Effects of waterbirds on water quality

The effect of cormorants, egrets, herons and a species of duck were studied on the eutrophication of Bhanderaj and Pandloli reservoirs in Matar tahsil of Kheda district, Gujarat, India. The quantity of consumed food and of excrement were estimated. The Little Cormorants (1000 pairs and their fledglings) inhabiting the area of reservoir complex took up 11.8 tonnes of N and 3.9 tonnes of P, while the Cattle Egrets and Pond Herons together took up 13.47 tonnes of N and 3.98 tonnes of P in 1999. The effect of fish-eating cormorants, egrets and herons can be quantified better than those of coots which feed only on plant materials.     

Buoyancy and its constraints on the underwater foraging behaviour of Reed Cormorants Phalacrocorax africanus and Darters Anhinga melanogaster

The effects of changing buoyancy on the diving and feeding behaviour of Reed Cormorants Phalacrocorax africanus and Darters Anhinga melanogaster was investigated at Lake Kariba, Zimbabwe. A qualitative model of the energetic constraints caused by buoyancy changes on the diving behaviour of these two birds is presented and the predictions from the model are tested. The buoyancy of both species declined exponentially at different rates with water depth. Reed Cormorants were neutrally buoyant at 5–6 m while Darters were neutrally buoyant at 2–4 m depth. Buoyancy changes affect underwater swimming speed, which for Reed Cormorants is twice as fast on the bottom than when commuting, and for the Darter is significantly slower when diving than at any other time. Cormorants feeding in water deeper then 6 m spent less time on the bottom and fed less successfully than those birds feeding in shallower water. This is because their bottom times were significantly reduced as a result of the energetic constraints caused by changes in their buoyancy.     

The effects of breathing different levels of O2 and CO2 on the diving responses of ducks (Anas platyrhynchos) and cormorants (Phalacrocorax auritus)

Summary The effects of breathing different levels of O₂ and CO₂ before forced dives were investigated in 5 dabbling ducks (White Pekin) and 5 deep divers (Double Crested Cormorants). Breathing and heart rates, blood gases, and blood pH, were monitored. After breathing air before diving, ducks exhibited a slow decrease in heart rate that reached a minimum of 20 beats·min⁻¹ after 50 s submergence. The development of bradycardia was retarded if the duck breathed a hyperoxic gas mixture before diving and was accelerated if the gas mixture was hypoxic and hypercapnic. The cormorants' diving heart rate decreased to a minimum of about 60 beats·min⁻¹ in less than 20 s and development of bradycardia was unaffected by different levels of O₂ and CO₂ breathed before diving. Consequently, bradycardia in forced dived cormorants was unrelated to changes in blood gases in the dives which suggests that intravascular chemoreceptors are unimportant in initiating diving bradycardia in cormorants.     

Spread-winged behaviour of Double-crested and Flightless Cormorants Phalacrocorax auritus and P. harrisi: wing drying or thermoregulation?

The behaviour of free-living Double-crested and Flightless Cormorants, and the thermoregulation of Flightless Cormorants, were studied in the field to determine the influence of weather and the function of wing-spreading. The behaviour of both species was sensitive to changes in ambient temperature and insolation intensity. Spread-winged behaviour in both species w-as displayed only by wet individuals and was never accompanied by gular flutter. The frequency of spread-winged behaviour in Double-crested Cormorants was not correlated with ambient (shade) temperature or solar intensity. In Flightless Cormorants, however, the frequency of wing-spreading was positively correlated with ambient temperature, and negatively correlated with insolation intensity. Body temperatures in Flightless Cormorants were statistically higher during the day than during the night, while gular fluttering than while not gular fluttering, and before entering the water than after leaving the water. There were no significant differences in the body temperatures of Flightless Cormorants after wing-spreading as compared to before 'sunning'. Spread-winged behaviour in these cormorants appears to function primarily in wing drying and not in gaining or losing heat, although the ultimate goal of wing drying may be to conserve metabolic energy.     

Body temperature and insulation in diving Great Cormorants and European Shags

1. Cormorants are typically considered as wettable diving birds with high thermoregulatory costs and are presumed to exert substantial predatory pressure on fish stocks.
2. The stomach temperatures of seven Great Cormorants and three European Shags were recorded during a total of 108 foraging trips undertaken near the Chausey Islands breeding colony (France).
3. Both species kept a constant body temperature during the dive series which lasted up to 158 min and were conducted in 12°C water. Consequently, assuming that heat loss to the water is equal to heat production in diving Great Cormorants, the minimal insulating plumage air volume was calculated to be 0·371 × 10^–3 m³ (corresponding to a 1·62-mm air layer) in males and 0·347 × 10^–3 m³ (corresponding to a 1·90-mm air layer) in females.
4. Furthermore, it is shown that plumage air volume and dive depth are the major factors influencing heat flux to the water and that the energetics of diving Great Cormorants may also vary substantially according to fat layer thickness, water temperature and body temperature. Swim speed plays only a minor role.
5. Considering these results, it is postulated that Great Cormorants may have optimized plumage air volume so as to minimize both mechanical costs (upthrust) and thermoregulatory costs of swimming in cold, shallow water.
6. Finally, body temperature patterns recorded in different cormorant species while diving are compared.     

Seasonal pattern of breeding by Cape and Crowned Cormorants off western South Africa

Crawford, R.J.M., Dyer, B.M. & Upfold, L. 1999. Seasonal pattern of breeding by Cape and Crowned Cormorants off western South Africa. Ostrich 70(3&4): 193–195.

At Bird Island, Lambert's Bay, and Malgas Island, South Africa, small numbers of Cape Cormorants Phalacrocorax capensis may breed at any time of the year, but the main breeding season is from September to February. At Malgas Island, Crowned Cormorants P. coronatus may also breed throughout the year, but mostly from December to March. Counts of the breeding population of Cape Cormorants should be undertaken between October and December, and of Crowned Cormorants in January or February.     

Is ability to hepatic steatosis influenced by age at the beginning of the overfeeding period in Muscovy and Pekin ducks?

The aim of this study was to analyse the effects of species (Muscovy and Pekin ducks) and age at the beginning of the overfeeding period on fatty liver production, carcass composition and lipid and moisture content of the liver and breast muscle. We reared four groups of 40 ducks per species for the study, starting at 2-week intervals in order to have four different ages together at the beginning of the overfeeding period (10, 12, 14 and 16 weeks). At the end of the overfeeding period, all ducks were slaughtered. Our results confirmed the high levels of difference in carcass composition and lipid content in the plasma, liver and breast muscle between Muscovy and Pekin ducks at all ages. Pekin ducks were not able to develop a high degree of hepatic steatosis, but had increased lipid storage in peripheral adipose and muscle tissues than Muscovy ducks. However, the fatty liver weight of Pekin ducks increased with age, with lipid deposition in the liver and peripheral tissues. The ability of Muscovy ducks to produce fatty livers remained unchanged with age in line, with lipid deposition in the liver and peripheral tissues. The sites of lipid deposition thus depend on species and not on the physiological maturity of ducks.     

Energetics and Spread-winged Behavior in Anhingas and Double-crested Cormorants: The Risks of Generalization

SYNOPSIS. Spread-winged behavior is observed in a variety ofavian species, and a number of different functions have beenascribed to it. Anhingas and Double-crested Cormorants, representingclosely allied avian families, share a spread-winged behaviorthat is superficially identical. This paper examines the behaviorand energetics of these two species to determine whether theprimary function of this behavior is wing drying or the supplementationof metabolism. Double-crested Cormorants and Anhingas differboth in the frequency and the contexts in which spread-wingedbehavior is displayed: Double-crested Cormorants display thebehavior sparingly and without relation to ambient temperatureor solar radiant intensity, whereas Anhingas exhibit the behavioroften, particularly when ambient temperatures are low and solarradiant intensity is high. Similarly Double-crested Cormorantsshow no significant reduction in metabolic rate at ambient temperaturesbelow thermoneutrality when provided with incident simulatedsolar radiation, whereas Anhingas significantly reduce theirrates of metabolism when exposed to ambient temperatures belowthermoneutrality in the presence of incident simulated insolation.Despite the apparent similarities between these two speciestaxonomically, ecologically, and behaviorally, spread-wingedbehavior has quite different functions and energetic/ecologicalconsequences for Anhingas as opposed to Double-crested Cormorants.This example illustrates the risks of generalizing from superficialitiesand of relying on inference and speculation as opposed to data.     

Flexible foraging techniques in breeding Cormorants Phalacrocorax carbo and Shags Phalacrocorax aristotelis: benthic or pelagic feeding?

A total of 8772 dive durations were recorded during 117 diving bouts in five Cormorants Phalacrocorax carbo and five Shags Phalacrocorax aristotelis breeding at the Chausey Islands, France. Diet of the birds was assessed by analysis of 526 pellets containing 13,016 otoliths. Radio-tracking data indicated that Cormorants fed exclusively on pelagic fish during social fishing (5% of the trips) and executed 11% pelagic and 60% benthic dives during the remaining 95% of the trips. In Shags, 44% of all trips were pelagic, and the remaining 56% included 9% pelagic and 67% benthic dives. The proportions of benthic to pelagic dives varied widely between dive sequences of single birds and between individuals and sexes in both species. The prey spectrum of the Cormorants contained both pelagic (29%) and benthic fish (67%) and confirmed considerable flexibility in foraging. In Shags, birds may adjust their diving patterns to accommodate the behaviour of their main prey, sandeels Ammodytidae (87% of all prey). We propose that the wetability of plumage may explain this flexibility.     

Effect of wind farms on wintering ducks at an important wintering ground in China along the East Asian–Australasian Flyway

Wind farms offer a cleaner alternative to fossil fuels and can mitigate their negative effects on climate change. However, wind farms may have negative impacts on birds. The East China Coast forms a key part of the East Asian–Australasian Flyway, and it is a crucial region for wind energy development in China. However, despite ducks being the dominant animal taxon along the East China Coast in winter and considered as particularly vulnerable to the effects of wind farms, the potential negative impacts of wind farms on duck populations remain unclear. We therefore assessed the effects of wind farms on duck abundance, distribution, and habitat use at Chongming Dongtan, which is a major wintering site for ducks along the East Asian–Australasian Flyway, using field surveys and satellite tracking. We conducted seven paired field surveys of ducks inside wind farm (IWF) and outside wind farm (OWF) sites in artificial brackish marsh, paddy fields, and aquaculture ponds. Duck abundance was significantly higher in OWF compared with IWF sites and significantly higher in artificial brackish marsh than in aquaculture ponds and paddy fields. Based on 1,918 high‐resolution satellite tracking records, the main habitat types of ducks during the day and at night were artificial brackish marsh and paddy fields, respectively. Furthermore, grid‐based analysis showed overlaps between ducks and wind farms, with greater overlap at night than during the day. According to resource selection functions, habitat use by wintering ducks was impacted by distance to water, land cover, human activity, and wind farm effects, and the variables predicted to have significant impacts on duck habitat use differed between day and night. Our study suggests that wintering ducks tend to avoid wind turbines at Chongming Dongtan, and landscape of paddy fields and artificial wetlands adjoining natural wetlands is crucial for wintering ducks.     

The frequency of Sarcocystis spp. and its effect on winter carcass composition of mottled ducks

Macrocysts of the protozoan parasite Sarcocystis spp. occurred in 34 of 241 (14%) adult and 6 of 70 (8.6%) immature mottled ducks (Anas fulvigula) that were collected in southwestern Louisiana from 1987 to 1989. The prevalence of Sarcocystis spp. among immature ducks was higher than previously reported, possibly because of a longer exposure period. No differences in carcass composition variables were found between heavily infected and uninfected adult mottled ducks during the winter period of the annual cycle. We concluded that macrocysts of Sarcocystis spp. did not influence carcass composition and probably exert negligible effects on survival of parasitized mottled ducks during winter.     

Breeding ecology of Red‐faced Cormorants in the Pribilof Islands,Alaska

ABSTRACT Red‐faced Cormorants (Phalacrocorax urile) are North Pacific endemics recognized as a vulnerable species, but little is known about their breeding ecology. We studied Red‐faced Cormorants on St. Paul Island, Alaska, from 1975 to 2009, with more detailed data collected in 2004 and 2005. Mean clutch sizes in 2004 (3.2 ± 0.8 [SD] eggs) and 2005 (3.1 ± 0.8 eggs) were similar to the long‐term average (2.9 ± 0.3 eggs from 1976 to 2009). The mean laying interval in 2004 and 2005 was 2.15 ± 0.80 d (N= 407), and the mean egg period (number of days between laying of an egg and hatching) was 31.1 ± 1.4 d (N= 158). Approximately 64 ± 17% of eggs hatched during the period from 1975 to 2009. The mean number of chicks per nest in 2004 and 2005 was 2.8 ± 0.8 (N= 232), and the mean number of fledglings per initiated nest in all years was 1.22 ± 0.52. Chicks fledged 46 to 66 d posthatching. In 2004 and 2005, the primary causes of egg loss were predation by Arctic foxes (Vulpes lagopus) and destruction of eggs and abandonment of nests due to storms. Starvation was the primary cause of nestling mortality in both years. Because chicks are dependent on parents to provide food for over 45 d, consistent near‐shore foraging opportunities must be available. From 1975 to 2009, Red‐faced Cormorants experienced only 1 yr of complete reproductive failure (1984). The consistent reproductive success of Red‐faced Cormorants suggests that conditions may be relatively stable for this species on St. Paul Island, or that the variability in their breeding ecology (e.g., phenology, clutch sizes, and incubation strategies) provides the flexibility needed to successfully fledge some chicks nearly every year.     

鸭稻共作生态农业模式的功能与效益分析

对鸭稻共作生态农业模式的结构、功能和效益进行了综合分析。结果表明,鸭子和水稻可以较好地全天候地同生共长在稻田生态系统中,平均每公顷大约300-375只鸭子。利用鸭子的野性和杂食性在一定程度上可防除病、虫、草害,提高土壤肥力,因而可代替人耕耙田、施肥、施药等,避免了农药和化肥的大量投入;鸭群的活动可刺激和促进水稻的生长发育。利用这种模式可以生产出有机食品或绿色稻米,其经济效益比常规稻作高。鸭稻共作系统的每公顷净收入比常规稻作系统要高出808.5元。若按绿色食品价格高出同类商品市场价格的20%计算,则鸭稻共作系统每公顷比常规稻作系统大约多增加2000元左右的收入。这种模式的推广应用可产生良好的生态-经济-社会效益。     

Does overfeeding enhance genotype effects on liver ability for lipogenesis and lipid secretion in ducks?

We evaluated the effects of genotype (Muscovy, Pekin and their crossbreed hinny and mule ducks) and feeding levels (overfeeding between 12 and 14 weeks of age vs ad libitum feeding) on liver ability for lipogenesis and lipid secretion in ducks. Samples of liver and blood were collected at 14 weeks of age from 8 birds per group. Plasma levels of insulin was considerably increased in overfed ducks (1.9-fold), stimulating the hepatic activity of the main enzymes involved in lipogenesis from glucose (glucokinase, GK, glucose-6-phosphate dehydrogenase, G6PDH, malic enzyme, ME, acetyl CoA carboxylase, ACX), while cytochrome-c oxidase (COX) activity, indicating overall oxidation ability of energy-yielding substrates, remained unchanged. Plasma levels of triglycerides, phospholipids and total cholesterol were therefore increased (1.9, 3.7, 1.6 and 1.6-fold, respectively). Glycaemia also significantly increased (+8%). Pekin ducks exhibited higher levels of GK and G6PDH activity in the liver than Muscovy ducks, suggesting a greater ability to use glucose consistent with their lower glycaemia. Muscovy ducks had greater ACX activity, suggesting greater ability to synthesise lipids. However, plasma lipid levels were much higher in Pekin ducks than in Muscovy ducks, suggesting a greater ability to export lipids from the liver. Values for the different criteria measured in this study were intermediate or similar in hinny and mule ducks to those of parental species. The high values for GK, G6PDH, ME and ACX activity in hybrid ducks enabled them to produce heavy fatty livers with the same chemical and lipid composition as Muscovy ducks and characterised by high amounts of triglycerides (around 96% of total lipids), and saturated and mono-unsaturated fatty acids.     

Patterns of habitat and invertebrate diet overlap between tiger salamanders and ducks in prairie potholes

During the breeding season, migratory waterfowl are attracted to wetlands characterized by high macroinvertebrate availability. Many of these prairie potholes are fishless and this apparent void is filled, at least partially, by tiger salamanders. Based on gut contents from 98 tiger salamanders and published diet data from over 1500 ducks, we show that there is general overlap in diet between both larval and adult tiger salamanders and 10 duck species. Furthermore, when the ducks were split into foraging guilds and compared with tiger salamanders, prey type overlap was 1.7 times higher and prey size was 1.8 times higher with dabbling ducks than diving ducks. Field surveys show that tiger salamander density is more highly correlated with diving duck density across potholes than dabbling duck density. Tiger salamanders have higher diet overlap with dabbling ducks than diving ducks whereas tiger salamanders have higher spatial overlap with diving ducks than dabbling ducks suggesting that these consumers coarsely partition diet and habitat resources. It has been reported that tiger salamanders have specialized diets that are associated with foraging preferences for benthic habitats. This view is too narrow: in southwestern Manitoba, Canada, tiger salamanders are more general consumers with diets more like dabbling ducks that forage mostly in planktonic and littoral habitats. Our results suggest that dabbling and diving ducks are, to different extents, liable to the effects of indirect interactions, specifically competition for common prey, with tiger salamanders.     

Foraging strategies of Great Cormorants Phalacrocorax carbo carbo wintering north of the Arctic Circle

This study describes how 30 Great Cormorants Phalacrocorax carbo carbo managed to catch sufficient food for their daily energetic needs under conditions of reduced daylight and cold while wintering north of the Arctic Circle. Activity observations showed that the Great Cormorants' daily foraging pattern was generally bimodal, with morning and evening feeding peaks. They compensated for shorter daylengths in midwinter by starting to forage later and ending progressively earlier at lower light intensities. Fishing constituted only a minor part of their time–activity budget, and was one of the most efficient reported in marine birds. The Great Cormorants spent less than 60 minutes a day fishing in midwinter. Although subzero ambient temperatures and blizzards contributed to increased heat loss in midwinter, this potential energy loss did not seem to be compensated for by an increase in fish intake. Instead the Great Cormorants seemed to economize energy expenditure by halving the time spent at sea, and halving the number but doubling the mass of each fish taken.     

Does overfeeding enhance genotype effects on energy metabolism and lipid deposition in breast muscle of ducks?

We evaluated the effects of genotype (Muscovy, Pekin and their crossbreed hinny and mule ducks) and feeding levels (overfeeding between 12 and 14 weeks of age vs ad libitum feeding) on energy metabolism and lipid deposition in breast muscle of ducks. Samples of breast muscle (Pectoralis major) were collected at 14 weeks of age from 8 birds per group. Overfeeding induced an accumulation of lipids in breast muscle (1.5- to 1.7-fold, depending on genotype) mainly induced by triglyceride deposition. It also induced a considerable increase in the amounts (expressed as g/100 g of tissue) of saturated and mono-unsaturated fatty acids (SFA, MUFA), while the amounts of poly-unsaturated fatty acids (PUFA) remained unchanged in hinny and Muscovy ducks or slightly increased in Pekin and mule ducks. In breast muscle, overfeeding decreased the activity of the main enzymes involved in lipogenesis from glucose (glucose-6-phosphate dehydrogenase, G6PDH, malic enzyme, ME, acetyl CoA carboxylase, ACX). Lipoprotein lipase (LPL) activity in Pectoralis major muscle was also significantly decreased (-21%). The ability of muscle tissues to catabolize long-chain fatty acids, as assessed by beta-hydroxyacyl CoA dehydrogenase (HAD) activity, was increased in Pectoralis major muscle, as was cytochrome-c oxidase (COX) activity. Hybrid and Pekin ducks exhibited higher levels of ACX and LPL activity in Pectoralis major muscle than Muscovy ducks, suggesting a greater ability to synthesise lipids in situ, and to take up circulating lipids. Total lipid content in breast muscle of hybrid and Pekin ducks was higher than in that of Muscovy ducks. In hybrid and Pekin ducks, lipid composition of breast muscle was characterized by higher amounts of triglycerides, SFA and MUFA than in Muscovy ducks. Finally, oxidative metabolism was greater in Pectoralis major muscles of hybrid and Pekin ducks than in Muscovy ducks, suggesting an adaptative strategy of muscle energy metabolism according to lipid level.     

鸭生长激素基因内含子2、3多态性分析

根据鸭生长激素基因内含子2、3的序列设计5对引物,利用PCR-SSCP方法对北京鸭、西湖野鸭、金定鸭、山麻鸭、荆江鸭、绍兴鸭等6个鸭品种进行了单核苷酸多态性分析, 并检测其多态性。结果共发现8个突变位点, 其中内含子2有7个: 2593处C-T, 2770处G-A, 2813处T-A, 2829处C-A, 2894处C-T, 2896处T-C,3100处C-G; 内含子3有1个: 3270处A-G。统计结果显示, 这8个变异位点的基因型频率分布与品种有关, 在这些基因座的变异水平上, 北京鸭和绍兴鸭表现出了相当的品种保守性, 本研究所检测到的这些基因座可能与鸭的生产性能有关。     

Effects of ACTH, capture, and short term confinement on glucocorticoid concentrations in harlequin ducks (Histrionicus histrionicus).

Little is known about baseline concentrations of adrenal hormones and hormonal responses to stress in sea ducks, although significant population declines documented in several species suggest that sea ducks are exposed to increased levels of environmental stress. Such declines have been observed in geographically distinct harlequin duck populations. We performed an adrenocorticotropic hormone (ACTH) challenge to evaluate adrenal function and characterize corticosterone concentrations in captive harlequin ducks and investigated the effects of capture, surgery, and short term confinement on corticosterone concentrations in wild harlequin ducks. Harlequin ducks responded to the ACTH challenge with an average three-fold increase in serum corticosterone concentration approximately 90 min post injection, and a four- to five-fold increase in fecal glucocorticoid concentration 2 to 4 h post injection. Serum corticosterone concentrations in wild harlequin ducks increased within min of capture and elevated levels were found for several hours post capture, indicating that surgery and confinement maintain elevated corticosterone concentrations in this species. Mean corticosterone concentrations in wild harlequin ducks held in temporary captivity were similar to the maximum response levels during the ACTH challenge in captive birds. However, large variation among individuals was observed in responses of wild birds, and we found additional evidence suggesting that corticosterone responses varied between hatch year and after hatch year birds.     

Effects of ACTH, capture, and short term confinement on glucocorticoid concentrations in harlequin ducks (Histrionicus histrionicus)

Little is known about baseline concentrations of adrenal hormones and hormonal responses to stress in sea ducks, although significant population declines documented in several species suggest that sea ducks are exposed to increased levels of environmental stress. Such declines have been observed in geographically distinct harlequin duck populations. We performed an adrenocorticotropic hormone (ACTH) challenge to evaluate adrenal function and characterize corticosterone concentrations in captive harlequin ducks and investigated the effects of capture, surgery, and short term confinement on corticosterone concentrations in wild harlequin ducks. Harlequin ducks responded to the ACTH challenge with an average three-fold increase in serum corticosterone concentration approximately 90 min post injection, and a four- to five-fold increase in fecal glucocorticoid concentration 2 to 4 h post injection. Serum corticosterone concentrations in wild harlequin ducks increased within min of capture and elevated levels were found for several hours post capture, indicating that surgery and confinement maintain elevated corticosterone concentrations in this species. Mean corticosterone concentrations in wild harlequin ducks held in temporary captivity were similar to the maximum response levels during the ACTH challenge in captive birds. However, large variation among individuals was observed in responses of wild birds, and we found additional evidence suggesting that corticosterone responses varied between hatch year and after hatch year birds.