Simon J. Lane

The impact of changes in irrigation practices on the distribution of foraging egrets and herons (Ardeidae) in the rice fields of central Japan

Abstract Traditionally rice Oryza sativa fields in Japan are irrigated by diverting river water through shallow earth ditches using sluices and weirs. However this ‘old-style’ method is being replaced rapidly by a ‘new-style’ system in which water is pumped into paddy fields via taps and drained into deep concrete-sided canals. Concern has been expressed that the changes may cause paddy fields to decline in value as foraging habitats for egrets and herons, Ardeidae, because their aquatic prey are unable to move easily into new-style fields. We tested this hypothesis by comparing numbers of Ardeidae and their prey in paired old- and new-style areas at six sites in central Japan from May to August 1995. Few grey herons Ardea cinerea, great egrets Egretta alba or little egrets E. garzetta were recorded at our sites and no differences were observed in their use of old-and new-style areas. In contrast cattle Bubulcus ibis and intermediate E. intermedia egrets were common but only the latter preferred old-style areas. With respect to prey animals, we found greater numbers and biomasses of frogs, crayfish Procambarus clarkii, loach Misgurnus anguillicaudatus, and other fish in old-style paddy fields, and in old-style ditches we found more frogs, tadpoles and fish, but generally fewer crayfish. There were no differences in the numbers or biomass of terrestrial invertebrates between the two types of paddy field. Reason for these observations are discussed. We suggest other topics which require investigation in order that effective wildlife management strategies for rice fields may be formulated.

The role of introduced mosquitofish (Gambusia holbrooki) in excluding the native green and golden bell frog (Litoria aurea) from original habitats in south-eastern Australia

Abstract. The introduction of fish has decimated many amphibian populations through increased predation, primarily on their larvae. Some amphibian species now occupy marginal habitats as a response to the presence of introduced fish predators. Such habitats may include ephemeral water bodies where fish do not usually occur, although breeding in these suboptimal environments may incur some cost to a species if its larvae are not adapted to develop under these conditions. We investigated this scenario of amphibian decline using the endangered green and golden bell frog (Litoria aurea) and the introduced mosquitofish (Gambusia holbrooki) in a factorial experiment to determine the responses of tadpoles to declining water levels and the introduced predator. Tadpoles metamorphosed asynchronously but did not accelerate development in declining water or when housed with mosquitofish. Mass at metamorphosis was 30% less in declining water. Mass increased with time to metamorphosis in constant water-level treatments, but decreased in declining water. Tadpoles did not respond to mosquitofish and were therefore assumed to be naive to this predator. These results suggest that ephemeral habitats may be suboptimal for breeding, and tadpoles appear better suited to develop in permanent water bodies free of introduced fish. Intra-clutch variability in larval development (i.e. bet-hedging) may allow L. aurea to cope with unpredictable pond duration, whereby even permanent water bodies may occasionally dry out. The responses observed in L. aurea suggest that introduced fish may have reduced the suitability of permanent water bodies as breeding sites for other pond-breeding amphibian species. The use of less favourable ephemeral habitats as breeding sites may be responsible for some of the declines reported in amphibians since the 1970s.

Habitat switching by dark-bellied brent geese Branta b. bernicla (L.) in relation to food depletion

Seasonal changes in the distribution and feeding behaviour of dark-bellied brent geese Branta b. bernicla (L.) and the biomass of their food plants were studied in three successive winters on the Norfolk coast. The data was used, in conjunction with published information, to show how depletion, productivity and mortality of food plants drive the pattern of habitat switching in this species. It is then possible to explain the habitat shifts observed over the last 35 years and predict future changes. On arrival, geese fed first on algal beds and then on salt marsh, grass and arable fields before returning to feed entirely on the salt marsh in spring. The biomass of green algae, and subsequently the salt marsh vegetation, declined during the autumn and this could be attributed to depletion through goose grazing and natural mortality. As depletion occurred the geese fed more intensively, for a greater percentage of time and with an increasing pace rate, the net result, however, was a declining intake rate (as measured by defaecation rate). The algal biomass at which the geese switched from the algal beds to salt marsh was consistent between years, with heavy storm-induced loss of algae in one year resulting in an earlier switch. That the timing of habitat switches may be explained by depletion of food plants was further supported by historical data: the number of brent geese wintering at the site has increased dramatically over the last 30–35 years and the time of switching from algal beds to salt marsh and from salt marsh to salt marsh and fields has become progressively earlier, as expected from the increased depletion. The expected further increase in brent goose numbers will increase the rate of depletion of intertidal vegetation so that the switches between habitats will be more rapid and the geese will move inland earlier and remain inland longer. The expected increase in the brent goose population will thus result in a disproportionate increase in the levels of conflict between brent geese and agriculture.

Management of freshwater wetlands for the endangered green and golden bell frog (Litoria aurea): roles of habitat determinants and space

The range of the green and golden bell frog (Litoria aurea) has undergone a widespread yet unexplained contraction in south-eastern Australia since the mid 1970s, and the species is now listed as endangered in the New South Wales Threatened Species Conservation Act 1995 and as vulnerable in the federal Environmental Protection and Biodiversity Conservation Act 2000. Although the cause of the range contraction is unknown, remedial action is necessary to ensure the long-term viability of remaining populations. This can include habitat creation around existing populations and reintroduction projects. However, the habitat requirements of this species are poorly understood. We examined the habitat at 43 waterbodies on Kooragang Island, Australia, with the aim of producing a set of variables which could differentiate between those occupied by L. aurea and those where the species was absent. L. aurea was found in 21 waterbodies and breeding was confirmed in four. Aspects of waterbody physiognomy and water chemistry could not explain L. aurea distribution. The plant species Juncus kraussii, Schoenoplectus litoralis and Sporobolus virginicus were significant predictors of the presence of L. aurea, as was the diversity of vegetation on the banks of waterbodies. The presence of the eastern mosquitofish (Gambusia holbrooki) did not influence waterbody occupancy and tadpoles were found co-existing with this introduced fish. The distribution of waterbodies occupied by L. aurea was aggregated. A waterbody was more likely to be occupied if neighbouring waterbodies within 50 m were also occupied. Habitat creation projects for this species are most likely to succeed if wetland habitat is created in proximity to an existing population.

Movement Patterns of Adult Green and Golden Bell Frogs Litoria aurea and the Implications for Conservation Management

Abstract Conservation of pond-breeding frogs requires information on movement patterns within populations. The Green and Golden Bell Frog (Litoria aurea) is endangered in New South Wales, Australia; yet little is known about its movement biology. To inform conservation planning and habitat restoration, we conducted a mark-recapture study to describe the movement patterns of adult L. aurea among permanent and ephemeral waterbodies, on Kooragang Island, New South Wales, Australia. Twenty-nine percent and 18% of 551 males and 228 females marked, respectively, were recaptured on ≥ 1 occasions over two breeding seasons (2000 and 2001). Most recaptures were in the same permanent waterbody as the original capture (53% males, 65% females). Twenty-seven (24%) male and seven (50%) female movements were from a permanent waterbody to the nearest permanent waterbody (<50 m), respectively. Male L. aurea, usually large individuals, moved relatively long distances (>200 m) to ephemeral waterbodies from permanent waterbodies after prolonged heavy rain. Of the total number of male and female movements recorded, 44 (39%) and two (14%) were to or from ephemeral waterbodies, respectively. Our results demonstrated high site fidelity of L. aurea to individual waterbodies and groups of neighboring waterbodies, especially permanent ones. Our results showed that L. aurea tended to breed in more permanent waterbodies but reproduced opportunistically in ephemeral waterbodies where recruitment was less successful. Habitat restoration projects for L. aurea should construct permanent and ephemeral waterbodies and provide adequate buffer zones that protect the terrestrial habitat.

Pummerer rearrangements using chlorotrimethylsilane

Abstract Pummerer rearrangements of 3-carbomethoxythian-4-one S -oxide ( 1 ) have been investigated and chlorotrimethylsilane found to be the reagent of choice for preparing the corresponding α,β-unsaturated sulphides ( 2 and 3 ). Related chlorotrimethylsilane-induced Pummerer rearrangements are also reported.

Retreat Site Selection during Winter in the Green and Golden Bell Frog, Litoria aurea Lesson

Abstract Amphibians use a range of microhabitats as retreat sites to escape adverse climatic conditions. We conducted two outdoor experiments using a brick pile and shallow trays of water containing aquatic vegetation to assess retreat site selection during winter in the endangered frog Litoria aurea. A multivariate habitat model in the first experiment indicated that frogs preferred to rest close to the edges of the brick pile that received afternoon sunlight and in small gaps between bricks, whereas in the second experiment, frogs showed no preference for terrestrial or aquatic habitats. These results suggest that L. aurea is a generalist in winter habitat choice, although resting positions in terrestrial situations are likely related to site aspect, microhabitat, and temperature.

The effect of night grazing by wigeon (Anas penelope) on winter-sown wheat in Japan and the efficacy of black plastic flags as scaring devices

Abstract From November 1994 to April 1995 a flock of up to 247 wigeon (Anas penelope) roosted on an artificial pond during the day at Misato City, Japan. At night some or all of this flock fed on nearby winter-sown wheat (Triticum aestivum L.). We conducted an experiment to test the effectiveness of black plastic flags as scaring devices. Flags were deployed at 50 flags ha−1 in five wheat fields which were each paired with an adjacent unprotected field. Grazing intensity on the flagged fields was reduced significantly as measured by dropping density. Only 7.7|X% of all droppings counted were found in the flagged fields. The wigeon did not habituate to the scaring devices during the experiment. In an unprotected field, loss of yield was estimated at 83% by comparing differences inside and outside exclosures. In an adjacent protected field with exclosures there was no statistically significant loss.

Estimation of apparent metabolizability in herbivorous wildfowl with plant pigments

If the feeding habitat requirements of herbivorous wildfowl are to be understood completely, then knowledge of plant metabolizability is essential. Use of a suite of plant pigments or chromogen as a naturally occurring indigestible marker to estimate apparent metabolizability (AM) in free-ranging herbivorous wildfowl is assessed as a simple, inexpensive, and potentially accurate method. The analytical procedure is described and 3 stages identified as possible areas that could give rise to inconsistent AM estimates. These stages were examined accordingly and as a result the following recommendations made: (1) food and fecal samples collected in the field must be frozen quickly, (2) samples to be analyzed should be freeze-dried, not dried in an oven or vacuum oven, and (3) light must be excluded from the chromogen extracts once in solution. Once the procedure had been verified, AM of cut grass eaten by a captive brent goose (Branta bernicla) was measured directly (by measuring ingestion and egestion) and indirectly (by measuring chromogen concentrations in freeze-dried food and fecal samples). Results of AM given by the 2 methods were in close agreement. Recovery of chromogen in the feces was 101.3 ± 11.2% (mean ± SD, n = 3) indicating that chromogen can be used to estimate AM for free-ranging geese and herbivorous ducks, but variation was high and sample size small and so further trials would be valuable to consolidate this result.

Applications of Organocopper Reagents in Organic Synthesis

The importance of organocopper reagents in organic synthesis is highlighted and the different types of organocopper reagents available are briefly reviewed. Applications of organocopper reagents in the synthesis of natural products and related compounds of biological interest are then discussed commencing with synthetic approaches to thia-thromboxane analogues based on the organocopper conjugate addidon-enolate alkylation reaction. The extension of this methodology to the preparation of 2,3- disubstituted cyclopentenones, illustrated by the synthesis of the antimicrobial natural product, tetrahydrodicranenone B, is then discussed. Finally, synthetic applications of the organocopper alkyne addition reaction are described with emphasis on the use of double acetylene carbocupration for the stereospecific preparation of Z,Z-dienes. The use of this methodology for the synthesis of the Navel Orangeworm pheromone is discussed.