Avian Piscivores as Vectors for Myxobolus cerebralis in the Greater Yellowstone Ecosystem

Myxobolus cerebralis, the cause of whirling disease in salmonids, has dispersed to waters in 25 states within the USA, often by an unknown vector. Its incidence in Yellowstone cutthroat trout Oncorhynchus clarkii bouvieri within the highly protected environment of Yellowstone Lake, Yellowstone National Park, is a prime example. Given the local abundances of piscivorous birds, we sought to clarify their potential role in the dissemination of M. cerebralis. Six individuals from each of three bird species (American white pelican Pelecanus erythrorhynchos, double-crested cormorant Phalacrocorax auritus, and great blue heron Ardea herodias) were fed known-infected or uninfected rainbow trout O. mykiss. Fecal material produced during 10-d periods before and after feeding was collected to determine whether M. cerebralis could be detected and, if so, whether it remained viable after passage through the gastrointestinal tract of these birds. For all (100%) of the nine birds fed known-infected fish, fecal samples collected during days 1–4 after feeding tested positive for M. cerebralis by polymerase chain reaction. In addition, tubificid worms Tubifex tubifex that were fed fecal material from known-infected great blue herons produced triactinomyxons in laboratory cultures, confirming the persistent viability of the parasite. No triactinomyxons were produced from T. tubifex fed fecal material from known-infected American white pelicans or double-crested cormorants, indicating a potential loss of parasite viability in these species. Great blue herons have the ability to concentrate and release viable myxospores into shallow-water habitats that are highly suitable for T. tubifex, thereby supporting a positive feedback loop in which the proliferation of M. cerebralis is enhanced. The presence of avian piscivores as an important component of aquatic ecosystems should continue to be supported. However, given the distances traveled by great blue herons between rookeries and foraging areas in just days, any practices that unnaturally attract them may heighten the probability of M. cerebralis dispersal and proliferation within the Greater Yellowstone Ecosystem.

Avian Use of Harvested Crop Fields in North Dakota During Spring Migration

Broad-spectrum herbicide applications and improved harvesting efficiency of crops have reduced the availability of weed seeds and waste grains for game and nongame wildlife. Over the last decade, corn and soybean plantings have steadily increased in the Prairie Pothole Region (PPR) of North Dakota, while sunflower plantings have declined. The PPR is an important corridor for migratory birds, and changes in food availabilities at stopover habitats may affect how food resources are used. In early spring 2003 and 2004, we compared bird use of harvested fields of sunflower, soybeans, small grains, and corn in the PPR of North Dakota. Across both years and all crop types, we observed 20,400 birds comprising 29 species. Flocks of Lapland Longspurs (Calcarius lapponicus) and Horned Larks (Eremophila alpestris) and flocks of Red-winged Blackbirds (Agelaius phoeniceus) made up 60% and 15%, respectively, of the bird counts. We found that species richness and bird densities were higher in harvested sunflower fields and cornfields than in harvested small-grain and soybean fields, with soybean fields harboring the fewest species and lowest bird density. Blackbird densities tended to be lower in fields tilled after fall harvest than in fields not tilled. These results suggest that some granivorous bird populations in the Northern Great Plains could be positively affected by planting of row crops with postharvest vertical structure (e.g., sunflower, corn) and use of no-till land management practices.

EC28-234 Nebraska System for Tattooing Hogs for Identification after Slaughter

A plan to identify the individual farm upon which hogs reaching markets are produced has been developed in connection with the efforts toward eradicating tuberculosis among farm animals. While primarily intended as a means of tracing back to determine sources of disease infection, the system of tattooing which is being developed has other significant possibilities. With the growing emphasis on quality products in the market, it is only fair that the producers of high quality commodities receive the premiums paid by processors and consumers. Health of farm animals is a quality factor. The producer of healthy hogs should be rewarded. Likewise, the producer of diseased hogs profits from knowledge that his animals are infected and can institute efforts to control that source fo loss. This 1928 extension circular covers what each letter of a tattoo stands for, where it is to be placed on an animal, and material used in tattooing.

Hidden Effects of Chronic Tuberculosis in African Buffalo

Infectious diseases can bring about population declines and local host extinctions, contributing significantly to the global biodiversity crisis. Nonetheless, studies measuring population-level effects of pathogens in wild host populations are rare, and taxonomically biased toward avian hosts and macroparasitic infections. We investigated the effects of bovine tuberculosis (bTB), caused by the bacterial pathogen Mycobacterium bovis, on African buffalo (Syncerus caffer) at Hluhluwe-iMfolozi Park, South Africa. We tested 1180 buffalo for bTB infection between May 2000 and November 2001. Most infections were mild, confirming the chronic nature of the disease in buffalo. However, our data indicate that bTB affects both adult survival and fecundity. Using an age-structured population model, we demonstrate that the pathogen can reduce population growth rate drastically; yet its effects appear difficult to detect at the population level: bTB causes no conspicuous mass mortalities or fast population declines, nor does it alter host-population age structure significantly. Our models suggest that this syndrome—low detectability coupled with severe impacts on population growth rate and, therefore, resilience—may be characteristic of chronic diseases in large mammals.

Experimental Infection of Contracaecum tipapillatum (Nematoda: Anisakinae) from Mexico in the Domestic Cat

Juveniles of Contracaecum multipapillatum infected the Mayan cichlid (Cichlasoma urophthalmus) and adults infected the olivaceous cormorant (Phalacrocorax olivaceus) and the great egret (Casmerodius albus) in the coastal lagoon at Celestun, State of Yucatan, Mexico. All are new host records, and, even though the geographic locality record of Mexico for the species has not been published, unidentified but presumably conspecific specimens have been reported from there. When juveniles of C. multipapillatum were fed to a kitten, but not rats, ducks, or chickens, they developed into adults. Measurements and morphological data are provided on the specimens from the kitten. Development of an avian ascaridoid in the intestine of a mammal increases the potential of this widespread species to infect other mammals, including humans.

SCWDS Briefs: Volume 23, Number 1 (April 2007)

Table of Contents: SCWDS History Continued: The Domestic Animal Connection WNV Still With Us: Other Arboviruses May Follow Avian Influenza Update – Spring 2007 Scholarship in Memory of Ed Couvillion Chronic Lead Poisoning in Raptors Unusual Deer Tumor Kevin Keel Receives Award New Edition of Wild Bird Diseases Book

Review of issues concerning the use of reproductive inhibitors, with particular emphasis on resolving human-wildlife conflicts in North America

This manuscript provides an overview of past wildlife contraception efforts and discusses the current state of research. Two fertility control agents, an avian reproductive inhibitor containing the active ingredient nicarbazin and an immunocontraceptive vaccine, have received regulatory approval with the Environmental Protection Agency and are commercially available in the USA. OvoControl G Contraceptive Bait for Canada Geese and Ovo Control for pigeons are delivered as oral baits. An injectable immunocontraceptive vaccine (GonaCon Immunocontraceptive Vaccine) was registered with the Environmental Protection Agency for use in female white-tailed deer in September 2009. An injectable product (GonaCon Immunocontraceptive Vaccine) is registered for use in female white-tailed deer. Both products are labeled for use in urban/suburban areas where these species are overabundant. Several other compounds are currently being tested for use in wildlife in the USA, Europe, Australia and New Zealand that could have promise in the future. The development and use of reproductive inhibitors for resolving human–wildlife conflicts will depend on a number of factors, including meeting the requirements of regulatory agencies for use in the environment and on the biological and economical feasibility of their use. Use will also be dependent on health and safety issues and on public acceptance of the techniques.

An Evaluation of Diazacon as a Potential Contraceptive in Non-Native Rose-Ringed Parakeets

Rose-ringed parakeets (Psittacula krameri) have become widely established outside their native range through accidental or deliberate release. Potential economic impacts on agriculture, conservation concerns, and mixed public opinion regarding the species have highlighted the need to develop effective but humane management options. Fertility control might provide such a solution if a safe and environmentally benign contraceptive was available. The chemical 20,25-diazacholesterol dihydrochloride (diazacon) has previously been used to reduce reproductive output in avian species through reduction of blood cholesterol and cholesterol-dependent reproductive hormones. We orally dosed captive rose-ringed parakeets with a solution of either 9 mg/kg or 18 mg/kg of diazacon for up to 10 days and found that a dose of 18 mg/kg for 10 days temporarily reduced blood cholesterol levels with no adverse side effects. We evaluated this dose level in a captive population in semi-natural conditions during the 2008 breeding season and found a significant decrease in fertility. We concluded that diazacon has potential for fertility control in this species if a suitable formulation and delivery system is developed for free-living populations.

Seeking a Second Opinion: Uncertainty in Disease Ecology

Analytical methods accounting for imperfect detection are often used to facilitate reliable inference in population and community ecology. We contend that similar approaches are needed in disease ecology because these complicated systems are inherently difficult to observe without error. For example, wildlife disease studies often designate individuals, populations, or spatial units to states (e.g., susceptible, infected, post-infected), but the uncertainty associated with these state assignments remains largely ignored or unaccounted for. We demonstrate how recent developments incorporating observation error through repeated sampling extend quite naturally to hierarchical spatial models of disease effects, prevalence, and dynamics in natural systems. A highly pathogenic strain of avian influenza virus in migratory waterfowl and a pathogenic fungus recently implicated in the global loss of amphibian biodiversity are used as motivating examples. Both show that relatively simple modifications to study designs can greatly improve our understanding of complex spatio-temporal disease dynamics by rigorously accounting for uncertainty at each level of the hierarchy.

Epizootiologic Survey of Mycobacterium Bovis in Wildlife and Farm Environments in Northern Michigan

Bovine tuberculosis (bovine TB), caused by Mycobacterium bovis, has reemerged in northern Michigan, USA, with detections in white-tailed deer (Odocoileus virginianus) in 1994 and in cattle in 1998. Since then, significant efforts have been directed toward reducing deer densities in the area in the hopes of reducing the bovine TB prevalence rate in deer and eliminating spillover of the disease into cattle. Despite the success of the efforts to reduce deer densities, additional cattle herds have become infected. Other mammals can be infected with M. bovis, and some carnivores and omnivores had been found to be infected with the disease in northern Michigan, USA. We conducted a multiyear surveillance effort to detect bovine TB in wild species of mammals in the Michigan, USA, outbreak area. From 2002 to 2004, tissue samples from 1,031 individual animals of 32 species were collected, processed, and cultured for M. bovis. Only 10 (1.0%) were culture-positive for M. bovis (five raccoons [Procyon lotor], four opossums [Didelphis virginiana], and one grey fox [Urocyon cinereoargenteus]). We also found two raccoons and four opossums to be positive for Mycobacterium avium. We collected 503 environmental samples from cattle farms recently identified as bovine TB positive; none yielded positive M. bovis culture results. Finally, we used infrared cameras to document wildlife use of four barns in the area. Many avian and mammalian species of wildlife were observed, with raccoons being the most commonly observed species. This surveillance study identified no new wildlife species that should be considered significant reservoirs of bovine TB in the outbreak area in northern Michigan, USA. However, the relatively high, apparent bovine TB prevalence rates in some carnivorous and omnivorous species, their relatively long life spans, and their frequent use of barns, suggests that removal of raccoons, opossums, foxes, and coyotes (Canis latrans) should be considered when a newly infected farm is depopulated of cattle.

Ecology, stable isotopes, and management of grassland songbirds at National Park Service properties on the Great Plains

Grassland ecosystems have been severely reduced and grassland bird populations have experienced consistent declines. National Park Service (NPS) properties on the Great Plains provide breeding habitat for grassland songbirds, though little is known about the quality of this habitat. A short-term study on songbirds at three NPS properties complemented current monitoring, providing an among park comparison addressing grassland bird productivity and fidelity relative to NPS property size. During 2008-2009, I assessed avian species richness, and estimated bird density and grassland songbird nest success. Bird species richness was greatest at small and medium sites, while number of nesting obligate species was greatest at the large site. Species-specific densities varied among sites, with few grassland obligates occurring at all three sites. Nest success estimates for grassland obligates were highest at the small site and lower at the large site. Another method to quantify habitat quality is assessment of breeding site fidelity. Current extrinsic markers used in monitoring site fidelity are inadequate for small birds; stable isotope analyses provide an alternative. I compared two techniques for assigning stable isotope tissue origin and measured grassland songbird site fidelity. My method of assigning origin provided site-specific variances of expected stable isotope values, an improvement over the most commonly used method. Fidelity tended to be higher at the large site, which may indicate a more robust breeding community of grassland birds. The small size of two of my sites precluded large sample sizes and made strong inferences difficult. To quantify how scientists cope with weak inference, I conducted a literature review. Strong inference was rarely observed, and most authors of weak-inference papers provided specific management recommendations. I suggest that adaptive management is an ideal method to resolve uncertainty from weak inference. Managers should consider my results within the context of regional and global management and the extent to which their unit might aide songbird conservation.

Temporal and Spatial Patterns of Avifauna on Wetlands in the Vicinity of Bush Field Airport, Augusta, Georgia, USA

Responding to a U.S. Federal court order to improve discharged wastewater quality, Augusta, Georgia initiated development of artificial wetlands in 1997 to treat effluents. Because of the proximity to Augusta Regional Airport at Bush Field, the U.S. Federal Aviation Administration expressed concern for potential increased hazard to aircraft posed by birds attracted to these wetlands. We commenced weekly low-level aerial surveys of habitats in the area beginning January, 1998. Over a one-year period, 49 surveys identified approximately 42,000 birds representing 52 species, including protected Wood Storks and Bald Eagles, using wetlands within 8 km of the airport. More birds were observed during the mid-winter and fall/spring migratory seasons (1,048 birds/survey; October - April) than during the breeding/post-breeding seasons (394 birds/survey; May - September). In winter, waterfowl dominated the avian assemblage (65% of all birds). During summer, wading birds were most abundant (56% of all birds). Habitat changes within the artificial wetlands produced fish kills and exposed mudflats, resulting in increased use by wading birds and shorebirds. No aquatic birds were implicated in 1998 bird strikes, and most birds involved could safely be placed within songbird categories. Airport incident reports further implicated songbirds. These findings suggested that efforts to decrease numbers of songbirds on the airport property must be included in the development of a wildlife hazard management plan. Seasonal differences in site use among species groups should also be considered in any such plan. Other wetlands within 8 km of the airport supported as many or more birds than the artificial wetlands. With proper management of the artificial wetlands, it should be possible to successfully displace waterfowl and wading birds to other wetlands further from the airport.

Bird Depredation

A survey of catfish producers by the United States Department of Agriculture, Centers for Epidemiology and Animal Health (CEAH) in 1996 indicated that the two primary sources of catfish losses in commercial operations were disease (45%) and wildlife (37%) (CEAH 1997a). A variety of avian and mammalian predators are amracred to aquaculture facilities in the United States (Parkhurs: er al. 1992) because ponds and open raceways provide a constant and readily accessible food supply for these animals. However, the mere presence of these predators arcund aquaculture faciliries does not necessarily mean that significant depredation problems are occurring. At catfish farms, three species or species groups of birds are primarily cited by catfish producers as causing most depredation problems (Wywialowski 1999). These include doublecrested cormorants, wading birds (herons and egrets), and American white pelicans, in order of importance to catfish producers (Wywialowski 1993). Although all of these species consume catfish, their biology, distribution, dietary preferences dictare the extent of depredation problems they cause and the approaches needed to alleviate their depredations. With the exception of total bird exclusion from ponds, there are no simple solutions for resolving all bird depredation problems in catfish aquaculture. Thus, in most cases, an integrated management approach to alleviating bird depredations must be considered.

METHIOCARB, A CHEMICAL BIRD REPELLENT: A REVIEW OF ITS EFFECTIVENESS ON CROPS

Since 1964, when the effectiveness of methiocarb for preventing pheasants (Phasianus colchicus) from damaging sprouting corn was proven in South Dakota, an aggressive program has been carried out by personnel of the Denver Wildlife Research Center and many cooperators to develop methiocarb as a broad spectrum avian repellent. The successful use of methiocarb for preventing damage caused by several species of birds to sprouting corn in several states and to sprouting soybeans in South America is reviewed. Recent results obtained from spraying methiocarb on ripening rice in California, ripening sorghum in Colorado and Oklahoma, cherries in Michigan, and grapes in New Hampshire are summarized.

The Probe, Issue 174 – March 1997

Outwitting Urban Beaver, by C. E. "Ki" Faulkner, Regional Director, Region 0, NADCA Bear Gets Attention in Southeast Chinese disease Threatens Rabbits Product Announcements: BEAR BE GONE™ -- a device designed to deter bears from foraging in trash cans. Booklet: "Using Guard Animals to Protect Livestock" Abstracts Published at the 3rd Annual Conference of The Wildlife Society: A case study of black bear movements and survival after landfill closure in the central Adirondacks, by Ann M. Russell and S.L. Simek Ecology of coyotes in a sheep ranching environment, by Ben N. Sacks, J.C.C. Neale, M. Jaeger, and D. R. McCullough Design and analysis of carnivore scent-station surveys, by Glen Sargeant, Douglas H. Johnson, and William Berg Public attitudes toward wildlife damage management, by Robert H. Schmidt, M.W. Brunson, andD. Reiter Human dimensions of wildlife contraception, by Robert H. Schmidt and D. E. Mclvor Economic assessment of rabies control efforts in Texas, by Randy M. Smith Methyl salicylate: a naturally occurring avian repellent, by Shirley Wager-Page A brief historical perspective on wildlife contraception research, by Robert J. Warren Wildlife-caused losses to agriculture in 1994, by Alice P. Wywialowski