Survival of Wood Duck Ducklings and Broods in Mississippi and Alabama

ABSTRACT Although North American wood ducks (Aix sponsa) are well-studied throughout their range, researchers know little about demographic and environmental factors influencing survival of ducklings and broods, which is necessary information for population management. We studied radiomarked female and duckling wood ducks that used nest boxes and palustrine wetlands at Noxubee National Wildlife Refuge (NNWR) in Mississippi, USA, in 1996–1999, and riverine wetlands of the Tennessee-Tombigbee Rivers and Waterway (TTRW) system in Alabama in 1998–1999. We estimated survival of ducklings and broods and evaluated potentially important predictors of duckling survival, including age and body mass of brood-rearing females, hatch date of ducklings, duckling mass, brood size at nest departure, inter-day travel distance by ducklings, site and habitat use, and daily minimum air temperature and precipitation. At NNWR, survival of 300 radiomarked ducklings ranged from 0.15 (95% CI = 0.04-0.27) to 0.24 (95% CI = 0.13-0.38) and was 0.21 (95% CI = 0.15-0.28) for 1996–1999. Our overall estimate of brood survival was 0.64 (n = 91; 95% CI = 0.54-0.73). At TTRW, survival of 129 radiomarked ducklings was 0.29 in 1998 (95% CI = 0.20-0.41) and 1999 (95% CI = 0.13-0.45) and was 0.29 (95% CI = 0.20-0.40) for 1998–1999. Our overall estimate of brood survival was 0.71 (n = 38; 95% CI = 0.56-0.85). At NNWR, models that included all predictor variables best explained variation in duckling survival. Akaike weight (w_i) for the best model was 0.81, suggesting it was superior to other models (<0.01 < w_i < 0.18). We detected 4 competing models for duckling survival at TTRW. Inter-day distance traveled by ducklings was important as this variable appeared in all 4 models; duckling survival was positively related to this variable. Patterns of habitat-related survival were similar at both study areas. Ducklings in broods that used scrub-shrub habitats disjunct from wetlands containing aggregations of nest boxes had greater survival probabilities than birds remaining in wetlands with such nest structures. Managers may increase local wood duck recruitment by promoting availability of suitable brood habitats (e.g., scrub-shrub wetlands) without aggregations of nest boxes that may attract predators and by dispersing nest boxes amid or adjacent to these habitats. We did not determine an optimal density of nest boxes relative to local or regional population goals, which remains important research and conservation needs.     

Landscape-level correlates of mallard duckling survival: Implications for conservation programs

Despite recent work, uncertainty remains concerning how abiotic and biotic factors affect duckling survival. Additionally, upland habitat characteristics may affect duckling survival rates but this potential relationship has largely been ignored. We evaluated several unresolved hypotheses about causes of mallard (Anas platyrhynchos) duckling survival variation, with an emphasis on assessing effects of managed and remnant natural upland habitats. During 1993–2000, 617 radio-marked females provided information about brood habitat use and duckling survival on 27 sites in prairie Canada. We contrasted a priori and exploratory models that incorporated effects of upland, wetland, weather, female, and brood-related variables on duckling survival rates. Survival was highest for ducklings when a greater proportion of their surrounding landscape (i.e., within a 500-m radius buffer around the brood) was comprised of wetlands characterized by a central expanse of open water and a peripheral ring of flooded emergent vegetation. Cold and wet weather in the first week of life resulted in lower duckling survival. In a post hoc analysis, duckling survival (of older ducklings) was negatively related to increasing proportions of managed hayland. © 2011 The Wildlife Society.     

雏鸭试验感染鸭肝炎病毒后血液常规指标的测定

用Ⅰ型鸭肝炎病毒标准强毒R85952株人工感染3日龄雏鸭,通过采集不同时期的血液进行细胞计数、血沉测定、血红蛋白测定等血常规检查。结果表明,感染DHV的试验组鸭的红细胞数量较对照组极显著减少(P<0 01);试验组鸭在感染DHV24h内白细胞数量与对照组相比无明显差异或略有下降,但24h后试验组鸭白细胞数量较对照组显著减少(P<0 05);试验组鸭的血红蛋白含量极显著低于对照组(P<0 01);试验组鸭的血液沉降速度极显著高于对照组(P<0 01)。     

Glucose Transport in the Malarial (Plasmodium lophurae) Infected Erythrocyte*

Plasmodium lophurae-infected red blood cells utilized considerably greater quantities of glucose than did uninfected duckling red cells. Kinetic analysis of glucose transport showed: (A). Below a concentration of 2 mM in the medium the uptake process followed Michaelis-Menten kinetics (carrier-mediated facilitated diffusion) whereas at concentrations greater than this simple diffusion became the main mode of entry. (B). The apparent transport constants, K_t, for normal and infected cells were similar. However there was an 8-fold increase in the maximal velocity, V_max, for infected cells. (C). “Free” malaria parasites had a significantly lower K_t and a higher V_max than did normal or infected red cells. Entry and exit studies with the nonmetabolizable sugar analog, 3-0-methyl glucose, demonstrated that the enhanced rate of uptake by infected cells involved an increase in the simple diffusion component and the degree of enhancement was correlated with the size of the intracellular parasite. Competition experiments suggested that in the malaria-infected cell one locus is involved in the carrier-mediated transport of glucose, mannose and galactose whereas another locus transports fructose and/or glycerol. These results indicate that the enhanced entry of glucose into the malaria-infected red cell is a consequence of factors other than increased glucose catabolism by the host-parasite complex, and the host cell's capacity to take up greater quantities of sugar directly involves the growing intracellular plasmodium.     

Structural and functional characteristics of primary cell cultures derived from the adrenal gland tissue of neonatal mallard ducklings (Anas platyrhynchos)

Summary Primary cell cultures were prepared from the adrenal glands of one-day-old mallard ducklings (Anas platyrhynchos). The cells attached equally well to uncoated plastic and glass surfaces and on surfaces that had been coated with collagen. The phase of logarithmic growth occurred between the second and the fourth day, and the cells became confluent between the fifth and the sixth day. Staining with Sudan black B and toluidine blue and viewing fixed preparations by transmission electron microscopy indicated that the cultures consisted mostly of steroidogenic cells. A smaller population of chromaffin cells was also present. Scanning electron microscopy showed that most of the cells had long filopodia, and some cells had numerous surface blebs that were interpreted as exocytotic vesicles. When incubated in Krebs-Henseleit buffer containing 1–24 ACTH the cultured cells released three corticosteroids, namely, corticosterone, aldosterone and deoxycorticosterone. These responses occurred within 15 min of exposure to medium containing 1–24 ACTH and continued throughout a 60-min period of continuous stimulation. The minimally effective concentration of 1–24 ACTH was 0.078 ng per ml (0.0234 nM) and, as the concentration was increased up to 10 ng per ml (2.99 nM), the total output of each hormone during the 60-min incubation period increased significantly according to the following semi-logarithmic relationship: Y=a+b log X, where Y=the total output of hormone, X=the concentration of 1–24 ACTH in the medium, and a=the total output of hormone when the medium contained 1.0 ng of 1–24 ACTH per ml. The total outputs of each hormone in the presence of a maximally effective concentration of 1–24 ACTH, however, were low compared to the responses of similarly stimulated tissue slices taken from the neonatal duckling. It is concluded that most of the cells comprising the confluent cultures were derived from steroidogenic cells in the neonatal adrenal. These cells appeared to retain corticotropin receptors during the course of developing into confluent monolayers, but their diminished steroidogenic capacity to respond when stimulated maximally suggests that some generational changes may have occurred.This work was supported by grants to James Cronshaw and W.N. Holmes from the University of California Committee on Research and the National Science Foundation (DIR-8820923), Washington, DC, USA     

On the mechanism of plasma membrane turnover in the salt gland of ducklings

Summary This study provides information on the rates of DNA synthesis, sites of DNA synthesis, and DNA content of the avian salt gland during the osmoticstressing (plasma membrane synthesis) and destressing (plasma membrane turnover) cycle, in an effort to better understand the relationship of cell turnover to the initial events in plasma membrane amplification, differentiation, and turnover. The rate of DNA synthesis increases 12–24 h after the onset of osmotic stress, is maximal at about 24 h of osmotic stress, and decreases thereafter in fully stressed and destressed glands. The maximum DNA and protein content, and the maximum protein/DNA ratio are obtained after about 3 days of stress. Autoradiograms show that at 24 h of stress 70–80% of DNA synthesis occurs in connective tissue cells and 20–30% in parenchymal cells, but by 6 days of stress, synthesis occurs about equally in these cell groups. Because destressing is characterized by a large decrease in plasma membrane and in glandular protein, but by little DNA turnover or loss, the loss of plasma membrane is likely due to some type of cell dedifferentiation rather than cell turnover.     

The role of predator removal,density-dependence,and environmental factors on mallard duckling survival in North Dakota

Duckling survival is an important component of mallard (Anas platyrhynchos) recruitment and population growth, yet many factors regulating duckling survival are poorly understood. We investigated factors affecting mallard duckling survival in the drift prairie of northeastern North Dakota, 2006–2007. Mammalian meso-predators were removed by trapping on 4 92.3 km² study sites and another 4 study sites served as controls. We monitored 169 broods using telemetry and periodic resighting, and we modeled cumulative survival to 30 days of age using the nest survival module in Program MARK. Duckling survival was not affected by predator removal ( , 85% CI: 0.182–0.234; , 85% CI: 0.155–0.211) and was only weakly negatively correlated with duckling density. Duckling survival was higher in 2007 ( , 85% CI: 0.193–0.355) than 2006 ( , 85% CI: 0.084–0.252) and increased with total seasonal and semipermanent wetland area and declined with perennial cover in the surrounding landscape. Broods that hatched earlier in the season (especially in 2006) and ducklings that were heavier at hatch also had higher survival. Our estimates of duckling survival are among the lowest reported for mallards and contradict previous research in Saskatchewan that found predator removal increased duckling survival. However, our results are consistent with other studies suggesting that earlier hatch date, increased wetland availability, and better duckling condition lead to increased survival. Management actions that increase wetland density, improve nest success early in the season, and potentially target brood-specific predators such as mink (Neovison vison) would likely lead to higher duckling survival. © 2011 The Wildlife Society.