Showing papers on "Heron published in 2001"

Temperature variation within and between nests of the green sea turtle, Chelonia mydas (Chelonia: Cheloniidae) on Heron Island, Great Barrier Reef

Abstract: Four temperature data-loggers were placed in each of five green sea turtle nests on Heron Island in the 1998-99 nesting season. Temperatures in all nests increased as incubation progressed due to general sand heating and increased metabolic heat production of the developing embryos. Even at the top of nests no daily diurnal fluctuation in temperature was evident. The temperature of eggs in the middle of the nest increased above those in the nest periphery during the last third of incubation. However, this metabolic nest heating would have little effect on hatchling sex ratio because it occurred after the sex-determining period. Small differences in temperature between regions of a nest persisted throughout incubation and may be important in ensuring the production of at least some individuals of the opposite sex in nests that have temperatures close to either the all-male or all-female determining temperatures. Location and degree of shading of nests had little effect on mean nest temperature, but deeper nests were generally cooler and therefore were predicted to produce a higher proportion of males than were shallower nests. Nest temperature profile data indicated that the 1998-99 nesting season on Heron Island would have produced a strongly female-biased sex ratio amongst hatchlings.

Monitoring Temporal and Spatial Trends in Polychlorinated Dibenzo-p-dioxins (PCDDs) and Dibenzofurans (PCDFs) in Eggs of Great Blue Heron (Ardea herodias) on the Coast of British Columbia, Canada, 1983–1998

Abstract: Eggs from 21 resident great blue heron (Ardea herodias) rookeries were monitored from 1983 to 1998 along the coast of British Columbia, Canada, for contamination with polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs) and biphenyls (PCBs). Dominant congeners (1,2,3,7,8-PnCDD, 1,2,3,6,7,8-HxCDD, 2,3,7,8-TCDD, 2,3,7,8-TCDF, 1,2,3,7,8,9-HxCDD and 2,3,4,7,8-PnCDF) fell markedly in the early 1990s after pulp mills changed from molecular chlorine bleaching to alternative bleaching technologies, and the use of chlorophenolic wood preservatives and anti-sapstains was severely restricted. Strong positive linear regressions between prey fish and heron egg contaminant levels suggested that local dietary uptake was an important route of exposure for herons. Toxic equivalent concentrations (TEQs) sufficient to produce embryotoxicity in great blue heron chicks were measured in eggs from 1985 to 1991 at some colonies. Despite reduction in PCDD/Fs, estimated TEQs remained elevated throughout the 1980s at some urban colonies due to contributions from PCBs.

Status update on White-eared Night Heron Gorsachius magnificus in South China

Abstract: Summary White-eared Night Heron Gorsachius magnificus is probably the most threatened heron species in the world, and the highest priority for heron species conservation. From 1990 to 1998, there were sightings from only six localities in the wild. There are none in captivity. In 1998 a caged bird was found in a wildlife market in the city of Nanning, Guangxi Zhuang Autonomous Region, People’s Republic of China. This finding prompted a 12month survey in 1998–1999 of both markets and potential habitats in Guangxi. Several captured birds provided direct evidence of the existence of small populations in Guangxi and Guangdong Provinces. The respective habitats were surveyed in spring 2000, with emphasis on observations at dusk. The species was seen at two locations. Although some of the captured birds came from highly degraded habitat, the best sites seemed to be in areas near extensive primary forests, with streams, rice fields and marshes. The information obtained will be used to compile a detailed Action Plan designed to prevent the extinction of the species.

Recent changes in the diet and breeding parameters of the Purple Heron Ardea purpurea in southern France

Abstract: The Purple Heron population in southern France suffered a 46% decline between 1981 and 1994. A study of breeding biology was instigated in 1997 in order to examine potential changes in the main breeding parameters between the early 1980s and the late 1990s. Here, we present data on the breeding biology and diet of breeding Purple Herons in the Camargue, southern France, collected from 1997 to 1999. These results were compared with those from a similar study conducted between 1979 and 1982. No difference in first spring arrival date on breeding grounds was noted between these two periods. Mean first egg date was 22 April during 1979–82, in contrast to 6 May during 1997–99. Mean colony size was c. 118 breeding pairs during 1979–82, but only c. 59 during 1997–99. For broods of three and four chicks, linear growth rates for rank A (first hatched) chicks were higher during 1979–82 than during 1997–99. For broods of four chicks linear growth rates were also higher for rank B (second hatched) chicks and tended t...

Nesting Waterbirds of Isla Montague, Northern Gulf of California, Mexico: Loss of Eggs Due to Predation and Flooding, 1993-1994

Abstract: -We studied seven species of waterbirds that nested on Isla Montague, Mexico, at the mouth of the Colorado River, during the 1993 and 1994 breeding seasons: Great Blue Heron (Ardea herodias), Snowy Egret (Egretta thula), Black-crowned Night Heron (Nycticorax nycticorax), Laughing Gull (Larus atricilla), Least Tern (Sterna antillarum), Gull-billed Tern (Sterna nilotica), and Black Skimmer (Rynchops niger). Breeding occurred along several tidal channels of the Estero del Chayo and on shell mounds near the lighthouse. There were low levels of predation, by at least one Coyote (Canis latrans), and unknown, but likely avian, predators. Tidal inundation was the major factor affecting the nesting of the birds, as it destroyed almost all nests, eggs and chicks on at least five occasions during one breeding season. It seems likely that the pattern of inundations we recorded does not happen all years. Received 21 August 2000, accepted 20 March 2001.

Some results on Heron triangles

Abstract: Mohammed Aassila, born 1968, studied mathematics in Fes, Tours and Strasbourg and received his Ph.D. in 1997. He is now an Assistant-Docteur at the University of Fribourg. During the academic years 1998–2000 he has been visiting the Centre de Recherches Mathematiques, at the University of Montreal, and he was an Alexandervon-Humboldt-fellow at the University of Cologne during the year 2000–2001.

Variation des effectifs nicheurs de hérons pourprés Ardea purpurea sur le littoral méditerranéen franÇais en relation avec la pluviométrie sur les quartiers d'hivernage

Abstract: An increasing number of studies have demonstrated a link between some demographic parameters for some species of Palearctic-African migrant and rainfall indices on their wintering quarters. Such relationships have been found for Purple Heron in several European populations but not in France, where variations in the population size seem not to depend on African wintering conditions. Here, we re-analysed long term population data of Purple Heron breeding in southern France in relation to a Sahel rainfall index, in the light of recent findings on factors affecting breeding numbers. After taking into account these factors in the analysis, there was a positive relationship between interannual population variation and the Sahel rainfall index in September (r = 0.653; n = 15; P = 0.008) and October (r = 0.643; n = 15; P = 0.01) over the period 1981-1998. The breeding population increased following high autumnal rainfall in the Sahel. These results are in agreement with previous studies on this species and highlight the necessity to take into account local confounding factors when investigating such broad scale relationships.

On Heron Simplices and Integer Embedding

Abstract: In "Unsolved Problems in Number Theory" problem D22 Richard Guy asked for the existence of simplices with integer lengths, areas, volumes... In dimension two this is well known, these triangles are called Heron triangles. Here I will present my results on Heron tetrahedra, their connection to the existence of an integer box (problem D18), the tools for the search for higher dimensional Heron simplices and my nice embedding conjecture about Heron simplices, which I can only proof in dimension two, but I verified it for a large range in dimension three.

Black-crowned Night Heron fishes with bait

Abstract: -A Black-crowned Night Heron (Nyticorax nyticorax) was observed manipulating bread to catch fish attracted to the bait. This is the second recorded instance of a Black-crowned Night Heron fishing with bait. Bait-fishing has also been observed in the Green Heron (Butorides virescens) and the closely-related Striated Heron (Butorides striatus); a related foraging technique has been reported in the Great Egret (Ardea alba) and the Great Blue Heron (Ardea herodias). Received 16 November 2000, accepted 6 December 2000.

Standardizing and interpreting nesting records for Great Blue Herons in British

Abstract: His tor i cal data on the number of nests and nesting success for 242 Great Blue Heron colonies in British Columbia from 1920 through 1999 were compiled. The meth od ol o gies for data col lec tion differed over the years. We have developed and applied a standard meth od ol ogy for col lect ing and inter pret ing nesting data to provide con sis tency for users of the data set.

Pisonia grandis does not appear to harbour fungi known to invade sea turtle nests at Heron Island, Eastern Australia

Abstract: Hatching success of loggerhead sea turtle nests is significantly lower at Heron I. (23°26´ S, 151°55´ E-Capricorn Group, southern Great Barrier Reef), than on the adjacent mainland1. Fungal invasion appears to play a major role in inter-specific and inter-habitat variation in egg mortality between loggerhead (Caretta caretta L.) and green (Chelonia mydas L.) sea turtles at coral cay and mainland rookeries1, and hawksbill (Eretmochelys imbricata L.) and flatback (Natator depressus Garman) turtles at other major rookeries in eastern Australia*.

Green Heron ( Butorides virescens ) predation at Village Weaver ( Ploceus cucullatus ) nests

Abstract: On 3 June 2000, I observed two incidences of a Green Heron (Butorides virescens) depredating nests and eating nestlings of Village Weaver (Ploceus cucullatus) at a colony in northeastern Dominican Republic. Keywords: Butorides virescens, depredation, Dominican Republic, Green Heron, Ploceus cucullatus, Village Weaver Resumen: Martinete (Butorides virescens) depredacion a nidos de Madam Saga (Ploceus cucullatus)- El 3 de junio de 2000 observe dos ocasiones en las que un Martinete (Butorides virescens) depredo los nidos y consumio los pichones de Madam Saga (Ploceus cucullatus) en una colonia en el nordeste de la Republica Dominicana.

On the Solution of a System of Heron Equations

Abstract: We study a system consisting of a finite number of Heron equations with a common variable and prove the equivalence of general formulas for all solutions of such a system.

[Organochlorine residues in eggs of night heron breeding in Yuantouzhu, Wuxi and their functions as bioindicator].

Abstract: This study analyzed chlorinated pesticides in eggs of night heron breeding in Yuantouzhu, Tai lake. The HCH isomers, DDT, DDD, DDE, endrine and heptachlor epoxide were detected out in egg samples. The residue level and the percent of detection of beta-HCH and p,p'-DDE were significantly high. The mean value of p,p'-DDE was 0.906 microgram/g dry weight. Most of the chlorinated pesticides in samples from Wuxi were higher than those of Gongqing city, Jiangxi province. Oppositely, the hatching rate of night heron egg in Wuxi region was lower than that in Gongqing city. It may be related to the difference of DDE residual levels. Using organochlorine residue in eggs of water-fowls as an indicator for environmental quality assessment is feasible.

Nocturnal foraging by the green heron ( Butorides virescens ) under artificial illumination in Tobago

Abstract: Few details have been published on nocturnal foraging in the Green Heron (Butorides virescens). We report an observation of a Green Heron feeding on frogs under artificial illumination about 90-150 min after sunset at Bon Accord, Tobago, on 19 June 1995. Keywords: Butorides striatus, Green Heron, nocturnal foraging, Tobago Resumen: Forrajeo nocturno en el Chicuaco Cuello Rojo (Butorides virescens) bajo iluminacion artificial en Tobago- Se han publicado pocos detalles sobre el forrajeo nocturno del Chicuaco Cuello Rojo (Butorides virescens). Se relata una observacion de un Chicuaco Cuello Rojo alimentandose de ranas bajo iluminacion artificial aproximadamente 90-150 minutos despues de la puesta del sol en Bon Accord, Tobago, el 19 de junio de 1995.