To fully understand the impact of oil exposure, it is important to understand sublethal effects l... more To fully understand the impact of oil exposure, it is important to understand sublethal effects like how increased thermoregulatory costs may affect survival and reproduction. However, it is difficult and time-consuming to measure these effects in wild animals. We present a novel use of a bioenergetics model, Niche Mapper™, to estimate thermoregulatory impacts of oiling, using data from captive Double-crested Cormorants (Phalacrocorax auritus) experimentally exposed to oil. Oiled cormorants had significant increases in surface body temperatures following exposure. Niche Mapper accurately predicted surface temperatures and metabolic rates for unoiled and oiled cormorants and predicted 13–18% increased daily energetic demands due to increased thermo-regulatory costs of oiling, consistent with increased food consumption observed in experimentally oiled cormorants. We show that Niche Mapper can provide valuable insight into sublethal oiling effects by quantifying the extent to which thermoregulatory costs divert energy resources away from important life processes like maintenance, reproduction and migration.
A B S T R A C T A series of toxicity tests were conducted to assess the effects of low to moderat... more A B S T R A C T A series of toxicity tests were conducted to assess the effects of low to moderate exposure to artificially weathered Deepwater Horizon Mississippi Canyon 252 crude oil on representative avian species as part of the Natural Resource Damage Assessment. The present report summarizes effects of oral exposure (n=26) of double-crested cormorants (DCCO; Phalacrocorax auritus) to 5 or 10 ml oil kg −1 day −1 for up to 21 days or dermal application (n=25) of 13 ml oil to breast and back feathers every three days totaling 6 applications in 21 days on organ weights and histopathology. Absolute and relative kidney and liver weights were increased in birds exposed to oil. Additionally, gross and/or histopathologic lesions occurred in the kidney, heart, pancreas and thyroid. Clinically significant renal lesions in the orally dosed birds included squamous metaplasia and increased epithelial hypertrophy of the collecting ducts and renal tubules and mineralization in comparison to controls. Gross cardiac lesions including thin walls and flaccid musculature were documented in both orally and dermally dosed birds and myocardial fibrosis was found in low numbers of dermally dosed birds only. Cytoplasmic va-cuolation of the exocrine pancreas was noted in orally dosed birds only. Thyroid follicular hyperplasia was increased in dermally dosed birds only possibly due to increased metabolism required to compensate damaged feather integrity and thermoregulate. Gastrointestinal ulceration was found in orally dosed birds only. There were no significant hepatic histopathologic lesions induced by either exposure route. Therefore, hepatic histo-pathology is likely not a good representation of oil-induced damage. Taken together, the results suggest that oral or dermal exposure of DCCOs to artificially weathered MC252 crude oil induced organ damage that could potentially affect survivability.
Injury assessment of birds following the Deepwater Horizon (DWH) oil spill in 2010 was part of th... more Injury assessment of birds following the Deepwater Horizon (DWH) oil spill in 2010 was part of the Natural Resource Damage Assessment. One reported effect was hemolytic anemia with the presence of Heinz bodies (HB) in birds, however, the role of route and magnitude of exposure to oil is unknown. The purpose of the present study was to determine if double-crested cormorants (Phalacocorax auritis; DCCO) exposed orally and dermally to artificially weathered crude oil would develop hemolytic anemia including HB and reticulocytosis. In the oral experiment, sub-adult, mixed-sex DCCOs were fed control (n = 8) or oil–injected fish with a daily target dose of 5 (n = 9) or 10 (n = 9) ml oil/kg for 21 days. Then, subadult control (n = 12) and treated (n = 13) cormorant groups of similar sex-ratio were dermally treated with approximately 13 ml of water or weathered MC252 crude oil, respectively, every 3 days for 6 dosages approximating 20% surface coverage. Collected whole blood samples were analyzed by light (new methylene blue) and transmission electron microscopy. Both oral and dermal treatment with weathered DWH MC252 crude oil induced regenerative, but inadequately compensated, anemia due to hemolysis and hematochezia as indicated by decreased packed cell volume, relative increase in re-ticulocytes with lack of difference in corrected reticulocyte count, and morphologic evidence of oxidant damage at the ultrastructural level. Hemoglobin precipitation, HB formation, degenerate organelles, and systemic oxi-dant damage were documented. Heinz bodies were typically < 2 µm in length and smaller than in mammals. These oblong cytoplasmic inclusions were difficult to see upon routine blood smear evaluation and lacked the classic button appearance found in mammalian red blood cells. They could be found as light, homogeneous blue inclusions upon new methylene blue staining. Ultrastructurally, HB appeared as homogeneous, electron-dense structures within the cytosol and lacked membranous structure. Oxidant damage in avian red blood cells results in degenerate organelles and precipitated hemoglobin or HB with different morphology than that found in mammalian red blood cells. Ultrastructural evaluation is needed to definitively identify HB and damaged or-ganelles to confirm oxidant damage. The best field technique based on the data in this study is assessment of PCV with storage of blood in glutaraldehyde for possible TEM analysis.
During the Deepwater Horizon Natural Resource Damage Assessment, gross morphologic cardiac abnorm... more During the Deepwater Horizon Natural Resource Damage Assessment, gross morphologic cardiac abnormalities, including softer, more distensible musculature, were noted upon gross necropsy in hearts from laughing gulls and double-crested cormorants exposed to weathered MC252 crude oil. A species specific, echocardiographic technique was developed for antemortem evaluation of function that was used to evaluate and better characterize cardiac dysfunction. Control (n=12) and treated (n=13) cormorant groups of similar sex-ratio and ages were dermally treated with approximately 13 ml of water or weathered MC252 crude oil, respectively, every 3 days for 6 dosages. This resulted in a low to moderate external exposure. Upon visualization and clinical assessment of the hearts of all test subjects, comprehensive diagnostic cardiographic measurements were taken twice, prior to oil application and after a 21 day dermal oil exposure. Oil-treated birds showed a decrease in cardiac systolic function, as characterized by an increased left ventricular internal dimension-systole and left ventricular stroke volume as well as concurrent decreased left ventricular ejection fraction and left ventricular fractional shortening when compared to both control birds' and the treated birds' time zero values. These changes are indicative of a possible dilative cardiomyopathy induced by oil exposure, although further eluci-dation of possible collagen damage is recommended. Arrhythmias including tachycardia in two treated birds and bradycardia in all treated birds were documented, indicating further clinically significant abnormalities induced by MC252 oil that warrant further investigation. A statistically significant increase in free calcium concentration, important to muscular and neurologic function in treated birds was also noted. This study documents that weathered MC252 oil caused clinically significant cardiac dysfunction that could result in mortality and decrease recruitment.
Scoping studies were designed whereby double-crested cormorants (Phalacocorax auritus) were dosed... more Scoping studies were designed whereby double-crested cormorants (Phalacocorax auritus) were dosed with artificially weathered Deepwater Horizon (DWH) oil either daily through oil injected feeder fish, or by application of oil directly to feathers every three days. Preening results in oil ingestion, and may be an effective means of orally dosing birds with toxicant to improve our understanding of the full range of physiological effects of oral oil ingestion on birds. Blood samples collected every 5–6 days were analyzed for a number of clinical endpoints including white blood cell (WBC) estimates and differential cell counts. Plasma biochemical evaluations were performed for changes associated with oil toxicity. Oral dosing and application of oil to feathers resulted in clinical signs and statistically significant changes in a number of biochemical endpoints consistent with petroleum exposure. In orally dosed birds there were statistically significant decreases in aspartate amino transferase (AST) and gamma glutamyl transferase (GGT) activities, calcium, chloride, cholesterol, glucose, and total protein concentrations, and increases in plasma urea, uric acid, and phosphorus concentrations. Plasma electrophoresis endpoints (pre-albumin, albumin, alpha-2 globulin, beta globulin, and gamma globulin concentrations and al-bumin: globulin ratios) were decreased in orally dosed birds. Birds with external oil had increases in urea, creatinine, uric acid, creatine kinase (CK), glutamate dehydrogenase (GLDH), phosphorus, calcium, chloride, potassium, albumin, alpha-1 globulin and alpha-2 globulin. Decreases were observed in AST, beta globulin and glucose. WBC also differed between treatments; however, this was in part driven by monocytosis present in the externally oiled birds prior to oil treatment.
A B S T R A C T The Oil Pollution Act of 1990 establishes liability for injuries to natural resou... more A B S T R A C T The Oil Pollution Act of 1990 establishes liability for injuries to natural resources because of the release or threat of release of oil. Assessment of injury to natural resources resulting from an oil spill and development and implementation of a plan for the restoration, rehabilitation, replacement or acquisition of natural resources to compensate for those injuries is accomplished through the Natural Resource Damage Assessment (NRDA) process. The NRDA process began within a week of the Deepwater Horizon oil spill, which occurred on April 20, 2010. During the spill, more than 8500 dead and impaired birds representing at least 93 avian species were collected. In addition, there were more than 3500 birds observed to be visibly oiled. While information in the literature at the time helped to identify some of the effects of oil on birds, it was not sufficient to fully characterize the nature and extent of the injuries to the thousands of live oiled birds, or to quantify those injuries in terms of effects on bird viability. As a result, the US Fish and Wildlife Service proposed various assessment activities to inform NRDA injury determination and quantification analyses associated with the Deepwater Horizon oil spill, including avian toxicity studies. The goal of these studies was to evaluate the effects of oral exposure to 1–20 ml of artificially weathered Mississippi Canyon 252 oil kg bw-1 day-1 from one to 28 days or one to five applications of oil to 20% of the bird's surface area. It was thought that these exposure levels would not result in immediate or short-term mortality but might result in physiological effects that ultimately could affect avian survival, reproduction and health. These studies included oral dosing studies, an external dosing study, metabolic and flight performance studies and field-based flight studies. Results of these studies indicated changes in hematologic endpoints including formation of Heinz bodies and changes in cell counts. There were also effects on multiple organ systems, cardiac function and oxidative status. External oiling affected flight patterns and time spent during flight tasks indicating that migration may be affected by short-term repeated exposure to oil. Feather damage also resulted in increased heat loss and energetic demands. The papers in this special issue indicate that the combined effects of oil toxicity and feather effects in avian species, even in the case of relatively light oiling, can significantly affect the overall health of birds.
Oral and external dosing methods replicating field exposure were developed using the double crest... more Oral and external dosing methods replicating field exposure were developed using the double crested cormorant (DCCO) to test the toxicity of artificially weathered Deepwater Horizon Mississippi Canyon 252 oil. The majority of previous oil dosing studies conducted on wild-caught birds used gavage methods to dose birds with oil and determine toxicity. However, rapid gut transit time of gavaged oil likely reduces oil absorption. In the present studies, dosing relied on injection of oil into live feeder fish for oral dosing of these piscivorous birds, or applying oil to body contour feathers resulting in transdermal oil exposure and oral exposure through preening. Both oral and external oil dosing studies identified oil-related toxicity endpoints associated with oxidative stress such as hemolytic anemia, liver and kidney damage, and immuno-modulation or compromise. External oil application allowed for controlled study of thermoregulatory stress as well. Infrared thermal images indicated significantly greater surface temperatures and heat loss in treated birds following external oil applications; however, measurements collected by coelomically implanted temperature transmitters showed that internal body temperatures were stable over the course of the study period. Birds exposed to oil externally consumed more fish than control birds, indicating metabolic compensation for thermal stress. Conversely, birds orally dosed with oil experienced hypothermia and consumed less fish compared to control birds.
For centuries, people have viewed double-crested cormorants Phalacrocorax auritus negatively, and... more For centuries, people have viewed double-crested cormorants Phalacrocorax auritus negatively, and human persecution coupled with environmental contamination severely reduced numbers of cormorants throughout North America. Shifts in paradigms for management of our natural resources resulted in reductions in environmental contaminants and regulatory protection of cormorants, allowing for an amazing population resurgence of this adaptable fish-eating bird. However, for cormorants, as with some other native wildlife species the populations of which have rebounded due to conservation efforts, there have been cormorant–societal conflicts with respect to commercial and natural resources such as aquaculture and sport fisheries. Increasing resource conflicts caused cormorants to be a priority with agencies responsible for their management, resulting in development of policy to facilitate addressing stakeholder concerns. Subsequent research and management in regard to cormorant issues have been subject to considerable challenges and debate. In this feature, we discuss the primary resource damage issues associated with cormorants, management efforts and outcomes, what we have learned, and the future with regard to cormorant management.
Here the intestinal helminth infracommunities of 218 double-crested cormorants (Phalacrocorax aur... more Here the intestinal helminth infracommunities of 218 double-crested cormorants (Phalacrocorax auritus) from 11 locations in Alabama, Minnesota, Mississippi and Vermont are documented. Trematode infections were present in 98% of hosts; 65% of cormorants carried cestode infections, 4% were infected with acanthocephalans and 66% had nematode intestinal parasites. Parasite infracommunities of hosts collected on wintering grounds had higher richness and diversity than did birds collected on breeding grounds. Differences in parasite richness and diversity between male and female P. auritus were also detected , but not between immature and mature bird hosts. Parasite intensity did not differ by sex, maturity, or between breeding and wintering season. The most common parasite was Drepanocephalus auritus (spathans), which is recognized as a disease agent that negatively impacts the catfish aquaculture industry in the US. Echinochasmus sp. in double-crested cormorants is documented for the first time in the United States. We suggest that the differences observed among parasite infracommunities could be associated with the foraging distances travelled by P. auritus during breeding and wintering seasons, which is limited by allocation of parental care during the breeding season.
Abstract.—Paired throat and cloacal swabs, along with feather samples, from nesting Double-crest... more Abstract.—Paired throat and cloacal swabs, along with feather samples, from nesting Double-crested Cormorants (Phalacrocorax auritus) at two sites in Illinois, USA, were tested for presence of invasive bigheaded carp (Hypophthalmi- chthys spp.) DNA. We also used DNA from the feather calamus to determine cormorant sex. Throat and cloacal swabs from cormorants at both locations tested positive for DNA from silver carp (H. molitrix), but none tested positive for bighead carp (H. nobilis). Hypophthalmichthys DNA was not detected on feathers. There were no significant differences among positive Hypophthalmichthys DNA detection frequencies between cormorant sexes. To our knowledge, this is the first demonstration of silver carp as part of the Double-crested Cormorant diet in North America. Hypophthalmichthys are major invasive species of concern in this region, the detection of water-borne environmental DNA of Hypophthalmichthys is an important monitoring tool, and the potential movement of DNA via piscivorous birds may have significant implications for interpreting environmental DNA monitoring data.
ABSTRACT Establishing the impact of double-crested cormorants on commercial farmed channel catfis... more ABSTRACT Establishing the impact of double-crested cormorants on commercial farmed channel catfish production using visual assessments of cormorant GI tract contents is complicated by, first, the difficulty in distinguishing between partially digested fish of different species, and secondly, the possibility that the fish appearing in the diet have a natural source of origin. We analyzed the fatty acid profiles of selected game fish and farm-raised channel catfish to establish profiles that may allow for the application of this technique in establishing cormorant foraging patterns. We obtained for analysis farm-raised channel catfish from three commercial producers and one research facility. For comparison, we also collected channel catfish, gizzard shad, green sunfish, bluegill, and largemouth bass from natural waterways. A total of 12 sample groups were analyzed. Lipids were extracted using a modified Folch extraction and trans-esterified in 3N HCl in methanol. The resultant fatty acids were identified using gas chromatography/mass spectrometry. The relative mass percent distributions for the major fatty acids were calculated for each individual. A classification tree analysis was performed to identify groupings based on these individual fish distributions. These preliminary results have led us to conclude that it is possible to distinguish not only between farm-raised channel catfish and game fish in the diet of cormorants, but that it may be possible to identify the source of the farm-raised channel catfish in the diet. The management implications are that it may be possible, based on fatty acid analysis of GI tract contents of cormorants, to assess the actual impact of birds from a given roost or colony on a specific channel catfish producer.
—Double-crested Cormorants (Phalacrocorax auritus) are intensely managed through culling in North... more —Double-crested Cormorants (Phalacrocorax auritus) are intensely managed through culling in North America to reduce presumed damage to commercial and natural resources. To evaluate this management, there is a critical need to understand the reproductive biology of Double-crested Cormorants. Gonadal development, reproductive potential and breeding status were determined by necropsy for 1,781 Double-crested Cormorants salvaged each month of the year from control programs in their wintering and breeding ranges in seven States in the USA. Gonadal development of males peaked earlier in the year than females. Mean and maximum reproductive potential was five and 13 ovum, respectively. The average proportion of non-breeding female Double-crested Cormorants culled from breeding colonies was 14.9% (n = 202) and from foraging flocks on the breeding grounds was 22.1% (n = 358). This demographic information should be considered when evaluating and modeling effects of Double-crested Cormorant management in North America.
Double-crested Cormorant (Phalacrocorax auritus) numbers have increased in North America, and con... more Double-crested Cormorant (Phalacrocorax auritus) numbers have increased in North America, and con-comitantly cormorants appear to be expanding their nesting range in the southeastern United States. Because colonial nesting waterbirds can impact water quality, soil chemistry and subsequent vegetation succession patterns, our goal was to assess the extent to which cormorant breeding colonies are influencing the biotic and abiotic attributes of forested islands in the southeastern United States. Our objectives were to (1) compare water quality characteristics in near-shore surface waters around forested islands with and without nesting cormorants during the peak-nesting/fledgling period and post-fledgling period, (2) measure soil chemistry parameters for forested islands with and without nesting cormorants, and (3) compare tree health metrics on forested islands with and without nesting cormorants. Our results indicate that cormorant colonies are not significant contributors to general coliforms or Escherichia coli levels in waters surrounding southern breeding colonies. Cormorants also do not appear to have significant direct effects on water chemistry. We did find that cormorant colonies are affecting soil chemistry. Soil from within the nesting colony was more acidic and had greater concentrations of phosphorous than soils on reference islands. In addition, we found evidence that cormorants are negatively affecting tree health within nesting colonies as evidenced by a greater number of trees of lower vigor class within the nesting colonies compared to reference sites. While cormorants do cause abiotic and biotic changes, these are part of the natural ecological processes that occur following waterbird colonization. Management to reduce unwanted impacts that nesting cormorants are having on forested island habitats should be considered within a framework that allows for natural ecological processes, including changes in soil chemistry and subsequent vegetation succession. Published by Elsevier B.V.
The increase of double-crested cormorant (Phalacrocorax auritus; hereafter, cormorant) population... more The increase of double-crested cormorant (Phalacrocorax auritus; hereafter, cormorant) populations during the last 2 decades has impacted many stakeholder groups. The negative effects of nesting cormorants on trees and other vegetation have motivated private organizations and government agencies to manage nesting colonies and reduce their impacts to private property and public resources. Management-induced reproductive failure has been shown to influence cormorant inter-annual nesting colony fidelity, but not complete abandonment from a nesting colony site. We attached very high frequency (VHF) transmitters and Global Positioning System (GPS) transmitters to nesting cormorants to monitor their movement response on a managed site (Young Island, VT [YI]) and an unmanaged site (Four Brothers Islands, NY [FB]). Additionally, we monitored these sites to determine the influence of management activities on subsequent-year colonization. On YI, management consisted of egg-oiling all cormorant nests (some nests had been oiled in previous years) and culling approximately 20% of adults. Annual dispersal rates did not differ between managed and unmanaged sites, but a nesting period interaction occurred with greater dispersal on the managed site following the incubation period. After 4 years of both egg oiling and culling, cormorant nesting on YI declined to zero. Simultaneously, cormorant numbers increased on the nearby unmanaged FB. We propose either the cumulative effect of partial or complete reproductive failure (8 yr) or simply the inclusion of adult culling (4 yr) caused the abandonment. From a colony-specific management perspective, the rapid decline was beneficial to the goal of restoring the vegetative community on YI. The effects of adult culling at nesting colonies, prior-year reproductive failure caused by egg oiling, or the combination of these factors may be required for complete and rapid nesting site abandonment. The use of culling adult breeders reduced nesting and likely limits the cost and logistics of control and allows more rapid initiation of mitigation measures and island habitat restoration. ß 2011 The Wildlife Society.
Knowledge of double-crested cormorant (Phalacrocorax auritus, hereafter cormorant) response to po... more Knowledge of double-crested cormorant (Phalacrocorax auritus, hereafter cormorant) response to population control activities is important for implementation of a science-based management regime. To better understand adult cormorant response to egg-oiling, we initiated a two-year satellite telemetry study in May 2000 to evaluate cormorant movements (n = 26/year), reproductive success, and nest-site fidelity at Little Galloo Island (LGI) in eastern New York. Egg-oiling effectively reduced reproductive success on LGI to < 6% in 2000 and 2001. Mean distance of core use areas (50% kernal home ranges) from LGI differed (P = 0.004) between control and egg-oiling treatments (n = 31). The distance of core use areas from LGI for the final 2-week treatment period was significantly (P < 0.05) greater than all other periods . Core use areas of 12 (39%) of 31 cormorants did not contain LGI during >1 treatment periods (2 May -9 July). However, 97% of these bird's core use areas contai...
To fully understand the impact of oil exposure, it is important to understand sublethal effects l... more To fully understand the impact of oil exposure, it is important to understand sublethal effects like how increased thermoregulatory costs may affect survival and reproduction. However, it is difficult and time-consuming to measure these effects in wild animals. We present a novel use of a bioenergetics model, Niche Mapper™, to estimate thermoregulatory impacts of oiling, using data from captive Double-crested Cormorants (Phalacrocorax auritus) experimentally exposed to oil. Oiled cormorants had significant increases in surface body temperatures following exposure. Niche Mapper accurately predicted surface temperatures and metabolic rates for unoiled and oiled cormorants and predicted 13–18% increased daily energetic demands due to increased thermo-regulatory costs of oiling, consistent with increased food consumption observed in experimentally oiled cormorants. We show that Niche Mapper can provide valuable insight into sublethal oiling effects by quantifying the extent to which thermoregulatory costs divert energy resources away from important life processes like maintenance, reproduction and migration.
A B S T R A C T A series of toxicity tests were conducted to assess the effects of low to moderat... more A B S T R A C T A series of toxicity tests were conducted to assess the effects of low to moderate exposure to artificially weathered Deepwater Horizon Mississippi Canyon 252 crude oil on representative avian species as part of the Natural Resource Damage Assessment. The present report summarizes effects of oral exposure (n=26) of double-crested cormorants (DCCO; Phalacrocorax auritus) to 5 or 10 ml oil kg −1 day −1 for up to 21 days or dermal application (n=25) of 13 ml oil to breast and back feathers every three days totaling 6 applications in 21 days on organ weights and histopathology. Absolute and relative kidney and liver weights were increased in birds exposed to oil. Additionally, gross and/or histopathologic lesions occurred in the kidney, heart, pancreas and thyroid. Clinically significant renal lesions in the orally dosed birds included squamous metaplasia and increased epithelial hypertrophy of the collecting ducts and renal tubules and mineralization in comparison to controls. Gross cardiac lesions including thin walls and flaccid musculature were documented in both orally and dermally dosed birds and myocardial fibrosis was found in low numbers of dermally dosed birds only. Cytoplasmic va-cuolation of the exocrine pancreas was noted in orally dosed birds only. Thyroid follicular hyperplasia was increased in dermally dosed birds only possibly due to increased metabolism required to compensate damaged feather integrity and thermoregulate. Gastrointestinal ulceration was found in orally dosed birds only. There were no significant hepatic histopathologic lesions induced by either exposure route. Therefore, hepatic histo-pathology is likely not a good representation of oil-induced damage. Taken together, the results suggest that oral or dermal exposure of DCCOs to artificially weathered MC252 crude oil induced organ damage that could potentially affect survivability.
Injury assessment of birds following the Deepwater Horizon (DWH) oil spill in 2010 was part of th... more Injury assessment of birds following the Deepwater Horizon (DWH) oil spill in 2010 was part of the Natural Resource Damage Assessment. One reported effect was hemolytic anemia with the presence of Heinz bodies (HB) in birds, however, the role of route and magnitude of exposure to oil is unknown. The purpose of the present study was to determine if double-crested cormorants (Phalacocorax auritis; DCCO) exposed orally and dermally to artificially weathered crude oil would develop hemolytic anemia including HB and reticulocytosis. In the oral experiment, sub-adult, mixed-sex DCCOs were fed control (n = 8) or oil–injected fish with a daily target dose of 5 (n = 9) or 10 (n = 9) ml oil/kg for 21 days. Then, subadult control (n = 12) and treated (n = 13) cormorant groups of similar sex-ratio were dermally treated with approximately 13 ml of water or weathered MC252 crude oil, respectively, every 3 days for 6 dosages approximating 20% surface coverage. Collected whole blood samples were analyzed by light (new methylene blue) and transmission electron microscopy. Both oral and dermal treatment with weathered DWH MC252 crude oil induced regenerative, but inadequately compensated, anemia due to hemolysis and hematochezia as indicated by decreased packed cell volume, relative increase in re-ticulocytes with lack of difference in corrected reticulocyte count, and morphologic evidence of oxidant damage at the ultrastructural level. Hemoglobin precipitation, HB formation, degenerate organelles, and systemic oxi-dant damage were documented. Heinz bodies were typically < 2 µm in length and smaller than in mammals. These oblong cytoplasmic inclusions were difficult to see upon routine blood smear evaluation and lacked the classic button appearance found in mammalian red blood cells. They could be found as light, homogeneous blue inclusions upon new methylene blue staining. Ultrastructurally, HB appeared as homogeneous, electron-dense structures within the cytosol and lacked membranous structure. Oxidant damage in avian red blood cells results in degenerate organelles and precipitated hemoglobin or HB with different morphology than that found in mammalian red blood cells. Ultrastructural evaluation is needed to definitively identify HB and damaged or-ganelles to confirm oxidant damage. The best field technique based on the data in this study is assessment of PCV with storage of blood in glutaraldehyde for possible TEM analysis.
During the Deepwater Horizon Natural Resource Damage Assessment, gross morphologic cardiac abnorm... more During the Deepwater Horizon Natural Resource Damage Assessment, gross morphologic cardiac abnormalities, including softer, more distensible musculature, were noted upon gross necropsy in hearts from laughing gulls and double-crested cormorants exposed to weathered MC252 crude oil. A species specific, echocardiographic technique was developed for antemortem evaluation of function that was used to evaluate and better characterize cardiac dysfunction. Control (n=12) and treated (n=13) cormorant groups of similar sex-ratio and ages were dermally treated with approximately 13 ml of water or weathered MC252 crude oil, respectively, every 3 days for 6 dosages. This resulted in a low to moderate external exposure. Upon visualization and clinical assessment of the hearts of all test subjects, comprehensive diagnostic cardiographic measurements were taken twice, prior to oil application and after a 21 day dermal oil exposure. Oil-treated birds showed a decrease in cardiac systolic function, as characterized by an increased left ventricular internal dimension-systole and left ventricular stroke volume as well as concurrent decreased left ventricular ejection fraction and left ventricular fractional shortening when compared to both control birds' and the treated birds' time zero values. These changes are indicative of a possible dilative cardiomyopathy induced by oil exposure, although further eluci-dation of possible collagen damage is recommended. Arrhythmias including tachycardia in two treated birds and bradycardia in all treated birds were documented, indicating further clinically significant abnormalities induced by MC252 oil that warrant further investigation. A statistically significant increase in free calcium concentration, important to muscular and neurologic function in treated birds was also noted. This study documents that weathered MC252 oil caused clinically significant cardiac dysfunction that could result in mortality and decrease recruitment.
Scoping studies were designed whereby double-crested cormorants (Phalacocorax auritus) were dosed... more Scoping studies were designed whereby double-crested cormorants (Phalacocorax auritus) were dosed with artificially weathered Deepwater Horizon (DWH) oil either daily through oil injected feeder fish, or by application of oil directly to feathers every three days. Preening results in oil ingestion, and may be an effective means of orally dosing birds with toxicant to improve our understanding of the full range of physiological effects of oral oil ingestion on birds. Blood samples collected every 5–6 days were analyzed for a number of clinical endpoints including white blood cell (WBC) estimates and differential cell counts. Plasma biochemical evaluations were performed for changes associated with oil toxicity. Oral dosing and application of oil to feathers resulted in clinical signs and statistically significant changes in a number of biochemical endpoints consistent with petroleum exposure. In orally dosed birds there were statistically significant decreases in aspartate amino transferase (AST) and gamma glutamyl transferase (GGT) activities, calcium, chloride, cholesterol, glucose, and total protein concentrations, and increases in plasma urea, uric acid, and phosphorus concentrations. Plasma electrophoresis endpoints (pre-albumin, albumin, alpha-2 globulin, beta globulin, and gamma globulin concentrations and al-bumin: globulin ratios) were decreased in orally dosed birds. Birds with external oil had increases in urea, creatinine, uric acid, creatine kinase (CK), glutamate dehydrogenase (GLDH), phosphorus, calcium, chloride, potassium, albumin, alpha-1 globulin and alpha-2 globulin. Decreases were observed in AST, beta globulin and glucose. WBC also differed between treatments; however, this was in part driven by monocytosis present in the externally oiled birds prior to oil treatment.
A B S T R A C T The Oil Pollution Act of 1990 establishes liability for injuries to natural resou... more A B S T R A C T The Oil Pollution Act of 1990 establishes liability for injuries to natural resources because of the release or threat of release of oil. Assessment of injury to natural resources resulting from an oil spill and development and implementation of a plan for the restoration, rehabilitation, replacement or acquisition of natural resources to compensate for those injuries is accomplished through the Natural Resource Damage Assessment (NRDA) process. The NRDA process began within a week of the Deepwater Horizon oil spill, which occurred on April 20, 2010. During the spill, more than 8500 dead and impaired birds representing at least 93 avian species were collected. In addition, there were more than 3500 birds observed to be visibly oiled. While information in the literature at the time helped to identify some of the effects of oil on birds, it was not sufficient to fully characterize the nature and extent of the injuries to the thousands of live oiled birds, or to quantify those injuries in terms of effects on bird viability. As a result, the US Fish and Wildlife Service proposed various assessment activities to inform NRDA injury determination and quantification analyses associated with the Deepwater Horizon oil spill, including avian toxicity studies. The goal of these studies was to evaluate the effects of oral exposure to 1–20 ml of artificially weathered Mississippi Canyon 252 oil kg bw-1 day-1 from one to 28 days or one to five applications of oil to 20% of the bird's surface area. It was thought that these exposure levels would not result in immediate or short-term mortality but might result in physiological effects that ultimately could affect avian survival, reproduction and health. These studies included oral dosing studies, an external dosing study, metabolic and flight performance studies and field-based flight studies. Results of these studies indicated changes in hematologic endpoints including formation of Heinz bodies and changes in cell counts. There were also effects on multiple organ systems, cardiac function and oxidative status. External oiling affected flight patterns and time spent during flight tasks indicating that migration may be affected by short-term repeated exposure to oil. Feather damage also resulted in increased heat loss and energetic demands. The papers in this special issue indicate that the combined effects of oil toxicity and feather effects in avian species, even in the case of relatively light oiling, can significantly affect the overall health of birds.
Oral and external dosing methods replicating field exposure were developed using the double crest... more Oral and external dosing methods replicating field exposure were developed using the double crested cormorant (DCCO) to test the toxicity of artificially weathered Deepwater Horizon Mississippi Canyon 252 oil. The majority of previous oil dosing studies conducted on wild-caught birds used gavage methods to dose birds with oil and determine toxicity. However, rapid gut transit time of gavaged oil likely reduces oil absorption. In the present studies, dosing relied on injection of oil into live feeder fish for oral dosing of these piscivorous birds, or applying oil to body contour feathers resulting in transdermal oil exposure and oral exposure through preening. Both oral and external oil dosing studies identified oil-related toxicity endpoints associated with oxidative stress such as hemolytic anemia, liver and kidney damage, and immuno-modulation or compromise. External oil application allowed for controlled study of thermoregulatory stress as well. Infrared thermal images indicated significantly greater surface temperatures and heat loss in treated birds following external oil applications; however, measurements collected by coelomically implanted temperature transmitters showed that internal body temperatures were stable over the course of the study period. Birds exposed to oil externally consumed more fish than control birds, indicating metabolic compensation for thermal stress. Conversely, birds orally dosed with oil experienced hypothermia and consumed less fish compared to control birds.
For centuries, people have viewed double-crested cormorants Phalacrocorax auritus negatively, and... more For centuries, people have viewed double-crested cormorants Phalacrocorax auritus negatively, and human persecution coupled with environmental contamination severely reduced numbers of cormorants throughout North America. Shifts in paradigms for management of our natural resources resulted in reductions in environmental contaminants and regulatory protection of cormorants, allowing for an amazing population resurgence of this adaptable fish-eating bird. However, for cormorants, as with some other native wildlife species the populations of which have rebounded due to conservation efforts, there have been cormorant–societal conflicts with respect to commercial and natural resources such as aquaculture and sport fisheries. Increasing resource conflicts caused cormorants to be a priority with agencies responsible for their management, resulting in development of policy to facilitate addressing stakeholder concerns. Subsequent research and management in regard to cormorant issues have been subject to considerable challenges and debate. In this feature, we discuss the primary resource damage issues associated with cormorants, management efforts and outcomes, what we have learned, and the future with regard to cormorant management.
Here the intestinal helminth infracommunities of 218 double-crested cormorants (Phalacrocorax aur... more Here the intestinal helminth infracommunities of 218 double-crested cormorants (Phalacrocorax auritus) from 11 locations in Alabama, Minnesota, Mississippi and Vermont are documented. Trematode infections were present in 98% of hosts; 65% of cormorants carried cestode infections, 4% were infected with acanthocephalans and 66% had nematode intestinal parasites. Parasite infracommunities of hosts collected on wintering grounds had higher richness and diversity than did birds collected on breeding grounds. Differences in parasite richness and diversity between male and female P. auritus were also detected , but not between immature and mature bird hosts. Parasite intensity did not differ by sex, maturity, or between breeding and wintering season. The most common parasite was Drepanocephalus auritus (spathans), which is recognized as a disease agent that negatively impacts the catfish aquaculture industry in the US. Echinochasmus sp. in double-crested cormorants is documented for the first time in the United States. We suggest that the differences observed among parasite infracommunities could be associated with the foraging distances travelled by P. auritus during breeding and wintering seasons, which is limited by allocation of parental care during the breeding season.
Abstract.—Paired throat and cloacal swabs, along with feather samples, from nesting Double-crest... more Abstract.—Paired throat and cloacal swabs, along with feather samples, from nesting Double-crested Cormorants (Phalacrocorax auritus) at two sites in Illinois, USA, were tested for presence of invasive bigheaded carp (Hypophthalmi- chthys spp.) DNA. We also used DNA from the feather calamus to determine cormorant sex. Throat and cloacal swabs from cormorants at both locations tested positive for DNA from silver carp (H. molitrix), but none tested positive for bighead carp (H. nobilis). Hypophthalmichthys DNA was not detected on feathers. There were no significant differences among positive Hypophthalmichthys DNA detection frequencies between cormorant sexes. To our knowledge, this is the first demonstration of silver carp as part of the Double-crested Cormorant diet in North America. Hypophthalmichthys are major invasive species of concern in this region, the detection of water-borne environmental DNA of Hypophthalmichthys is an important monitoring tool, and the potential movement of DNA via piscivorous birds may have significant implications for interpreting environmental DNA monitoring data.
ABSTRACT Establishing the impact of double-crested cormorants on commercial farmed channel catfis... more ABSTRACT Establishing the impact of double-crested cormorants on commercial farmed channel catfish production using visual assessments of cormorant GI tract contents is complicated by, first, the difficulty in distinguishing between partially digested fish of different species, and secondly, the possibility that the fish appearing in the diet have a natural source of origin. We analyzed the fatty acid profiles of selected game fish and farm-raised channel catfish to establish profiles that may allow for the application of this technique in establishing cormorant foraging patterns. We obtained for analysis farm-raised channel catfish from three commercial producers and one research facility. For comparison, we also collected channel catfish, gizzard shad, green sunfish, bluegill, and largemouth bass from natural waterways. A total of 12 sample groups were analyzed. Lipids were extracted using a modified Folch extraction and trans-esterified in 3N HCl in methanol. The resultant fatty acids were identified using gas chromatography/mass spectrometry. The relative mass percent distributions for the major fatty acids were calculated for each individual. A classification tree analysis was performed to identify groupings based on these individual fish distributions. These preliminary results have led us to conclude that it is possible to distinguish not only between farm-raised channel catfish and game fish in the diet of cormorants, but that it may be possible to identify the source of the farm-raised channel catfish in the diet. The management implications are that it may be possible, based on fatty acid analysis of GI tract contents of cormorants, to assess the actual impact of birds from a given roost or colony on a specific channel catfish producer.
—Double-crested Cormorants (Phalacrocorax auritus) are intensely managed through culling in North... more —Double-crested Cormorants (Phalacrocorax auritus) are intensely managed through culling in North America to reduce presumed damage to commercial and natural resources. To evaluate this management, there is a critical need to understand the reproductive biology of Double-crested Cormorants. Gonadal development, reproductive potential and breeding status were determined by necropsy for 1,781 Double-crested Cormorants salvaged each month of the year from control programs in their wintering and breeding ranges in seven States in the USA. Gonadal development of males peaked earlier in the year than females. Mean and maximum reproductive potential was five and 13 ovum, respectively. The average proportion of non-breeding female Double-crested Cormorants culled from breeding colonies was 14.9% (n = 202) and from foraging flocks on the breeding grounds was 22.1% (n = 358). This demographic information should be considered when evaluating and modeling effects of Double-crested Cormorant management in North America.
Double-crested Cormorant (Phalacrocorax auritus) numbers have increased in North America, and con... more Double-crested Cormorant (Phalacrocorax auritus) numbers have increased in North America, and con-comitantly cormorants appear to be expanding their nesting range in the southeastern United States. Because colonial nesting waterbirds can impact water quality, soil chemistry and subsequent vegetation succession patterns, our goal was to assess the extent to which cormorant breeding colonies are influencing the biotic and abiotic attributes of forested islands in the southeastern United States. Our objectives were to (1) compare water quality characteristics in near-shore surface waters around forested islands with and without nesting cormorants during the peak-nesting/fledgling period and post-fledgling period, (2) measure soil chemistry parameters for forested islands with and without nesting cormorants, and (3) compare tree health metrics on forested islands with and without nesting cormorants. Our results indicate that cormorant colonies are not significant contributors to general coliforms or Escherichia coli levels in waters surrounding southern breeding colonies. Cormorants also do not appear to have significant direct effects on water chemistry. We did find that cormorant colonies are affecting soil chemistry. Soil from within the nesting colony was more acidic and had greater concentrations of phosphorous than soils on reference islands. In addition, we found evidence that cormorants are negatively affecting tree health within nesting colonies as evidenced by a greater number of trees of lower vigor class within the nesting colonies compared to reference sites. While cormorants do cause abiotic and biotic changes, these are part of the natural ecological processes that occur following waterbird colonization. Management to reduce unwanted impacts that nesting cormorants are having on forested island habitats should be considered within a framework that allows for natural ecological processes, including changes in soil chemistry and subsequent vegetation succession. Published by Elsevier B.V.
The increase of double-crested cormorant (Phalacrocorax auritus; hereafter, cormorant) population... more The increase of double-crested cormorant (Phalacrocorax auritus; hereafter, cormorant) populations during the last 2 decades has impacted many stakeholder groups. The negative effects of nesting cormorants on trees and other vegetation have motivated private organizations and government agencies to manage nesting colonies and reduce their impacts to private property and public resources. Management-induced reproductive failure has been shown to influence cormorant inter-annual nesting colony fidelity, but not complete abandonment from a nesting colony site. We attached very high frequency (VHF) transmitters and Global Positioning System (GPS) transmitters to nesting cormorants to monitor their movement response on a managed site (Young Island, VT [YI]) and an unmanaged site (Four Brothers Islands, NY [FB]). Additionally, we monitored these sites to determine the influence of management activities on subsequent-year colonization. On YI, management consisted of egg-oiling all cormorant nests (some nests had been oiled in previous years) and culling approximately 20% of adults. Annual dispersal rates did not differ between managed and unmanaged sites, but a nesting period interaction occurred with greater dispersal on the managed site following the incubation period. After 4 years of both egg oiling and culling, cormorant nesting on YI declined to zero. Simultaneously, cormorant numbers increased on the nearby unmanaged FB. We propose either the cumulative effect of partial or complete reproductive failure (8 yr) or simply the inclusion of adult culling (4 yr) caused the abandonment. From a colony-specific management perspective, the rapid decline was beneficial to the goal of restoring the vegetative community on YI. The effects of adult culling at nesting colonies, prior-year reproductive failure caused by egg oiling, or the combination of these factors may be required for complete and rapid nesting site abandonment. The use of culling adult breeders reduced nesting and likely limits the cost and logistics of control and allows more rapid initiation of mitigation measures and island habitat restoration. ß 2011 The Wildlife Society.
Knowledge of double-crested cormorant (Phalacrocorax auritus, hereafter cormorant) response to po... more Knowledge of double-crested cormorant (Phalacrocorax auritus, hereafter cormorant) response to population control activities is important for implementation of a science-based management regime. To better understand adult cormorant response to egg-oiling, we initiated a two-year satellite telemetry study in May 2000 to evaluate cormorant movements (n = 26/year), reproductive success, and nest-site fidelity at Little Galloo Island (LGI) in eastern New York. Egg-oiling effectively reduced reproductive success on LGI to < 6% in 2000 and 2001. Mean distance of core use areas (50% kernal home ranges) from LGI differed (P = 0.004) between control and egg-oiling treatments (n = 31). The distance of core use areas from LGI for the final 2-week treatment period was significantly (P < 0.05) greater than all other periods . Core use areas of 12 (39%) of 31 cormorants did not contain LGI during >1 treatment periods (2 May -9 July). However, 97% of these bird's core use areas contai...
Oral and external dosing methods replicating field exposure were developed using the double crest... more Oral and external dosing methods replicating field exposure were developed using the double crested cormorant (DCCO) to test the toxicity of artificially weathered Deepwater Horizon Mississippi Canyon 252 oil. The majority of previous oil dosing studies conducted on wild-caught birds used gavage methods to dose birds with oil and determine toxicity. However, rapid gut transit time of gavaged oil likely reduces oil absorption. In the present studies, dosing relied on injection of oil into live feeder fish for oral dosing of these piscivorous birds, or applying oil to body contour feathers resulting in transdermal oil exposure and oral exposure through preening. Both oral and external oil dosing studies identified oil-related toxicity endpoints associated with oxidative stress such as hemolytic anemia, liver and kidney damage, and immuno-modulation or compromise. External oil application allowed for controlled study of thermoregulatory stress as well. Infrared thermal images indicated significantly greater surface temperatures and heat loss in treated birds following external oil applications; however, measurements collected by coelomically implanted temperature transmitters showed that internal body temperatures were stable over the course of the study period. Birds exposed to oil externally consumed more fish than control birds, indicating metabolic compensation for thermal stress. Conversely, birds orally dosed with oil experienced hypothermia and consumed less fish compared to control birds.
For centuries, people have viewed double-crested cormorants Phalacrocorax auritus negatively, and... more For centuries, people have viewed double-crested cormorants Phalacrocorax auritus negatively, and human persecution coupled with environmental contamination severely reduced numbers of cormorants throughout North America. Shifts in paradigms for management of our natural resources resulted in reductions in environmental contaminants and regulatory protection of cormorants, allowing for an amazing population resurgence of this adaptable fish-eating bird. However, for cormorants, as with some other native wildlife species the populations of which have rebounded due to conservation efforts, there have been cormorant–societal conflicts with respect to commercial and natural resources such as aquaculture and sport fisheries. Increasing resource conflicts caused cormorants to be a priority with agencies responsible for their management, resulting in development of policy to facilitate addressing stakeholder concerns. Subsequent research and management in regard to cormorant issues have been subject to considerable challenges and debate. In this feature, we discuss the primary resource damage issues associated with cormorants, management efforts and outcomes, what we have learned, and the future with regard to cormorant management.
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other native wildlife species the populations of which have rebounded due to conservation efforts, there have been cormorant–societal conflicts with respect to commercial and natural resources such as aquaculture and sport fisheries. Increasing resource conflicts caused cormorants to be a priority with agencies responsible for their management, resulting in development of policy to facilitate addressing stakeholder concerns. Subsequent research and management in regard to cormorant issues have been
subject to considerable challenges and debate. In this feature, we discuss the primary resource damage issues associated with cormorants, management efforts and outcomes, what we have learned, and the future with regard to cormorant management.
Cormorants (Phalacrocorax auritus) at two sites in Illinois, USA, were tested for presence of invasive
bigheaded carp (Hypophthalmi- chthys spp.) DNA. We also used DNA from the feather calamus to
determine cormorant sex. Throat and cloacal swabs from cormorants at both locations tested positive
for DNA from silver carp (H. molitrix), but none tested positive for bighead carp (H. nobilis).
Hypophthalmichthys DNA was not detected on feathers. There were no significant differences among
positive Hypophthalmichthys DNA detection frequencies between cormorant sexes. To our knowledge, this is the first demonstration of silver carp as part of the Double-crested Cormorant diet in
North America. Hypophthalmichthys are major invasive species of concern in this region, the detection of water-borne environmental DNA of Hypophthalmichthys is an important monitoring tool, and the potential movement of DNA via piscivorous birds may have significant implications for interpreting environmental DNA monitoring data.
other native wildlife species the populations of which have rebounded due to conservation efforts, there have been cormorant–societal conflicts with respect to commercial and natural resources such as aquaculture and sport fisheries. Increasing resource conflicts caused cormorants to be a priority with agencies responsible for their management, resulting in development of policy to facilitate addressing stakeholder concerns. Subsequent research and management in regard to cormorant issues have been
subject to considerable challenges and debate. In this feature, we discuss the primary resource damage issues associated with cormorants, management efforts and outcomes, what we have learned, and the future with regard to cormorant management.
Cormorants (Phalacrocorax auritus) at two sites in Illinois, USA, were tested for presence of invasive
bigheaded carp (Hypophthalmi- chthys spp.) DNA. We also used DNA from the feather calamus to
determine cormorant sex. Throat and cloacal swabs from cormorants at both locations tested positive
for DNA from silver carp (H. molitrix), but none tested positive for bighead carp (H. nobilis).
Hypophthalmichthys DNA was not detected on feathers. There were no significant differences among
positive Hypophthalmichthys DNA detection frequencies between cormorant sexes. To our knowledge, this is the first demonstration of silver carp as part of the Double-crested Cormorant diet in
North America. Hypophthalmichthys are major invasive species of concern in this region, the detection of water-borne environmental DNA of Hypophthalmichthys is an important monitoring tool, and the potential movement of DNA via piscivorous birds may have significant implications for interpreting environmental DNA monitoring data.
conflicts caused cormorants to be a priority with agencies responsible for their management, resulting in development of policy to facilitate addressing stakeholder concerns. Subsequent research and management in regard to cormorant issues have been subject to considerable challenges and debate. In this feature, we discuss the primary resource damage issues associated with cormorants, management efforts and outcomes, what we have learned, and the future with regard to cormorant management.