Mottled Ducks Research Articles

Role of Nonmigratory Mottled Ducks (Anas fulvigula) as Sentinels for Avian Influenza Surveillance

The objective of this study was to evaluate the mottled duck (Anas fulvigula), a nonmigratory dabbling duck, as a sentinel species for avian influenza virus (AIV) surveillance. A total of 235 cloacal swabs from 147 live-captured and 88 hunter-harvested mottled ducks during summer (June-August 2007) and winter (November 2007 to January 2008), respectively, were collected along the upper Texas coast. Samples were screened for AIV using real-time reverse transcription polymerase chain reaction (rRT-PCR); all rRT-PCR-positive samples were processed for virus isolation. Three samples were positive for AIV by AIV-matrix rRT-PCR. One of these samples also was positive for H5 by rRT-PCR, and a low pathogenic H5N2 AIV was isolated. Although isolation of AIVs from mottled ducks during the winter has been reported previously, to the authors' knowledge, this is the first H5 isolate from mottled ducks. Interestingly, this isolation was made during the same season that other H5N2 viruses were obtained from migratory waterfowl on the Texas coast, which suggests AIV transmission among waterfowl on the wintering grounds and the potential role of mottled ducks as a naturally occurring sentinel species for AIV surveillance.

An Extralimital Record of a Louisiana-Banded Mottled Duck Recovered in South Dakota

Anas fulvigula (Mottled Duck) primarily occupy coastal marshes along the western Gulf of Mexico and Florida. Previous extralimital records of Mottled Ducks have been recorded in Great Plains states and in some states along the Atlantic Coast. We report on a female Mottled Duck that was banded in 2007 on Rockefeller Wildlife Refuge (Cameron Parish, LA) and harvested near Alpena, SD (Sanborn County). This minimum movement of 1680 km is highly unusual in a species where individuals rarely stray more than 160 km from the coast. Among recent and reliably documented reports (since 1980), this observation represents the northernmost documented record for this species. We presume that this individual migrated north with wintering Anas platyrhynchos (Mallard) it associated with in coastal Louisiana.

Characteristics of Ponds Used by Breeding Mottled Ducks on the Chenier Plain of the Texas Gulf Coast

Abstract Mottled ducks Anas fulvigula are nonmigratory and primarily depend on habitats associated with coastal marshes of the Gulf Coast for their entire life cycle. Much of remaining available coastal marsh habitats of the Texas Gulf Coast are managed by state and federal agencies. The Texas Gulf Coast breeding population of mottled ducks has recently declined dramatically. To aid in development of management plans for breeding mottled ducks, we estimated the number of potential pair ponds available on the Texas Chenier Plain National Wildlife Refuge Complex relative to marsh type (fresh, intermediate, brackish, and saline), estimated occupancy, compared habitats of used and unused pair ponds, and evaluated pair pond selection relative to marsh type during spring 2004 and 2005. Greater than 18,000 ponds were recorded in >22,400 ha of coastal marsh with >74% of potential pair ponds in the intermediate marsh type. Average pond size of 425 randomly selected ponds across marsh types was 0.09 ha. Pond occupancy was estimated as 1.3% and 2.5% in 2004 and 2005, respectively, in 634 ponds surveyed for presence of mottled duck pairs. Mottled ducks selected for ponds in fresh marsh with short surrounding vegetation associated with recent cattle grazing, but avoided recently (<3 mo prior) burned areas. Pond area was greater with shallower water depth for used compared to unused ponds. The presence and coverage of submergent and emergent vegetation did not influence use of pair ponds by mottled ducks. Development of breeding habitat (pair ponds, nesting cover, brood habitat) in fresh marsh will benefit mottled ducks. Our results indicate development of breeding habitat on the Texas Gulf Coast, and vegetation management using cattle grazing timed for disturbance in fresh marsh during mid- to late winter and early spring will further attract breeding mottled ducks.

Waterbird Nest Density and Nest Survival in Rice Fields of Southwestern Louisiana

Rice fields in southwestern Louisiana provide breeding habitat for several waterbird species; however, little is known about nest density, nest survival and the importance of landscape context of rice fields in determining breeding activity. In 2004, 42 rice fields were searched for nests, and 40 were searched in 2005. Land uses surrounding rice fields, including irrigation canals, trees, crawfish ponds, rice, fallow and soybean fields, were examined to determine influence on nest density and survival. Nest densities were 13.5–16.0 nests/km2 for Purple Gallinules (Porphyrio maitinica), 3.0–13.7 nests/km2 for Fulvous Whistling Ducks (Dendrocygna bicoloi), 2.6–2.8 nests/km2 for Common Moorhens (Gallinula chloropus), 0.3–0.92 nests/km2 for Least Bitterns (Ixobiychus exilisi) and 0–0.6 nests/km2 for Mottled Ducks (Anas fulvigula). Nest survival was 52–79% for Purple Gallinules and 39–43% for Fulvous Whistling Ducks. Apparent nest success of Common Moorhens was 73–75%, 83% for Least Bitterns and 33% for Mottled Ducks. Purple Gallinule and Common Moorhen nest densities were highest in fields with a larger proportion of irrigation canals surrounding rice fields. Purple Gallinule nest densities were greater in fields devoid of trees and landscapes dominated by rice fields and pasture, rather than landscapes containing soybean fields and residential areas. Fulvous Whistling Duck nest densities were higher in agriculturally-dominated landscapes with few trees.

Survival and Cause-Specific Mortality of Adult Female Mottled Ducks in East-Central Florida

Abstract An understanding of survival and underlying causes of mortality is essential to the development of effective management strategies for the mottled duck (Anas fulvigula) in Florida. From radiotelemetry data we estimated season-specific survival rates for the entire annual cycle, cause-specific mortality rates, and annual survival rates. We also tested for variation in survival in relation to year and period of the annual cycle. Our results suggest a strong temporal influence on survival of adult female mottled ducks, both within and among years. We found variation among years in the influence of various mortality agents, with alligators (Alligator mississippiensis), raptors, mammals, and human hunters being the principal mortality factors. Our results also suggest a link between surface water conditions within the Upper St. Johns River Basin (USJRB) and surrounding areas and survival. Agencies managing water and wildlife should be aware of this relationship and consider potential detrimental effec...

Breeding Biology of Mottled Ducks on Agricultural Lands in Southwestern Louisiana

Breeding biology of Anas fulvigula maculosa (Mottled Ducks) has been described in coastal marsh and associated habitats, but little information is available for agricultural habitats in Louisiana. We located nests to determine nest-initiation dates and clutch sizes during the primary breeding season (February-May) in 1999 (n = 29) and 2000 (n = 37) on agricultural lands in southwestern Louisiana. In 1999, 60% of located nests were initiated between 22 March and 10 April, whereas in 2000, only 22% of nests were initiated during the same time period. Average clutch size was 0.9 eggs smaller in 2000 than in 1999. Annual differences in reproductive parameters corresponded with extremely dry conditions caused by low rainfall be- fore the laying period in 2000. Flooded rice fields appear to be important loafing and feeding habitat of Mottled Ducks nesting in agricultural lands, especially during drought periods when other wetland types are not available or where natural wetlands have been eliminated.

Regional differences and long-term trends in lead exposure in mottled ducks

We compared lead shot ingestion rates and bone lead levels in mottled ducks (Anas fulvigula maculosa) for regional differences and evaluated 16 years of lead shot ingestion data for evidence of decline. Gizzards (n=6,850) of hunter-killed mottled duck were collected from 1987–2002. The mean lead shot ingestion rate of mottled ducks from the Central Texas Coast and Upper Texas Coast was 7.32%±1.13% (SE) and 18.09%±1.55%, respectively. Lead shot ingestion rates declined gradually during the study period (P= 0.046). During the 1998–1999 hunting season, we examined lead concentrations in wing bones of 148 hunter-killed mottled ducks from the Central Texas, Upper Texas, and Southwest Louisiana coastal regions. Lead concentrations averaged 16.62 ppm±1.83 (SE) and did not differ among regions or age groups. Both lead shot ingestion rates and bone lead concentrations in mottled ducks remain high. Studies evaluating the effects of lead levels on mottled duck survival are needed.

Abundance and Community Composition of Waterbirds Using the Channelized Kissimmee River Floodplain, FL

We conducted aerial surveys during 1996–1998 to estimate abundance and species composition of waterbirds using the channelized Kissimmee River to help understand how river channelization has altered bird use. For waterfowl, mean monthly species richness was 1.5 ± 0.3 (mean ± SE, n = 11 surveys); mean monthly abundance was 86 ± 43, 191 ± 70, and 13 ± 16 birds in 1996–97, 1997–98, and 1998–99, respectively. Blue-winged Teal (Anas discors Linnaeus) were the most abundant duck (74%) followed by Mottled Ducks (Anas fulvigula Ridgway, 21%). Mean wading bird species richness was 8.48 ± 0.35 (n = 20 surveys). Cattle Egret (Bubulcus ibis Linnaeus) were the most abundant wading bird species during the wet season (64 ± 22% of individuals); White Ibis (Eudocimus albus Linnaeus) were most common during the dry season (39 ± 23%). Mean total wading bird abundance was greater during the wet than dry season (F1,15 = 6.29; P = 0.02), with the increase driven by increases in Cattle Egret (F1,15 = 5.46, P = 0.03) and large-prey visual foragers (F1,15 = 5.47, P = 0.03). Compared to the 1950s, waterfowl species richness has declined 70% and abundance has declined 95%. For wading birds, mixed species breeding colonies no longer occur in the floodplain, and the community composition is dominated by the largely terrestrial foraging Cattle Egret during the wet season.

Avian Influenza Viruses and Paramyxoviruses in Wintering and Resident Ducks in Texas

Cloacal swabs were collected from teal (Anas crecca, Anas cyanoptera, Anas discors), mottled duck (Anas fulvigula) and northern pintail (Anas acuta) in Brazoria County, Texas, USA, during February 2001, mottled ducks during August 2001, and blue-winged teal (A. discors) during February 2002. Prevalence of avian influenza virus (AIV) infections during each sampling period were 11, 0, and 15%, respectively. The hemagglutinin (H) subtypes H2 and H7 were detected in both years, while the H8 subtype was detected in 2001 and the H1 subtype was detected in 2002. Avian paramyxovirus type 1 (APMV-1) was isolated from 13% of mottled ducks sampled in August 2001 and 30.7% of teal in February 2002. The season of isolation of both viruses and the majority of the AIV subtypes detected in this study are not typical based on previous reports of these viruses from North American ducks.

A Comparison of Hybridization between Mottled Ducks (Anas fulvigula)and Mallards (A. platyrhynchos) in Florida and South Carolina using Microsatellite DNA Analysis

Interspecific hybridization has been implicated in population declines for some waterfowl species within the mallard complex, and hybridization with mallards (Anas platyrhynchos) is currently considered the largest threat to mottled ducks (A. fulvigula), one North American member of that complex. We assessed genetic variation among 225 mottled ducks and mallards using five microsatellite loci, and detected significant overall differences between these species within two geographic areas. We characterized hybridization in Florida, where mottled ducks are endemic and mallards are beginning to appear on the breeding grounds, and in South Carolina, where mottled ducks were introduced outside their native range. We used Bayesian genetic mixture analysis in an attempt to distinguish between these closely related species. In Florida, we detected two distinct genetic groups, and 10.9% of our samples from Florida mottled ducks were inferred to have been hybrids. In contrast only 3.4% of Florida mallards were inferred to have been hybrids, suggesting asymmetric hybridization. Populations from different geographic areas within Florida exhibited hybridization rates ranging from 0% to 24%. These data indicate a genetic component would be appropriate in actively managing interspecific hybridization in Florida mottled ducks. In contrast, South Carolina mottled ducks and mallards cannot be differentiated.

EVALUATION OF ALLOZYME AND MICROSATELLITE VARIATION IN TEXAS AND FLORIDA MOTTLED DUCKS

Abstract Genetic variation was evaluated in Florida Mottled Ducks (Anas fulvigula), and Mottled Ducks from the larger Texas population using 22 allozyme and 5 microsatellite loci. Both marker types revealed differences in allele frequencies between populations and each population possessed rare and unique alleles. Overall allelic distributions were significantly different between the two populations, primarily due to significant differences at three allozyme and four microsatellite loci. Significant genetic differentiation was revealed between populations with both marker types, however, over all loci, only 5–6% of the variation detected was partitioned between populations. The Florida population possessed lower levels of allozyme heterozygosity and allelic diversity than the Texas population. In contrast, microsatellite heterozygosities and allelic diversity were similar between populations. These data indicate that there is limited gene flow between populations, suggesting that populations should contin...

The American Alligator as a Predator of Mottled Ducks

Mottled Ducks (Anas fulvigula) are widely distributed in southeastern coastal marshes, as are American Alligators (Alligator mississippiensis). Although the alligator has been noted to prey upon Mottled Ducks, evidence of Mottled Duck consumption is rare in numerous studies of alligator food habits. This may be due to the season and habitat from which alligators were collected for evaluation (often autumn samples from deep water habitats preferred by adult alligators). We examined stomach contents of alligators in summer (when Mottled Duck broods and molting adults are flightless) from shallow water habitats preferred by Mottled Ducks. Mottled Duck remains were found in 20.9% of 43 alligator stomachs examined, far more than the highest frequency occurrence previously reported (1.27%). Unexpectedly, three relatively small alligators (1.51–1.70 m total length) consumed Mottled Ducks and the sixteen largest alligators did not. This study underscores the importance of season and location of collections when evaluating stomach content data.

Microsatellite Polymorphism and Genetic Structure of Florida Mottled Duck Populations

Abstract Little is understood concerning the effects regional isolation and habitat loss have had upon the genetic structure of Mottled Ducks (Anas fulvigula), a nonmigratory waterfowl species with a limited distribution. Our objective was to identify nuclear DNA-based markers for Mottled Ducks and determine levels of subdivision among populations in Florida. We screened 13 microsatellite primer pairs and identified six microsatellite loci that were variable in Mottled Ducks. These markers revealed a low level of genetic differentiation and a high level of genetic exchange among four Mottled Duck subpopulations within Florida. Over all populations, single-locus expected heterozygosities over the six loci surveyed ranged from 0.13–0.85. There were no significant differences in gene frequencies among the populations examined, and the Fst over 5 biparental loci was not different from zero. Our analysis of the Florida Mottled Duck population indicated high levels of heterozygosity and no evidence of genetic subdivision among breeding units. Polimorfismo en Microsatélites y Estructura Genética en Poblaciones de Anas fulvigula Resumen. Se tiene escaso conocimiento acerca de los efectos del aislamiento regional y de la pérdida de hábitat sobre la estructura genética de poblaciones de Anas fulvigula, un ave acuática no migratoria de distribución restringida. Nuestro objetivo fue identificar marcadores genéticos de ADN para A. fulvigula y determinar los niveles de subdivisión entre poblaciones en Florida. Examinamos 13 pares de iniciadores (i.e., primers) para microsatélites e identificamos seis loci que fueron variables en A. fulvigula. Estos marcadores revelaron un bajo nivel de diferenciación genética y un alto grado de intercambio genético entre cuatro subpoblaciones de A. fulvigula en Florida. Para todas las poblaciones, la heterocigocidad esperada en un locus varió entre 0.13–0.85 para los seis loci examinados. No hubo diferencias significativas en las frecuencias génicas entre las subpoblaciones examinadas, y el valor de Fst para los 5 loci biparentales no fue diferente de cero. Nuestros análisis de las poblaciones de A. fulvigula de Florida indicaron altos niveles de heterocigocidad y no mostraron evidencia de subdivisión genética entre las unidades reproductivas.

MICROSATELLITE POLYMORPHISM AND GENETIC STRUCTURE OF FLORIDA MOTTLED DUCK POPULATIONS

Abstract Little is understood concerning the effects regional isolation and habitat loss have had upon the genetic structure of Mottled Ducks (Anas fulvigula), a nonmigratory waterfowl species with a limited distribution. Our objective was to identify nuclear DNA-based markers for Mottled Ducks and determine levels of subdivision among populations in Florida. We screened 13 microsatellite primer pairs and identified six microsatellite loci that were variable in Mottled Ducks. These markers revealed a low level of genetic differentiation and a high level of genetic exchange among four Mottled Duck subpopulations within Florida. Over all populations, single-locus expected heterozygosities over the six loci surveyed ranged from 0.13–0.85. There were no significant differences in gene frequencies among the populations examined, and the Fst over 5 biparental loci was not different from zero. Our analysis of the Florida Mottled Duck population indicated high levels of heterozygosity and no evidence of genetic s...

Molecular population genetics, phylogeography, and conservation biology of the mottled duck (Anas fulvigula)

The mottled duck (Anas fulvigula) is a year-round endemic resident of the Gulf Coast and one of two non-migratory dabbling ducks that inhabit North America. To investigate population genetic structure of allopatric mottled duck populations, we collected 5’ control region sequences (bp 78–774) from the mitochondria of 219 mottled ducks sampled at 11 widely spaced geographic localities in Texas, Louisiana, and Florida and compared them to each other and to homologous sequences from 4 Mexican ducks (A. diazi), 13 American black ducks (A. rubripes), and 10 mallards (A. platyrhynchos). We identified 57 unique haplotypes composed of 665 or 666 nucleotides in the 246 control region sequences. Of the 665 homologous positions, 8.3% (n = 55) vary among haplotypes, and 98.2% (n = 54) of these occur within the first 351 nucleotides from the 5’ end of the outgroup sequence. Neighbor-joining analysis shows a large distal clade (52.5% of mottled ducks sampled in our study) composed of two reciprocally monophyletic clades of mottled duck haplotypes, one of which is endemic to Texas and Louisiana and the other endemic to Florida. No mottled ducks sampled in Florida occur in the clade composed of mottled ducks from Texas and Louisiana or vice versa, suggesting that (1) an enduring geographic split has existed for many years between east and west, and (2) gene flow currently is non-existent (or at least undetectable) across the central Gulf Coast. The remaining 47.5% of mottled ducks sampled in our study branch basally from this derived clade, show substantially less hierarchical structure, and fall into various lineage groups of mixed species composition with no geographic or species-specific pattern. Pairwise FST values corroborate the pattern of strong differentiation observed between Texas/Louisiana and Florida. Our findings are consistent with a pattern of partial lineage sorting from a polymorphic ancestral gene pool reshuffled by hybridizing mallards. Control region data and patterns of divergence in mallard-like species worldwide, furthermore, suggest that mottled ducks are close relatives of Mexican ducks, and in turn nested within black ducks. Genetic similarities to nominate mallards are less likely to be the product of common ancestry, but the result of past hybridization with a dichromatic mallard ancestor that invaded North America from Asia many generations ago. Our findings have several important consequences for the conservation biology of mottled ducks across the Gulf Coast and our understanding of the phylogeography of mallard-like species worldwide.

Monitoring and education help seismic crew protect environment in transition‐zone survey

A program based on active monitoring and education helped Western Geophysical late last year complete a large speculative 3-D seismic survey in a sensitive Louisiana transition zone without creating the need for environmental remediation. Environmental authorities praised the program for, among other things, enabling Western Geophysical to discover a rookery of the endangered mottled duck and avoid disturbing it. The company has decided to use the program in all transition‐zone surveys in the southeastern United States.

Bioaccumulation and Toxic Potential of Extremely Hydrophobic Polychlorinated Biphenyl Congeners in Biota Collected at a Superfund Site Contaminated with Aroclor 1268

Aroclor 1268, a highly chlorinated technical PCB mixture composed of primarily hexa- through decachlorobiphenyls, was used to lubricate high voltage process equipment at a chlor-alkali facility in coastal southeastern Georgia. Disposal of process wastes has resulted in extensive contamination of environmental media at the nearby intertidal marsh. In this study, congener distribution, bioaccumulation properties, and toxic potential of superhydrophobic PCBs were examined in blue crab, fish, terrapin, and birds collected at this site. Lipid-normalized mean concentrations of total PCBs in blue crab, striped mullet, yellow tail, sea trout, diamondback terrapin, red-winged blackbird, boat-tailed grackle, mottled duck, and clapper rail were 197, 283, 203, 56, 14, 385, 76, 135, and 10 μg/g, respectively. Hepta-, octa-, and nonachlorobiphenyls col lectively accounted for 85−93% of the total PCB concentrations. The PCB congener profile in biota resembled that of Aroclor 1268, although the relative proportions of nona- and decachlorobiphenyls were less. Bioaccumulation of superhydrophobic congeners in biota, including terrapins and birds, was less than would be predicted from Kow, which supports the hypothesis that these compounds have restricted membrane permeability. Superhydrophobic PCB congeners were less efficiently transferred in the food web. The concentrations of non-ortho coplanar congeners in blue crab were 7−8 orders of magnitude less than the total PCB concentrations. Despite notable concentrations of total PCBs, the 2,3,7,8-TCDD toxic equivalents (TEQs) estimated for non- and mono-ortho-PCBs in biota were minimal. The toxic effects of higher chlorinated PCBs, including di-ortho-substituted PCBs, need further investigation.

Helminth community structure and pattern in two allopatric populations of a nonmigratory waterfowl species (Anas fulvigula)

Helminth communities of mottled ducks (Anas fulvigula) from Florida and Texas were species rich and diverse. The helminth component community in the mottled duck population from Texas contained more species than were found in the Florida host population. However, infracommunities of birds from Florida and Texas contained 9.5 ± 0.7 (mean ± SE) and 9.3 + 0.7 species, respectively. Similarity indices indicated less commonality of helminth species between the 2 host populations; 23 of the 42 species found across the 2 populations co-occurred. Eight helminth species from each host population were recurrent group or associate members; however, only 3 species (Amidostomum acutum, Capillaria contorta, and Tetrameres spp.) maintained group membership across both host populations. Maritrema paracadiae and Psilochasmus oxyurus were absent in birds from Florida but were recurrent group members in the host population from Texas. Only 2 recurrent group members (A. acutum and Epomidiostomum uncinatum) in birds from Florida were members of the same feeding guild and shared the same microhabitat. Three distinct feeding guilds, each containing 2 species, were found in birds from Texas. Results suggest that habitat diversity of the host plays an important part in determining species richness; however, important helminth species in both mottled duck populations are those commonly found in other Anatini from North America.

TETRAMERES (PETROWIMERES) STRIATA IN DUCKS

Tetrameres (Petrowimeres) striata is an uncommon and incompletely described nematode from North American and Eurasian waterfowl. Specimens collected from mallards (Anas platyrhynchos) from the Playa Lakes Region (PLR) in western Texas (USA), the mottled duck (A. platyrhynchos fulvigula) in Florida (USA), the mallard in the Amur River Basin of eastern Russia and the blue-winged teal (Anas discors) from western Texas (USA) provide the basis for redescription of T. (P.) striata. This species is differentiated from the closely related T. (P.) zakharowi and T. (P.) galericulata by the size of the left spicule and the prominent cuff on the proximal end of the right spicule. In mallards from the PLR, one to several adult males and a single female occurred within distended mucosal glands or, more rarely, in cystic cavities in the submucosal tissue of the proventriculus; intensities ranged from one to seven nematodes per host (mean +/- SE = 2.9 +/- 0.8). Infected proventricular gland mucosae were compressed as a result of pressure atrophy by the large gravid females. In addition to nematodes, some lesions also contained necrotic debris with inflammatory cells and were surrounded by an intense inflammatory response of eosinophils, macrophages, lymphocytes, epithelioid cells and fibroblasts. Other lesions had little or no inflammatory response. Lesions in the submucosa were surrounded by a thin fibrous cyst with or without adjacent inflammatory cells.

Evaluation of Aerial Transect Surveys of Mottled Ducks

Aerial counts of mottled ducks (Anas fulvlgula maculosil) along random transects were used to establish population Indices In Louisiana and southeastern Texas. Samples were stratified by habitat type, and replicated flights were made In February 1985, August 1985, and February 1986 to count mottled duck, occurring In strips on both sides of the air· craft. The August 1985 population Index was 173% greater than the Index of February 1985 and consistent with a post-breedlng season Increase In mottled duck numbers. The August survey also had a higher coefficient of variation, that probably resulted from the presence of large flocks of mottled ducks at that time of the year. The population Index Increased from 16,793 in February 1985 to 34,022 in February 1986. Other species of ducks were abundant In February, and observers had to differentiate between those species and mottled ducks. The mottled duck Index was greater in 100-m strips than 200-m strips, but the coefficients of variation were similar. The 100-m strip Is recommended for surveys made In February, because of the difficulty of differentiating mottled duck from other species at distances >100m.