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USGS2010

Pancreatitis in wild zinc-poisoned waterfowl

Four waterfowl were collected in the TriState Mining District (Oklahoma, Kansas and Missouri, USA), an area known to be contaminated with lead, cadmium and zinc (Zn). They were part of a larger group of 20 waterfowl collected to determine the exposure of birds to metal contamination at the site. The four waterfowl (three Branta canadensis, one Anas platyrhynchos) had mild to severe degenerative abnormalities of the exocrine pancreas, as well as tissue (pancreas, liver) concentrations of Zn that were considered toxic. The mildest condition was characterized by generalized atrophy of exocrine cells that exhibited cytoplasmic vacuoles and a relative lack of zymogen. The most severe condition was characterized by acini with distended lumens and hyperplastic exocrine tissue that completely lacked zymogen; these acini were widely separated by immature fibrous tissue. Because the lesions were nearly identical to the lesions reported in chickens and captive waterfowl that had been poisoned with ingested Zn, and because the concentrations of Zn in the pancreas and liver of the four birds were consistent with the concentrations measured in Zn-poisoned birds, we concluded that these waterfowl were poisoned by Zn. This may be the first reported case of zinc poisoning in free-ranging wild birds poisoned by environmental Zn.

Kansas, Missouri, Oklahoma↗

USGS2021

Waterfowl use of wetland habitats informs wetland restoration designs for multi‐species benefits

Extensive global estuarine wetland losses have prompted intensive focus on restoration of these habitats. In California, substantial tracts of freshwater, brackish and tidal wetlands have been lost. Given the anthropogenic footprint of development and urbanization in this region, wetland restoration must rely on conversion of existing habitat types rather than adding new wetlands. These restorations can cause conflicts among stakeholders and species that win or lose depending on identified restoration priorities. Suisun Marsh on the San Francisco Bay Estuary is the largest brackish marsh on the U.S. Pacific coast. To understand how conversion of brackish managed wetlands to tidal marsh would impact waterfowl populations and whether future tidal marsh restorations could provide suitable habitat for dabbling ducks, we examined waterfowl wetland use with a robust GPS‐GSM tracking dataset (442,017 locations) from six dabbling duck species (N=315). Managed wetlands, which comprise 47% of Suisun Marsh, were consistently and strongly selected by waterfowl over tidal marshes, with use ~98% across seasons and species. However, while use of tidal marsh (only 14% of Suisun Marsh) was generally <2%, almost half our ducks (~44%) spent some time in this habitat and exhibited strong utilization of pond‐like features. Ponds only comprise ~10% of this habitat but attracted 44% use (~4.5 times greater than availability). Synthesis and applications : Managed wetlands were vital to dabbling ducks, but losses from conversion of these habitats may be partially mitigated by incorporating pond features that are more attractive to waterfowl, and likely to offer multi‐species benefits, into tidal marsh restoration designs. While waterfowl are presently a common taxon, previously seen calamitous population declines can be avoided through informed ecosystem‐based management that promotes species richness, biodiversity and helps “keep common species common”.

California↗

USGS2026

Waterfowl move less in heterogeneous and human-populated landscapes, with implications for spread of avian influenza viruses

Animal movements contribute to the spread of infectious diseases and are driven in part by environmental conditions. We investigated the links among the environment, animal movement, and infectious disease dynamics in waterfowl, which are among the primary wildlife hosts of avian influenza viruses. By combining telemetry data on 4606 individuals from 26 waterfowl species with data on land cover, weather, and vegetation, we found that waterfowl moved less in areas of higher land cover heterogeneity and higher human population density. Moreover, predicted waterfowl movement distances were weakly but positively correlated with distances between detections of H5N1 highly pathogenic avian influenza in wild waterfowl, suggesting that environmental conditions might contribute to the spread of this disease via their effects on bird movements. By considering wildlife movements alongside other drivers of infectious disease dynamics, such as livestock production and human mobility, we move closer to predicting outbreaks and informing interventions.

Ecology Letters↗

USGS2012

Presence of avian influenza viruses in waterfowl and wetlands during summer 2010 in California: Are resident birds a potential reservoir?

Although wild waterfowl are the main reservoir for low pathogenic avian influenza viruses (LPAIv), the environment plays a critical role for the circulation and persistence of AIv. LPAIv may persist for extended periods in cold environments, suggesting that waterfowl breeding areas in the northern hemisphere may be an important reservoir for AIv in contrast to the warmer southern wintering areas. We evaluated whether southern wetlands, with relatively small populations (thousands) of resident waterfowl, maintain AIv in the summer, prior to the arrival of millions of migratory birds. We collected water and fecal samples at ten wetlands in two regions (Yolo Bypass and Sacramento Valley) of the California Central Valley during three bi-weekly intervals beginning in late July, 2010. We detected AIv in 29/367 fecal samples (7.9%) and 12/597 water samples (2.0%) by matrix real time Reverse Transcription Polymerase Chain Reaction (rRT-PCR). We isolated two H3N8, two H2N3, and one H4N8 among rRT-PCR positive fecal samples but no live virus from water samples. Detection of AIv RNA in fecal samples was higher from wetlands in the Sacramento Valley (11.9%) than in the Yolo Bypass (0.0%), but no difference was found for water samples (2.7 vs. 1.7%, respectively). Our study showed that low densities of hosts and unfavorable environmental conditions did not prevent LPAIv circulation during summer in California wetlands. Our findings justify further investigations to understand AIv dynamics in resident waterfowl populations, compare AIv subtypes between migratory and resident waterfowl, and assess the importance of local AIv as a source of infection for migratory birds.

California↗

USGS2012

Mapping wintering waterfowl distributions using weather surveillance radar

The current network of weather surveillance radars within the United States readily detects flying birds and has proven to be a useful remote-sensing tool for ornithological study. Radar reflectivity measures serve as an index to bird density and have been used to quantitatively map landbird distributions during migratory stopover by sampling birds aloft at the onset of nocturnal migratory flights. Our objective was to further develop and validate a similar approach for mapping wintering waterfowl distributions using weather surveillance radar observations at the onset of evening flights. We evaluated data from the Sacramento, CA radar (KDAX) during winters 1998–1999 and 1999–2000. We determined an optimal sampling time by evaluating the accuracy and precision of radar observations at different times during the onset of evening flight relative to observed diurnal distributions of radio-marked birds on the ground. The mean time of evening flight initiation occurred 23 min after sunset with the strongest correlations between reflectivity and waterfowl density on the ground occurring almost immediately after flight initiation. Radar measures became more spatially homogeneous as evening flight progressed because birds dispersed from their departure locations. Radars effectively detected birds to a mean maximum range of 83 km during the first 20 min of evening flight. Using a sun elevation angle of -5° (28 min after sunset) as our optimal sampling time, we validated our approach using KDAX data and additional data from the Beale Air Force Base, CA (KBBX) radar during winter 1998–1999. Bias-adjusted radar reflectivity of waterfowl aloft was positively related to the observed diurnal density of radio-marked waterfowl locations on the ground. Thus, weather radars provide accurate measures of relative wintering waterfowl density that can be used to comprehensively map their distributions over large spatial extents.

PLoS ONE↗

USGS2014

Genomic characterization of H14 subtype influenza A viruses in New World waterfowl and experimental infectivity in mallards Anas platyrhynchos

Recent repeated isolation of H14 hemagglutinin subtype influenza A viruses (IAVs) in the New World waterfowl provides evidence to suggest that host and/or geographic ranges for viruses of this subtype may be expanding. In this study, we used genomic analyses to gain inference on the origin and evolution of H14 viruses in New World waterfowl and conducted an experimental challenge study in mallards ( Anas platyrhynchos ) to evaluate pathogenicity, viral replication, and transmissibility of a representative viral strain in a natural host species. Genomic characterization of H14 subtype IAVs isolated from New World waterfowl, including three isolates sequenced specifically for this study, revealed high nucleotide identity among individual gene segments (e.g. ≥95% shared identity among H14 HA gene segments). In contrast, lower shared identity was observed among internal gene segments. Furthermore, multiple neuraminidase subtypes were observed for H14 IAVs isolated in the New World. Gene segments of H14 viruses isolated after 2010 shared ancestral genetic lineages with IAVs isolated from wild birds throughout North America. Thus, genomic characterization provided evidence for viral evolution in New World waterfowl through genetic drift and genetic shift since purported introduction from Eurasia. In the challenge study, no clinical disease or lesions were observed among mallards experimentally inoculated with A/blue-winged teal/Texas/AI13-1028/2013(H14N5) or exposed via contact with infected birds. Titers of viral shedding for mallards challenged with the H14N5 IAV were highest at two days post-inoculation (DPI); however shedding was detected up to nine DPI using cloacal swabs. The distribution of viral antigen among mallards infected with H14N5 IAV was largely restricted to enterocytes lining the villi in the lower intestinal tract and in the epithelium of the bursa of Fabricius. Characterization of the infectivity of A/blue-winged teal/Texas/AI13-1028/2013(H14N5) in mallards provides support for similarities in viral replication and shedding as compared to previously described waterfowl-adapted, low pathogenic IAV strains in ducks.

PLoS ONE↗

USGS2025

Flooded wetland availability for breeding waterfowl in a Mediterranean climate: Mapping 38 years of historical data in Suisun Marsh, California

Most managed wetlands in California are ephemeral and are purposefully flooded during the fall and winter for over-wintering waterfowl and are dry during the spring and summer waterfowl breeding season. Only semi-permanent and permanent wetlands remain flooded through the critical summer brood-rearing period for ducklings. We examined flooded wetland availability for breeding waterfowl in the brackish Suisun Marsh (California, USA) annually during the spring (April 27–May 17, during peak nesting) and summer (June 17–July 7, during peak duckling brood rearing), for a 38-year period using Landsat satellite imagery and spectral mixture analysis. Flooded wetland area increased 43% in spring and 48% in summer from 1984 to 2021 but varied among years (spring: 37.6–88.6 km 2 ; summer: 17.7–57.5 km 2 ). This increase in flooded wetland area over the past four decades was due to just a few sites, with only 24% (spring) and 15% (summer) of the 198 land-owner parcels increasing in flooded area. Flooded wetland area in the spring was unrelated to annual precipitation between October and April (range: 25–104 cm) or spring precipitation between January and April (range: 8-65 cm), whereas flooded wetland area in the summer was weakly correlated to both annual and spring precipitation. Flooded wetland area in spring and summer was also weakly correlated with the median daily outflow from the Sacramento-San Joaquin River Delta between March 15 and June 15, which corresponds to a critical period of wetland water management for breeding waterfowl. Our results indicate that spring and summer flooded wetland habitat for breeding waterfowl has slightly increased over the past four decades, varies annually, and is mostly dependent on local wetland management practices rather than on precipitation or Delta outflows. Managing habitats as semi-permanent wetlands would increase flooded wetland habitat in the spring and summer and provide habitat for nesting hens and ducklings.

California↗

USGS2003

A voluntary program to curtail boat disturbance to waterfowl during migration

A voluntary waterfowl avoidance area (VWAA) was established on Lake Onalaska in Navigation Pool 7 of the Upper Mississippi River, Wisconsin, USA, in 1986, to reduce boating disturbance to migratory waterfowl. We monitored boater compliance with the VWAA program in 1993 and 1997. Of 1,664 "boating events" observed on Lake Onalaska, boats intruded into the VWAA on 127 occasions. Boating events have increased from 1.82 boating events/h in 1986-88 to 1.97 in 1993 and 2.58 in 1997. Despite a 60% increase in boating traffic, the lake-wide disturbance rates in 1997 were comparable to that in 1981. We attribute this to a significant reduction in the proportion of lake-wide boating events that resulted in disturbance, a direct consequence of the VWAA program. Rate of intrusion into the VWAA was 0.11 per boating event in 1997 compared to 0.18 per boating event in 1986-88. Boating disturbances to waterfowl within the VWAA occurred at about half the rate (0.24 to 0.28 disturbances∙hr -1 ) observed prior to establishment of the program (0.48 disturbances∙hr -1 ). We also identified access points used by boaters and boating activities that were most likely to result in intrusion into the VWAA and associated disturbance to waterfowl. Results of these analyses have provided useful information to resource managers for targeting public education efforts. The VWAA program has contributed to the value of Lake Onalaska as a waterfowl refuge and demonstrates an effective collaboration among government agencies and non-governmental organizations.

Wisconsin↗

USGS2008

Sediment ingestion rates in waterfowl (Anatidae) and their use in environmental risk assessment

When waterfowl (Anatidae) ingest sediment as they feed, they are exposed to the environmental contaminants in those sediments. The rate of ingestion may be key to assessing environmental risk. Rates of sediment ingestion were estimated as from <2% to 22% in 16 species of waterfowl collected in the northeastern United States. The piscivorous red-breasted merganser ( Mergus serrator ) ingested sediment at the lowest rate and the benthos-feeding canvasback ( Aythya valisineria ) at the highest rate. Sediment ingestion rates were related to diet and to the sediments where waterfowl fed. Waterfowl ingested the least sediment from hard-bottomed habitats with fast-moving water and ingested the most sediment from soft-bottomed areas with slow-moving water. Understanding the greater hazards from contaminants associated with low-flow habitats may help in prioritizing sites to be remediated. The tundra swan ( Cygnus columbianus ), which ingests sediment at an estimated 8.4% of its diet, dry weight, is suggested as a potential generic model for use in environmental risk assessments designed to protect waterfowl.

Integrated Environmental Assessment and Management↗

USGS1988

Post-epizootic surveys of waterfowl for duck plague (duck virus enteritis)

Surviving birds from nine duck plague outbreaks in urban and confined waterfowl were sampled for duck plague (DP) virus and DP antibody during 1979-86. Duck plague virus was found in combined oral and cloacal swabs of birds from three outbreaks, and DP-neutralizing antibody was demonstrated in some birds from all nine outbreaks. Greater prevalence of DP antibody and higher titers were found in survivors from confined populations than from free-flying urban populations. Free-flying waterfowl from within 52 km of four DP outbreak sites were also sampled; virus was not found in any birds, but DP antibody was found in urban waterfowl in the vicinity of an outbreak in Potterville, Michigan. No evidence of exposure to or shedding of DP virus in migratory waterfowl was found in two regions where DP appears enzootic in urban and confined waterfowl (Eastern Shore of Maryland and the vicinity of Sacramento, California).

Avian Diseases↗

USGS2000

Diagnosis of duck plague in waterfowl by polymerase chain reaction

A recently developed polymerase chain reaction (PCR) assay was used for diagnosis of duck plague in waterfowl tissues from past and current cases of waterfowl mortality and to identify duck plague virus in combined cloacal/oral-pharyngeal swab samples from healthy mallards (Anas platyrhynchos) after a disease outbreak. The PCR was able to detect viral DNA from all the individual or pooled tissues assayed from 10 waterfowl, including liver and spleen samples from three Muscovy ducks (Cairina moschata domesticus) that did not yield virus isolates. The strong staining intensity of the PCR products from the waterfowl tissues indicated that large amounts of virus were present, even when virus was not isolated. Duck plague DNA was also detected in a cloacal swab sample from a wood duck (Aix sponsa) carcass submitted for diagnosis. The PCR assay identified duck plague DNA in 13 swab samples that produced virus isolates from carrier mallards sampled in 1981 after a duck plague die-off. The duck plague PCR clearly demonstrated the ability to quickly diagnose duck plague in suspect mortality cases and to detect virus shed by carrier waterfowl.

Avian Diseases↗

USGS1979

The composite dynamic method as evidence for age-specific waterfowl mortality

For the past 25 years estimation of mortality rates for waterfowl has been based almost entirely on the composite dynamic life table. We examined the specific assumptions for this method and derived a valid goodness of fit test. We performed this test on 45 data sets representing a cross section of banded sampled for various waterfowl species, geographic areas, banding periods, and age/sex classes. We found that: (1) the composite dynamic method was rejected (P <0.001) in 37 of the 45 data sets (in fact, 29 were rejected at P <0.00001) and (2) recovery and harvest rates are year-specific (a critical violation of the necessary assumptions). We conclude that the restrictive assumptions required for the composite dynamic method to produce valid estimates of mortality rates are not met in waterfowl data. Also we demonstrate that even when the required assumptions are met, the method produces very biased estimates of age-specific mortality rates. We believe the composite dynamic method should not be used in the analysis of waterfowl banding data. Furthermore, the composite dynamic method does not provide valid evidence for age-specific mortality rates in waterfowl.

Journal of Wildlife Management↗

USGS1984

A survey of North American migratory waterfowl for duck plague (duck virus enteritis) virus

A survey of migratory waterfowl for duck plague (DP) virus was conducted in the Mississippi and Central flyways during 1982 and in the Atlantic and Pacific flyways during 1983. Cloacal and pharyngeal swabs were collected from 3,169 migratory waterfowl in these four flyways, principally mallards ( Anas platyrhynchos L.), black ducks ( Anas rubripes Brewster), and pintails ( Anas acuta L). In addition 1,033 birds were sampled from areas of recurrent DP outbreaks among nonmigratory and captive waterfowl, and 590 from Lake Andes National Wildlife Refuge, the site of the only known major DP outbreak in migratory waterfowl. Duck plague virus was not found in any of the samples. Results support the hypothesis that DP is not established in North American migratory waterfowl as an enzootic disease.

Pacific, Central, Mississippi, and Atlantic Flyway↗

USGS1999

Waterfowl density on agricultural fields managed to retain water in winter

Managed water on private and public land provides habitat for wintering waterfowl in the Mississippi Valley, where flood control projects have reduced the area of natural flooding. We compared waterfowl densities on rice, soybean, and moist-soil fields under cooperative agreements to retain water from 1 November through 28 February in Arkansas and Mississippi and assessed temporal changes in waterfowl density during winter in 1991-1992 and 1992-1993. Fields flooded earlier in Arkansas, but retained water later in Mississippi. Over winter, waterfowl densities decreased in Arkansas and increased in Mississippi. Densities of waterfowl, including mallard (Anas platyrhynchos), the most abundant species observed, were greatest on moist-soil fields. However, soybean fields had the greatest densities of northern shoveler (Spatula clypeata).

Wildlife Society Bulletin↗

USGS2005

Post-harvest field manipulations to conserve waste rice for waterfowl

Rice seeds escaping collection by combines during harvest (hereafter, waste rice) provide quality forage for migrating and wintering waterfowl in the Lower Mississippi Alluvial Valley (MAV) and other rice growing regions in the United States. Recent sample surveys across the MAV have revealed abundance of waste rice in fields declined an average of 71% between harvest and late autumn. Thus, we evaluated the ability of common post-harvest, field-management practices to conserve waste rice for waterfowl until early winter via controlled experiments in Mississippi rice test plots in 2001 and 2003 and analyses of data from MAV-wide surveys of waste rice in rice production fields in 2000-2002. Our experiments indicated test plots with burned rice stubble that were not flooded during autumn contained more waste rice than other treatments in 2001 (P?0.10). Waste-rice abundance in test plots did not differ among postharvest treatments in 2003 (P = 0.97). Our analyses of data from the MAV sample surveys did not detect differences in abundance of waste rice among fields burned, rolled, disked, or left in standing stubble post-harvest (P?0.04; Bonferroni corrected critical ( a= 0.017). Because results from test-plot experiments were inconclusive, we based our primary inference regarding best post-harvest treatments on patterns of rice abundance identified from the MAV surveys and previously documented environmental and agronomic benefits of managing harvested rice fields for wintering waterfowl. Therefore, we recommend leaving standing stubble in rice fields after harvest as a preliminary beneficial management practice. We suggest future research evaluate potential of postharvest practices to conserve waste rice for waterfowl and reduce straw in production rice fields managed for wintering waterfowl throughout the MAV.

Proceedings of the Annual Conference of the Southe↗

USGS2003

A voluntary program to curtail boat disturbance to waterfowl during migration

A voluntary waterfowl avoidance area (VWAA) was established on Lake Onalaska in Navigation Pool 7 of the Upper Mississippi River, Wisconsin, USA, in 1986, to reduce boating disturbance to migratory waterfowl. We monitored boater compliance with the VWAA program in 1993 and 1997. Of 1,664 "boating events" observed on Lake Onalaska, boats intruded into the VWAA on 127 occasions. Boating events have increased from 1.82 boating events/h in 1986-88 to 1.97 in 1993 and 2.58 in 1997. Despite a 60% increase in boating traffic, the lake-wide disturbance rates in 1997 were comparable to that in 1981. We attribute this to a significant reduction in the proportion of lake-wide boating events that resulted in disturbance, a direct consequence of the VWAA program. Rate of intrusion into the VWAA was 0.11 per boating event in 1997 compared to 0.18 per boating event in 1986-88. Boating disturbances to waterfowl within the VWAA occurred at about half the rate (0.24 to 0.28 disturbances ?? hr1) observed prior to establishment of the program (0.48 disturbances ?? hr1 . We also identified access points used by boaters and boating activities that were most likely to result in intrusion into the VWAA and associated disturbance to waterfowl. Results of these analyses have provided useful information to resource managers for targeting public education efforts. The VWAA program has contributed to the value of Lake Onalaska as a waterfowl refuge and demonstrates an effective collaboration among government agencies and non-governmental organizations.

Waterbirds↗

USGS2014

The effects of harvest on waterfowl populations

Change in the size of populations over space and time is, arguably, the motivation for much of pure and applied ecological research. The fundamental model for the dynamics of any population is straightforward: the net change in the abundance is the simple difference between the number of individuals entering the population and the number leaving the population, either or both of which may change in response to factors intrinsic and extrinsic to the population. While harvest of individuals from a population constitutes a clear extrinsic source of removal of individuals, the response of populations to harvest is frequently complex, reflecting an interaction of harvest with one or more population processes. Here we consider the role of these interactions, and factors influencing them, on the effective harvest management of waterfowl populations. We review historical ideas concerning harvest and discuss the relationship(s) between waterfowl life histories and the development and application of population models to inform harvest management. The influence of population structure (age, spatial) on derivation of optimal harvest strategies (with and without explicit consideration of various sources of uncertainty) is considered. In addition to population structure, we discuss how the optimal harvest strategy may be influenced by: 1) patterns of density-dependence in one or more vital rates, and 2) heterogeneity in vital rates among individuals within an age-sex-size class. Although derivation of the optimal harvest strategy for simple population models (with or without structure) is generally straightforward, there are several potential difficulties in application. In particular, uncertainty concerning the population structure at the time of harvest, and the ability to regulate the structure of the harvest itself, are significant complications. We therefore review the evidence of effects of harvest on waterfowl populations. Some of this evidence has focussed on correspondence of data with more phenomenological models and other evidence relates to specific mechanisms, including densitydependence and heterogeneity. An important part of this evidence is found in the evolution of model weights under various adaptive harvest management programmes of the U.S. Fish and Wildlife Service for North American waterfowl. Overall, there is substantial uncertainty about system dynamics, about the impacts of potential management and conservation decisions on those dynamics, and how to optimise management decisions in the presence of such uncertainties. Such relationships are unlikely to be stationary over space or time, and selective harvest of some individuals can potentially alter life history allocation of resources over time – both of which will potentially influence optimal harvest strategies. These sources of variation and uncertainty argue for the use of adaptive approaches to waterfowl harvest management.

Wildfowl↗

USGS1978

Use of Landsat data to assess waterfowl habitat quality

This report is a discussion of the feasibility of using Landsat data to generate information of value for effective management of migratory waterfowl. Effective management of waterfowl includes regulating waterfowl populations through hunting regulations and habitat management. This report examines the ability to analyze annual production by monitoring the number of breeding and brood ponds that are present, and the ability to assess waterfowl habitat based on the various relationships between ponds and the surrounding upland terrain types. The basic conclusions of this report are that: 1) Landsat data can be used to improve estimates of pond numbers which may be correlated with duck production; and 2) Landsat data can be used to generate information on terrain types which subsequently can be used to assess relative waterfowl habitat quality.

Report↗