Underwater hearing in sea ducks with applications for reducing gillnet bycatch through acoustic deterrence.

As diving foragers, sea ducks are vulnerable to underwater anthropogenic activity, including ships, underwater construction, seismic surveys and gillnet fisheries. Bycatch in gillnets is a contributing source of mortality for sea ducks, killing hundreds of thousands of individuals annually. We researched underwater hearing in sea duck species to increase knowledge of underwater avian acoustic sensitivity and to assist with possible development of gillnet bycatch mitigation strategies that include auditory deterrent devices. We used both psychoacoustic and electrophysiological techniques to investigate underwater duck hearing in several species including the long-tailed duck (Clangula hyemalis), surf scoter (Melanitta perspicillata) and common eider (Somateria mollissima). Psychoacoustic results demonstrated that all species tested share a common range of maximum auditory sensitivity of 1.0-3.0 kHz, with the long-tailed ducks and common eiders at the high end of that range (2.96 kHz), and surf scoters at the low end (1.0 kHz). In addition, our electrophysiological results from 4 surf scoters and 2 long-tailed ducks, while only tested at 0.5, 1 and 2 kHz, generally agree with the audiogram shape from our psychoacoustic testing. The results from this study are applicable to the development of effective acoustic deterrent devices or pingers in the 2-3 kHz range to deter sea ducks from anthropogenic threats.

The pathogenesis of a North American H5N2 clade 2.3.4.4 group A highly pathogenic avian influenza virus in surf scoters (Melanitta perspicillata).

BACKGROUND: Aquatic waterfowl, particularly those in the order Anseriformes and Charadriiformes, are the ecological reservoir of avian influenza viruses (AIVs). Dabbling ducks play a recognized role in the maintenance and transmission of AIVs. Furthermore, the pathogenesis of highly pathogenic AIV (HPAIV) in dabbling ducks is well characterized. In contrast, the role of diving ducks in HPAIV maintenance and transmission remains unclear. In this study, the pathogenesis of a North American A/Goose/1/Guangdong/96-lineage clade 2.3.4.4 group A H5N2 HPAIV, A/Northern pintail/Washington/40964/2014, in diving sea ducks (surf scoters, Melanitta perspicillata) was characterized. RESULTS: Intrachoanal inoculation of surf scoters with A/Northern pintail/Washington/40964/2014 (H5N2) HPAIV induced mild transient clinical disease whilst concomitantly shedding high virus titers for up to 10 days post-inoculation (dpi), particularly from the oropharyngeal route. Virus shedding, albeit at low levels, continued to be detected up to 14 dpi. Two aged ducks that succumbed to HPAIV infection had pathological evidence for co-infection with duck enteritis virus, which was confirmed by molecular approaches. Abundant HPAIV antigen was observed in visceral and central nervous system organs and was associated with histopathological lesions. CONCLUSIONS: Collectively, surf scoters, are susceptible to HPAIV infection and excrete high titers of HPAIV from the respiratory and cloacal tracts whilst being asymptomatic. The susceptibility of diving sea ducks to H5 HPAIV highlights the need for additional research and surveillance to further understand the contribution of diving ducks to HPAIV ecology.

Spatially explicit network analysis reveals multi-species annual cycle movement patterns of sea ducks.

Conservation of long-distance migratory species poses unique challenges. Migratory connectivity, that is, the extent to which groupings of individuals at breeding sites are maintained in wintering areas, is frequently used to evaluate population structure and assess use of key habitat areas. However, for species with complex or variable annual cycle movements, this traditional bimodal framework of migratory connectivity may be overly simplistic. Like many other waterfowl, sea ducks often travel to specific pre- and post-breeding sites outside their nesting and wintering areas to prepare for migration by feeding extensively and, in some cases, molting their flight feathers. These additional migrations may play a key role in population structure, but are not included in traditional models of migratory connectivity. Network analysis, which applies graph theory to assess linkages between discrete locations or entities, offers a powerful tool for quantitatively assessing the contributions of different sites used throughout the annual cycle to complex spatial networks. We collected satellite telemetry data on annual cycle movements of 672 individual sea ducks of five species from throughout eastern North America and the Great Lakes. From these data, we constructed a multi-species network model of migratory patterns and site use over the course of breeding, molting, wintering, and migratory staging. Our results highlight inter- and intra-specific differences in the patterns and complexity of annual cycle movement patterns, including the central importance of staging and molting sites in James Bay, the St. Lawrence River, and southern New England to multi-species annual cycle habitat linkages, and highlight the value of Long-tailed Ducks (Calengula haemalis) as an umbrella species to represent the movement patterns of multiple sea duck species. We also discuss potential applications of network migration models to conservation prioritization, identification of population units, and integrating different data streams.

INTRANASAL ADMINISTRATION OF MIDAZOLAM HYDROCHLORIDE IMPROVES SURVIVAL IN FEMALE SURF SCOTERS (MELANITTA PERSPICILLATA) SURGICALLY IMPLANTED WITH INTRACOELOMIC TRANSMITTERS.

The intracoelomic implantation of satellite transmitters is associated with lower survival in surf scoters (Melanitta perspicillata) compared with other species of diving ducks, potentially due to physiologic alterations following physical exertion and stress caused by handling and confinement. The effect of intranasal administration of midazolam hydrochloride on survival of surf scoters surgically implanted with intracelomic transmitters was evaluated. Shortly after their capture in Forestville (QC, Canada) in the fall of 2013, 26 randomly selected adult female surf scoters were administered midazolam hydrochloride (4.6-5.9 mg/kg) intranasally. The same volume of saline (1 mL) was given to another 26 adult female surf scoters as a control group. All birds were surgically implanted with an intracoelomic transmitter equipped with a percutaneous antenna. Transmitters were programmed to transmit 2 hr each day for 30 days after implantation, and mortality was estimated for each group using the telemetry data. The association between the administration of midazolam and survival was assessed while controlling for other factors such as body mass, transmitter-mass-to-body-mass ratio, hematocrit, total solids, and duration of surgery, anesthesia, and confinement. The odds of presumed death in the saline group were 5.3 times higher than in the midazolam group (95% confidence interval: 1.7, 19.0; P = 0.004). The presumed mortality at 30 days for the midazolam group (23%) was lower than for the saline group (61%). No other variable was significantly associated with survival. These results suggest that sedation with midazolam shortly after capture increased the postsurgical survival of female surf scoters surgically implanted with intracoelomic transmitters.

Black Scoter habitat use along the southeastern coast of the United States.

While the Atlantic Coast of the United States and Canada is a major wintering area for sea ducks, knowledge about their wintering habitat use is relatively limited. Black Scoters have a broad wintering distribution and are the only open water species of sea duck that is abundant along the southeastern coast of the United States. Our study identified variables that affected Black Scoter (Melanitta americana) distribution and abundance in the Atlantic Ocean along the southeastern coast of the United States. We used aerial survey data from 2009 to 2012 provided by the United States Fish and Wildlife Service to identify variables that influenced Black Scoter distribution. We used indicator variable selection to evaluate relationships between Black Scoter habitat use and a variety of broad- and fine-scale oceanographic and weather variables. Average time between waves, ocean floor slope, and the interaction of bathymetry and distance to shore had the strongest association with southeastern Black Scoter distribution.

The broader isotopic niche of Long-tailed Duck Clangula hyemalis implies a higher risk of ingesting plastic and non-plastic debris than for other diving seabirds.

This study presents the first data relating to debris ingestion by diving seabirds wintering in the south-eastern Baltic Sea, sets baselines for further studies and presents the first global record of plastic ingestion in Long-tailed Duck (Clangula hyemalis). Three of the six studied seabird species, and 2.1% of all 524 examined individuals collected from fishery bycatch, had ingested marine debris. Frequency of ingestion of Long-tailed Duck, Common Murre (Uria aalge) and Red-throated Loon (Gavia stellata) were 5.0%, 4.5% and 3.0% debris respectively, dominated by plastic objects. Providing detailed information about the studied individuals and the debris, this initiates discussion about diving birds' sensitivity to marine debris - it may depend on the feeding preferences of the birds, expressed as isotopic niches in this paper.

First Evidence of Fatal Usutu Virus Natural Infections in an Anatidae, the Common Scoter (Melanitta nigra).

While fatal infections caused by the Usutu virus appeared to concern only passerines (especially the blackbird) and Strigiformes (especially the great gray owl), we report herein that the virus also naturally causes a fatal disease in an anseriforme species, the common scoter (Melanitta nigra).

Detection of Wellfleet Bay Virus Antibodies in Sea Birds of the Northeastern USA.

Wellfleet Bay virus (WFBV) is a recently described orthomyxovirus isolated from the tissues of Common Eiders (Somateria mollissima) collected during recurrent mortality events on Cape Cod, Massachusetts, US. Coastal Massachusetts is the only location where disease or mortality associated with this virus has been detected in wild birds, and a previous seroprevalence study found a significantly higher frequency of viral exposure in eiders from this location than from other areas sampled in North America. This suggests that coastal Massachusetts is an epicenter of WFBV exposure, but the reason for this is unknown. Opportunistic sampling of sympatric species and testing of banked serum was used to investigate potential host range and spatiotemporal patterns of WFBV exposure. Antibodies were detected in Herring Gulls (Larus argentatus), Ring-billed Gulls (Larus delawarensis), a White-winged Scoter (Melanitta fusca), and a Black Scoter (Melanitta nigra). These findings demonstrate the likely occurrence of fall/winter transmission, expand our understanding of the host range of the virus, and provide further insight into the epidemiology of WFBV in the northeastern US.

Baseline glucocorticoids are drivers of body mass gain in a diving seabird.

Life-history trade-offs are influenced by variation in individual state, with individuals in better condition often completing life-history stages with greater success. Although resource accrual significantly impacts key life-history decisions such as the timing of reproduction, little is known about the underlying mechanisms driving resource accumulation. Baseline corticosterone (CORT, the primary avian glucocorticoid) mediates daily and seasonal energetics, responds to changes in food availability, and has been linked to foraging behavior, making it a strong potential driver of individual variation in resource accrual and deposition. Working with a captive colony of white-winged scoters (Melanitta fusca deglandi), we aimed to causally determine whether variation in baseline CORT drives individual body mass gains mediated through fattening rate (plasma triglycerides corrected for body mass). We implanted individuals with each of three treatment pellets to elevate CORT within a baseline range in a randomized order: control, low dose of CORT, high dose of CORT, then blood sampled and recorded body mass over a two-week period to track changes in baseline CORT, body mass, and fattening rates. The high CORT treatment significantly elevated levels of plasma hormone for a short period of time within the biologically relevant, baseline range for this species, but importantly did not inhibit the function of the HPA (hypothalamic-pituitary-adrenal) axis. Furthermore, an elevation in baseline CORT resulted in a consistent increase in body mass throughout the trial period compared to controls. This is some of the first empirical evidence demonstrating that elevations of baseline CORT within a biologically relevant range have a causal, direct, and positive influence on changes in body mass.