Showing papers on "Heron published in 1984"

Field confirmation of laboratory observations on the differential antimosquito behavior of herons

Abstract: In the early 1970s, Edman, Kale and Webber published a series of papers (by various combinations of authors, 1971, 1972, 1974) detailing the defensive behavior of caged birds and mammals exposed to biting mosquitoes. The authors showed conclusively that, under large, outdoor, cage conditions: (1) vertebrate species differ greatly in their tolerance of mosquitoes, and (2) host defensive behavior is an important regulator of mosquito blood-feeding success. These studies emphasized herons and in 1977, Maxwell and Kale published data on the anti-insect behavior of some of the same heron species under natural conditions. While essentially confirmatory, their observations near an island rookery in the estuarine Indian River near Vero Beach, Florida, were from a location and time when mosquito annoyance was minimal. Data presented in these previous reports support the suggestion that in different species of herons, the birds' defensive behavior against mosquitoes may be related to their foraging posture (Meyerriecks 1960:149). Active insect-eating herons (e.g., Cattle Egret, Bubulcus ibis) are the most defensive (repelling up to 90+ percent of attacking mosquitoes), whereas passive (i.e., stand-and-wait) fisheating species (e.g., Black-crowned Night Heron, Nycticorax nycticorax) that forage in early evening are the most tolerant (allowing up to 90+ percent of landing mosquitoes to blood-engorge). Active fish-eating species such as the Little Blue Heron (Egretta caerulea) are somewhat less defensive than the insect-eating species; passive day-feeders such as the Green-backed Heron (Butorides striatus) are somewhat less tolerant than night-feeding herons. Still, the Little Blue Heron must be classified as a relatively intolerant species and the Green-backed Heron as a relatively mosquito-tolerant species. Both these herons may be found foraging in the same habitat at the same time of day-thus making field observations more comparative. We now report recent observations of these two species from the Florida Everglades, which further validate earlier laboratory observations of heron defensive behavior against mosquitoes. We made our observations between 10:00 and 14:00 on 7-8 January 1983 at Mrazek Pond and along the Bear Lake canoe trail, both near Flamingo in the Everglades National Park. All observations were made with the aid of 8 x binoculars. Owing to a warm and unusually wet December, mosquitoes (almost exclusively Aedes taeniorhynchus Weidemann during the day) were extremely abundant in coastal areas of the park. On shaded dikes within mangrove swamp, they landed on us at a rate often exceeding 100/min. This mosquito flies primarily during crepuscular periods (Bidlingmayer 1964), but hosts entering its shaded daytime resting habitat are opportunistically attacked by blood-hungry females. Little Blue Herons, although not the most defensive heron studied in the laboratory, were in the group that acted most intensely against mosquitoes, preventing most attacking mosquitoes from obtaining a blood meal. In one of our previous studies, they made about 46 defensive movements per min and allowed less than 25% of 300 attacking mosquitoes to feed (Webber and Edman 1972). In the Everglades, we observed an undisturbed adult Little Blue Heron actively foraging for small fish in a shallow tidal pool under a canopy of red mangroves. During the few minutes we were able to watch this bird, both the heron and the observers were attacked by numerous mosquitoes (presumably all Ae. taeniorhynchus). When not chasing after and capturing fish, the bird was constantly defending itself, primarily by shaking its head, fluffing its entire plumage and using its bill to peck at and rub mosquitoes from its upper legs and body. We did not see any mosquitoes successfully engorging on this bird. In the laboratory, roosting Little Blue Herons engaged in a great deal of foot-slapping and foot-stamping behavior (Webber and Edman 1972) but these defensive behaviors were not observed in this particular field situation, presumably because the bird was foraging in water ca. 2-3 cm in depth. Green-backed Herons were relatively tolerant of mosquito annoyance in our previous cage studies. Their defensive movements consisted mainly of mild head-shaking (63% of total defensive activity). Both the frequency (11 per min) and intensity of anti-mosquito behavior were lower than in the Little Blue Heron (Webber and Edman 1972). Over 50% of 300 attacking mosquitoes generally obtained a blood meal in these outdoor cage experiments. At the edge of Mrazek Pond, we observed for several minutes an adult Green-backed Heron fishing from a red mangrove branch just above the water. The bird crouched quietly in a striking position waiting for a fish to come within range, and it captured several fish while we watched it. Between strikes at fish, it tolerated attacks from many mosquitoes. We could see mosquitoes resting on branches around the bird as well as landing, probing, and feeding, principally on the bird's head, legs, and feet. The only defensive movement was a frequent slight sideways tossing of the head accompanied by an eye-blink that caused some of the mosquitoes sitting about the head to take temporary flight, but they soon landed and resumed probing. Mosquitoes that had started to engorge appeared undisturbed by this head movement unless they were sitting directly on the eyelid. Occasionally the bird would flip its tail but this was probably not a defensive movement. Also, the heron temporarily performed other defensive movements immediately after capturing a fish and before again assuming the watching stance. These included a more aggressive tossing of the head, rubbing the legs with the bill, and mild foot-stamping. Nonetheless, we saw many engorged mosquitoes feeding on the bird and resting on nearby vegetation. These field observations strengthen earlier laboratory comparisons of avian defensive behavior. Furthermore, they fortify the argument that the tolerance level of different herons to mosquitoes is associated with their specific mode of foraging and the latitude for extraneous movement that is allowable without jeopardizing the rate of capturing prey.

Resource partitioning in colonial herons, with particular reference to the grey heron Ardea cinerea L. and the purple heron Ardea purpurea L., in the Camargue, S. France

Abstract: There have been major changes in the relative abundance of the six species of colonial Ardeidae (herons and egrets) which breed in the Camargue, since I9680 Two species, the Grey Heron and the Cattle Egret, started nesting in the delta in the mid-sixties and have increased dramatically in numbers, whilst there has been a simultaneous decline in the breeding population of Purple Herons. Examination of counts and of the patterns of resource use by these species show that although Grey and Purple Herons overlap extensively in morphology, breeding sites (reedbeds), feeding sites and diet, competition during the breeding season cannot have been responsible for the observed changes, since numbers of Purples have remained stable in those areas where the greatest increases of Greys have occurred, whilst they have completely disappeared in some areas where there were no Greys. Instead, breeding sites have been destroyed to such an extent within the delta that they now limit the number of Purple Herons below the level set by winter mortality, which has been shown to limit breeding populations in other areas. For Purple Herons, the relationship between colony size and food resources was examined at a breeding-site where colony size was not limited by the availability of adequate breeding habitat. Adults exploited feeding areas near (<2km) to the colony in preference to those further away (max. 15km); near areas were the first to be filled and remained filled throughout the breeding season. Early breeders held feeding territories in areas adjacent to the colony, to the exclusion of later breeders. Breeding partners did not share the same feeding territories, nor associate in any way on the feeding areas. It is suggested that the increasing costs of flight-time and flight-energy incurred by adults foraging further from the colony may set an upper limit to colony size. Aspects of the breeding biology of the Purple Heron are described. The average clutch-size in the Camargue is the lowest reported for Europe, and declined significantly through the summer. Siblings differed considerably in size as a result of the asynchronous hatching of the clutch, and not of egg-size differences. The first two chicks in broods of three, and the first three chicks in broods of four, grew fastest and a high proportion of the youngest chicks in a brood died of starvation. It is argued that the number of young fledged is limited by the ability of the adults to deliver food to the nest. Changes in clutch-size are used to adjust brood-size to predictable changes in food availability, while brood reduction through sibling hierarchies provides a fine tuning at the time of peak nestling demand. The diet of Grey and Purple Herons was examined from nestling regurgitations; both species are highly piscivorous. The Grey Heron specialises on large Eels, Carp and Mullet whilst the Purple Heron takes Eels and a wide variety of other fish, plus some invertebrates. Mechanisms of prey selection were examined for the Grey Heron. Large Carp and similar fish are the most profitable prey for adults whilst small fish and species which possess protective spines, such as Catfish, are of low profitability. Young chicks cannot consume prey as large as can the adults, although this ability develops by the time they are ca 30 days old. Evidence is presented that adults select prey in relation to the age of their chicks. The results of this study are discussed in relation to the conservation of breeding heron populations in Europe. Recommendations for the management of breeding areas are proposed.

Diversity and zoogeography of marine Tubificidae (Annelida, Oligochaeta) with notes on variation in widespread species

Abstract: The specific and generic diversities of the marine Tubificidae (Annelida, Oligochaeta) of the NE Pacific are compared to those of the NE and NW Atlantic as well as to those of Heron Island, Australia. Diversity in the NE Pacific is relatively high when compared to that of the NE Atlantic. The Tubificidae of the NW Atlantic (limited to the eastern coast of the USA) show two distinct zoogeographic regions: Florida to Cape Hatteras; Cape Hatteras to Massachusetts. Diversity, both in terms of the number of species and number of genera, is approximately the same in these two regions, and is similar to that of both the NE Pacific and Heron Island. Evidence suggests that the widespread marine species, in particular Tubificoides pseudogaster, have a range of morphotypes across their distributions. The apparent wide distributions of these species may be due to a taxonomy unable to resolve the differences between the morphotypes. The tubificid oligochaete fauna of the NE Atlantic appears impoverished compared to the other regions examined. The NE Pacific, NW Atlantic, and Heron Island regions are not dominated by one group of species while the NE Atlantic fauna is dominated by Tubificoides benedeni and Clitellio arenarius.

Population trends and environmental contaminants in herons in the Tennessee Valley, 1980-81

Abstract: -Great Blue Heron (Ardea herodias) eggs (N = 40) collected in 1980 from four of the largest colonies in the Tennessee Valley contained organochlorine pesticide, polychlorinated biphenyl (PCB), and chromium concentrations below those associated with reduced productivity. Low concentrations of organochlorine pesticide and PCB residues also were found in eggs (N = 31) from three of the larger Black-crowned Night-Heron (Nycticorax nycticorax) colonies in the Tennessee Valley. However, DDE concentrations in two of the Black-crowned Night-Heron eggs exceeded levels associated with reduced nesting success. Mercury was found in all eggs of both species with residues ranging to a high of 2.0 ppm; residues of this magnitude have not been identified as reducing nesting success of either of these two species. Green-backed Heron (Butorides striatus) eggs collected in 1981 near a former DDT manufacturing site in the Tennessee Valley had the highest DDE concentrations ever reported for this species; the effect of these high concentrations on productivity is not known. Eggshell thickness of Great Blue Heron, Green-backed Heron, and Black-crowned NightHeron eggs averaged 7.5%, 7.6%, and 3% thinner, respectively, than shell thickness of eggs collected before 1947. This amount of thinning is not deleterious; intraclutch variation in shell thickness is often this high. Shell thickness in all three species was correlated (P < 0.1) with DDE concentrations. The number of nesting pairs of Great Blue Herons and Black-crowned Night-Herons at each of the colonies studied has been stable or increasing during the previous decade. These population data, combined with the residue data, suggest that organochlorine pesticides, PCBs, mercury, and chromium are not adversely affecting these populations. However, we did not assess nesting success which would be a requisite for confirming this.

Late Pleistocene glacial sequence in the Lake Heron basin, mid Canterbury

Abstract: Extensive areas of glacial and fluvioglacial landforms are preserved in the Lake Heron basin, mid Canterbury, New Zealand. Five main late Pleistocene glacial advances, representing at least 3 glaciations, are recognised (from oldest to youngest): Pyramid, Dogs Hill, Trinity, Emily, and Lake Heron advances. Landforms of the Emily and Lake Heron advances are particularly well preserved, and an unusually complete sequence of ice-front landforming events is determined.

Scanning and the Distribution of Attention: The Current Status of Heron’s Sensory-Motor Theory

Abstract: Speech is presented to the senses as a series of phonemes extended in time. Written material is presented as a parallel spatial array, but thought, like speech, is extended in time. Reading, therefore, involves conversion from a parallel spatial representation to a temporal one. Heron (1957) addressed the problem of spatial-to-temporal conversion by postulating an attentional process that sweeps, or scans, an internal neural representation of the spatial array in an orderly way. In this chapter, I shall reconsider some of Heron’s ideas about visual processing, trace the development of the problem, and, finally, re-cast his theory in the form of an information-processing account.

Environmental Uptake of Lead in Black-Crowned Night Herons

Abstract: Samples of black-crowned night heron tissue were examined for lead using spectrophotome tric analysis. Average lead content in tissues (in ppm wet weight) were 4.87 in eggshell, 3.6 in egg contents, 0.35 in developing embryos, and 18.3 in young heron tissues. These data suggest ontogenic dilution of lead and then dosage, presumably by food, in young herons. Heron -foods contained lead. It is contended that lead -from spent gunshot was dissolved, taken up by resident organisms, and then accumulated by young herons through the ingesting of food species. There are other pathways by which herons can take up lead. Though the amount of lead concentratable through the process described in this paper does not appear to be extraordinarily great, it is something about which to be aware, especially in this species whose breeding range and habitat seem to be decreasing.

Walter Heron Taylor and His Era

Abstract: WALTER HERRON TAYLOR AND HIS ERA Emanuel Meyer Old Dominion University Director: Dr. Peter C. Stewart This biography examines Colonel Walter Herron Taylor’s involvement in the development of Norfolk, Virginia, into a modern urban seaport. Although this thesis depicts Taylor’s role as Robert E. Lee’s adjutant and Civil War historian, it clearly demonstrates that his civic accomplish­ ments in the post-war era considerably outweighed his efforts for the Confederacy. Colonel Taylor's lifetime career in banking and commerce reflected the changing society of the South from a backward province into a modern industrial and sophisticated section. The author illustrates the Colonel’s participation in Nor­ folk's growth from the stormy Reconstruction period to the eve of World War I. Throughout these years many signifi­ cant municipal and social reforms were aided by, or were a direct result of, Colonel Taylor’s activities. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.