Intermediate Egret Research Articles

Are Rice Fields in Southeastern Australia an Adequate Substitute for Natural Wetlands as Foraging Areas for Egrets?

Within the Murray-Darling Basin of eastern Australia there has been a general decline in the abundance of wading birds. Loss of wetlands caused by river regulation and irrigated agriculture is considered to be the main cause. We assessed the adequacy of irrigated rice fields as substitutes for natural wetlands for foraging egrets during the breeding season in one study area around a mixed colony of egrets in southeast Australia. For aerially sown rice crops, which represented 85% of all rice in the general area, the densities of foraging Intermediate Egret (Egretta intermedia) and Great Egret (Ardea alba) tended to reach a maximum four to six weeks after sowing of the rice crop, and declined thereafter. The decline phase was correlated with decreasing prey capture rates and a shift from vertebrate prey to less profitable invertebrate prey, and coincided with the start of the egrets’ main chick rearing period when food demands would have been high. Even at maximum densities it was estimated that only 5-13% of the Intermediate Egrets and Great Egrets that were available to feed actually did so in the rice growing areas within 6.5 km of the colony. In contrast, Cattle Egret (Bubulcus ibis) densities in rice fields did not decline until after their young fledged. They fed almost exclusively on insects and their prey capture rates showed no seasonal decrease. Up to 60% of the available Cattle Egrets were found feeding in the rice fields within 6.5 km of the colony. It is concluded that rice fields provide a good foraging habitat for the Cattle Egret and may be contributing to the spread of this invasive species, but that they are probably not a preferred foraging habitat for the Intermediate Egret and the Great Egret.

The Foraging Ecology of Egrets in Rice Fields in Southern New South Wales, Australia

-Numbers of wading birds are declining throughout the Murray-Darling Basin in Australia, and the loss of wetland habitats to agriculture is the most likely cause. This study describes the foraging of egrets in irrigated rice fields that occur extensively in areas of former wetlands. Tadpoles were the main prey of Great and Intermediate Egrets (Ardea alba and A. intermedia), with insects important secondary prey. Insects were the main prey of Cattle Egrets (A. ibis). Prey capture rates for Great and Intermediate Egrets declined by around 40% between November and January as the rice plants grew from seedling to mature stages. Cattle Egret prey capture rates did not decline. The abundance of tadpoles and most aquatic insects in the rice fields declined significantly between November and February. All three egret species laid eggs mainly during December and had young in the nest duringJanuary and February. Thus the declining profitability of rice fields as foraging sites coincided with the maximum demand for food by the birds to rear their young. Rice fields may not be an adequate substitute for natural wetlands for Great and Intermediate Egrets. Received 14 February 2001, accepted 20 March 2001.

Utilization of Wetlands by Ardeids in Starling Inlet, Hong Kong: A Year-Round Study and a Comparison between the Census and Flight-Line Methods

-Habitat use by ardeids in Starling Inlet, Hong Kong, was assessed by walking a fixed 6 km route, two or three times a month, during low tide between August 1997 and August 1998. A total of 36 surveys were made, with a mean count of 452 individuals per survey (S.E. ? 128). Eight species of ardeids and two species of bitterns were recorded. In the winter, non-breeding season, the dominant species was the Great Egret (Casmerodius albus), while in the summer (breeding season) it was the Black-crowned Night Heron (Nycticorax nycticorax). Shallow coastal waters and mudflats were the most important habitats at low tide for Great and Little Egrets (Egretta garzetta), and Grey Herons (Ardea cinerea), while fishponds were the most important for Black-crowned Night Herons. A freshwater marsh was used mainly by Cattle Egrets (Bubulcus ibis) and Intermediate Egrets (Mesophoyx intermedia). During the 1998 breeding season, a comparison was made between the census and a flight-line methods in evaluating ardeid habitat use. Both methods gave similar results for habitat use by Great and Little Egrets, but the census method underestimated the use of mangrove habitats by Black-crowned Night Herons and missed the use of wet grassland habitats outside the inlet by Cattle Egrets. We suggest that the census method is more efficient for assessing the use of particular open habitats, while the flight-line method is more accurate for investigating overall use of a landscape during the breeding season. Received 2 August 2000, accepted 30 December 2000.

Digenetic trematodes of the genus Clinostomum Leidy, 1856 (Digenea: Clinostomidae) from birds of Queensland, Australia, including C. wilsoni n. sp. from Egretta intermedia

Two species of Clinostomum previously described from Australia, C. hornum from Botaurus poiciloptilus (Australian bittern) and Nycticorax caledonicus (Nankeen night heron) and C. australiense from Pelecanus conspicillatus (Australian pelican), which have previously been synonymised with C. complanatum, are redescribed and recognised as valid species. In addition, C. complanatum is recorded from Egretta alba (large egret), E. garzetta (little egret), E. intermedia (plumed egret), N. caledonicus and Ardea novaehollandiae (white-faced heron). C. wilsoni n. sp. is described from E. intermedia from Queensland. C. wilsoni differs from the other three species in size and shape of the body and in the oral collar, oral sucker, intestinal caeca, caecal diverticula and position of testes. Taxonomic problems within the genus Clinostomum are discussed.

Impact of Water Diversions on Colonially-Nesting Waterbirds in the Macquarie Marshes of Arid Australia

-The building of dams and subsequent diversion of water from the Macquarie River have had a significant impact on the breeding of colonial waterbirds in the Macquarie Marshes, New South Wales, southeastern Australia. Annual flows (1978, 1986-1996), measured at Oxley where the Marshes begin, were significantly related to total colony size (number of nests) and sizes of six nesting Ciconiidae (Intermediate Egret Ardea intermedia, Rufous Night Heron Nycticorax caledonicus, Glossy Ibis Plegadisfalcinellus, Straw-necked Ibis Threskiornis spinicollis, Australian White Ibis Threskiornis mollucca and Royal Spoonbill Platalea regia) colonies. We used these results and available historical flow data extending back to 1944 to demonstrate the probable impact of water diversions on breeding in these colonial nesting species. The impact of Burrendong Dam, opened in 1967, and Windamere Dam, opened in 1984, on the numbers of nests would have been significant. Instead of a colony of more than 100,000 nests in 1969, a colony of less than 10,000 probably established. Similarly, in 1984, a colony of more than 100,000 could have been established with no water diversions, but in all likelihood the colony was less than 5,000. Generally colony sizes were significantly less (100,000 over 11 years) than would be expected without diversions of water upstream. Colony sizes of more than 100,000 nests estimated during the floods of the 1950s are unlikely to occur again. Numbers of annual breeding events also declined with water diversions from ten to seven (1963-1973); eight to seven (1974-1984) and eight to five (1985-1995). Received 18 December 1997, accepted 18 May 1998.

Heavy metal and selenium concentrations in feathers of egrets from Bali and Sulawesi, Indonesia.

Herons and egrets are ideal organisms to use asindicators of heavy metal exposure in an ecosystem because different speciesfeed at different levels of the food chain and live in both coastal andinland habitats. This paper reports on the concentration of heavy metals andselenium in the feathers of cattle egrets Bubulcus ibis that wereexamined from nesting and roosting sites in Bali and Sulawesi, Indonesia, andin feathers of little egrets Egretta garzetta and intermediate egretsE. intermedia from the same colony in Bali. Mercury and manganeseconcentrations were significantly higher in cattle egrets from Bali comparedto Sulawesi, but otherwise there were no significant differences. There weresignificant differences in lead, cadmium and mercury among the three egretspecies nesting on Bali: 1) the cadmium and mercury concentrations related tosize and trophic level (insectivorous cattle egrets had the lowestconcentrations, fish-eating intermediate egrets had the highestconcentrations), and 2) cattle egrets had significantly lower concentrationsof lead than the other two species. For cattle egrets, secondary flightfeathers had significantly higher levels of cadmium and mercury, and lowerlevels of manganese, than mixed breast and tertiary feathers, reflectingtemporal differences in exposure.

Preliminary report on the investigation of birds in North Korea

The paper presents the results of investigations conducted during eight expeditions to the Korean People's Democratic Republic. The observations included faunistic rarities (Pernis ptilorhyncus, Gallinago solitaria, Emberiza sulphurata) and species with under breeding ranges (Actitis hypoleucos, Corvus dauuricus, Turdus chrysolaus) Changes of ranges and numbers of some species (Phalacrocorax carbo, Otis tarda, Falco tinnunculus, Falco subbuteo, Accipiter soloensis) are discussed, and the status of rare and endangered species throughout the world (Egretta intermedia, Egretta eulophotes, Ciconia boyciana, Nipponia nippon, Larus saundersi, Eurynorhynchus pygmaeus) is also commented on.

Habitat Selection, Foraging Behaviour and Prey of Five Heron Species in Japan

Habitat selection, foraging behaviour and prey items of five species of herons were studied at an estuary in Chiba Prefecture, central Japan. The two largest species, the Grey Heron Ardea cinerea and the Great White Egret Egretta alba modesta fed mainly on the tidal flat and in the river. The three smaller species, the Intermediate Egret E.intermedia, the Little Egret E.garzetta and the Cattle Egret Bubulcus ibis fed mainly on farmland. The Great White Egret and Little Egret were habitat generalists using all types of habitat, whilst the three other species seemed to be habitat specialists. Grey Herons fed only in large bodies of water; Cattle Egrets were highly terrestrial feeders; Intermediate Egrets preferred farmlands or wet habitats but avoided both large bodies of water and dry habitats. The primary foraging behaviour of Grey Herons was Standing by which method they captured large prey. Great White Egrets adopted a Walking Slowly method as well as Standing, and they took significantly smaller prey than Grey Herons. Intermediate Egrets adopted mainly Walking Slowly, Standing and slow foraging behaviours, in contrast to Little Egrets that used Walking Quickly and very active foraging behaviours. Cattle Egrets foraged mainly by Walking Slowly, but also adopted active foraging behaviours. In their feeding ecology, the Grey Heron, Intermediate Egret and Little Egret in Japan seemed to be, respectively, ecological counterparts to the Great Blue Heron A.herodias, Little Blue Heron E. caerulea and Snowy Egret E.thula in North America. Recent population declines of the Intermediate Egret may be related to deterioration of the farmland habitats upon which this species depends.

Foraging Site Preference of Intermediate Egrets Egretta intermedia during the Breeding Season in the Eastern Part of the Kanto Plain, Japan

Habitat selection of Intermediate Egrets Egretta intermedia was studied in the Kokaigawa and Sakuragawa areas of Ibaraki Prefecture in the eastern part of the Kanto Plain, Honshu, Japan, during the breeding season between June and August in 1993. Selection may be for areas with easier hunting and food availability; i. e., they avoided rivers and dry fields throughout the season and flooded fields with deep concrete waterways and pipelines in June. Flooded rice fields were favored by the egrets in June but avoided in July and August because rice plants grew too thick for them to hunt. Fish, crustaceans and insects were recorded as the main prey items in flooded fields, and only insects were taken in fallow fields in August.

Phosphorus and nitrogen in wetlands with and without egret colonies

Abstract Colonially nesting birds have been implicated in the destruction of their nest site vegetation, the most likely mechanism being through an overload or imbalance of soil nutrients. The numbers of egrets in coastal New South Wales colonies have increased rapidly in the second half of this century since cattle egrets (Ardeola ibis) were introduced. This species now nests colonially with three native species: great (Egretta alba), intermediate (Egretta intermedia) and little egrets (Egretta garzetta). Thus there is potential for more rapid degradation of the colony site. We measured the levels of phosphorus in surface sediments, and phosphorus and nitrogen in water at eight colony site wetlands, and compared each to four other wetlands in the same region where there were no egret colonies. We conclude that levels of both nutrients were elevated in colony wetlands. The implications of this result for death of colony site vegetation and the conservation of the three native egret species are briefly discussed.

The Influence of Synchronous Breeding, Natal Tree Position and Rainfall on Egret Nesting Success

Factors commonly thought to influence the breeding success of colonial egrets were measured over 4 years. No significant difference in breeding success occurred between years, and the position of the natal tree in the colony did not affect breeding success. Evidence of synchronous breeding was found, but only intermediate Egrets had a higher fledging success for nests that fledged young during the peak nesting month. The amount of rainfall in the five months prior to the onset of nesting was positively correlated with the fledging success of Intermediate Egrets, suggesting the importance of food availability for this species. Nesting success found in New South Wales was compared to that reported elsewhere, and found to be less than that calculated to maintain stable populations. The problem of comparing fledging success between different studies with different criteria for determining is discussed.

Distribution and abundance of herons, egrets, ibises and spoonbills in the Alligator Rivers Region, Northern Territory

Aerial surveys between 1981 and 1984 were used to identify monthly trends in the abundance of Pacific herons (Ardea pacifica), pied herons (Ardea picata), cattle egrets (Ardeola ibis), great egrets (Egretta alba), little egrets (Egretta garzetta), intermediate egrets (Egretta intermedia), glossy ibis (Plegadis falcinellus), sacred ibis (Threskiornis aethiopica), straw-necked ibis (Threskiornis spinicollis) and royal spoonbills (Platalea regia) on five floodplains of the Alligator Rivers region, 250 km east of Darwin in the monsoonal Northern Territory. Ground surveys were conducted during the same period on one of the floodplains, the Magela. The aerial surveys indicated that the Magela floodplain was inhabited by few of these birds during the wet season (November-March), but that numbers then increased substantially in the dry season. The Nourlangie floodplain and Boggy Plain (a large backswamp of the South Alligator floodplain) showed similar patterns, but the numbers of birds tended to be lower. Birds were generally uncommon on the shallower East Alligator and Cooper floodplains, except for egrets in the wet season. Ground surveys suggested that the birds sought out the persistent swamps that characterise the Magela foodplain in the dry season. Ground surveys also indicated that aerial surveys underestimated densities. On the basis of correction factors calculated from ground surveys, peak numbers on the five floodplains were roughly estimated to be about 4000 pacific herons, 50 000 pied herons, 300 000 egrets (primarily intermediate egrets), 60 000 glossy ibis, 16 000 sacred ibis, 80 000 straw-necked ibis and 35 000 royal spoonbills. Great-billed herons (Ardea sumatrana), white-faced herons (Ardea novaehollandiae), striated herons (Butorides striata), rufous night herons (Nycticorax caledonicus), black bitterns (Dupetor flavicollis) and yellow-billed spoonbills (Platalea flavipes) were recorded sporadically in low numbers. The Alligator Rivers region acted as a dry-season refuge for herons, egrets, ibises and spoonbills because of the unusually persistent fresh waters of the Magela and Nourlangie floodplains and some of the backswamps of the South Alligator, such as Boggy Plain.

Natural infections of Clinostomum complanatum (Trematoda: Clinostomatidae) in wild herons and egrets, Tottori Prefecture, Japan.

Nycticorax nycticorax, Ardea cinerea, Egretta garzetta, and Egretta intermedia were naturally infected with Clinostomum complanatum (Trematoda: Clinostomatidae) among fourteen wild herons, seven wild egrets and one wild bittern evaluated at the Veterinary Hospital of Tottori University, Tottori, Japan. The latter three species of heron and egrets are reported for the first time as definitive hosts of this parasite in Japan.

Comparison of the Diets of Nestling Cattle Egrets and Intermediate Egrets in the Hunter Valley, New-South-Wales

The foods of Ardeola ibis coromandus and Egretta intermedia plumijera were determined from boluses regurgitated by chicks. There were 61 boluses collected from A. ibis and 33 from E. intermedia over four breeding seasons. A. ibis ate orthopteran insects (66% bulk weight) with fewer vertebrates (23%). E. intermedia relied on vertebrates (69%), mainly fish (58%), but also ate orthopterans (22%). Each species was largely opportunistic in its feeding but probably selected different habitats in which to forage. From the small dietary overlap revealed in this study, we conclude that interspecific competition for food was unlikely during the 1985-1987 breeding seasons.

To Drain or Not to Drain?—Intermittent Swamp Drainage and Waterbird Breeding

The breeding activity of waterbirds - ducks, cormorants, ibises, herons and grebes - are examined in relation to water level fluctuations at Booligal, N.S.W. In the swamp complex studied, most species bred best after a flood on a previously dried out basin. A rise in water level in an already wet basin had no effect. However, the specialist fishers - Darters, Little Black Cormorants and Intermediate Egrets - bred best when the swamps had been filled for some time and a climax of Ribbonweed and tish had developed. The importance of a previous drying phase to waterbird breeding rather than a flood is stressed and the usefulness of drying swamps intermittently in waterbird management considered.

A New Species of Blankaartia (Megaciella) Parasitic on a Migratory Bird in Irian, New Guinea (Acari: Trombiculidae)1

Blankaartia ( Megaciella ) dohanyi , n. sp. is described from specimens collected from the Plumed Egret, Egretta intermedia , in Irian, New Guinea. The subgenus is known only from the Old World and all 6 known species are from birds.

Nestling Development of Green Herons at San Blas, Nayarit, Mexico

Although many recent papers have described methods for determining general age classes and growth rates of nestling birds, few have dealt with members of the order Ciconiiformes. Meyerriecks (in Palmer 1962) and Wheelock (1906) briefly presented some data on growth in nestling Green Herons ( Butorides virescens) and Hindwood (1933) described the development of nestlings of Butorides striatus in Australia. Gross (1923) studied development of the Black-crowned Night Heron (Nycticorax nycticorax), and McClure et al. (1959) made extensive measurements of the growth of nestlings of that species as well as of Plumed and Little Egrets (Egretta intermedia and E. garzetta) in Japan. Lowe (1954) described the development of young Gray Herons (Ardea cinerea) and Kahl analyzed in detail growth rates of nestling Wood Storks (1962) and Marabou Storks (1966). Because of the possible importance of age in susceptibility of birds in general to infection with arboviruses, i.e., viruses transmitted by mosquitoes (see reviews by Scherer 1963 and Stamm 1966), and because of the involvement of ciconiiform birds in the natural cycles of arboviruses, more accurate methods of aging birds are needed.

FIELD NOTES ON BIRDS OF THE EASTERN SOLOMON ISLANDS

Summary. Field notes on the birds of Guadalcanal, San Cristobal, Ugi and Ulawa, based on the work of the Oxford University (Dept. of Zoology) Expedition to the eastern Solomons, are given. These include the first account of the behaviour and nesting habits of Aplonis brunneocapillus. New records for the Solomons are Pelecanus conspicillatus (Guadalcanal), Egretta intermedia (San Cristobal, based on a specimen in the British Museum, Natural History), and Cichlornis whitneyi (Guadalcanal). New records for islands in the Solomons (in addition to the above) are:—Guadalcanal: Cacomantis pyrrhophanus, Coracina caledonica, Turdus poliocephalus, Zoothera margaretae, Petroica multicolor.San Cristobal: Collocalia spodiopygia, C. vanikorensis.Ugi: Collocalia spodiopygia, Hirundo tahitica (others based as yet only on native reports are given for further investigation). A revised list for Ugi, with rejection of some previous records, is given, also a short list of the birds of Ulawa (not investigated before) and a list of species from the Three Sisters, taken from specimens in the British Museum (Natural History).

FIELD NOTES ON BIRDS OF THE EASTERN SOLOMON ISLANDS

Summary. 1 Field notes on the birds of Guadalcanal, San Cristobal, Ugi and Ulawa, based on the work of the Oxford University (Dept. of Zoology) Expedition to the eastern Solomons, are given. These include the first account of the behaviour and nesting habits of Aplonis brunneocapillus. 2 New records for the Solomons are Pelecanus conspicillatus (Guadalcanal), Egretta intermedia (San Cristobal, based on a specimen in the British Museum, Natural History), and Cichlornis whitneyi (Guadalcanal). 3 New records for islands in the Solomons (in addition to the above) are:— Guadalcanal: Cacomantis pyrrhophanus, Coracina caledonica, Turdus poliocephalus, Zoothera margaretae, Petroica multicolor. San Cristobal: Collocalia spodiopygia, C. vanikorensis. Ugi: Collocalia spodiopygia, Hirundo tahitica (others based as yet only on native reports are given for further investigation). 4 A revised list for Ugi, with rejection of some previous records, is given, also a short list of the birds of Ulawa (not investigated before) and a list of species from the Three Sisters, taken from specimens in the British Museum (Natural History).