Conservation and Ecology of Birds – Waterfowl I

Contributed Paper
ROOM: Rooms 16 – Acoma, 32 – Teseque and 15 – Zuni Combined
SESSION NUMBER: 76
 

1:30PM Habitat Selection of Wintering Waterfowl Communities at Anahuac National Wildlife Refuge
Tiffany C. Lane; Blake A. Grisham; Jena A. Moon; David A. Haukos; Warren C. Conway
Waterfowl conservation focuses on managing and conserving important habitats across their range. To understand habitat selection, studies typically describe resource selection by single species. However, management efforts that target single waterfowl species can affect multiple species, especially on wintering ground when waterfowl communities aggregate around shared resources. Our goal was to assess habitat selection by waterfowl communities that overwinter on Anahuac National Wildlife Refuge to develop effective conservation plans targeting multiple species of dabbling ducks. We observed mixed-flocks of 6 Anas species defined as a guild of migratory, shallow-water dabblers overwintering on the upper Texas Coast. We conducted aerial surveys on Anahuac NWR to track monthly waterfowl habitat use from October-February, 2014-2016. We visited sites with >500 birds in an aggregated flock (used) and randomly selected locations (available) and recorded water salinity, temperature, depth, submerged aquatic vegetation (SAV), and invertebrate biomass. We developed a resource selection function using used/available data in a generalized linear model to assess community habitat selection at multiple spatial and temporal scales. Habitat selection between years was best predicted by water depth, salinity, and temperature. Habitat selection within winter was best predicted by the water characteristics and submerged aquatic vegetation. We extrapolated our data to the entire NWR using habitat metrics best supported by our model set to produce predictive habitat use maps for large flocks of dabbling ducks on the refuge and predicted use on ~65% of Anahuac NWR. Overlap in resource use among similar species of dabbling ducks occurred during the winter, and therefore, using the guild concept in lieu of single species is likely a more efficient strategy for waterfowl habitat management.
1:50PM Long-Term Trends and Future Projects of Weather Severity Indices for Dabbling Ducks in Eastern North America
Michael L. Schummer; Michael Notaro; Lena Van Den Elsen Van Den Elsen; John Coluccy; Michael Mitchell
Each year, millions of waterfowl migrate from their breeding grounds in Arctic, northern and mid-latitudes of North America to more southern locales to exploit abundant food and wetland resources as freezing wetlands and snowfall progress north to south. These migrating birds consume and distribute an abundance of seeds and invertebrates, are a cultural resource for waterfowl watchers and hunters, and provide economic benefit through the activities of waterfowl enthusiasts. Recognition of the tangible and intangible importance of this diverse group of birds by waterfowl enthusiasts also gave rise to substantial international efforts to conserve wetlands and associated habitats throughout North America. We developed weather severity indices (WSIs) to estimate autumn-winter distributions of gadwall (Anas strepera), American wigeon (A. americana), American black duck (A. rubripes), mallard (A. platyrhynchos), northern shoveler (A. clypeata), northern pintail (A. acuta), and green-winged teal (A. crecca carolinensis) based on contemporary weather conditions (1980-2000), describe historic changes to weather known to influence their migration (October – April 1979 – 2013), and forecast their future spatial distributions based on dynamically downscaled climate change scenarios (mid-21st [2046-2065], late-21st [2091-2100]). Timing of migration was best explained by WSI models including temperature and snow depth. Our analyses suggest that weather severity known to elicit southerly migration by dabbling ducks has decreased (1979 – 2013) and that arrival of these ducks from Canada into the U.S. and on to more southern latitudes may become delayed by at least a month or more by the late 21st century; such a shift could have substantial ecological, cultural, and economic consequences, and may necessitate changes to North American-wide conservation efforts for waterfowl during the non-breeding period.
2:10PM Adaptive Nest Site Selection Influences Cinnamon Teal Nest Survival In Colorado
Casey M. Setash; William L. Kendall; David Olson
Nest survival of ducks is partially a function of the spatiotemporal characteristics of the site at which a bird chooses to nest. It is also a fundamental component of population growth in waterfowl, and remains almost entirely unstudied for cinnamon teal (Anas cyanoptera). Where an individual chooses to nest directly influences how successful they will be in their reproductive efforts, with the potential to be adaptive or maladaptive to the individual’s fitness. We investigated cinnamon teal nest survival in an intensively managed wetland complex in southern Colorado using a multi-state, multi-stage framework and assessed nest site selection using discrete choice models to explore whether the nest-site characteristics teal selected were adaptive. We monitored 80 nests from 2015-2016 on Monte Vista National Wildlife Refuge with overall nest survival estimates of 27.3% and 11.3%, respectively. Nest sites selected by teal were farther from shrub-dominated upland areas (βShrub = 0.062; CI = 0.030-0.093), closer to water (βWater = -0.227; CI = (-0.349)-(-0.105)), and characterized by lower vegetation structure (βVOR = -0.050; CI = (-0.080)-(-0.019)) than available sites. The relationships between habitat characteristics and nest survival varied both in direction and by nest stage. Higher nest site vegetation structure was positively associated with nest survival (βVOR_Lay = 0.079; CI = 0.065-0.093) during the laying stage but not during the incubation stage (βVOR_Inc = 0.002; CI = -0.025-0.021) and nests farther from water were marginally associated with lower nest survival during the incubation stage (βWater_Inc = -0.086; CI=-0.189-0.007). Nest site selection was predictive of future nest survival for some nest site characteristics but not others, suggesting teal might be selecting nest locations for reasons other than future reproductive success or that they are selecting at a different scale than the one measured here.
2:30PM Body Condition of Arctic Geese Wintering in Arkansas
Ethan R. Massey; Douglas C. Osborne
Arctic geese, including greater white-fronted geese (Anser albifrons frontalis), lesser snow geese (Chen caerulescens caerulescens), and Ross’s geese (Chen rossii) have experienced increases in abundance and geographic shifts in winter distribution. Consequently, competition among waterfowl species for food resources for maintenance of body condition and stored nutrients has increased in the Mississippi Alluvial Valley. The purpose of our research was to track temporal changes in body condition of Arctic geese from time of arrival on the wintering grounds to spring departure. We collected foraging Arctic geese in rice, soybeans, corn, and moist-soil wetlands from October – February, 2015-16 and 2016-17 across six counties in eastern Arkansas. We conducted proximate analysis to determine lipid and protein as an index of body condition. Lipid stores increased by 7.7% immediately upon arrive in late-October to mid-November. Average lipid stores were highest in November at (x = 44.3, SE±1.9 %) and lowest in February (x = 23.0, SE±0.9 %). Mean protein stores however, were stable through the winter period (xOctober = 9.3, SE±0.3 % and xFebruary = 9.4, SE±0.3 %). Temporal trends in body condition demonstrate lipid storage is important during early winter when high-energy food resources are abundant. A decline in stored lipids as winter progresses may be driven by numerous factors such as food depletion, physiological changes in the body to require more nitrogen rich foods, or the effects of hunting pressure in rice growing regions of Arkansas. Arctic geese do not appear to be building protein reserves on the southern portion of the wintering grounds to be used during the breeding season. An increased understanding of the role that the wintering grounds play on the nutrient dynamics of Arctic geese may aid managers in mitigating the unprecedented populations of geese we are experiencing.
2:50PM Refreshment Break
3:20PM Quantifying Changes and Drivers of Mottled Duck Density in Texas
Beth E. Ross; David A. Haukos; Patrick Walther
As warming occurs, and sea level rises, coastal marshes will either be lost entirely or experience dramatic environmental alterations that may change the function of the affected coastal ecosystem. The combined effect of increasing severe weather events, sea level rise, and intensive drought will likely have non-linear effects on coastal marsh wildlife species and their associated habitats. A species of conservation concern that persists in these coastal areas is the mottled duck (Anas fulvigula). Mottled ducks in the Western Gulf Coast are more than 50% below target abundance numbers established by the Gulf Coast Joint Venture. While Texas mottled ducks are declining in abundance, specific causes influencing the population decrease remain unknown. Our goals were to determine where the largest declines in mottled duck population were occurring along the system of Texas Gulf Coast National Wildlife Refuges and quantify the relative contribution of environmental and intrinsic effects on changes to relative population density. To address these goals, we developed a hierarchical approach to directly test the effects of environmental covariates on density dependence. We modeled aerial survey data of mottled duck density along the Texas Gulf Coast from 1986-2015 to quantify effects of extreme weather events on mottled duck density using the U.S. Climate Extremes Index and Palmer Drought Severity Index. Our results indicate that decreases in abundance are best described by an increase in days with extreme one-day precipitation from June to November (hurricane season), a decrease in wet, cool summers, and an increase in drought. Increases in extreme one-day precipitation resulted in an increase in density dependence. Better understanding what portions of the life cycle are affected by environmental conditions, and how to manage mottled duck habitat in combination with these events will likely be key to persistence of the species under future environmental conditions.
3:40PM Habitat Selection of Adult Female Mallards in the Lake St. Clair Region During Autumn and Winter
Matthew D. Palumbo; Scott A. Petrie; Michael L. Schummer
Waterfowl select habitats for survival and courtship during the non-breeding period. Thus, waterfowl are thought to modify their timing and location of feeding and resting in response to hunting disturbance and food resources. Great Lakes mallards (Anas platyrhynchos) are subject to different conditions than mid-continent mallards and require additional study and possibly different management strategies. Mallards are ideal candidates to evaluate risk-avoidance strategies during autumn-winter because they are abundant, hunted, and use a diversity of habitats differing in quality, including refugia. The Lake St. Clair region is one of the most important areas in the Great Lakes for waterfowl during migration. During late-summer 2014 and 2015, we trapped adult female mallards at Lake St. Clair and equipped 59 individuals with backpack style GPS transmitters. We used discrete-choice modeling to analyze local scale movements (n = 10,155 fixes) of these marked mallards and to estimate the influence of landscape composition on habitat selection before, during, and after the hunting season, September – January. We categorized habitat types by ownership to describe relative differences in management practices influencing intensity of disturbance from hunting and food resource quality. Throughout our 158 d monitoring period, mallards consistently selected for refugia on government and privately managed lands, despite differences in quality and types of food resources on these properties. Diurnal selection for other privately managed habitat types of marsh, flooded agriculture, and dry agriculture decreased by 97%, 49%, and 34%, respectively, throughout the monitoring period. Open water areas, accessible to the public were assumed to experience the greatest disturbance from hunting and were selected by mallards before and after the hunting season. Our research provides information on how female mallards navigate a landscape of risks and benefits, and models useful to conservation planners for future targeted management of the Great Lakes population of mallards.
4:00PM Hybridization and Population Structure of the Chihuahuan Desert Endemic Mexican Duck
Joshua I. Brown; Philip Lavretsky
Little is known about the evolutionary and life history of the Chihuahuan desert endemic Mexican duck (Anas platyrhynchos diazi), which is one of fourteen mallard-like species found around the world that make up the Mallard-complex. Hybridization with Mallards (Anas platyrhynchos) was originally thought to be a major conservation concern for Mexican ducks, but recent molecular work suggests otherwise. Specifically, Lavretsky et al. (2015; Molecular Ecology) found no evidence of hybridization in interior Mexican states, with few possible cases of late generation backcrosses in Sonora and US. My objectives were to fill in the geographical gaps in the sampling scheme of Lavretsky et al. by obtaining ̴75 Mexican duck samples from the state of Chihuahua, Mexico, and using Double Digest Restriction-Site Associated DNA sequencing (ddRAD-seq) methods to attain genomic data ( ̴3,500 markers) to further test for population structure, hybridization, and the origin of the recently ( ̴1990s) colonized Mexican duck population of coastal Sonora. In general, strong population structure following geographical patterns was found within Chihuahua, Mexico and further supports an isolation-by-distance pattern in Mexican ducks likely due to high levels of regional fidelity, with low or no long-distance dispersal. Importantly, the first genetically confirmed hybrids were identified, and suggests that unlike the interior southern states, mallards and Mexican ducks continue to interact in the Mexican duck’s northern range. Finally, we recovered a similar genetic signal between Chihuahuan and Sonoran samples, supporting the hypothesis that Sonora was recently colonized by Mexican ducks using new irrigation canals towards Western coastal habitat. We present a more comprehensive molecular analysis of Mexican ducks that strongly suggests hybridization may not be as prevalent as once thought, and clear population structure within Mexican ducks. Moreover, the significant differentiation from mallards begs to reevaluate their taxonomic status.
4:20PM Determining Hybrids and Rates of Hybridization: Population Genomics of Lesser and Greater Scaup
Philip Lavretsky
Estimating the frequency of hybridization is important when attempting to incorporate such interactions into conservation efforts. Along with the mitochondrial DNA (mtDNA) control region, 3,589 nuclear markers across the Z-chromosome (N = 140) and autosomes (N = 3,448) were isolated using ddRAD-seq methods to estimate the extent of hybridization between lesser (Aythya affinis) and greater (A. marila) scaup. Overall marker divergence was consistent with a scenario of genetic drift acting on markers with different effective population sizes. Population structure recovered across marker types followed current taxonomy, which included significant structure between lesser and greater scaup, no structure within lesser scaup, but differentiation between Eurasian and North American greater scaup subspecies. Estimated gene flow rates using autosomal markers suggested asymmetrical gene flow from lesser into greater scaup, which corresponded with mtDNA results in which four greater and one lesser scaup were found with introgressed mtDNA. Finally, methods were developed to mimic a breeding experiment in which empirical data was used to simulate a hybridization event (F1) and nine generations (F2-F10) of backcrossing to determine whether assignment probabilities of <99% were indicative of hybrid ancestry. In short, a total of four hybrid classes (i.e., F1, F2, F3/F4, and F5/F6) were distinguishable, with admixed histories effectively lost within the sixth generations of backcrossing. We concluded that the low interspecific assignment probabilities (range = 0.011 – 0.043) recovered for two lesser and nineteen greater scaup were consistent with the F4/F5 generation, which further supported asymmetric gene flow. These results suggest that although the two species are known to hybridize in captivity, the propensity to do so in the wild appears to be relatively low. In general, conservation efforts can benefit from these methods, which provide power for classifying hybrids and estimating the time until admixed histories are effectively lost, and thus “purity” restored.
4:40PM Survival and Reproductive Success of Mottled Ducks on the Upper Texas Coast
Trey McClinton; Heather A. Mathewson; Stephen K. McDowell; Jared D. Hall
Mottled ducks (Anas fulvigula) are non-migratory waterfowl dependent upon coastal marshes, such as those along the Texas Gulf Coast. Populations on the upper Texas coast have experienced long-term declines due to factors such as urban development, changes and land use, and low nesting success. Considering these declines our objectives were (1) generate annual mottled duck survival probabilities, and (2) determine if total rainfall during peak nesting season influenced annual nest success. We analyzed bandings (n = 6,499) and recoveries (n = 832) from 2001–2016 on the J.D. Murphree WMA. We used Program MARK to generate survival and recovery estimates by age and sex. To analyze rainfall as an influencing factor, we used the proportion of hatch year (HY) birds banded as an index of reproductive success. We ran a linear regression model in Program R to examine the ability of peak nesting period rainfall to predict annual reproduction. We found HY survival to be 0.57 ± 0.02 and AHY survival to be 0.60 ± 0.02. We found male survival to be 0.56 ± 0.02 and female survival to be 0.56 ± 0.02. We found a non-significant but negative relationship between rainfall during peak nesting and the proportion of HY birds (r = -0.3, F(1,14) = 1.41, p = 0.255, n = 16). As expected, our survival by age results showed that mature individuals had a higher probability of survival as compared to juveniles, while we found no significant difference between sexes. Our relationship results did not support the prediction that total peak nesting rainfall would significantly influence reproductive success in mottled ducks.

 

Contributed Paper
Location: Albuquerque Convention Center Date: September 26, 2017 Time: 1:10 pm - 5:00 pm