Phalacrocorax Auritus Research Articles

Modeling the economic impacts of double-crested cormorant damage to a recreational fishery

The double-crested cormorant (Phalacrocorax auritus) has undergone a significant range expansion in the Great Lakes area of the United States since the 1970s, negatively impacting native fish populations and sport fisheries. Effective management of wildlife requires policies and practices that quantify their economic impacts, which is often complicated by multiplier effects in the regional economy. This analysis estimates the potential direct and regional economic impacts of the cormorant to a recreational fishery. We estimated that the potential economic loss was on average $5 million to $66 million annually, as well as 66 to 929 job-years in the region annually over a 20-year period (1990 to 2009). This approach to calculating the economic impacts of wildlife damage can be applied to other wildlife to provide the most accurate estimate of total economic impacts.

Aquaculture depredation by double‐crested cormorants breeding in Eastern North America

ABSTRACTThe double‐crested cormorant (Phalacrocorax auritus) has undergone population expansion throughout much of its historical range since the 1970s, resulting in increased pressure on foraging habitats including real and perceived competition with commercial and sport fisheries and impacts on the aquaculture industry. The specific objectives of this study were to determine the stable isotope ratios of birds wintering at aquaculture facilities and natural freshwater and marine habitats, and to determine what percent of birds at distinct breeding colonies wintered in each of these habitats. We exploited natural variation in isotopic ratios of carbon, nitrogen, and sulfur (from feathers) to determine the winter habitat use (i.e., aquaculture, natural freshwater, or marine) of birds collected on their summer breeding grounds in the eastern United States (from Minnesota to Vermont). The distribution of winter habitat use varied significantly across breeding colonies and between male and female cormorants. More specifically, use of aquaculture winter habitat was most prevalent in birds breeding in Lake Huron and Lake Erie. Overall, aquaculture habitats were used more by males, and marine habitats were used more by females. The stable isotope approach used in this study provided dietary confirmation of previously observed migratory patterns in the double‐crested cormorant. Because aquaculture was primarily used by males, and these males migrated to a broad range of breeding colonies, we suggest that targeting breeding birds to reduce aquaculture depredation is a less efficient strategy than managing birds at depredation sites on the wintering grounds. Published 2015. This article is a U.S. Government work and is in the public domain in the USA.

Developing nondestructive techniques for managing conflicts between fisheries and double-crested cormorant colonies

Double-crested cormorants (Phalacrocorax auritus) have been identified as the source of significant mortality to juvenile salmonids (Oncorhynchus spp.) in the Columbia River Basin. Management plans for reducing the size of a large colony on East Sand Island (OR, USA) in the Columbia River estuary are currently being developed. We evaluated habitat enhancement and social attraction as nondestructive techniques for managing cormorant nesting colonies during 2004–2007. We tested these techniques on unoccupied plots adjacent to the East Sand Island cormorant colony. Cormorants quickly colonized these plots and successfully raised young. Cormorants also were attracted to nest and raised young on similar plots at 2 islands approximately 25 km from East Sand Island; 1 island had a history of successful cormorant nesting whereas the other was a site where cormorants had previously nested unsuccessfully. On a third island with no history of cormorant nesting or nesting attempts, these techniques were unsuccessful at attracting cormorants to nest. Our results suggest that some important factors influencing attraction of nesting cormorants using these techniques include history of cormorant nesting, disturbance, and presence of breeding cormorants nearby. These techniques may be effective in redistributing nesting cormorants away from areas where fish stocks of conservation concern are susceptible to predation, especially if sites with a recent history of cormorant nesting are available within their foraging or dispersal range. Published 2015. Wiley Periodicals, Inc. This article is a US Government work and, as such, is in the public domain in the United States of America.

A PREDICTIVE MODEL TO INFORM ADAPTIVE MANAGEMENT OF DOUBLE‐CRESTED CORMORANTS AND FISHERIES IN MICHIGAN

ABSTRACTThe proliferation of double‐crested cormorants (DCCOs; Phalacrocorax auritus) in North America has raised concerns over their potential negative impacts on game, cultured and forage fishes, island and terrestrial resources, and other colonial water birds, leading to increased public demands to reduce their abundance. By combining fish surplus production and bird functional feeding response models, we developed a deterministic predictive model representing bird–fish interactions to inform an adaptive management process for the control of DCCOs in multiple colonies in Michigan. Comparisons of model predictions with observations of changes in DCCO numbers under management measures implemented from 2004 to 2012 suggested that our relatively simple model was able to accurately reconstruct past DCCO population dynamics. These comparisons helped discriminate among alternative parameterizations of demographic processes that were poorly known, especially site fidelity. Using sensitivity analysis, we also identified remaining critical uncertainties (mainly in the spatial distributions of fish vs. DCCO feeding areas) that can be used to prioritize future research and monitoring needs. Model forecasts suggested that continuation of existing control efforts would be sufficient to achieve long‐term DCCO control targets in Michigan and that DCCO control may be necessary to achieve management goals for some DCCO‐impacted fisheries in the state. Finally, our model can be extended by accounting for parametric or ecological uncertainty and including more complex assumptions on DCCO–fish interactions as part of the adaptive management process.

Tracking the History and Ecological Changes of Rising Double-Crested Cormorant Populations Using Pond Sediments from Islands in Eastern Lake Ontario.

In the Laurentian Great Lakes region, the double-crested cormorant (Phalacrocorax auritus) has seen a thousand-fold population increase in recent decades. These large colonies of birds now often conflict with socioeconomic interests, particularly due to perceived competition with fisheries and the destruction of terrestrial vegetation in nesting habitats. Here we use dated sediment cores from ponds on islands in eastern Lake Ontario that receive waste inputs from dense colonies of cormorants and ring-billed gulls (Larus delawarensis) to chronicle the population rise of these species and assess their long-term ecological impacts. Modern water chemistry sampling from these sites reveals drastically elevated nutrient and major ion concentrations compared to reference ponds not influenced by waterbirds. Geochemical tracers in dated sediment cores, particularly δ15N and chlorophyll-a concentrations, track waterbird influences over time. Fossil diatom assemblages were dominated by species tolerant of hyper-eutrophic and polluted systems, which is in marked contrast to assemblages in reference sites. In addition to establishing long-term ecological impacts, this multi-proxy paleoecological approach can be used to determine whether islands of concern have been long-term nesting sites or were only recently colonized by cormorant or ring-billed gull populations across the Great Lakes, facilitating informed management decisions about controversial culling programs.

Reproductive Success of Colonial Tree-nesting Waterbirds in Prairie Pothole Wetlands and Rivers throughout Northeastern South Dakota

The northern Great Plains of North America provides critical breeding habitat for many colonial tree-nesting waterbirds, but reproductive success and population parameters for these species are largely unknown within the Prairie Pothole Region, specifically in South Dakota. The objective of this study was to evaluate reproductive success of colonial tree-nesting waterbirds on selected wetlands and rivers in northeast South Dakota. During the 2008 and 2009 breeding seasons, nesting and fledging success of Black-crowned Night-Heron (Nycticorax nycticorax), Great Blue Heron (Ardea herodias), Cattle Egret (Bubulcus ibis), Great Egret (A. alba), Snowy Egret (Egretta thula), and Double-crested Cormorant (Phalacrocorax auritus) were estimated in 39 individual colonies. A total of 2551 individual nests were monitored from 15 Apr. - 15 Aug. in 2008 and 2009. Overall apparent nest and fledge success (respectively) were: Black-crowned Night-Heron (52.1%, 47.9%), Great Blue Heron (58.2%, 35.9%), Cattle Egret (73.1%, 69.2%), Great Egret (61.5%, 50.7%), Snowy Egret (83.6%, 81.7%), and Double-crested Cormorant (70.4%, 54.2%). Nest abandonment accounted for an average of 47.6% of nest failures for all species combined. Nest structure failure and young dying within nests accounted for most failures to fledge. Nesting success increased with the area of wetland habitat in the landscape for all species analyzed. Lower reproductive success of Black-crowned Night-Heron and Great Blue Heron, compared to other findings across the U.S. and Canada, suggests that these breeding populations in northeast South Dakota may be declining. Cattle Egret, Great Egret, Snowy Egret, and Double-crested Cormorant reproductive success is relatively high in northeast South Dakota compared to other North American populations. Preserving and restoring wetland habitat surrounding waterbird colonies will provide successful nesting habitat as well as foraging areas and opportunities for new colony site locations.

Coastal zone occupancy by double-crested cormorants on a Laurentian Great Lake before, during, and after a food web regime shift

The Lake Huron food web has been undergoing change since the invasion of driessenid mussels (Dreissena spp.) (late 1990s), especially in 2003 featuring the lake-wide loss of alewife (Alosa pseudoharengus) among other elements that year. Collectively the changes in 2003 satisfy a number of criteria for a regime shift. Based on multiflight surveys (2001–2005), we modeled coastal zone occupancy of foraging double-crested cormorants (Phalacrocorax auritus) in the North Channel and Georgian Bay of Lake Huron during the regime shift period. At the start of the regime shift (2003), there were a number of plausible occupancy models based on a set of spatial covariates, the only year in the study when this occurred. Annual shifts in the magnitude and sign of coefficients indicated movement of cormorants between the two coastal regions, especially during and immediately after the regime shift period. Declines in cormorant occupancy of coastal habitat were not confined to 2003 but extended through 2004, with declines in occupancy in the North Channel (2003) preceding that in Georgian Bay (2004). Declines in occupancy in offshore areas in both coastal regions preceded declines in nearshore areas, possibly reflecting the loss of alewife at the time. The spatial response of predators or prey in regime shifts could serve as early indicators of tipping points in ecosystems.

Species Identity and Nest Location Predict Agonistic Interactions at a Breeding Colony of Double-Crested Cormorants (Phalacrocorax auritus) and Great Blue Herons (Ardea herodias)

Abstract. Recent dramatic growth of the North American Interior population of Double-crested Cormorants (Phalacrocorax auritus) has led to concern about potential impacts of this species on co-nesting colonial waterbirds. Previous investigations of these concerns have focused on Double-crested Cormorant interactions with other species within homogeneous breeding environments, making broad patterns difficult to identify. The present study examined how nest location, nest density, and species identity mediate agonistic interactions among Double-crested Cormorants and Great Blue Herons (Ardea herodias) nesting at a colony site in central Minnesota, USA. Twenty-six Double-crested Cormorant nests and 27 Great Blue Heron nests were observed for 30 min weekly for 8 weeks during the breeding season to estimate frequency of agonistic behavior and identify species-level patterns of interaction. Most agonistic interactions observed (81%) were intraspecific interactions among Double-crested Cormorants; Great Blue Her...

Influence of Simulated Double‐crested Cormorant, Phalacrocorax auritus, Predation on Multiple‐batch Production of Channel Catfish, Ictalurus punctatus

AbstractThe double‐crested cormorant, Phalacrocorax auritus, is considered the primary depredating bird species on commercially produced channel catfish, Ictalurus punctatus, in the southeastern USA. We simulated different levels of cormorant predation on losses at harvest and economic effects on channel catfish production in a multiple‐batch cropping system. We observed significant (P < 0.05) declines in catfish production at increasing levels of cormorant predation in this study. This decline was mitigated by increased individual growth of catfish at higher predation rates (i.e., lower catfish densities). This mitigating effect produced a non‐linear relationship with total kg of catfish harvested per pond resulting in a non‐linear incremental increase in breakeven price related to predation. Costs of production ($/kg) increased with increasing predation levels up to very high levels of predation with a cumulative maximum increase in breakeven price of $0.143/kg. These results indicate that losses at harvest due to cormorant predation occur immediately but are mitigated in part by compensatory growth of individual catfish. Losses due to cormorant predation in multi‐batch systems can be considerable, but there is not a 1:1 relationship between losses and kg of catfish harvested due to compensatory factors.

Temporal trends of perfluoroalkyl substances (PFAS) in eggs of coastal and offshore birds: Increasing PFAS levels associated with offshore bird species breeding on the Pacific coast of Canada and wintering near Asia.

Perfluoroalkyl substances (PFAS) such as perfluoroalkyl carboxylates (PFCAs) and perfluoroalkyl sulfonates (PFSAs) have become virtually ubiquitous throughout the environment, and, based on laboratory studies, have known toxicological consequences. Various national and international voluntary phase-outs and restrictions on these compounds have been implemented over the last 10 to 15 years. In the present study, we examine trends (1990/1991-2010/2011) in aquatic birds (ancient murrelet, Synthliboramphus antiquus [2009 only]; Leach's storm-petrels, Oceanodroma leucorhoa; rhinoceros auklets, Cerorhinca monocerata; double-crested cormorants, Phalacrocorax auritus; and great blue herons, Ardea herodias). The PFCA, PFSA, and stable isotope (δ(15) N and δ(13) C) data collected from these species from the Pacific coast of Canada, ranging over 20 to 30 years, were used to investigate temporal changes in PFAS coupled to dietary changes. Perfluorooctane sulfonic acid (PFOS), the dominant PFSA compound in all 4 species, increased and subsequently decreased in auklet and cormorant eggs in line with the manufacturing phase-out of PFOS and perfluorooctanoic acid (PFOA), but concentrations continuously increased in petrel eggs and remained largely unchanged in heron eggs. Dominant PFCA compounds varied between the offshore and coastal species, with increases seen in the offshore species and little or variable changes seen in the coastal species. Little temporal change was seen in stable isotope values, indicating that diet alone is not driving observed PFAS concentrations.

Little Galloo Island, Lake Ontario: Two decades of studies on the diet, fish consumption, and management of double-crested cormorants

The double-crested cormorant (Phalacrocorax auritus) colony at Little Galloo Island, Lake Ontario has been a Great Lakes focal point of controversy regarding cormorant–fish interactions for over two decades. We examined cormorant diet and fish consumption at the colony from 1992 to 2013. During this time period, two events, management actions and round goby (Neogobius melanostomus) invasion, occurred that affected the number of fish consumed by cormorants and their diet composition. The purpose of this study was to evaluate the effects of round goby on the feeding ecology of cormorants and evaluate the efficacy of management actions on meeting cormorant population targets at the colony. Round goby first appeared in the diet in 2004 (0.8%) and within one year were the primary prey (29.3%). The presence of round goby in the diet of cormorants: (1) eliminated seasonal variability in diet composition, (2) reversed seasonal trends in the number of fish consumed daily, (3) increased daily fish consumption, and (4) significantly reduced the consumption of other species including yellow perch and smallmouth bass. Management actions, such as egg oiling and culling, were also effective in reducing nesting activity and the number of cormorant feeding days at the Little Galloo Island colony. There is evidence that the combination of management actions and round goby may have allowed some population recovery of yellow perch and smallmouth bass in eastern Lake Ontario.

Avian botulism type E in waterbirds of Lake Michigan, 2010–2013

During 2010 to 2013, waterbird mortality surveillance programs used a shared protocol for shoreline walking surveys performed June to November at three areas in northern Lake Michigan. In 2010 and 2012, 1244 total carcasses (0.8 dead bird/km walked) and 2399 total carcasses (1.2 dead birds/km walked), respectively, were detected. Fewer carcasses were detected in 2011 (353 total carcasses, 0.2 dead bird/km walked) and 2013 (451 total carcasses, 0.3 dead bird/km walked). During 3 years, peak detection of carcasses occurred in October and involved primarily migratory diving and fish-eating birds, including long-tailed ducks (Clangula hyemalis; 2010), common loons (Gavia immer; 2012), and red-breasted mergansers (Mergus serrator; 2013). In 2011, peak detection of carcasses occurred in August and consisted primarily of summer residents such as gulls (Larus spp.) and double-crested cormorants (Phalacrocorax auritus). A subset of fresh carcasses was collected throughout each year of the study and tested for botulinum neurotoxin type E (BoNT/E). Sixty-one percent of carcasses (57/94) and 10 of 11 species collected throughout the sampling season tested positive for BoNT/E, suggesting avian botulism type E was a major cause of death for both resident and migratory birds in Lake Michigan. The variety of avian species affected by botulism type E throughout the summer and fall during all 4 years of coordinated surveillance also suggests multiple routes for bird exposure to BoNT/E in Lake Michigan.

Prey consumption and trace element concentrations in double-crested cormorants ( Phalacrocorax auritus ) from Lake Winnipeg, Canada

Abstract Double-crested cormorants ( Phalacrocorax auritus ) have generally increased throughout their range in North America over the last 40 years, leading to increased conflict with commercial and recreational fisheries that often view cormorants as competitors. Lake Winnipeg, Manitoba, Canada and adjacent large lakes support a significant portion of the continent's breeding population, and have high economic value for recreational and commercial fisheries; no recent assessment of cormorant diet has been conducted in this region. We measured stable isotopes ( δ 13 C, δ 15 N, and δ 34 S) in cormorant muscle and used a Bayesian mixing model approach to estimate cormorant diet composition throughout the Lake Winnipeg system, including the contribution of commercially and recreationally harvested walleye ( Sander vitreus ) and sauger ( Sander canadensis ). We estimated that cormorants occupied a trophic position around 4.0, which corresponds to a generalist diet, and consumed a small proportion of walleye (range of mean estimates: 6–12%) and sauger (range of mean estimates: 7–12%). We also examined the concentrations of 15 trace elements in cormorant muscle to evaluate the potential role that these birds played in contaminant flow and how these elements behaved trophically. Cd, Fe, Mn, Hg, and Se showed evidence of biomagnification in Lake Winnipeg's north basin, but only Hg biomagnified in the south basin; nutrient source (benthic vs. pelagic) had little effect on elemental concentrations. Our results add to the growing evidence that the two main basins of Lake Winnipeg are biologically distinct from each other, and that cormorants likely have little effect on the populations of harvested fishes.

Molecular and morphological characterization of Austrodiplostomum ostrowskiae Dronen, 2009 (Digenea: Diplostomatidae), a parasite of cormorants in the Americas.

The diplostomid genus Austrodiplostomum currently contains two species, i.e. A. mordax and A. ostrowskiae. Adults of these species inhabit the intestine of cormorants of the genus Nannopterum, whereas larval forms (metacercariae) are found in the eyes (vitreous humor) of freshwater fishes. Records of both species have been established across a wide geographic range in the Americas. Diplostomid adults and metacercariae were collected from a wide geographical range that spans from south-eastern Mexico, southwards to Central and South America. Even though the diplostomid has been largely reported in Mexico as Diplostomum (Austrodiplostomum) compactum, our specimens were identified morphologically as A. ostrowskiae. Sequences of the mitochondrial gene cytochrome c oxidase (cox 1) were obtained for 86 individuals, including 15 adults recovered from the intestine of Nannopterum brasilianus, in five localities, and 71 metacercariae from the eyes of ten fish species, in 13 localities. Sequences were used to evaluate the genetic diversity, and to test conspecificity of these specimens with the available sequence of A. ostrowskiae. Sequences were aligned with another 12 taxa representing five genera of Diplostomatidae, forming a dataset of 104 taxa with 478 nucleotides. The genetic divergence estimated among the 86 sequenced individuals, and that of A. ostrowskiae from the double-crested cormorant, Nannopterum auritus, in the USA, was very low, ranging from 0 to 0.8%. The maximum likelihood (ML) and Bayesian consensus trees showed that all sequences nested within a monophyletic lineage, with strong bootstrap and Bayesian posterior probability support values (100/1.0). In conclusion, a link between the metacercariae in fish and the adults in cormorants was established, indicating also that a single species is found in the distribution range comprising southern USA, southwards to Venezuela. Previous records of this species, particularly from Mexico, need to be corrected.

Quantifying Avian Predation on Fish Populations: Integrating Predator‐Specific Deposition Probabilities in Tag Recovery Studies

AbstractAccurate assessment of specific mortality factors is vital to prioritize recovery actions for threatened and endangered species. For decades, tag recovery methods have been used to estimate fish mortality due to avian predation. Predation probabilities derived from fish tag recoveries on piscivorous waterbird colonies typically reflect minimum estimates of predation due to an unknown and unaccounted‐for fraction of tags that are consumed but not deposited on‐colony (i.e., deposition probability). We applied an integrated tag recovery modeling approach in a Bayesian context to estimate predation probabilities that accounted for predator‐specific tag detection and deposition probabilities in a multiple‐predator system. Studies of PIT tag deposition were conducted across three bird species nesting at seven different colonies in the Columbia River basin, USA. Tag deposition probabilities differed significantly among predator species (Caspian terns Hydroprogne caspia: deposition probability = 0.71, 95% credible interval [CRI] = 0.51–0.89; double‐crested cormorants Phalacrocorax auritus: 0.51, 95% CRI = 0.34–0.70; California gulls Larus californicus: 0.15, 95% CRI = 0.11–0.21) but showed little variation across trials within a species or across years. Data from a 6‐year study (2008–2013) of PIT‐tagged juvenile Snake River steelhead Oncorhynchus mykiss (listed as threatened under the Endangered Species Act) indicated that colony‐specific predation probabilities ranged from less than 0.01 to 0.17 and varied by predator species, colony location, and year. Integrating the predator‐specific deposition probabilities increased the predation probabilities by a factor of approximately 1.4 for Caspian terns, 2.0 for double‐crested cormorants, and 6.7 for California gulls compared with traditional minimum predation rate methods, which do not account for deposition probabilities. Results supported previous findings on the high predation impacts from strictly piscivorous waterbirds nesting in the Columbia River estuary (i.e., terns and cormorants), but our findings also revealed greater impacts of a generalist predator species (i.e., California gulls) than were previously documented. Approaches used in this study allow for direct comparisons among multiple fish mortality factors and considerably improve the reliability of tag recovery models for estimating predation probabilities in multiple‐predator systems.Received August 1, 2014; accepted November 11, 2014

Lake Use by Three Avian Piscivores and Humans: Implications for Angler Perception and Conservation

Humans and colonial piscivorous birds are often perceived to be in conflict over shared aquatic habitats and fisheries resources in inland lakes. We examined angler perception of birds and the relative abundance of American white pelicans (Pelecanus erythrorhynchos), double-crested cormorants (Phalacrocorax auritus), western grebes (Aechmophorus occidentalis), and boats on two lakes in Saskatchewan, Canada. Anglers perceived cormorants to be the biggest threat to fisheries (60%), compared to pelicans (47%), and western grebes (34%). The density of these birds and boats varied significantly between sections of the two study lakes. Boat density was higher in developed sections with shoreline communities (range 0-7/km2) compared to those surrounded by agricultural land or native prairie (0-1/km2). In contrast, cormorant and pelican densities were highest in areas with an undeveloped shoreline (0-22/km2), and were reduced to near zero in developed sections. Western grebes did not follow the same pattern as the other two species; grebe density was generally more uniform within lakes (0-23/km2 in all sections). Boat density was a negative predictor of pelican and cormorant density on one lake, but was a positive predictor for grebes on both lakes. Our results indicate that pelicans and cormorants avoid sections of lakes that have higher levels of human development, potentially altering the location of their foraging sites on the scale of kilometres. In contrast, western grebes were abundant in all areas of the two lakes and did not appear to avoid human development or activity. We conclude that angler perceptions are not congruent with levels of habitat use overlap with birds. In addition, western grebe responses to human activities appear counterintuitive, making interpretations difficult in a conservation context; further study is required.

Colonial Marine Birds Influence Island Soil Chemistry Through Biotransport of Trace Elements

Marine birds are important vectors of nutrient and contaminant transfer from sea to land. In eastern Nova Scotia, Canada, colonial marine birds nest on specific nearshore islands within archipelagoes, and we predicted that soils on islands with bird colonies would have higher concentrations of selected trace elements (notably K, Ca, As, Cd, Cu, Pb, Se, Hg, and Zn) than soils on islands without colonies. In this study, common eider (Somateria mollissima), Leach’s storm petrel (Oceanodroma leucorhoa), black guillemot (Cepphus grylle), double-crested cormorant (Phalacrocorax auritus), great black-backed gull (Larus marinus), and herring gull (Larus argentatus) were considered to be the principal avian vectors for contaminant transfer. Results indicate that soils from islands with bird colonies had unique chemical compositions and commonly displayed elevated concentrations of K, Ca, Cu, Se, and Zn when compared to islands without colonies. Thus, marine birds feeding in the nearby marine zone move pollutants and nutrients from the ocean to nesting islands, potentially influencing habitat quality for coastal terrestrial species.

A new species of Drepanocephalus Dietz, 1909 (Digenea: Echinostomatidae) from the double-crested cormorant Phalacrocorax auritus (Lesson) (Aves: Phalacrocoracidae) in North America.

Drepanocephalus auritus n. sp. is described based on specimens from the double-crested cormorant Phalacrocorax auritus (Lesson) in North America. The new species differs from its congeners in its very narrow, elongate body, long uterine field and widely separated testes. Sequences of the nuclear rRNA gene cluster, spanning the 3' end of the nuclear ribosomal 18S rRNA gene, internal transcribed spacer region (ITS1+5.8S gene+ITS2) and partial 28S gene (2,345 bp), were identical in specimens collected from North Dakota, Minnesota and Mississippi, USA. Sequences of the 651 bp long fragment of the mitochondrial cox1 gene exhibited very low intraspecific variability (< 1%). Comparisons of the newly-generated sequences with those available in the GenBank indicate that the sequences from North America published under the name D. spathans Dietz, 1909 in fact represent D. auritus n. sp.

From yellow perch to round goby: A review of double-crested cormorant diet and fish consumption at Three St. Lawrence River Colonies, 1999–2013

The number of double-crested cormorants (Phalacrocorax auritus) in the upper St. Lawrence River has increased markedly since the early 1990s. In 1999, a binational study was initiated to examine the annual diet composition and fish consumption of cormorants at colonies in the upper river. Since 1999, 14,032 cormorant pellets, collected from May through September each year, have been examined from St. Lawrence River colonies to estimate fish consumption and determine temporal and spatial variation in diet. Seasonal variation in diet composition within a colony was low. Prior to 2006 yellow perch was the primary fish consumed by cormorants in the upper St. Lawrence River. Round goby were first observed in cormorant diets in 2003 and by 2006 were the main fish consumed at two of the three colonies. The time interval it took from the first appearance of round goby in the diet at a colony to when goby were the dominant prey species varied by island, ranging from two to five years. Daily fish consumption at each cormorant colony increased significantly from the pre-round goby to post-round goby period. The mean annual biomass of yellow perch consumed decreased significantly during the post-round goby period at the three colonies. Reduced consumption of yellow perch by cormorants may alleviate suspected localized impacts on perch near some of the larger river colonies.

Don&amp;#8217;t shoot the messenger!

Every year brings with it a host of issues and developments that impinge directly or indirectly on the conservation of birds from local to global scales and 2015 was no exception. Most readers will be familiar with the usual list of concerns that collectively describe the threats to birds and other wildlife caused by the emergence of the Anthropocene, or the era that now typifies the impact of humans on all aspects of life on earth. Within this milieu, we find ourselves challenged to conserve the world’s avifauna with an urgency that is unprecedented. In Canada our challenges are compounded, in part, by a perception among many that most factors affecting populations of birds must be happening elsewhere and that we still occupy a land of endless wilderness punctuated by a relatively small human population. The facts of course speak otherwise. At Avian Conservation and Ecology, we see our role primarily as one of providing the best scientifically defensible evidence possible that bears on the conservation of birds in Canada and throughout the world by publishing high-quality, peer-reviewed scientific papers. However, we also try to promote an open dialogue among our readers on current issues and concerns and part of this will be through the publication of guest editorials. The first of these was by Dr. Linda Wires who bravely challenged the practice of massive population reduction practices directed at Double-crested Cormorants (Phalacrocorax auritus) underway in the United States (Wires 2015). We plan to continue this tradition and readers are encouraged to contact the editors with suggestions. Within the realm of avian conservation, two events in 2015 will also be of interest to our readers. The first was the release of a film that featured a number of studies underway largely in Canada and the USA that pertain directly to the conservation of songbirds, and the other was a paper reminding us of the generally inadequate protection of most of the world’s migratory birds. Together, these very different developments serve to underline a new urgency in avian conservation in general, and the need for a paradigm shift in the way we deal with landbird conservation in the Americas in particular.