Anatinae Research Articles

Variation in the Diet of Ducks During Spring Migration

ABSTRACTBecause management practices that promote the production of plant foods may differ from management practices that promote the production of aquatic invertebrates, a thorough understanding of the diet is needed to develop management strategies for various stages of the annual cycle for dabbling and diving ducks. Diet of dabbling (tribe Anatini) and diving (tribe Aythyini) ducks during breeding, autumn migration, and winter has been documented. Our goal was to estimate and compare the diet of blue‐winged teal (Spatula discors), gadwall (Mareca strepera), mallard (Anas platyrhyncos), lesser scaup (Aythya affinis), and ring‐necked duck (Aythya collaris) during spring migration in the Mississippi Flyway in the United States and evaluate variation among species. We collected 919 ducks for diet analysis from multiple wetlands at 6 sites across 4 states during the spring migration of 2006 and 2007. We collected ≥10 individuals of each species at each of the 6 study sites except we collected only 1 gadwall at the Scioto River site and 2 lesser scaup at the Cache River site. We detected that the proportion of plant and animal material in foods of each spring migrating duck species was in general intermediate of that found in wintering and breeding birds. Furthermore, the proportion of plant and animal material in the diet of species varied even among closely related species, indicating species are partitioning food sources along a protein‐carbohydrate gradient during spring migration. We recommend that resources for ducks be managed to provide diverse wetlands to support the varied diets of even closely related species. © 2021 The Wildlife Society.

A method to identify the areas at risk for the introduction of avian influenza virus into poultry flocks through direct contact with wild ducks.

Wild dabbling ducks are the main reservoir for avian influenza (AI) viruses and pose an ongoing threat to commercial poultry flocks. Combining the (i) size of that population, (ii) their flight distances and (iii) their AI prevalence, the density of AI-infected dabbling ducks (DID) was calculated as a risk factor for the introduction of AI viruses into poultry holdings of Emilia-Romagna region, Northern Italy. Data on 747 poultry holdings and on 39 AI primary outbreaks notified in Emilia-Romagna between 2000 and 2017 were used to validate that risk factor. A multivariable Bayesian logistic regression was performed to assess whether DID could be associated with the occurrence of AI primary outbreaks. DID value, being an outdoor flock, hobby poultry trading, species reared, length of cycle and flock size were used as explanatory variables. Being an outdoor poultry flock was significantly associated with a higher risk of AI outbreak occurrence. The probability of DID to be a risk factor for AI virus introduction was estimated to be 90%. A DID cut-off of 0.23 was identified to define high-risk areas for AI virus introduction. Using this value, the high-risk area covers 43% of the region. Seventy-four per cent of the primary AI outbreaks have occurred in that area, containing 39% of the regional poultry holdings. Poultry holdings located in areas with a high DID value should be included in a risk-based surveillance programme aimed at AI early detection.

The North American Perching and Dabbling Ducks

This volume, the fourth in a series of books that collectively update and expand P. A. Johnsgard’s 1975 The Waterfowl of North America, summarizes research findings on this economically and ecologically important group of waterfowl. The volume includes the mostly tropical perching duck tribe Cairinini, of which two species, the muscovy duck and the wood duck, are representatives. Both species are adapted for foraging on the water surface, mostly on plant materials, but typically perch in trees and nest in elevated tree cavities or other elevated recesses. This volume also includes the dabbling, or surface-feeding, duck tribe Anatini, a large assemblage of duck species that mainly forage on the water surface but nest on the ground, or only very rarely in elevated locations. Of this tribe, 12 species that regularly breed in North America are included, among them such familiar species as mallards, wigeons, pintails, and teal. Descriptive accounts of the distributions, populations, ecologies, social-sexual behaviors, and breeding biology of all these species are provided, together with distribution maps. Five additional Eurasian and West Indian species have been reported several times in North America; these have been included with more abbreviated accounts, but all 17 species are illustrated by drawings, photographs, or both. The text includes about 84,000 words and contains more than 1,000 references. There are also 12 distribution maps, 21 drawings, 28 photographic plates, and 58 anatomical or behavioral sketches.

Environmental variability and population dynamics: do European and North American ducks play by the same rules?

Density dependence, population regulation, and variability in population size are fundamental population processes, the manifestation and interrelationships of which are affected by environmental variability. However, there are surprisingly few empirical studies that distinguish the effect of environmental variability from the effects of population processes. We took advantage of a unique system, in which populations of the same duck species or close ecological counterparts live in highly variable (north American prairies) and in stable (north European lakes) environments, to distinguish the relative contributions of environmental variability (measured as between‐year fluctuations in wetland numbers) and intraspecific interactions (density dependence) in driving population dynamics. We tested whether populations living in stable environments (in northern Europe) were more strongly governed by density dependence than populations living in variable environments (in North America). We also addressed whether relative population dynamical responses to environmental variability versus density corresponded to differences in life history strategies between dabbling (relatively “fast species” and governed by environmental variability) and diving (relatively “slow species” and governed by density) ducks. As expected, the variance component of population fluctuations caused by changes in breeding environments was greater in North America than in Europe. Contrary to expectations, however, populations in more stable environments were not less variable nor clearly more strongly density dependent than populations in highly variable environments. Also, contrary to expectations, populations of diving ducks were neither more stable nor stronger density dependent than populations of dabbling ducks, and the effect of environmental variability on population dynamics was greater in diving than in dabbling ducks. In general, irrespective of continent and species life history, environmental variability contributed more to variation in species abundances than did density. Our findings underscore the need for more studies on populations of the same species in different environments to verify the generality of current explanations about population dynamics and its association with species life history.

Discussing implications of fast depleting rural ponds on the globally threatened wetland winter migratory bird in Haryana: a Case Study of Nigdu village pond in Karnal District

The Nigdu-Sarovar is located in Nilokheri block in Karnal district in Haryana (29°50°N, 76°55°E). The duration of observations span over seven years (September, 2005 to March, 2012). The recording of wetland winter visitor birds during 2005-08 in winter season included atleast 58 species of birds belonging to 10 orders and 18 families. It is important to mention that 29 species of wetland birds were winter migratory, 17 residents, 9 local migratory and three species of wetland birds like Lesser-whistling Duck Dendrocygna javanica, Pheasant-tailed Jacana Hydrophasianus chirurgus and Blue-cheeked Bee-eater Merops persicus were summer migratory. The special features of 2005-06 winter was the huge populations of birds like Northern Shoveller Anas clypeata, Northern Pintail Anas acuta, Common Teal Anas crecca, Spot-billed Duck Anas poecilorhynchus, Common Pochard Aythya ferina, Bar-headed Goose Anser indicus, Greylag Goose Anser anser, Gadwall Anas strepera, Great Cormorant Phalacrocorax carbo, Mallard Anas platyrhynchos and Common Redshank Tringa totanus etc.In successive years, the scenario was more or less a substantial one depicting stability with respect to diversity of birds, number of birds upto the year of 2008. The popular birds included Painted Stork Mycteria leucocephala, Openbill Stork Anastomus oscitans, White-necked Stork Ciconia episcopus, Black-necked Stork Ephippiorhynchus asiaticus, Eurasian Spoonbill Platalea leucorodia, Spotted Greenshank Tringa guttifer and Kentish Plover Charadrius alexandrines. The sharp decline in winter migratory birds at Nigdu-Sarovar started in the year of 2008 when the pond was leased out for FISH-FARMING as per the policies of Govt. of Haryana. Fish Farming based deepening of the pond by excavation of bottom resulting in total decimation of rooted, floating, submerged and ejecting plants along with its subsidiary fauna, Zooplanktons, phytoplankton etc. The age old structural regime of the pond was obliterated to turn it in a scientifically managed fish pond. The year of 2009-10, 2010-11 and 2011-12 (March, 2012) showed the total absence of migratory birds like Mallards, several Geese, Dabbling Ducks, Pochards and Teals etc. As of today (2012), the sarovar is a clean sheet of water with bird repelling devices installed in places.

Diet and Feeding Habitats of Camargue Dabbling Ducks: What Has Changed Since the 1960s?

Abstract. In the Camargue (southern France), drastic changes in wetlands have occurred (notably extension of agriculture and salt extraction) since the 1960s, which affect the resources available to migratory waterbirds. Winter diets of Mallard (Anas platyrhynchos) and Teal (A. crecca) in 2006–2008 were assessed by analyses of gullet contents. Using PCA-based methods, duck diets were described and the main feeding habitats used by each duck species were then determined with a typology analysis. The same four food items were most important (in terms of occurrence and average dry weight) in the diet of Mallard and Teal: Oryza sativa (rice), Echinochloa sp., Scirpus maritimus and Potamogeton pusillus seeds. However, Teal diet was more diversified, with eleven feeding habitat types, compared to only five in Mallard. Both species were found to be dependent on ricefields and ricefield-like habitats. Compared to previous studies in the same area between 1964 and 1981, permanent freshwater habitats now appear to ...

The Food Preference Paradigm: A Review of Autumn–Winter Food Use by North American Dabbling Ducks (1900–2009)

Abstract Studies describing food use (i.e., diet) of nonbreeding dabbling ducks Anas spp. are essential to understanding physiological needs of and recommending habitat management for these birds. We conducted a review of published autumn and winter food-use studies of dabbling ducks in North America to characterize the current state of knowledge and identify remaining research needs. We initiated our review to determine whether valuations of duck foods and the term “preference” commonly used by researchers and in waterfowl management guides (i.e., the food preference paradigm) were supported by available peer-reviewed literature. We analyzed peer-reviewed literature (1900–2009) on autumn–winter food use of dabbling ducks (n = 59 studies). Most studies (68%) used methods known to contain substantial bias including data from gizzards and hunter-collected ducks. Only 5% of published articles reliably determined food selection by concurrently measuring food use and availability, and no study determined food use at a scale appropriate for winter home ranges of dabbling ducks. In some habitats commonly managed for waterfowl (e.g., agricultural lands), few if any collections of ducks are available to obtain data on food use. The limited geographic and habitat scope of unbiased food use and selection studies for dabbling ducks during autumn and winter suggests that the food-preference paradigm found in waterfowl management literature is not supported by empirical evidence and that managers must continue to use best judgment in managing foraging habitats for waterfowl. Researchers and conservation planners should aim to reduce uncertainty regarding the value of waterfowl foods by conducting contemporary food-selection studies using unbiased collection and processing methodologies. Further, we suggest future researchers conduct concurrent behavioral observations, habitat use, and food selection studies within winter home ranges of dabbling ducks to aid managers in meeting the nutritional requirements of dabbling ducks during autumn and winter in North America.

Feeding Ecology and Development of Juvenile Black Ducks in Maine

Feeding Ecology and Development of Juvenile Black Ducks in Maine

Weather‐Related Indices of Autumn– Winter Dabbling Duck Abundance in Middle North America

ABSTRACT Research on effects of key weather stimuli influencing waterfowl migration during autumn and winter is limited. We investigated relationships between changes in relative abundances of mallard (Anas platyrhynchos) and other dabbling ducks (Anas spp.) and weather variables at midlatitude locations in North America. We used waterfowl survey data from Missouri Conservation Areas and temperature and snow cover data from the Historical Climatology Network to evaluate competing models to explain changes in relative abundance of ducks in Missouri, USA, during autumn‐winter, 1995–2005. We found that a cumulative weather severity index model (CumulativeWSI; calculated as mean daily temp ‐ degrees C + no. of consecutive days with mean temp ≤ 0° C + snow depth + no. of consecutive days with snow cover) had the greatest weight of evidence in explaining changes in relative abundance of ducks. We concluded the CumulativeWSI reflected current and cumulative effects of ambient temperatures on energy expenditure by ducks, and snow cover and wetland icing, on food availability for ducks. The CumulativeWSI may be useful in determining potential changes in autumn‐winter distributions of North American waterfowl given different climate change projections and associated changes in habitat conservation needs. Future investigations should address interactions between CumulativeWSI and landscape habitat quality, regional waterfowl populations, hunter harvest, and other anthropogenic influences to increase understanding of waterfowl migration during autumn‐winter.

Signatures of High‐Altitude Adaptation in the Major Hemoglobin of Five Species of Andean Dabbling Ducks

Hypoxia is one of the most important factors affecting survival at high altitude, and the major hemoglobin protein is a likely target of selection. We compared population genetic structure in the alphaA and betaA hemoglobin subunits (HBA2 and HBB) of five paired lowland and highland populations of Andean dabbling ducks to unlinked reference loci. In the hemoglobin genes, parallel amino acid replacements were overrepresented in highland lineages, and one to five derived substitutions occurred at external solvent-accessible positions on the alpha and beta subunits, at alpha(1)beta(1) intersubunit contacts, or in close proximity to inositolpentaphosphate (IPP) binding sites. Coalescent analyses incorporating the stochasticity of drift and mutation indicated that hemoglobin alleles were less likely to be transferred between highland and lowland populations than unlinked alleles at five other loci. Amino acid replacements that were overrepresented in the highlands were rarely found within lowland populations, suggesting that alleles segregating at high frequency in the highlands may be maladaptive in the lowlands and vice versa. Most highland populations are probably nonmigratory and locally adapted to the Altiplano, but gene flow for several species may be sufficiently high to retard divergence at unlinked loci. Heterozygosity was elevated in the alphaA or betaA subunits of highland populations exhibiting high gene flow between the southern lowlands and the highlands and in highland species that disperse seasonally downslope to midelevation environments from the central Andean plateau. However, elevated heterozygosity occurred more frequently in the alphaA subunit but not simultaneously in both subunits, suggesting that selection may be more constrained by epistasis in the betaA subunit. Concordant patterns among multiple species with different evolutionary histories and depths of historical divergence and gene flow suggest that the major hemoglobin genes of these five dabbling duck species have evolved adaptively in response to high-altitude hypoxia in the Andes.

Differences in Plumulaceous Feather Characters of Dabbling and Diving Ducks

AbstractAbstractWe examined variation in five microscopic plumulaceous (downy) feather characters of eighteen species of dabbling (Anatini) and diving (Aythyini, Mergini) ducks to quantify the differences between these tribes, and to explain how the plumulaceous feather ultrastructure in ducks may be influenced by different ecological requirements. Over 75% of the variation in feather characters among these ducks was explained by the first two components of a principal components analysis (PCA). Component 1 explained 51% of the variation and was positively correlated with the characters that quantified the number of barbules with expanded nodes and the number of expanded nodes on barbules. The microscopic feather characters of dabbling ducks (Anatini) have triangular-shaped, expanded nodes on most proximal barbules, whereas diving ducks (Aythyini and Mergini) lack expanded nodes on some barbules. Anatini also have a greater density of expanded nodes per barbule, wider nodes, shorter distance between expanded nodes, and longer barbule length. Further analysis of node density across all taxa showed that as dive depths increase, the number of expanded nodes per barbule decreases, and in the deepest divers many of the barbules completely lack expanded nodes. The significantly greater density of expanded nodes in dabbling ducks suggests that the downy nodes may function to trap more air. Diving species have fewer expanded nodes, less buoyant plumage, and are more efficient at foraging in deeper water than dabbling ducks.

DIFFERENCES IN PLUMULACEOUS FEATHER CHARACTERS OF DABBLING AND DIVING DUCKS

Abstract ABSTRACT We examined variation in five microscopic plumulaceous (downy) feather characters of eighteen species of dabbling (Anatini) and diving (Aythyini, Mergini) ducks to quantify the differences between these tribes, and to explain how the plumulaceous feather ultrastructure in ducks may be influenced by different ecological requirements. Over 75% of the variation in feather characters among these ducks was explained by the first two components of a principal components analysis (PCA). Component 1 explained 51% of the variation and was positively correlated with the characters that quantified the number of barbules with expanded nodes and the number of expanded nodes on barbules. The microscopic feather characters of dabbling ducks (Anatini) have triangular-shaped, expanded nodes on most proximal barbules, whereas diving ducks (Aythyini and Mergini) lack expanded nodes on some barbules. Anatini also have a greater density of expanded nodes per barbule, wider nodes, shorter distance between exp...

Cockle-opening by a Dabbling Duck, the Brown Teal

Many birds feed on bivalve molluscs, but only oystercatchers (Haematopus spp.) are known to prise open the shells. Brown Teal (Anas chlorotis), a dabbling duck endemic to New Zealand, were observed opening Common Cockles (Austrovenus stutchburyi) on Great Barrier Island. The teal jackhammered into the open shells of feeding cockles and quickly scooped out the flesh. Despite having the bill morphology of a typical dabbling duck, they were adept at this feeding method.

Comparing Molecular Evolution in Two Mitochondrial Protein Coding Genes (Cytochromeband ND2) in the Dabbling Ducks (Tribe: Anatini)

Rates of sequence evolution were estimated for the cytochromeb(cytb) and NADH dehydrogenase subunit 2 (ND2) genes using a phylogeny of the dabbling ducks (Tribe: Anatini) and outgroups. This speciose group was densely sampled, reducing the impact of undetected homoplasy on rate comparisons. Phylogenies based on sequences of the two gene regions and various weighting schemes differed, but most of the differences involved weakly supported nodes. In addition, partition homogeneity tests show that these differences were not due to statistically significant conflict between the data sets. Cytband ND2 also showed similar rates and types of both nucleotide and amino acid substitutions. For both genes, substitutions between isoleucine and valine and between alanine and threonine were most common; both of these substitution types are the result of A–G transitions at first positions of codons. Rates of sequence evolution varied substantially and significantly among nucleotide positions, and even within a given codon position (first, second, or third), rates were significantly heterogeneous among sites. Within Anatini, cytband ND2 show similar levels of variation and homoplasy, and are equally useful for reconstructing the species level phylogeny of this group.

Evaluation of an Aerial Quadrat Survey for Monitoring Wintering Duck Populations

We designed and conducted an aerial survey for monitoring trends in duck populations in Florida during January. The state's wetland habitats were represented by a stratified random sample of 150 62.2-km 2 units. Statewide estimates for total ducks averaged about 538,000 during 1989-93. Total dabbling duck population estimates averaged 117,000, and total diving duck estimates averaged 399,000. Annual population estimates generally were imprecise (coefficients of variation [CVs] averaged 0.52 and ranged from 0.20 to 0.97), resulting in generally low probability (<0.70) of detecting annual rates of change of <0.09 over 10-years (α = 0.10). Serial correlation of population estimates from repeated sampling of survey units potentially inflated Type I error rates above the nominal α = 0.10 level, and were accounted for in our analyses by specifying lower α levels for rejection. We recommend that winter surveys of ducks be spatially replicated to assure CV <25% of annual abundance estimates. Replicates should be randomly drawn each year of the survey to avoid serial correlation in the estimates; if precluded by logistical constraints, investigators should estimate, ideally through simulation, the effect of serial correlation on Type I error rates.

Parental Attendance and Brood Care in Four Argentine Dabbling Ducks

Parental Attendance and Brood Care in Four Argentine Dabbling Ducks

Foraging Niche Shifts in Multispecies Dabbling Duck (Anas spp.) Feeding Groups: Harmful and Beneficial Interactions between Species

Foraging Niche Shifts in Multispecies Dabbling Duck (Anas spp.) Feeding Groups: Harmful and Beneficial Interactions between Species

Effect of Strychnine Control on Nest Predators of Dabbling Ducks

This paper reports the results of efforts to reduce predation on nests of dabbling ducks on a part of the Delta marsh in Manitoba by the use of eggs injected with strychnine. Effectiveness was assessed by comparing rates of destruction of simulated nests on strychnine-treated versus control