American White Pelicans Pelecanus Erythrorhynchos Research Articles

Bayesian integrated species distribution models for hierarchical resource selection by a soaring bird

Migratory birds exhibit seasonal geographic range (hereafter, range) dynamics during the annual cycle. Few studies have examined how migratory birds select their habitats for range occupancy at the species level and space use at the individual level simultaneously. We hypothesized that environmental variables directly related to fitness components would affect the range occupancy probabilities of migrants, whereas environment variables related to movements and flights would affect the space use intensities of migrants. We built Bayesian integrated species distribution models (ISDMs) to evaluate the effects of climate conditions, wind conditions, and landcover compositions on the seasonal range dynamics of American white pelicans Pelecanus erythrorhynchos (hereafter, pelican) during summer and winter. The ISDMs estimated the summer range occupancy probabilities of pelicans with Breeding Bird Survey data, winter range occupancy probabilities with Christmas Bird Count data, and summer and winter space-use intensity rates with eBird data jointly. We evaluated the predictive performance of ISDMs using independent datasets of pelican GPS locations. Integrated species distribution models outperformed the occupancy-only models in the predictive performance of occupancy probabilities. Climate conditions had opposite effects on the range occupancy probabilities between the breeding and non-breeding grounds, whereas landcovers had relatively consistent effects on range occupancy probabilities between the seasons.

Eimeria erythrorhynchosi n. sp. (Apicomplexa: Eimeriidae) from the American white pelican Pelecanus erythrorhynchos Gmelin, 1789 (Pelecaniformes: Pelecanidae) in Toluca, Mexico

A new coccidian species, Eimeria erythrorhynchosi n. sp. (Apicomplexa: Eimeriidae) collected from the American white pelican Pelecanus erythrorhynchos Gmelin 1789, is reported from Toluca city, Mexico. Sporulated oocysts of the new species are ovoidal, 17.5–19.6 × 14.1−14.8 (18.5 × 14.5) μm, with a length/width (L/W) ratio of 1.0–1.5 (1.25); micropyle present, robust and protruding, W: 4.5–5.5, and polar body (1 or 2), L × W: 2.5 (2–3), associated with the micropyle; oocyst residuum absent. Sporocysts are ovoidal, 10.1–11.2 × 6.4−7.1 (10.7 × 6.8) μm, with a length/width (L/W) ratio of 1.0–1.6 (1.3); Stieda and sub-Stieda bodies are both present, but para-Stieda body is absent; sporocyst residuum of diffuse granules. Sporozoites are vermiform, 9.6 × 2.4 μm. The new species is the seventh species of Eimeria recorded in Pelecaniformes and the third in Pelecanidae.

Estimating Cause‐Specific Mortality and Survival of Juvenile Fall Chinook Salmon: An Investigation of Avian Predation across Large Spatial Scales

AbstractTo investigate the effects of piscivorous colonial waterbird predation on juvenile salmonids (smolts) and to determine what proportion of all sources of smolt mortality was due to predation, we analyzed a data set describing fall Chinook Salmon Oncorhynchus tshawytscha that were marked with PIT tags in the Columbia River, USA. We used a state‐space Bayesian model that incorporated live detections of tagged fish and recoveries of tags from dead fish to jointly estimate predation and survival over multiple river reaches and years (2008–2019). By incorporating recoveries of tags on bird colonies, the model was also able to increase the precision and spatial extent of survival estimates compared with a more traditional capture–recapture model. Results indicated that the avian predation probability (proportion of available fish consumed) varied depending on the predator species, colony location, and the fish's rearing type. Estimates of cumulative predation probability ranged annually from 0.066 (95% credible interval = 0.049–0.089) to 0.283 (0.210–0.419), and predation accounted for 7.3% (4.3–11.9%) to 29.1% (19.7–40.2%) of all sources of smolt mortality during out‐migration to Bonneville Dam. Probabilities of predation on wild smolts were significantly higher than those for hatchery smolts in most river reaches and years. Predation probabilities were the highest for colonies of American white pelicans Pelecanus erythrorhynchos and double‐crested cormorants Nannopterum auritum, which were located near where wild smolts rear and congregate. Estimates of predation by Caspian terns Hydroprogne caspia, California gulls Larus californicus, and ring‐billed gulls L. delawarensis were often <0.03 of available smolts annually. Collectively, results indicated that the cumulative effects of predation on Chinook Salmon smolts were substantial in some but not all river reaches and years. Future models that consider biological and environmental factors influencing smolt susceptibility to avian predation may provide a more holistic understanding of the degree to which predation limits fish survival.

Copper Toxicity to the Ghost Rams‐Horn Snail Biomphalaria havanensis

AbstractAvian piscivores cause direct economic losses to the aquaculture industry through predation, as well as indirect losses through transmission of digenetic trematodes. Bolbophorus damnificus is a trematode parasite associated with significant losses in catfish aquaculture. The complex life cycle involves the American white pelican Pelecanus erythrorhynchos, planorbid snails, and ictalurid catfish. With no approved therapeutics for B. damnificus in catfish Ictalurus spp. and federal protections on American white pelican, management is restricted to controlling snail hosts. Two snail species, marsh rams‐horn snail Planorbella trivolvis and ghost rams‐horn snail Biomphalaria havanensis, are common inhabitants of commercial catfish ponds and known to transmit B. damnificus. Previous work evaluated copper sulfate toxicity on marsh rams‐horn snails; however, data are lacking for ghost rams‐horn snails. Herein, laboratory‐reared adults of ghost rams‐horn snails and marsh rams‐horn snails were exposed to copper concentrations ranging from 0.16 to 3.38 mg/L Cu to evaluate 24‐, 48‐, and 72‐h acute toxicity. Additionally, sequential low‐dose treatments ranging from 0.1 to 0.8 mg/L Cu were evaluated on eggs, juveniles, and adults of ghost rams‐horn snails as a potentially safer treatment regime for ponds. Acute toxicity was similar between snail species for all exposure times. A 72‐h exposure produced an LC50 of 0.10 and 0.37 mg/L Cu for ghost rams‐horn snails and marsh rams‐horn snails, respectively. The LC50 values increased to 1.1 mg/L Cu for both species with 48‐h exposure. However, in the multiple low‐dose study, a single dose of 0.4 or 0.8 mg/L Cu was lethal to all adult snails after 1 week, as was 0.2 mg/L Cu after two doses. Four doses of 0.1 mg/L Cu or greater killed all ghost rams‐horn snail juveniles. Results indicate that marsh rams‐horn snails and ghost rams‐horn snails have similar sensitivity to copper, and multiple low‐dose treatments were effective against all life stages of ghost rams‐horn snails. These data indicate that copper can be an effective treatment for snail control in commercial catfish ponds.

Migratory Movements and Home Ranges of Geographically Distinct Wintering Populations of a Soaring Bird

Migratory soaring birds exhibit spatiotemporal variation in their circannual movements. Nevertheless, it remains uncertain how different winter environments affect the circannual movement patterns of migratory soaring birds. Here, we investigated annual movement strategies of American white pelicans Pelecanus erythrorhynchos (hereafter, pelican) from two geographically distinct wintering grounds in the Southern and Northern Gulf of Mexico (GOM). We hypothesized that hourly movement distance and home range size of a soaring bird would differ between different geographic regions because of different thermals and wind conditions and resource availability. We calculated average and maximum hourly movement distances and seasonal home ranges of GPS-tracking pelicans. We then evaluated the effects of hour of the day, seasons, two wintering regions in the Southern and Northern GOM, human footprint index, and relative pelican abundance from Christmas Bird Count data on pelican hourly movement distances and seasonal home ranges using linear mixed models and generalized linear mixed models. American white pelicans moved at greatest hourly distance near 1200 h at breeding grounds and during spring and autumn migrations. Both wintering populations in the Northern and Southern GOM exhibited similar hourly movement distances and seasonal home ranges at the shared breeding grounds and during spring and autumn migrations. However, pelicans wintering in the Southern GOM showed shorter hourly movement distances and smaller seasonal home ranges than those in the Northern GOM. Hourly movement distances and home ranges of pelicans increased with increasing human footprint index. Winter hourly movements and home ranges of pelicans differed between the Northern and Southern GOM; however, the winter difference in pelican movements did not carry over to the shared breeding grounds during summers. Therefore, exogenous factors may be the primary drivers to shape the flying patterns of migratory soaring birds.

Evaluating Target Levels of American White Pelican Abundance to Achieve Management Objectives for Adfluvial Yellowstone Cutthroat Trout

AbstractRecent declines in abundance of Yellowstone Cutthroat Trout Oncorhynchus clarkii bouvieri in the upper Blackfoot River drainage in Idaho coincided with establishment of a nearby nesting colony and increased abundance of American white pelicans Pelecanus erythrorhynchos (hereafter, “pelicans”). Published pelican predation rates have been estimated to be as high as 70% on Yellowstone Cutthroat Trout in the Blackfoot River. Consequently, the Idaho Department of Fish and Game established management objectives for pelicans of less than 350 breeding pairs or 700 adults. However, a thorough assessment has not been conducted to evaluate if the pelican abundance objective would reduce predation to an extent that would allow Yellowstone Cutthroat Trout to recover to levels that meet minimum objectives for abundance. A Bayesian state‐space model that integrated survival and abundance data was used in this study to evaluate the effects of local pelican abundance on survival, abundance, and population growth rate of Yellowstone Cutthroat Trout. Survival of both juvenile and adfluvial adult Yellowstone Cutthroat Trout decreased as pelican abundance increased, and there was a positive relationship between survival of both life stages and population growth rate. If the current management objective for abundance of 700 breeding pelicans was met, the probability of meeting or exceeding the Yellowstone Cutthroat Trout objective was 0.44 and declined substantially as simulated pelican abundance increased beyond 700. Results of this study suggest that if pelican abundance can be maintained at or below the current management objective, there is a reasonable chance of meeting the management objective for Yellowstone Cutthroat Trout.

Colonial Waterbird Predation and Angler Catch of Hatchery Rainbow Trout Stocked in Southern Idaho Fisheries

AbstractThe abundance of piscivorous colonial waterbirds such as double‐crested cormorants Phalacrocorax auritus and American white pelicans Pelecanus erythrorhynchos has increased dramatically in recent decades in North America, resulting in increased conflict between these birds and fisheries resources, which raises the need to quantify the effects of waterbird predation on fisheries. We estimated avian predation and angler use of two sizes of hatchery‐reared Rainbow Trout Oncorhynchus mykiss (250 mm and 300 mm on average; termed standard catchables and magnum catchables) at 15 Idaho waters with known cormorant and pelican presence. Fish were tagged with passive integrated transponder (PIT), radio, and T‐bar anchor tags prior to release; the tags were subsequently recovered from bird nesting, roosting, and loafing sites. Estimated angler use, which included fish harvested as well as those that were catch‐and‐release, averaged 17%, while avian predation averaged 35%. Angler catch at study waters declined exponentially as avian predation increased. Predation specifically attributed to double‐crested cormorants and American white pelicans was related to their relative abundance at the waterbodies where the fish were stocked. Avian predation rates were similar for standard and magnum catchables, suggesting that larger fish were not able to escape predation any better than smaller ones. Our results add to existing evidence indicating that in some southern Idaho fisheries, piscivorous birds, rather than anglers, are the dominant consumers of hatchery trout. This study further contributes to the larger issue of competition between humans, wildlife, and fisheries populations.

Colonial Waterbird Predation on Lost River and Shortnose Suckers in the Upper Klamath Basin

AbstractWe evaluated predation on Lost River Suckers Deltistes luxatus and Shortnose Suckers Chasmistes brevirostris by American white pelicans Pelecanus erythrorhynchos and double‐crested cormorants Phalacrocorax auritus nesting at mixed‐species colonies in the Upper Klamath Basin of Oregon and California during 2009–2014. Predation was evaluated by recovering (detecting) PIT tags from tagged fish on bird colonies and calculating minimum predation rates, as the percentage of available suckers consumed, adjusted for PIT tag detection probabilities but not deposition probabilities (i.e., probability an egested tag was deposited on‐ or off‐colony). Results indicate that impacts of avian predation varied by sucker species, age‐class (adult, juvenile), bird colony location, and year, demonstrating dynamic predator–prey interactions. Tagged suckers ranging in size from 72 to 730 mm were susceptible to cormorant or pelican predation; all but the largest Lost River Suckers were susceptible to bird predation. Minimum predation rate estimates ranged annually from <0.1% to 4.6% of the available PIT‐tagged Lost River Suckers and from <0.1% to 4.2% of the available Shortnose Suckers, and predation rates were consistently higher on suckers in Clear Lake Reservoir, California, than on suckers in Upper Klamath Lake, Oregon. There was evidence that bird predation on juvenile suckers (species unknown) in Upper Klamath Lake was higher than on adult suckers in Upper Klamath Lake, where minimum predation rates ranged annually from 5.7% to 8.4% of available juveniles. Results suggest that avian predation is a factor limiting the recovery of populations of Lost River and Shortnose suckers, particularly juvenile suckers in Upper Klamath Lake and adult suckers in Clear Lake Reservoir. Additional research is needed to measure predator‐specific PIT tag deposition probabilities (which, based on other published studies, could increase predation rates presented herein by a factor of roughly 2.0) and to better understand biotic and abiotic factors that regulate sucker susceptibility to bird predation.Received January 19, 2016; accepted June 25, 2016 Published online October 7, 2016

Austrodiplostomum sp., Bolbophorus sp. (Digenea: Diplostomidae), and Clinostomum marginatum (Digenea: Clinostomidae) metacercariae in inland silverside Menidia beryllina from catfish aquaculture ponds, with notes on the infectivity of Austrodiplostomum sp. cercariae in channel catfish Ictalurus punctatus.

In the southeastern USA, catfish aquaculture is burdened by predation from piscivorous birds and the digenetic trematodes they carry. In addition to cultured ictalurid fish, other forage or incidental fish species inhabit catfish production ponds. Of these, the inland silverside Menidia beryllina was recently found to harbor larval metacercariae of several trematode species. Three species of metacercariae were reported, two of which represent the first morphological descriptions of an Austrodiplostomum sp. and Bolbophorus sp. metacercaria, respectively. A total of 15 silversides were collected from a commercial catfish pond and examined for trematode infection. These fish were parasitized by metacercariae of an Austrodiplostomum sp. (100% prevalence) in the eyes and brain, a Bolbophorus sp. (86.7% prevalence) in the musculature, and Clinostomum marginatum (33.3% prevalence) in the musculature and fins. All three trematode species were characterized morphologically and molecularly by sequencing of the cytochrome c oxidase subunit 1 gene (CO1). In addition, the internal transcribed spacer 1 region (ITS1), 5.8S rRNA gene, and ITS2 region were determined for the Bolbophorus sp., which linked this metacercaria to a Bolbophorus sp. cercaria from a planorbid snail Planorbella trivolvis and an unnamed Bolbophorus sp. adult from the American white pelican Pelecanus erythrorhynchos. Furthermore, Biomphalaria havanensis snails were collected from the same pond and found actively shedding cercariae morphologically and molecularly consistent with a diplostomid cercaria reported from Bi . havanensis in catfish ponds in Mississippi, USA. Sequence comparisons deemed these cercariae conspecific to the Austrodiplostomum sp. from inland silverside described here. Channel catfish fingerlings were exposed to these cercariae at doses of 50 and 100 cercariae per fish. The infectivity of this Austrodiplostomum sp. in channel catfish was assessed at 10 and 20days post exposure (dpe). Metacercariae were observed in both the eyes and brain of infected channel catfish, supporting molecular data that suggests the cercaria and metacercaria are both stages of a previously unidentified Austrodiplostomum sp. life cycle.

Avian Predation on Juvenile Salmonids: Spatial and Temporal Analysis Based on Acoustic and Passive Integrated Transponder Tags

AbstractWe evaluated the impact of predation on juvenile steelhead Oncorhynchus mykiss and yearling and subyearling Chinook Salmon O. tshawytscha by piscivorous waterbirds from 11 different breeding colonies in the Columbia River basin during 2012 and 2014. Fish were tagged with both acoustic tags and PIT tags and were tracked via a network of hydrophone arrays to estimate total smolt mortality (1 – survival) at various spatial and temporal scales during out‐migration. Recoveries of PIT tags on bird colonies, coupled with the last known detections of live fish passing hydrophone arrays, were used to estimate the impact of avian predation relative to total smolt mortality. Results indicated that avian predation was a substantial source of steelhead mortality, with predation probability (proportion of available fish consumed by birds) ranging from 0.06 to 0.28 for fish traveling through the lower Snake River and the lower and middle Columbia River. Predation probability estimates ranged from 0.03 to 0.09 for available tagged yearling Chinook Salmon and from 0.01 to 0.05 for subyearlings. Smolt predation by gulls Larus spp. was concentrated near hydroelectric dams, while predation by Caspian terns Hydroprogne caspia was concentrated within reservoirs. No concentrated areas of predation were identified for double‐crested cormorants Phalacrocorax auritus or American white pelicans Pelecanus erythrorhynchos. Comparisons of total smolt mortality relative to mortality from colonial waterbirds indicated that avian predation was one of the greatest sources of mortality for steelhead and yearling Chinook Salmon during out‐migration. In contrast, avian predation on subyearling Chinook Salmon was generally low and constituted a minor component of total mortality. Our results demonstrate that acoustic and PIT tag technologies can be combined to quantify where and when smolt mortality occurs and the fraction of mortality that is due to colonial waterbird predation relative to non‐avian mortality sources.Received November 4, 2015; accepted February 1, 2016 Published online June 27, 2016

Comparative susceptibility of Channel Catfish, Blue Catfish, and their hybrid cross to experimental challenge with Bolbophorus damnificus (Digenea: Bolbophoridae) cercariae.

The digenetic trematode Bolbophorus damnificus has been implicated in significant losses in catfish aquaculture since the late 1990s. The complex life cycle sequentially involves the American white pelican Pelecanus erythrorhynchos, the marsh rams horn snail Planorbella trivolvis, and Channel Catfish Ictalurus punctatus. Research supports anecdotal reports from the industry, suggesting that the hybrid of Channel Catfish×Blue Catfish I. furcatus is less susceptible to disease agents that have been historically prohibitive to Channel Catfish production, namely the gram-negative bacteria Edwardsiella ictaluri and Flavobacterium columnare, as well as the myxozoan parasite Henneguya ictaluri. This current research compared the susceptibility of Channel Catfish, Blue Catfish, and their hybrid cross to an experimental challenge by B. damnificus. Fish were exposed to 0, 100, 200, and 400 B. damnificus cercariae per fish, and the numbers of metacercariae per fish were determined 14 d postchallenge. Metacercariae were recovered from all challenged fish. There were no significant differences among fish groups challenged with the same dose, suggesting Channel and Blue Catfish and their hybrid are comparably susceptible to B. damnificus infection. As such, it is recommended that producers raising hybrid catfish remain diligent in controlling populations of the snail intermediate host to prevent production losses attributed to B. damnificus, especially when loafing pelicans have been observed at the aquaculture operation.

American White Pelican Predation on Cui‐ui in Pyramid Lake, Nevada

AbstractAnthropogenic changes to the Pyramid Lake–Truckee River ecosystem in Nevada are suspected to have altered the predator–prey balance between American white pelican Pelecanus erythrorhynchos and Cui‐ui Chasmistes cujus. We estimated the loss of the adult Cui‐ui population to pelican predation over a 13‐year period by netting and tagging Cui‐uis as they aggregated at the mouth of the Truckee River prior to their spawning migration into the Truckee River. Cui‐ui access to the Truckee River typically required traversing a shallow delta (a foraging advantage for these American white pelicans). Dams and greater frequency of low stream flows also contributed to American white pelican foraging success. We used tag recoveries from Pyramid Lake's nesting colony of American white pelicans along with an experiment to estimate the chance of tag recovery within the colony to calculate the number of tagged fish taken by American white pelicans. We also used numbered tags to test whether there was a size preference for Cui‐uis taken. Our results showed that the primary source of adult Cui‐ui mortality was from American white pelican predation in the Truckee River. Within a 13‐year period American white pelicans had taken 90% of the tags deployed during the first 7 years of the interval. There was no preference for the size of Cui‐uis taken. A better understanding of the effects of heavy cropping by American white pelicans on Cui‐ui population dynamics is still needed.Received March 26, 2013; accepted October 8, 2013Published online January 24, 2014

Systemwide Evaluation of Avian Predation on Juvenile Salmonids from the Columbia River Based on Recoveries of Passive Integrated Transponder Tags

AbstractWe recovered passive integrated transponder (PIT) tags from nine piscivorous waterbird colonies in the Columbia River basin to evaluate avian predation on Endangered Species Act (ESA)‐listed salmonid Oncorhynchus spp. populations during 2007–2010. Avian predation rates were calculated based on the percentage of PIT‐tagged juvenile salmonids that were detected as passing hydroelectric dams and subsequently were consumed and deposited by birds on their nesting colonies. Caspian terns Hydroprogne caspia (hereafter, “terns”) and double‐crested cormorants Phalacrocorax auritus (hereafter, “cormorants”) nesting on East Sand Island in the Columbia River estuary consumed the highest proportions of available PIT‐tagged salmonids, with minimum predation rates ranging from 2.5% for Willamette River spring Chinook salmon O. tshawytscha to 16.0% for Snake River steelhead O. mykiss. Estimated predation rates by terns, cormorants, gulls of two species (California gull Larus californicus and ring‐billed gull L. delawarensis), and American white pelicans Pelecanus erythrorhynchos nesting near the confluence of the Snake and Columbia rivers were also substantial; minimum predation rates ranged from 1.4% for Snake River fall Chinook salmon to 13.2% for upper Columbia River steelhead. Predation on ESA‐listed salmonids by gulls and American white pelicans were minor (<2.0% per ESA‐listed salmonid population) relative to predation by terns and cormorants. Cumulative impacts were greater for Snake River and upper Columbia River salmonids than for salmonids originating closer to the estuary because upriver salmonids must migrate past more bird colonies to reach the ocean. Predation rates adjusted for colony size (per capita rates) were significantly higher for terns and cormorants nesting at inland colonies (upstream of Bonneville Dam) than for those nesting in the estuary, suggesting that inland colonies have a greater reliance on salmonids as a food source. Management actions to increase salmonid survival by reducing avian predation in the estuary could be offset if birds that disperse from the estuary relocate to inland nesting sites on or near the Columbia River.

Avian Piscivores as Vectors forMyxobolus cerebralisin the Greater Yellowstone Ecosystem

AbstractMyxobolus cerebralis, the cause of whirling disease in salmonids, has dispersed to waters in 25 states within the USA, often by an unknown vector. Its incidence in Yellowstone cutthroat troutOncorhynchus clarkii bouvieriwithin the highly protected environment of Yellowstone Lake, Yellowstone National Park, is a prime example. Given the local abundances of piscivorous birds, we sought to clarify their potential role in the dissemination ofM. cerebralis. Six individuals from each of three bird species (American white pelicanPelecanus erythrorhynchos, double‐crested cormorantPhalacrocorax auritus, and great blue heronArdea herodias) were fed known‐infected or uninfected rainbow troutO. mykiss. Fecal material produced during 10‐d periods before and after feeding was collected to determine whetherM. cerebraliscould be detected and, if so, whether it remained viable after passage through the gastrointestinal tract of these birds. For all (100%) of the nine birds fed known‐infected fish, fecal samples collected during days 1–4 after feeding tested positive forM. cerebralisby polymerase chain reaction. In addition, tubificid wormsTubifex tubifexthat were fed fecal material from known‐infected great blue herons produced triactinomyxons in laboratory cultures, confirming the persistent viability of the parasite. No triactinomyxons were produced fromT. tubifexfed fecal material from known‐infected American white pelicans or double‐crested cormorants, indicating a potential loss of parasite viability in these species. Great blue herons have the ability to concentrate and release viable myxospores into shallow‐water habitats that are highly suitable forT. tubifex, thereby supporting a positive feedback loop in which the proliferation ofM. cerebralisis enhanced. The presence of avian piscivores as an important component of aquatic ecosystems should continue to be supported. However, given the distances traveled by great blue herons between rookeries and foraging areas in just days, any practices that unnaturally attract them may heighten the probability ofM. cerebralisdispersal and proliferation within the Greater Yellowstone Ecosystem.

Biomphalaria havanensis Identified as a Potential Intermediate Host for the Digenetic Trematode Bolbophorus damnificus

AbstractThe digenetic trematode Bolbophorus damnificus has been associated with mortalities in commercial channel catfish Ictalurus punctatus in the Mississippi Delta. In the life cycle of B. damnificus, the only confirmed first intermediate host is the ram's horn snail Planorbella trivolvis. Recently, the exotic snail Biomphalaria havanensis has been isolated in several channel catfish ponds in the Mississippi Delta. The aim of this study was to determine whether this invasive snail species could also serve as a first intermediate host in the B. damnificus life cycle. Bolbophorus damnificus ova were collected from an American white pelican Pelecanus erythrorhynchos that had been artificially infected with B. damnificus metacercariae; the ova were then introduced into an aquarium with parasite‐negative B. havanensis. Bolbophorus damnificus cercariae (confirmed by polymerase chain reaction) were detected in B. havanensis 45 d after exposure to B. damnificus ova. The snails continued to shed B. damnificus cercariae throughout the 80‐d postexposure examination period. Before this research, the only reported natural B. damnificus infection of snails involved P. trivolvis. This study indicates that the range of snail hosts is broader than previously suspected. A survey should be implemented to identify additional snail species that can serve as hosts for B. damnificus. Further research should determine whether B. havanensis is a natural host for B. damnificus, and if so the prevalence of B. havanensis in commercial channel catfish ponds should be assessed.

Diel Foraging Behavior of American White PelicansPelecanus erythrorhynchoson Experimental Aquaculture Ponds

AbstractVideography and night vision equipment were used to observe the diurnal and nocturnal activities of American white pelicansPelecanus erythrorhynchos(N=6) foraging on three experimental (0.04 ha) channel catfish (Ictalurus punctatus) aquaculture ponds in March 2001. Captive pelicans spent most time foraging per hour from 1700 through 2300 h (CST). No foraging was observed from 0700 through 0800 h. Fish captures per hour were greatest from 1700 through 1900 h. On average, captive pelicans (N= 5) consumed 1.0 ± 0.2 kg of catfish per bird per day during the 10‐d foraging trial. This consumption corresponds with an average intake of over 60,000 kJ of energy per bird during the trial. Relative to morning hours, the average number of bill dips per min was greater during afternoon foraging bouts. Fish captures per bill dip, however, did not differ among trial hours. Thus, pelicans were observed to increase foraging effort subsequent to 1500 h and thereby consumed 224 to 532 catfish (average = 313 ± 74 fish;N =4) during the 10‐d foraging trial in ponds stocked with approximately 74,000 catfish/ha.

Bolbophorus damnificus n. sp. (Digenea: Bolbophoridae) from the channel catfish Ictalurus punctatus and American white pelican Pelecanus erythrorhynchos in the USA based on life-cycle and molecular data

The common pathogenic prodiplostomulum metacercaria in the flesh, mostly near the skin, of pond-produced channel catfish Ictalurus punctatus has been demonstrated to be Bolbophorus damnificus Overstreet & Curran n. sp. The catfish acquires the infection from the snail Planorbella trivolvis, the only known first intermediate host, and the species is perpetuated through the American white pelican Pelecanus erythrorhynchos, as confirmed by experimental infections with nestling and dewormed adult pelican specimens in conjunction with molecular data. It differs from the cryptic species Bolbophorus sp., also found concurrently in the American white pelican, by having eggs 123-129 microm rather than 100-112 microm long and consistent low values for nucleotide percentage sequence similarity comparing COI, ITS 1/2, 18S rRNA and 28S rRNA fragments. Bolbophorus sp. is comparable but most likely distinct from B. confusus (Kraus, 1914), which occurs in Europe and has eggs 90-102 microm long. Its intermediate hosts were not demonstrated. The adults of neither of the confirmed North American species of Bolbophorus were encountered in any bird other than a pelican, although several shore birds feed on infected catfish, and B. damnificus can survive but not mature when protected in the mouse abdominal cavity. B. ictaluri (Haderlie, 1953) Overstreet & Curran n. comb., a species different from B. damnificus, is considered a species inquirenda.

Effects of piscivory on the fatty acid profiles and antioxidants of avian yolk: studies on eggs of the gannet, skua, pelican and cormorant

AbstractPiscivorous birds consume diets which are rich in highly‐polyunsaturated n‐3 fatty acids; these play vital roles in embryonic development but are very susceptible to oxidative damage. The effects of such diets on the fatty acid composition and antioxidant content of the yolk were investigated in the northern gannet Morus bassanus, the great skua Catharacta skua, the American white pelican Pelecanus erythrorhynchos and the double‐crested cormorant Phalacrocorax auritus. The phospholipid fraction of the eggs of these four species contained high proportions of the n‐3 fatty acid, docosahexaenoic acid, which formed 7.5–11.3% (w/w) of the fatty acids of this fraction. The presence of eicosapentaenoic and docosapentaenoic acids also contributed to the total n‐3 content of the phospholipid. The n‐6 polyunsaturate, arachidonic acid, formed between 8% and 19% (w/w) of the phospholipid fatty acids. For the pelican and cormorant, this is consistent with the consumption of freshwater fishes in which arachidonic acid may be a significant acyl constituent. This finding is, however, more difficult to explain for the gannet and skua which largely consume marine fish with a low arachidonic acid content. The yolks of all four species contained relatively high concentrations of vitamin E (90.2–302.3 μg g−1 wet yolk) which was mainly present as α‐tocopherol. The eggs of the pelican and cormorant were especially enriched in carotenoids (150.9 and 115.7 μg g−1 wet yolk, respectively).