of DDT and polychlorinated biphenyl (PCB) contaminants identified in addled osprey eggs contributed to this reduced productivity. We repeated egg and prey sampling initially conducted in 1989 to evaluate the trends of contaminants in the last decade. Most organochlorine contaminants declined in osprey eggs in 1998 relative to 1989. Across three study areas, PCBs decreased from 4.1–7.7 ppm in 1989 to 1.8–3.2 ppm in 1998; DDE decreased from 1.2–3.2 ppm in 1989 to 0.7–1.2 ppm in 1998. Lead in eggs increased from an average of 0.01 to 0.30 ppm wet weight, and mercury averaged 0.12 ppm and increased only in Atlantic coast eggs. Most of these contaminant changes were also found in typical prey fish: PCBs decreased from 0.18–1.2 ppm in 1989 to 0.06–0.43 ppm in 1998; DDE decreased from 0.05–0.69 ppm in 1989 to 0.03–0.13 ppm in 1998. Lead and mercury increased in most fish samples. The improvement in most organochlorine contaminants in osprey eggs and prey reflected improved nest success in the Delaware Bay study area, and the nesting populations in the Atlantic and Maurice River study areas increased approximately 200% since 1989. PCBs and DDE in osprey eggs were below levels considered to be toxic to egg development. This study documents significant improvements in organochlorine contaminants in southern New Jersey ospreys, but justifies continued monitoring of heavy metals, such as lead and mercury, in aquatic ecosystems.