Showing papers on "Heron published in 2002"

The effects of prey availability on the numerical response of wading birds

Abstract: Reduced prey availability has emerged as a primary hypothesis to explain population constraints on wading birds in numerous wetlands around the world. However, there is almost no understanding of which component of prey availability (i.e., prey density or vulnerability of prey to capture) is affecting populations and whether the relative effects of each component differ among species. In this study, I manipulated prey density and water depth (i.e., prey availability) in 12 0.2-ha ponds to determine their relative effects on the numeric response of eight species of free-ranging wading birds (White Ibis, Eudocimus albus; Wood Stork, Mycteria americana; Snowy Egret, Egretta thula; Glossy Ibis, Plegadis falcinellus; Great Egret, Ardea alba; Tricolored Heron, Egretta tricolor; Great Blue Heron, Ardea herodias; and Little Blue Heron, Egretta caerulea). The experiment was conducted in a constructed wetland adjacent to, and west of, the northern tip of the remnant Everglades, in Palm Beach County, Florida, USA. Each pond was set to a water depth of 10 cm, 19 cm, or 28 cm, and was stocked with golden shiners (Notemigonus crysoleucas) at a density of either 3 fish/m2 or 10 fish/m2. Total bird use (all treatments pooled) increased from day 1 (day after stocking) to day 6, stabilized for several days at ∼280 birds, and then decreased until day 16, when bird use nearly ceased. Fish were depleted most rapidly in the shallow treatment and least rapidly in the deep treatment. The giving-up-density (GUD) of prey increased with increasing water depth. There was no significant difference among species in the slope of that relationship; however, a visual inspection of the data showed that differences in GUDs were becoming more apparent in the deepest treatment. At that depth, the White Ibis, Wood Stork, and Snowy Egret had higher GUDs than did the Glossy Ibis, Great Egret, Tricolored Heron, Great Blue Heron, and Little Blue Heron. Also, the first three species were affected significantly by both prey density and water depth, whereas the latter five species showed a decidedly weaker response to one or the other component of prey availability. The first three species were more abundant in the shallow treatments and the high prey density treatments, and they abandoned the study site before other species reached their maximum density. The feeding strategy of the first group appeared to be one of searching for new high-quality food patches rather than staying and exploiting food patches that were declining in quality. Species that employed a searching strategy also have shown the most severe population declines, suggesting that factors affecting bird density at feeding sites may also have affected population size.

Food intake, feeding behaviour and stock losses of cormorants, Phalacrocorax carbo, and grey herons, Ardea cinerea, at a fish farm in Arcachon Bay (Southwest France) during breeding and non-breeding season

Abstract: The feeding ecology of cormorants and grey herons were investigated at a fish farm in Arcachon Bay (southwest France) during both breeding and non-breeding season. Cormorants were mainly recorded during winter and grey herons during both breeding and wintering seasons. Adult cormorants and herons were the most abundant age clas at the fish farm. Adult cormorants and herons were more successful at feeding than first-years and although younger birds spent more time feeding and their biomass intake rates remained lower than those of adults birds. Cormorants and herons took the same biomass intake per feeding session at the fish farm during the non-breeding season, about 200 g. The impact of the two ichthyophagous birds (cormorant and grey heron) was estimated as 53.0% (average predation of cormorant per year) and 10.8% (mean predation of heron per year) of the annual yield of the fish farm. This imposed a significant economic loss due to low productivity of the farm.

Reedbed selection and colony size of breeding Purple Herons Ardea purpurea in southern France

Abstract: Reedbeds of Phragmites australis have declined in Europe in recent decades. Moreover, in some European countries the remaining reedbeds are intensively managed for industrial reed cutting, hunting or grazing. Several species of conservation concern, such as herons and pelicans, use reedbeds as their principal breeding habitat. At the same time, data on habitat use and colony size of these species in relation to reedbed management practices are scarce. We investigated habitat characteristics of 71 reedbeds occupied or unoccupied by breeding Purple Herons Ardea purpurea in the Rhone delta (Camargue) and in other Mediterranean coastal marshes in southern France. In addition, data on colony size in occupied reedbeds were collected from aerial surveys. Reedbeds occupied by breeding Purple Herons were unharvested, or only partially harvested, in winter and had higher water levels in spring compared with unoccupied reedbeds. A logistic regression model with reed harvesting intensity and water levels in mid-April as independent variables correctly classified reedbed use for 94.7% of the reedbeds in the study. A model with water levels in mid-April alone was only 90.9% accurate, suggesting that low water level in spring is the most important factor limiting reedbed occupation by breeding Purple Herons. A general linear model indicated significant effects of harvesting intensity and reedbed surface area on colony size. Within occupied reedbeds there was a strong tendency for colony size to increase with increasing reedbed surface area. Given the recent developments in reed harvesting and wetland management in southern France and elsewhere in Europe, these results provide the first information on potential effects of these practices on reed nesting herons, and suggest that Purple Heron conservation is likely to be favoured by maintaining large uncut reedbeds with relatively high water levels in spring. The possible effect of changes in habitat on the Purple Heron population in southern France is discussed.

Assessment of Contamination and Biomarker Responses in Two Species of Herons on the St. Lawrence River

Abstract: This study was undertaken to validate potential biomarkers of exposure and effects due to chemical contaminants in breeding colonies of the Great Blue Heron and the Black-crowned Night-Heron on the St. Lawrence River. Eggs and fledglings from both species were collected from many colonies along the River. The fledglings from colonies in freshwater and brackish water were more contaminated by mercury and PCBs than those from estuarine and gulf colonies. With respect to fledglings of the two heron species, some morphometric and blood biochemical measurements, including plasma thyroid hormones and retinol, were significantly different among colonies. Significant differences were also observed in liver retinoids, EROD and porphyrins among colonies. The results of this study suggest that plasma retinoids and thyroid hormones are good biomarkers of exposure and effects, and are sufficiently sensitive to reflect local and regional variations in contamination. Along with the measure of contaminants in egg and plasma, they constitute non-invasive biomarkers which represent an important criteria for long term monitoring of wildlife species. It is concluded that the Great Blue Heron is an appropriate sentinel species in the surveillance network for the St. Lawrence River.

Foraging ecology and depredation management of great blue herons at mississippi catfish farms

Abstract: Great blue herons (Ardea herodias) occur at high densities at catfish farms in the southern United States. They are perceived by farmers to prey heavily on fish stocks. After a field study at selected catfish farms in Mississippi, we describe (1) the pond conditions where great blue herons intensively foraged, (2) the prevalence of disease in catfish that were captured by herons, and (3) predation rates and economic effects of herons among selected pond situations. Heron abundance was significantly associated with season and was greatest during the fall (Sep-Oct). We characterized catfish ponds as having high (≥6 birds) or low (≤3 birds) foraging activity by herons and characterized pond type, disease prevalence, and water quality. Categorical models showed a significant association of heron activity with disease prevalence in ponds (diseased) and fingerling ponds. Based on model parameters and associated odds ratios, high heron activity was 6.6 times greater at fingerling ponds than at food-fish ponds, and 40.1 times greater at diseased ponds than at those without diseased fish. This was presumably because fingerlings are a more desirable prey size, and disease makes catfish more vulnerable to heron predation. Based on pathology reports, 85% (n = 55) of the live catfish captured by herons from high-activity ponds were diseased, of which 76% were considered to have a terminal condition. In contrast, 75% (n = 63) of the catfish captured by herons congregated at ponds where catfish were being fed were diagnosed as healthy and only 3 (5%) were considered to have a terminal condition. Although both disease and fish feeding bring catfish to the surface and increase their vulnerability to heron predation, we suggest that heron harassment efforts by farmers be focused during fish feeding when heron capture rates are the highest and the greatest predation on healthy catfish occurs. Based on heron foraging rates, average numbers of herons seen, and the duration of foraging activity, we estimated low expected heron predation losses at catfish ponds over time. Assuming that predation losses observed in this study are representative, we conclude that catfish predation losses from great blue herons are either insignificant or readily preventable.

Urban visualization and public inquiries: the case of the Heron Tower, London

Abstract: Computers are now used routinely to create high-quality images of proposed buildings but the extent to which these images are contributing to the quality of the final product remains questionable.

Breeding biology of the little blue heron (egretta caerulea) in southeastern brazil

Abstract: The breeding biology of Little Blue Herons (Egretta caerulea) nesting in Santos-Cubatao, south- eastern Brazil, was studied during the 1997 (75 monitored nests) and 1998 (65 nests) breeding seasons in one colony (Saboo River), and during the 1997 season (58 nests) in another colony nearby (Morrao River). Both mixed-species colonies were in mangroves affected by pollution and port activities. Colonies were active in September-March (Saboo River), and November-March (Morrao River). Little Blue Herons built their nests lower in the red mangrove (Rhizophora mangle) Morrao River colony where Scarlet Ibises (Eudoci- mus ruber) were the commonest nesting species, and nested higher in trees of the white mangrove (Laguncu- laria racemosa) Saboo River colony, where they were most common. Breeding chronology was similar to North American populations but clutch sizes were smaller (mean 2.21 to 2.57 eggs/nest), productivity lower (mean 0.53 to 0.98 young/breeding attempt) and young remained with adults for longer. Nest col- lapse, followed by predation, accounted for most failures. Parasitism by nematode worms may be an important source of mortality in some years. Differences in nest-sites between colonies resulted both from the vegetation structure and interactions with other nesting species; male herons likely tend to select the more exposed display territories (where nests will be built). Accepted 8 May 2001.

Relocation of a Large Black-crowned Night Heron Colony in Southern California

Abstract: The Port of Long Beach is currently developing the former U.S. Naval Station Long Beach into a marine container terminal. When the Naval Station was operational, a large Black-crowned Night Heron (Nycticorax nycticorax) colony (up to 500 pairs) occupied mature Indian Laurel (Ficus microcarpa) and Olive (Olea europaea) trees that lined the Station streets. Although Black-crowned Night Herons are abundant throughout southern California, a nesting colony of this size is unusual. As part of an agreement with the U.S. Fish and Wildlife Service under the Migratory Bird Treaty Act, the Port agreed to relocate the colony prior to construction of the terminal. In 1999, 50 mature Indian Laurel, Olive, and Paperbark (Melaleuca sp.) trees were boxed and transported to a location in the port approximately two km from the original site. The relocated trees supplemented approximately 70 trees and bushes already at the location, formerly a park. Black-crowned Night Heron decoys were placed in the trees, heron vo...

Kleptoparasitism in wintering grey heron Ardea cinerea

Abstract: A b s t r a c t. Eighty-six cases of kleptoparasitism in grey herons, most of which were intraspecific, were observed in northern Spain and southwest France during four winters (19921995). Herons more often attacked individually than in groups, but the success was similar in both cases. Robbing success was significantly higher when herons attacked a young bird (44.4%) compared to adults (17.6%). Adult herons were significantly more successful (37.5%) than young herons (10.0%). Handling time had a great effect on the size of the prey item robbed by the herons. Adult herons were more frequently attacked by both young and adult birds. Agerelated differences in winter foraging parameters (total time foraging, feeding success and biomass intake) may favour discrimination between victim age classes by kleptoparasites. Adult heron ingested 0.82 g min -1 during the winter season and young heron 0.45 g min -1 . For kleptoparasites adult herons seems to be a more profitable species than young. Kleptoparasitism increased the biomass intake of the pirate (62.8 g more than the normal intake of a young heron), probably to compensate for the inefficiency of young birds.

Endohelminths from the Little Blue Heron Egretta caerulea from the Texas Gulf Coast

Abstract: Fourteen species of endohelminths, including 1 acanthocephalan, 3 cestodes, 1 nematode, and 9 trematodes, were collected from 13 little blue herons Egretta caerulea from the area of Galveston, Texas, U.S.A. A mean of 4.3 (3–6) species of endohelminths per host was found. Five species (3 cestodes and 2 trematodes) represent new host records. Comparison of results from this study with a similar survey by Sepulveda et al. (1996) from Florida, U.S.A., suggests some hypotheses concerning possible roles of composition and complexity of trophic structures of these 2 regions in establishment of their respective endohelminth communities in little blue herons.

Romantic Flight in Jewett's "White Heron"

Abstract: Mr. Howells thinks that this age frowns upon the romantic, that it is no use to write romance any more; but dear me, how much of it there is left in every-day life after all. It must be the fault of the writers that such writing is dull, but what shall I do with my "White Heron" now she is written? She isn't a very good magazine story, but I love her....--Sarah Orne Jewett, letter to Annie Fields (ca. 1885) Sarah Orne Jewett's "A White Heron" (1886) tells the story of Sylvia, a young girl who spends her first years in an oppressive manufacturing town, then, at eight, to her great joy, goes to live with her grandmother on a farm in coastal New England. There, amid animals and forest, she begins to feel at home and express her affectionate nature. The following year, however, she faces a new difficulty when, walking in the woods, she meets a stranger, an amateur ornithologist, lost gunning for birds, who asks for and obtains lodging from the girl and her grandmother. Although Sylvia at first fears the tall young man, she soon becomes comfortable, indeed infatuated, with the "charming" and "handsome stranger." (1) Thus, the next day, though troubled by his killing of birds, she joins him in the hunt, and when she learns he has come into their region pursuing the rare white heron, she resolves to surprise and please the youth by climbing a tall pine early the next morning and locating the heron's nest for him. As it happens, atop the tree at dawn, she discovers the nest in a hemlock far below, but then watches in awe as the heron itself rises "through the golden air" (239) and alights on a branch near hers. Thereupon, in a brief conjunction, the rapt girl and the bird behold "the sea and the morning together" (239). Later, making her way home to disclose the nest's location, Sylvia finds her moment with the bird become so affecting that despite the urging of the grandmother and the hunter, she "cannot speak; she cannot tell the heron's secret and give its life away" (239). The young man leaves "disappointed" (239), and, long after, Sylvia continues to miss him. The story ends with the narrator's sympathetic plea: "Were the birds better friends than their hunter might have been,--who can tell? Whatever treasures were lost to her, woodlands and summertime, remember! Bring your gifts and graces and tell your secrets to this lonely country child!" (239). Although "A White Heron" can be read as a species of realism--nothing in the story appears inconceivable--the tale is best understood, I believe, as a romance. (2) In her rendering, Jewett pays little attention to particularities and instead establishes the setting and characters as largely symbolical, representative: a manufacturing town, dark woods, an affectionate girl, a kindly grandmother, a nameless hunter. Romance of course requires that we work to determine what these elements symbolize, what the romance allegorizes. Critics of "A White Heron" have generally agreed that Sylvia represents an innocent, aspiring girl, newly awakened to sexuality, who finds herself greatly attracted to a charming but finally dangerous young man, that this scientist-hunter typifies man's egotism and arrogance with respect to nature and women in nineteenth-century America, and that the heron embodies an eminent expression of nature, of a world apart from man's dominion and worthy of the girl's devotion. From this perspective, then, Sylvia's ominous relation to the hunter allegorizes the predicament of young women in Jewett's culture. Girls desire a transcendent life, but, growing up in a patrilineal culture, they find themselves constrained to seek ascendancy in what often prove destructive alliances with men. Sylvia has escaped the oppression of a manufacturing town, has gotten free of a "great red-faced boy who used to chase and frighten her" (229), and thus for now avoided her impoverished mother's fate (a "houseful of children" [228]). …

Noteworthy waterbird records in the delta of the colorado, mexico, 2002

Abstract: Surveys of the Rfo Colorado delta in summer 2002 revealed abandonment of one large heronry but the existence of another large and several small, inconspicous heronries previously nonexistent or undetected. Most notable among these mixed-species colonies were two nests of the Tricolored Heron and two fledglings of the Reddish Egret, representing considerable northward extensions of these species' breeding ranges. The waterbirds of the Mexican portion of the Rfo Colorado delta are relatively well known (see Patten et al. 2001), especially those breeding on Isla Montague and at the Cerro Prieto evaporation ponds (Peresbarbosa and Mellin k 2001, and references therein; Molina and Garrett 2001). During the 2002 breeding season, however, while collecting samples for a study of trophic relationships in this region, we made some noteworthy observations of breeding waterbirds and of some nonbreeding species for which few records exist. We visited the delta region 4-6 March, 15-19 April, 29 April-3 May, 2- 5 June, 12 June, 24-26 July, 30-31 July, and 8 September. Additionally, on 24 April, using a Beechcraft twin-engine airplane to fly over the delta's major watercourses (Rfo Hardy, Rfo Colorado, Canal Pescaderos) and the Cinega de Santa Clara, we conducted an aerial survey for rookeries. On 30 July 2002, we inspected the large heronry on an islet in the middle of an agricultural drain reported by Mora (1989, 1991, 1992, 1997) near Colonia Venustiano Carranza, hereafter called the "Carranza heronry." The drain channel beneath the heronry was dry, and the shrubby tamarisks (Tamarix rarnosissirna) on which the herons had nested were charred from a recent fire. There were no signs of herons at this place, nor in nearby large patches of tamarisk that seemed suitable as breeding habitat. A farmer (Roberto Viridiola) indicated that the heronry was active as of 2000.

Helping the Client - A Creative Practical Guide' John Heron Sage Publications 276pp £15.99 0 7619 7289 7 0761972897

Abstract: This text is based on the six-category intervention system. Each category is explored in depth, providing the practitioner with a range of analytical and behavioural tools that can be used to support and enable clients' personal development.

Breeding ecology of the four herons

Abstract: The breeding ecology of the four herons (Ardeola bacchus, Bubulcus ibis, Egretta garzetta, Nycticorax nycticorax), such as ingression time, breeding behavior and nestling growth were observed and studied from 1999 to 2001. The results indicate that the numbers of herons are increasing every year. The species of heron were raised from two to four in this region. The community of four heron can build nests, look for food and live with its habits in harmony of population. The four heron differ partly in food components. The food components of Black-crowned Night Heron chiefly consist of frog and fish. Those of Little Egret are mainly composed of fish and crustacean. Cattle Egret live on insects and frog, Chinese Pond Heron on fish. There is a negative correlation between the weight growth and the adult size of the four young of heron. Analysis of the growth curve shows that Chinese Pond Heron and Cattle Egret have faster growth rate than the other two.