Tachyeres Research Articles

Steamer Ducks: To Fly or Not to Fly

Steamer Ducks: To Fly or Not to Fly

Understanding ground-nesting habitat selection by waterbirds to prioritize invasive predator control on islands

The introduction of carnivores to islands affects the conservation status of native prey. For two decades, American mink (Neogale vison) has expanded its distribution in the sub-Antarctic archipelago of Austral Patagonia, while preying on nests of solitary ground-nesting birds. Here, upland geese (Chloephaga picta) and flightless steamer ducks (Tachyeres pteneres) are naïve to such predation risk because of the lack of native terrestrial predators. We used nest occupancy models to reveal preferred breeding habitats of those two ground-nesting waterbirds to prioritize areas for future mink control programs. We searched for nests along 80 transects on Navarino Island, southernmost Chile, and 11 transects on 10 nearby islets (3 ± 2.9 ha). Our results showed that islets were essential for breeding in comparison to the main island (5.3 nests/km versus 0.8 nests/km, respectively). The occupancy models revealed that islets were particularly important for flightless steamer ducks, endemic to western Patagonia. As breeding habitat, upland geese preferred medium-dense shrubland, and flightless steamer ducks preferred rocky coastlines. Nest detection was negatively affected by dense vegetation and, in the case of the upland geese, towards the end of the survey. Ten camera traps (n = 385 trap nights) revealed mink presence on all islets, highlighting their capacity to swim in cold water, up to 340 m distance from the main island. We conclude that islets represent breeding refuges for ground-nesting waterbirds and therefore advocate allocating resources for mink control during the warm season on islets. We also provide predictive maps of nesting habitat preference of upland geese and flightless steamer ducks for conservation managers to focus their often scarce human and financial resources on areas critical for breeding. Finally, we argue that detection probability should be an integral part of bird breeding studies, which can be methodologically achieved through targeting transects, not nests, as sample units.

Using Next-Generation Sequencing to Disentangle the Diet and Incidence of Intestinal Parasites of Falkland Flightless Steamer Duck Tachyeres brachypterus and Patagonian Crested Duck Lophonetta specularioides Sharing a South Atlantic Island

Species overlapping in habitat use can cohabit depending on how they exploit resources. To understand segregation in resource use, an exhaustive knowledge of the diet is required. We aimed to disentangle the diet composition of the Falkland Flightless Steamer Duck Tachyeres brachypterus and the Patagonian Crested Duck Lophonetta specularioides sharing a coastal environment. Using DNA extracted from scats and Illumina sequencing, we generated a list of molecular operational taxonomic units. Both ducks consumed a variety of invertebrates, frequently overlapping in the taxa consumed. However, only the Falkland Flightless Steamer Ducks consumed fish, which might be indicative of dietary specialization and inter-specific segregation in the restricted space that these birds share. Moreover, the female and male Falkland Flightless Steamer Ducks consumed different fish prey, with almost one-third of the fish taxa being consumed by females only and another similar number consumed by males only. This result might suggest a case of intra-specific competition, triggering sexual segregation. Additionally, we detected parasitic Platyelminthes (Cestoda and Trematoda), with different frequencies of occurrence, probably related to the different diet compositions of the ducks. This study provides the necessary baseline for future investigations of the ecological segregation of these ducks.

Relationships between off-bottom bivalve aquaculture and the Magellanic steamer duck Tachyeres pteneres in southern Chile

Relationships between off-bottom bivalve aquaculture and the Magellanic steamer duck Tachyeres pteneres in southern Chile

Gradual evolution towards flightlessness in steamer ducks.

Flightlessness in birds is the product of changes in suites of characters-including increased body size and reduced anterior limbs-that have evolved repeatedly and independently under similar ecological conditions (generally insularity). It remains unknown whether this phenotypic convergence extends to the genomic level, partially because many losses of flight occurred long ago (such as in penguins or ratites), thus complicating the study of the genetic pathways to flightlessness. Here, we use genome sequencing to study the evolution of flightlessness in a group of ducks that are current and dynamic exemplars of this major functional transition. These recently diverged Tachyeres steamer ducks differ in their ability to fly: one species is predominantly flighted and three are mainly flightless. Through a genome-wide association analysis, we identify two narrow candidate genomic regions implicated in the morphological changes that led to flightlessness, and reconstruct the number of times flightlessness has evolved in Tachyeres. The strongest association is with DYRK1A, a gene that when knocked out in mice leads to alterations in growth and bone morphogenesis. These findings, together with phylogenetic and demographic analyses, imply that the genomic changes leading to flightlessness in Tachyeres may have evolved once, and that this trait remains functionally polymorphic in two species.

Dieta del pato quetru no volador Tachyeres pteneres en un humedal marino de Chiloé, sur de Chile

The Magellanic Flightless Steamer Duck (Tachyeres pteneres) is the only marine anatid founded along the coastline of Chile and Argentina, from Valdivia to Tierra del Fuego. There is little published information about the quantitative diet of this species. Previously, a single study of its breeding diet was reported for Guapiquilan Island, Chiloe, southern Chile. We studied T. pteneres' winter diet during 2011 and 2012 in Bahia Caulin, Chiloe, southern Chile. We found that statistically Cancridae crabs (100 and 100%, respectively) and Majidae (96.0-71.4%, respectively) were the most common items in the diet of this species.

Stomach nematodes of three sympatric species of anatid birds off the coast of Patagonia.

The present study focuses on the nematode community in the stomachs of three sympatric anatid bird species from the Central Patagonian coast, Argentina. The bird species include the Chubut steamer duck, Tachyeres leucocephalus, the crested duck, Lophonetta specularioides, and the black-necked swan, Cygnus melancoryphus. Up to 138 nematodes representing five species were recovered from 10 of the 13 ducks examined, with an overall prevalence of 77% and a mean intensity of 13.8. Nematodes isolated from the gizzard were Streptocara formosensis and Sciadiocara legendrei (Acuariidae) in T. leucocephalus, and Epomidiostomum vogelsangi (Amidostomatidae) in C. melancoryphus, whereas Echinuria uncinata (Acuariidae) and Tetrameres (Petrowimeres) fissispina (Tetrameriidae) were found in the proventiculus of L. specularioides. In particular, S. legendrei was registered for the first time in South America and T. leucocephalus, whereas T. fissispina represents a new record in Argentina and L. specularioides. Moreover, E. vogelsangi and E. uncinata were isolated in Patagonia for the first time. The birds studied herein are sympatric in their distribution, and two of them are syntopic breeders; however, they were infected with different parasite species. This situation could be partially due to their diet or their seasonal movements, or a combination of both. Despite the low number of hosts examined, this work enhances our knowledge about parasites from a frequently occurring group of birds on the Patagonian coast, a subject that has not been studied extensively in South America.

Variation in the size of eggs of Chubut Steamer Ducks (Tachyeres leucocephalus)

Although several studies have analysed spatial or temporal variation in the size of eggs in waterfowl (Anseriformes), no study has analysed variation throughout the breeding range of a species. Chubut Steamer Ducks (Tachyeres leucocephalus) are flightless marine waterfowl endemic to a small section of coastline in Patagonia, Argentina. We partitioned and analysed sources of variation in the size of 989 Chubut Steamer Duck eggs, from 175 clutches, obtained during the breeding seasons of 1998 and 2004–08 at 31 islands throughout the range of the species. In relation to other Anseriformes, we found a low level of variation (coefficient of variation = 6.4%) at the species level. Most variation in the size of eggs were within clutches (59.0%) and among clutches (34.5%); variation between islands within geographical areas accounted for only 6.5% of variation, and there was no variation among geographical areas. Variation in size of eggs was not related to year, apparent clutch-size or latitude. The low variation at the species level and the lack of variation in size of eggs between geographical areas could be a consequence of the low genetic diversity and restricted distribution of the species. This study highlights the potential importance of variation in egg-size for understanding ecological processes linked to the natural history of avian species.

Abundances of waterbird species on lakes in Argentine Patagonia as a function of season, lake size and the presence of mink

Regular counts from 2005 to 2009 were made of the waterbirds inhabiting lakes and ponds in Lanin National Park in the southwestern part of Neuquen Province, Argentina, a landscape dominated by Andean–Patagonian wetlands and forests. Bird surveys conducted on 21 wetland areas detected 8,311 individuals belonging to 27 species from 9 families. The most abundant and frequent species were Ashy-headed Goose (Chloephaga poliocephala), Speckled Teal (Anas flavirostris), Red-gartered Coot (Fulica armillata) and White-winged Coot (Fulica leucoptera). The presence and abundance of bird species with respect to wetland surface area was examined. Small lakes (<100 ha) had higher numbers of individuals, but some species such as the Neotropic Cormorant (Phalacrocorax olivaceus), Great Grebe (Podiceps major), Flying Steamer Duck (Tachyeres patachonicus) and Spectacled Duck (Anas specularis) were more abundant at larger lakes. Speckled Teal, Red Shoveler (Anas platalea) and Chiloe Wigeon (A. sibilatrix) were more common in small- and medium-sized lakes. Most waterbird species were found at a smaller percentage of the lakes where mink were present than at mink-free lakes. Although the ponds and lakes studied are protected within the network of this Argentine National Park, such protection is not implemented effectively. Hence, their future conservation faces several potential threats such as American mink expansion, tourism, fishing and hunting. This information could contribute to the development of management guidelines for the effective conservation of Patagonian wetlands.

Multiple losses of flight and recent speciation in steamer ducks

Steamer ducks (Tachyeres) comprise four species, three of which are flightless. The flightless species are believed to have diverged from a flying common ancestor during the Late Pleistocene; however, their taxonomy remains contentious. Of particular interest is the previously unstudied population of flying steamer ducks in the Falkland Islands. We present the first genetic data from this insular population, and illustrate that the flying and flightless steamer ducks on the Falkland Islands are genetically indistinguishable, in contrast to their traditional classification as separate species. The three species that reside in continental South America form a genetically distinct lineage from the Falkland Island ducks. The Falkland steamer ducks diverged from their continental relatives 2.2-0.6 million years ago, coincident with a probable land bridge connecting the Falkland Islands to the mainland. The three continental species share a common ancestor approximately 15 000 years ago, possibly owing to isolation during a recent glacial advance. The continental steamer duck species are not reciprocally monophyletic, but show some amount of genetic differentiation between them. Each lineage of Tachyeres represents a different stage between flight and flightlessness. Their phylogenetic relationships suggest multiple losses of flight and/or long-term persistence of mixed-flight capability. As such, steamer ducks may provide a model system to study the evolution of flightlessness.

Elucidating the role of select cytoplasmic proteins in altering diffusion of integrin receptors

Cytoplasmic proteins that affect integrin diffusion in the cell membrane are identified using a combination of fluorescence recovery after photobleaching (FRAP) and RNA interference. Integrin receptors are essential for many cellular events, and alterations in lateral diffusion are one mechanism for modulating their function. In cells expressing native cytoplasmic protein concentrations and spread on a slide containing integrin extracellular ligand, 45 ± 2% of the integrin is mobile with a time-dependent 5.2 ± 0.9 × 10(-9) cm(2)/s diffusion coefficient at 1 s. The time exponent is 0.90 ± 0.07, indicating integrin diffusion moderately slows at longer times. The role of a specific cytoplasmic protein in altering integrin diffusion is revealed through changes in the FRAP curve after reducing the cytoplasmic protein's expression. Decreased expression of cytoplasmic proteins rhea, focal adhesion kinase (FAK), or steamer duck decreases the integrin mobile fraction. For rhea and FAK, there is a concomitant shift to Brownian (i.e., time-independent) diffusion at reduced concentrations of these proteins. In contrast, when the expression of actin 42A, dreadlocks, paxillin, integrin-linked kinase (ILK), or vinculin is reduced, integrin diffusion generally becomes more constrained with an increase in the integrin mobile fraction. This same change in integrin diffusion is measured in the absence of integrin extracellular ligand. The results indicate breaking the extracellular ligand-integrin-cytoskeletal linkage alters integrin diffusion properties, and, in most cases, there is no correlation between integrin and lipid diffusion properties.

Nesting habitat of Chubut Steamer Ducks in Patagonia, Argentina

We studied nest-site selection of the flightless Chubut Steamer Duck (Tachyeres leucocephalus) along 292 km of continental coastline and 59 km of island coastline in Patagonia, Argentina, between 2004 and 2006. This area encompasses the main breeding range of the species. Almost all nests were on islands and islets, which ranged in area from 0.5 to 54.4 ha and were 0.01-5.6 km from the mainland. Nesting sites were within bays and inlets with shallow waters and protected from waves, winds and strong currents. Using logistic regression analyses in an information-theoretic framework to compare habitat characteristics between nesting sites and randomly chosen sites, we found that Chubut Steamer Duck nesting sites were strongly and positively associated with higher proportions of shrub vegetation cover. To a lesser degree, the percentage of silt—clay sediment was also positively associated with nesting sites. Nest-site selection is thought to be associated with concealment from aerial predators and protection from weather. This is the first study of breeding habitat and nest-site selection of Chubut Steamer Ducks, and will contribute to management and habitat conservation for this rare flightless duck through identification of both general and specific habitat features that should be preserved or enhanced.

Phylogenetic relationships of Amazonetta, Speculanas, Lophonetta, and Tachyeres: four morphologically divergent duck genera endemic to South America

We studied the phylogenetic relationships of four duck genera endemic to South America: Brazilian teal Amazonetta brasiliensis, spectacled duck Speculanas specularis, crested duck Lophonetta specularioides, and four species of steamer ducks Tachyerespatachonicus, T. leucocephalus, T. pteneres, T. brachypterus. Genetic divergence within and among species was compared using population‐level sampling of the mitochondrial DNA (mtDNA) control region, supplemented with three additional mtDNA genes and six independent nuclear loci from one individual of each species and a variety of outgroup taxa. The monophyly of these four morphologically divergent South American genera was strongly supported. Within this clade, Amazonetta and Speculanas were supported as sister species in all analyses, but different gene regions yielded conflicting or ambiguous results for Lophonetta and Tachyeres. This lack of resolution resulted from little informative variation in nuclear loci and high levels of homoplasy in the mtDNA control region. Control region sequences from the four Tachyeres species fell into two distinct clades. In one clade, T. patachonicus and T. leucocephalus share a set of closely related haplotypes (≤0.6% sequence divergence); while no identical haplotypes were shared between species, the control region phylogeny was insufficiently resolved to either support or reject reciprocal monophyly. The second clade, ~1.7% divergent from the first, comprised haplotypes of the Falkland Islands species T. brachypterus and a captive individual of T. pteneres. These distinctive South American ducks likely experienced two bouts of rapid diversification, thus making analysis of their phylogenetic relationships difficult. Incomplete lineage sorting, founder effects, and perhaps introgression likely have contributed to obscuring the relationships among steamer ducks.

Identifying cytoplasmic proteins that affect receptor clustering using fluorescence resonance energy transfer and RNA interference

Unraveling the complex, dynamic organization of the cell membrane can provide vital information about many aspects of cellular functions. Reported herein is a method for identifying cytoplasmic proteins that affect cell membrane protein organization. RNA interference (RNAi) is used to reduce the expression of select cytoplasmic proteins and a fluorescence resonance energy transfer (FRET) assay is used to measure changes in receptor microclustering. The advantage of this assay is that it does not require attaching fluorescent tags to the receptor. A change in energy transfer after reducing the expression of a cytoplasmic protein provides information about the protein's role in altering receptor organization. As a demonstration of the method, cytoplasmic proteins involved in integrin microclustering have been identified. The cytoplasmic proteins targeted in this study include: dreadlock, integrin-linked kinase, paxillin, steamer duck, vinculin, rhea, focal adhesion kinase, and actin 42A. Reducing the expression of vinculin, paxillin, rhea, and focal adhesion kinase increased integrin microclustering, as measured by an increase in energy transfer in cells expressing alphaPS2CbetaPS integrins. No change in integrin microclustering was measured in a control cell line. Integrin mutants exhibited different microclustering properties compared to the wild-type integrins after reducing the expression of the listed cytoplasmic proteins. The results demonstrate the utility of this assay format, and provide insight into the function of cytoplasmic proteins in integrin microclustering.

Analysis of PINCH function in Drosophila demonstrates its requirement in integrin-dependent cellular processes.

Integrins play a crucial role in cell motility, cell proliferation and cell survival. The evolutionarily conserved LIM protein PINCH is postulated to act as part of an integrin-dependent signaling complex. In order to evaluate the role of PINCH in integrin-mediated cellular events, we have tested directly the in vivo function of PINCH in Drosophila melanogaster. We demonstrate that the steamer duck (stck) alleles that were first identified in a screen for potential integrin effectors represent mutations in Drosophila pinch. stck mutants die during embryogenesis, revealing a key role for PINCH in development. Muscle cells within embryos that have compromised PINCH function display disturbed actin organization and cell-substratum adhesion. Mutation of stck also causes failure of integrin-dependent epithelial cell adhesion in the wing. Consistent with the idea that PINCH could contribute to integrin function, PINCH protein colocalizes with betaPS integrin at sites of actin filament anchorage in both muscle and wing epithelial cells. Furthermore, we show that integrins are required for proper localization of PINCH at the myotendinous junction. The integrin-linked kinase, ILK, is also essential for integrin function. We demonstrate that Drosophila PINCH and ILK are complexed in vivo and are coincident at the integrin-rich muscle-attachment sites in embryonic muscle. Interestingly, ILK localizes appropriately in stck mutant embryos, therefore the phenotypes exhibited by the stck mutants are not attributable to mislocalization of ILK. Our results provide direct genetic evidence that PINCH is essential for Drosophila development and is required for integrin-dependent cell adhesion.

Distribution and Density of Kelp Geese and Flightless Steamer Ducks Along the Beagle Channel, Tierra del Fuego, Argentina

Abstract We describe the distribution and estimate the density of the Flightless Steamer Duck (Tachyeres pteneres) and the Kelp Goose (Chloephaga hybrida) along the Beagle Channel, Tierra del Fuego, during the summer season (February and March) 1997. Using a 10-min transects method from a vessel; we estimated density and evaluated its relation with different characteristics of habitats. The study area was divided a priori into six zones. Due to the scarcity of information about these species, we reviewed previous literature to evaluate seasonal movements and made comparisons with other regions of Tierra del Fuego. Differences in habitat distribution compared with the previous studies in the same area are reported. In the Beagle Channel, the Flightless Steamer Duck was more abundant than the Kelp Goose. The observed distribution seems to be a result of a preference for the inner waters of the Beagle Channel, at the western sector of the study area. In spite of the difference in the distribution of the two ...

Sea bird fowling in southern Patagonia: a contribution to understanding the nomadic round of the Canoeros Indians

As well as providing data on meat yield, avian remains can be expected to give information on seasonality, an important parameter for understanding prehistoric hunting economies. An archaeological survey conducted in the Skyring Sea (Province of Magellan, Chile) between 1992 and 1994 provided bird bone assemblages that have been analysed with this aim in mind, of which 12 are discussed here. Cormorants and steamer ducks constitute 97 per cent of the specimens identified. The proportions of avian remains are compared with the mammals remains, and mostly show a predominance of the former. The status and seasonal distribution of animal resources are discussed in order to understand the motivation for such a specialization on bird hunting, when mammals (Artiodactyls and Pinnipeds) can bring a much higher yield of meat. This nomadic marine economy can best be understood when comparisons are made with other sites from the same cultural area. © 1997 John Wiley & Sons, Ltd.

Autosomal mutations affecting adhesion between wing surfaces in Drosophila melanogaster.

Integrins are evolutionarily conserved transmembrane alpha,beta heterodimeric receptors involved in cell-to-matrix and cell-to-cell adhesions. In Drosophila the position-specific (PS) integrins mediate the formation and maintenance of junctions between muscle and epidermis and between the two epidermal wing surfaces. Besides integrins, other proteins are implicated in integrin-dependent adhesion. In Drosophila, somatic clones of mutations in PS integrin genes disrupt adhesion between wing surfaces to produce wing blisters. To identify other genes whose products function in adhesion between wing surfaces, we conducted a screen for autosomal mutations that produce blisters in somatic wing clones. We isolated 76 independent mutations in 25 complementation groups, 15 of which contain more than one allele. Chromosomal sites were determined by deficiency mapping, and genetic interactions with mutations in the beta PS integrin gene myospheroid were investigated. Mutations in four known genes (blistered, Delta, dumpy and mastermind) were isolated. Mutations were isolated in three new genes (piopio, rhea and steamer duck) that affect myo-epidermal junctions or muscle function in embryos. Mutations in three other genes (kakapo, kiwi and moa) may also affect cell adhesion or muscle function at hatching. These new mutants provide valuable material for the study of integrin-dependent cell-to-cell adhesion.

Sexual Dimorphism in Continental Steamer-Ducks

Analyse du dimorphisme sexuel chez les trois especes continentales (133 specimens, biometrie du squelette et des muscles, mensurations externes): Tachyeres pteneres, T. leucocephalus, T. patachonicus et recherche des causes de ce dimorphisme

Diving behaviour of steamer ducks Tachyeres spp.

Diving behaviour of steamer ducks <i>Tachyeres spp</i>.