Feeding site selection by Wigeon Anas penelope in relation to water

The feeding sites of European Wigeon Anas penelope are always close to water. Initial studies suggest that this is primarily an anti-predator behaviour rather than a requirement for drinking and bathing. Vigilance and flock-size measurements at varying distances from water support this hypothesis. However, birds will feed away from water if grass biomass is greater further away. The end of the shooting season also causes birds to feed further away from water.     

Tits and their caterpillar food supply

In this paper I review what is known about the relationship between the tits' clutch-size and the timing of their breeding season and the numbers of their caterpillar prey. The results come from the Edward Grey Institute's long-term study of Great and Blue Tits in Wytham Wood, near Oxford. This study was started in 1947 by Drs D. Lack and J. A. Gibb (Lack 1966, Perrins 1979)- These results could only have been obtained from a long-term study and emphasize the value of such studies for our understanding of certain aspects of ecology. In addition, they could not have been obtained by a study of the birds alone, being dependent on a knowledge of their insect food; most of this information was made available as a result of a parallel long-term study of the insect fauna of the oak trees, made by a number of people from the Hope Department of Entomology, University of Oxford.     

Variation in spring migration routes and breeding distribution of northern pintails Anas acuta that winter in Japan

In North America, spring migration routes and breeding distribution of northern pintails Anas acuta vary because some individuals opportunistically nest at mid‐latitudes in years when ephemeral prairie wetlands are available, whereas others regularly nest in arctic and sub‐arctic regions where wetland abundance is more constant. Less was known about migration routes and breeding distribution of pintails in East Asia. From 2007–2009 we marked 198 pintails on their wintering areas in Japan with satellite transmitters to: 1) document spring migration routes and summer distribution, 2) evaluate migratory connections and breeding season sympatry with North American pintails, and 3) determine if pintails used the same migration routes in fall as in spring. Most pintails (67%) migrated to the Kamchatka or Chukotka peninsulas in eastern Russia either directly from Japan or via Sakhalin Island, Russia. Remaining pintails primarily migrated to the Magadan region or Kolyma River Basin in eastern Russia via Sakhalin Island. The Chukotka Peninsula was the most common summer destination, with highest densities in the Anadyr Lowlands; a region also used by pintails that migrate from North America. One pintail migrated to St. Lawrence Island, Alaska, in spring and another briefly migrated to the western coast of Alaska in fall. Autumn migration routes generally mirrored spring migration although most pintails bypassed Sakhalin Island in fall. Compared to North American pintails, pintails that winter in Japan exhibited less variation in migration routes and breeding distribution, and nested at higher latitudes. In the Russian Far East there is no region with habitats comparable in extent to the ephemeral mid‐latitude wetlands of North America. Consequently, East Asian pintails mainly nest in arctic and sub‐arctic regions where annual consistency in wetlands promotes constancy in migration routes and breeding distribution. Breeding season sympatry between pintails from different continents results more from North American pintails migrating to eastern Russia than from Japanese pintails migrating to North America.     

Territorial defense of an excess food supply by an algal grazing fish, ayu

The size of the territory defended by the grazing fish ayu, Plecoglossus altivelis, often increases with decreasing intruder pressure. This territorial extension occurs even after additional growth of the fish reaches a plateau due to a surplus supply of algal food. This raises questions about the ecological advantages of defending an apparently enlarged territory. Enclosures were used to carry out observations on fish maintained as: (i) individuals with algae attached to the whole bottom area (2.4m²); (ii) individuals with algae covering 0.8m²; and (iii) with three conspecifics (competitive use) with algae attached to 2.4m². In the competitive use enclosures, one (occasionally two) fish that exclusively foraged the area appeared in each of the groups. Algal resources were sufficiently renewable that no significant difference in growth rate was detected between the dominants of the competitive groups and the two types of solitary enclosures, indicating that the defended area supplied algal resources that exceeded the dominants ability to grow. All the territorial holders realized an increase in relative body weight, suggesting the occurrence of inhibition, which corresponds to Verners concept of superterritory. However, as inferred from the pheophytin/chlorophylla ratios, algae within a territory showed less senescence, perhaps owing to cropping by the dominant, and this was considered to be an adaptive response by the fish to an unpredictable food supply. In conclusion, the ayu conditionally defends a territory for long-term benefits, and inhibition is a consequence of facultative territory size and not a cause of it.     

Moulting diving ducks and their food supply

Numbers of moulting diving ducks at Myvatn, north Iceland, were monitored over a period of 25 years; aquatic insects (Chironomidae and Simuliidae), a major food resource, were monitored with window traps for 23 years. The response of the duck populations to changes in the food situation during the moulting period varied between species. Histrionicus histrionicus and Melanitta nigra invariably go to the sea to moult. Three species (Aythya fuligula, Clangula hyemalis and Mergus serrator) have shown long term variation in moult migration habits. Aythya marila and Bucephala islandica stay for moulting, their numbers supplemented by birds from elsewhere. A. marila is a generalist feeder and therefore at low risk of starving, the strategy of Bucephala islandica is to move within the water system where the food situation tends to alternate between the lake and the river. Numbers of Bucephala islandica males moulting on Lake Myvatn were strongly and positively correlated with chironomid numbers and those moulting on the river Laxá with Simulium vittatum, the main food resource there. We did not find convincing evidence that numbers of moulting A. marila and C. hyemalis responded to variation in the food supply during the study period. This applied also to A. fuligula in the South Basin of Myvatn, but numbers in the North Basin were positively associated with chironomid numbers. M. serrator moulting on Myvatn showed negative correlations with the chironomids, perhaps reflecting a negative association between chironomids and its main food, Gasterosteus aculeatus. Apart from safety considerations for a flightless bird, the choice of a moulting site is apparently influenced by the local food conditions on one hand and by the opportunities and risks involved in migrating to distant moulting sites with an unknown food situation on the other hand.     

Seasonal grazing rates and food processing by tropical herbivorous fishes

Seasonal variability in grazing rates and food-processing characters were assessed for three abundant fishes in a tropical rocky shore: the damselfish Stegastes fuscus , the parrotfish Sparisoma atomarium , and the surgeonfish Acanthurus bahianus . Significant differences were found in grazing rates among hour of day and seasons, and in food-processing characters among seasons for the three fishes. Grazing rates for S. atomarium and A. bahianus peaked at 1300 and 1400 hours for S. fuscus . Three main periods of different intensity in bite rates, low, intermediate and intense, were identified for all fishes. As expected, total bite rates, ingestion rates and gut fullness were highest in A. bahianus , the largest species studied, followed by S. atomarium and S. fuscus. S. atomarium with fused jaw teeth, holds the highest bite size and S. fuscus the lowest one. Gut turnover was high for S. fuscus and similar for S. atomarium and A. bahianus . Grazing rates and food-processing characters seem to vary between seasons not only due to changes in temperature, but also affected by other factors. Fishes employ different food-processing mechanisms and bear some differences in food-processing characters to achieve optimal energetic supplies from a poor nutrient food resource.     

A long-term study of winter and early spring tree pollen in the Tulsa, Oklahoma atmosphere

Since 1986 the atmosphere in Tulsa, Oklahoma has been monitored for airborne pollen and spores with a Burkard 7-day spore trap situated on the roof of a building at The University of Tulsa. The present study specifically examined the early spring tree pollen season for several local taxa and the occurrence of pre-season pollen during December and January. Knowledge of the local pollen season will help identify the presence of out-of-season pollen and possible long distance transport (LDT) events. Average daily concentrations of airborne pollen for species ofBetula, Quercus, Ulmus, and Cupressaceae were determined for each year from 1987 to 1996. The data showed that during the early spring the precise pollination periods for these allergenic tree species are highly variable. There were considerable variations in start date, season length, peak concentration, date of peak, and cumulative season total. The start dates forUlmus, Betula, andQuercus varied by 30 days or more, while the early spring Cupressaceae pollen showed the least variation in start date (only 23 days). More research is needed to understand the mechanisms which govern the onset and magnitude of pollen release. Although several reports have documented episodes of long distance transport (LDT) of pollen, the actual contribution of out-of-season or out-of-region pollen to local air spora is poorly known. The current study also re-examined the LDT ofJuniperus ashei pollen in Oklahoma.Juniperus pollen appeared in the Tulsa atmosphere on 40% of the days in December and January with concentrations as high as 2400 pollen grains/m³ of air; however, no local populations ofJuniperus pollinate at this time of the year. High concentrations occurred on days with southerly winds suggesting thatJuniperus ashei populations in southern Oklahoma and Texas were the pollen source. Since no local pollen is present in the Tulsa atmosphere in December and January, this example of LDT has been easy to document.     

Food of the emperor penguin Aptenodytes forsteri on the Antarctic fast ice edge in late winter and early spring

Summary The food of emperor penguins Aptenodytes forsteri at the edge of the sea ice off the Vestfold Hills was studied by faecal analysis. Fish, crustacean, cephalopod and gastropod remains were found in 151 droppings collected between August and October 1984. The main fish identified from otoliths was Pleurogramma antarcticum with an average standard length of 129.5 mm. Amphipods increased in frequency from August to October with gammarids predominating.     

Effects of tillage on the activity density and biological diversity of carabid beetles in spring and winter crops

The effects of tillage regimen (conventional [CT] and no-tillage [NT]) on the activity density and diversity of carabid beetles (Coleoptera: Carabidae) was studied by pitfall trapping within a rain-fed cropping system in northwestern Idaho, 2000-2002. The cropping rotation consisted of a spring cereal (barley, Hordeum vulgare L., in 2000 and 2001; and wheat, Triticum aestivum L., in 2002), spring dry pea (Pisum sativum L.) 2000-2002, and wheat (T. aestivum), spring in 2000 and 2001, and winter in 2002. A total of 14,480 beetles comprised of 30 species was captured, with five numerically dominant species [Poecilus scitulus L., Poecilus lucublandus Say, Microlestes linearis L., Pterostichus melanarius Ill., and Calosoma cancellatum (Eschscholtz)], accounting for 98% of all captures. All species including the dominants responded idiosyncratically to tillage regimen. Adjusting for trapping biases did not significantly change seasonal activity density of Poecilus spp. or Pt. melanarius to tillage. More beetles were captured in CT than in NT crops because of the dominance of P. scitulus in CT, whereas species richness and biological diversity were generally higher in NT crops. Observed patterns suggest that direct effects of tillage affected some species, whereas indirect effects related to habitat characteristics affected others. CT may provide habitat preferable to xerophilic spring breeders. A relationship was found between beetle species size and tillage regimen in pea and to a lesser extent across all spring crops, with large species (>14 mm) conserved more commonly in NT, small species (<7 mm) in CT, and intermediate species (7-14 mm) conserved equally between tillage systems.     

The effect of grazing and nutrient supply on periphyton associated bacteria

The effects of nutrient additions and grazing by macro-invertebrates on periphyton-associated algae and bacteria were studied by performing an enclosure experiment on three occasions from early spring to summer at mesotrophic Lake Erken and V?dd?, at the Swedish Baltic coast. There were significant interactions between nutrient additions and grazing on bacterial biomass and specific activity in Lake Erken. Thus, the importance of either bottom-up or top-down effects could not be singled out. Bacterial biomass increased with enrichment only in the absence of grazers. Grazer presence tended to increase bacterial biomass in ambient nutrient conditions, but to decrease bacterial biomass under enrichment. For specific activity the positive response to enrichment was restricted to grazer presence. Hence, grazing by macro-invertebrates may have an indirect positive effect on bacterial activity by enhancing nutrient conditions through their feeding activities and/or fecal pellets production. In addition, we found a significant relationship between bacterial production and chlorophyll a at both sites. This relationship weakened in the presence of macro-invertebrates. Thus, the importance of internal nutrient regeneration by bacteria and algae decreased, possibly due to increased nutrient availability, in the presence of macro-invertebrate grazers.     

The effect of food supply and larval cannibalism on adult size and biomass of the grazing caddis-fly Melampophylax mucoreus (Limnephilidae)

Abstract. 1. Larvae of the grazing caddis‐fly Melampophylax mucoreus were reared in a laboratory experiment investigating the effect of food availability on different substrates and cannibalism on the size and biomass of emergent adults. All experiments were performed in stream‐water filled, aerated aquaria under controlled temperature and light conditions. Larvae (fourth and fifth instar) were reared in aquaria (50 larvae in each) with three substrate scenarios: (i) limestone (LS), (ii) limestone and leaf litter (LS + L), and (iii) silicate stone (SS). 2. Cannibalism among the larvae in the LS scenario led to the highest adult dry masses (male = 5.13 ± 0.25 mg, female = 7.64 ± 0.63 mg) and to the highest mortality rate (88.7%). The SS scenario displayed the most unfavourable condition for larval growth indicated by the lowest adult dry masses (males = 3.12 ± 0.15 mg, females = 4.69 ± 0.25 mg) and a high mortality rate (81.7%). The limestone supplemented with leaf litter (ii) offered the most balanced nutrients to complete larval development and enough shelter to avoid excessive encounter rates of larvae within the aquaria, indicated by the lowest mortality rate (43.6%). Adults from the LS + L scenario showed biomasses (male = 3.94 ± 0.12 mg, female = 6.48 ± 0.24 mg) intermediate between the two other scenarios. 3. The results implied that cannibalism among larvae can lead to higher adult biomasses and therefore to increased fitness, if cannibalism supplements larval feeding requirements. Larvae developing under insufficient food availability can not compensate for this by cannibalism. Additionally, leaf litter not only provided a complementary food source for developing larvae, but also provided shelter, which reduced encounter rates. 4. Increased stress induced by high larval encounter rates (resulting in enhanced cannibalism) in the LS scenario and low food availability in the SS scenario could be indicated by premature emergence times compared with the LS + L scenario.     

Effects of growth temperature and winter duration on leaf phenology of Erythronium japonicum,a forest spring geophyte

The effects of growth temperature and winter duration on the leaf phenology of Erythronium japonicum were examined in two experiments. Bulbs wintered in the field were cultivated at 10 and 20° C and the bulbs were cultivated at 15° C after chilling treatment at 3° C for 60 and 120 days and without chilling in winter. The plants cultivated at 20° C showed significantly earlier leaf emergence, a more rapid rate of leaf extension and shorter leaf longevity than those cultivated at 10° C. The decrease in the leaf longevity at 20° C resulted from the decreases in the durations of all of the developmental, mature, and senescent phases. The bulbs without chilling treatment did not sprout leaves and those with chilling treatment sprouted leaves. The increase in the length of chilling treatment from 60 to 120 days affected leaf phenology in same manner as the increase in the growth temperature from 10 to 20° C.     

Dietary daidzein influences laying performance of ducks (Anas platyrhynchos) and early post-hatch growth of their hatchlings by modulating gene expression

Our previous studies demonstrated that dietary supplementation of daidzein improves egg production in duck breeders during late periods of the laying cycle. The present study was aimed to clarify whether the growth of ducklings hatched from eggs laid by daidzein-treated hens would be affected, and to elucidate the mechanisms underlying potential trans-generational effects, by determining changes of hormone levels and mRNA expression of relevant genes. Daidzein was added to the basal diet of 415-day-old duck breeders at the level of 5 mg/kg. During 9 weeks of daidzein treatment, laying rate increased by 7.70%, average egg mass tended to increase, whereas yolk/albumen ratio decreased significantly. These changes were accompanied by significantly elevated plasma T4 and E2 levels, enhanced gonadotropin releasing hormone (GnRH) mRNA, but diminished estrogen receptor (ER)-beta mRNA expression in hypothalamus of daidzein-treated hens. Ducklings hatched from daidzein-treated eggs were significantly smaller at hatching, but they caught up with their control counterparts by 4 weeks of age. Serum levels of T4, pituitary GH, hepatic GH receptor (GHR) and type-1 IGF receptor (IGF-1R) mRNA expression were all suppressed markedly in the daidzein-treated group at hatching, but this suppression proved to be temporary, as at 4 weeks of age, expression levels of all investigated genes were restored. However, it is noteworthy that at 4 weeks of age an obvious down-regulation of hypothalamic GnRH mRNA expression was detected in ducklings maternally exposed to daidzein. Our results provide evidence that maternal exposure to daidzein affects post-hatch growth in the duck with accompanying changes in the secretion of metabolic hormones and expression of growth-related genes. Although the negative effect of maternal daidzein on embryonic growth could be eliminated 4 weeks after hatching, the long-term effect of maternal daidzein on reproductive function is not to be ignored and awaits further investigation.     

Spatial distributions of floating seaweeds in the East China Sea from late winter to early spring

Floating seaweeds play an important role as a habitat for many animals accompanying or attaching to them in offshore waters. It was in 2000 that the first report described abundant distributions of floating seaweeds in offshore waters in the East China Sea in spring. Young individuals of the yellowtail Seriola quinqueradiata are captured for aquaculture purposes from floating seaweeds in the East China Sea. Therefore, a sound understanding of the distributions of floating seaweeds in the East China Sea is needed. Detailed information is especially important during the late winter to early spring, which corresponds to the juvenile period of the yellowtail. Thus, field surveys using R/V Tansei-Maru were conducted in the Japanese Exclusive Economic Zone in the East China Sea from late winter to early spring in 2010 and 2011. We obtained positions of the vessel by GPS and transversal distances from the vessel to a raft by visual observation. Distance sampling method (Thomas et al. 2010) was applied to estimation of floating seaweed densities (rafts km^?2). Seaweed rafts were also randomly sampled using nets during the research cruises. In the East China Sea, seaweed rafts were distributed mainly on the continental shelf west of the Kuroshio, especially in waters between 26° N and 30° N. Collected rafts consisted of only one species, Sargassum horneri (Turner) C. Agardh. Taking into account surface currents and geographical distribution of S. horneri, it is estimated that these floating seaweeds originated from natural beds along the coast between mid and south China. Considering the approximate travel times, it is suggested that floating patches are colonized by yellowtails early on during their trips, i.e., close to the Chinese coast.     

On the quantitative relationship between survival rate of larvae and their food supply

The survival rate of fishes in their earlier stages of development and the influencing factors present one of the most fundamental problems of fish population dynamics. After I. Hjort's (Cons. L.'explor. Ner.,20, 3–228, 1914) work, there have been many investigators in this field and there is no doubt about the very important role of ova and larvae mortality in the fate of a given fish generation. Less clear are the ideas concerning factors determining the high mortality of fishes in their earlier stages of development; especially the factor of food supply of larvae during the period of transition to exogenic nutrition. The value of this factor has been estimated differently from different points of view. For example, R. J. H. Beverton and S. J. Holt (On the Dynamics of Exploited Fish Population, 1957) have given to the food supply factor its deserved importance. On the other hand, T. V. Dekhnik (Trudy Sevastopolskoi Biologicheskoi Stantsii,13, 216–244, 1960;Ibid.,14, 222–243, 1961) has proved in her investigations that at least for pelagic larvae of Black Sea fishes there is an excessive amount of food, and that therefore food cannot play an important role in larva survival. Not wanting to stop to review the literature of the problem (see Dekhnik,Trudy Sevastopolskoi Biologicheskoi Stantsii,13, 216–244, 1960), we will only remark that the problem as a whole needs further investigation. Not only new data are needed, but also methods for following up analysis have to be worked out.     

Effects of nutrient supply (NPK) on spring wheat response to elevated atmosperic CO2

The effects of increased atmospheric CO₂ on crop growth and dry matter allocation may change if nutrient supply becomes insufficient for maximal growth. Increased atmospheric CO₂ may also cause changes in minimum nutrient concentration in plant tissue and hence in the nutrient use efficiency or yield-nutrient uptake ratios of crops. To study these effects for spring wheat, pot experiments have been carried out in two glass houses at ambient and doubled CO₂ concentration. Wheat plants were grown at different supplies of N, P or K. Doubling of ambient CO₂ resulted in a large increase in total biomass (+70%) and grain yield when the nutrient supply was optimum. With strong N and K limitation this CO₂ effect was about halved and with strong P limitation it became almost nil. Doubling of ambient CO₂ resulted in a 10% lower minimum N concentration in plant tissue and in no change in the minimum P concentration.     

Temperature responses of membrane-associated activities from spring and winter oats

Abstract Two-week old, glasshouse-grown seedlings of spring and winter oats (Avena sativa cv. Margam and Pennal respectively) were transferred to growth rooms where the daylength was 8 h and the temperature was either 20° or 5°C. Leaves from the 20°C treatment were harvested 1 week after transfer and those from the 5°C treatment after 3 weeks. Measurements were made, at temperatures in the range 5–20°C, of the rate of senescence of excised leaf sections; the rate of in vivo tetrazolium (TTC) reduction; the NADH-MTT tetrazolium diaphorase (NMD) activity of a membrane preparation isolated by sucrose gradient centri-fugation; and Hill activity of isolated chloroplasts. Data from these experiments, either untransformed or plotted in accordance with the Arrhenius equation, were analysed by the method of maximum likelihood for the occurrence of rate-temperature discontinuities. Distinct breakpoints at 14.2–16.3°C were detected for senescence, TTC reduction and NMD in winter oat leaves from the 20°C treatment, but spring oats grown at the same temperature gave a significant discontinuity only in the rate of senescent yellowing. After the hardening treatment, 3 weeks at 5°C, senescence and TTC reduction in winter oats exhibited breakpoints at 10.1–12.4°C and spring oats gave breaks at 11.8–17.3°C. No breakpoint was observed for Hill activity from either variety under either temperature treatment. The use of this approach in studies of growth at chilling temperatures and its potential as a screening method are discussed.