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Rufus B. Sage - One of the best experts on this subject based on the ideXlab platform.
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Predation of released Pheasants Phasianus colchicus on lowland farmland in the UK and the effect of predator control
European Journal of Wildlife Research, 2018Co-Authors: Rufus B. Sage, Clare V. Turner, Maureen I. A. Woodburn, Roger A. H. Draycott, Andrew N. Hoodless, Nicolas W. SothertonAbstract:We present data accumulated over the last 25 years on predation of radio-tracked released Pheasants. In studies of birds during the autumn/winter at six pheasant shoots with high-density releases managed by full-time gamekeepers, predation of released Pheasants by foxes before the shooting season began (July–September) averaged 19.2 ± 4.0% per site, and during the shooting season (October 1st–February 1st), a further 15.9 ± 1.9% were predated. The range in 3-year average predation rates between sites before shooting began was 8.6 to 42.4%. At seven different sites during the spring and summer, between 20 and 71% of released or wild hens that survived the shooting season were predated, mainly by foxes, between mid-March and mid-July. Predation was significantly higher at sites with low-level predator control (59 ± 4.7%) compared to those with high-level control (30 ± 5.3%). At three of the four sites with low predator control between 5 and 22% of nest failures were caused by incubating hens being predated by foxes. Our data quantify for the first time highly variable predation rates of released Pheasants before and during the winter shooting season which we suggest was influenced by a range of site and management factors. During the spring and summer, our data provide evidence that predation of adult hen Pheasants as well as nest predation can suppress breeding success and that predator control can reduce these losses.
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releasing of Pheasants for shooting in the uk alters woodland invertebrate communities
Biological Conservation, 2015Co-Authors: Jessica L Neumann, Rufus B. Sage, Graham J Holloway, Andrew N. HoodlessAbstract:Abstract The management of Pheasants ( Phasianus colchicus ) in pens and their subsequent release within woodland for game shoots is widely practised in Britain. With the exception of ground flora and songbirds, the impacts on other taxa have not been well documented. We investigated the effects of Pheasants on invertebrate abundance and community composition, using pitfall trapping. We compared release pens with control plots located in the same woods and in woods where no pheasant releasing had occurred for at least 25 years. Conditions for invertebrates within release pens were altered, with more annual plants and disturbance-tolerant perennials and a reduced leaf litter layer. No major differences in invertebrate abundance, or Carabidae or Staphylinidae richness, were found in spring at either the pen scale or the wood scale. However, pheasant release pens resulted in significant changes in the species composition of Carabidae, with shifts towards species typical of arable fields and grassland. Carabid species active in spring and those that are very large (> 17.0 mm) declined at pheasant release densities higher than 1000 birds/ha. Both effects are likely to be due to predation by Pheasants at the peak of release in July–August, operating separately on larvae and adults respectively. There was an overall increase in the abundance of detritivores, including Diplopoda, Oniscoidea, Gastropoda (snails), at higher release densities. Mean release density in our study was 1489 ± 126 birds/ha (range 174–3409, n = 37 pens) and we suggest that detrimental effects on specialist woodland invertebrates would be minimized if releasing was conducted at the recommended density of 700 birds/ha.
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nest predation of common Pheasants phasianus colchicus
Ibis, 2008Co-Authors: Roger A. H. Draycott, Maureen I. A. Woodburn, Andrew N. Hoodless, Rufus B. SageAbstract:The Common Pheasant Phasianus colchicus is currently the most abundant, widespread and economically important gamebird in Europe. The Game and Wildlife Conservation Trust has undertaken several recent studies of Pheasant breeding ecology to improve the management of this species. Although predation is often the most important cause of nest failure in declining ground-nesting birds in agricultural landscapes, the causes of predation and the identity of predators are often unknown. In this paper, we analyse data from approximately 450 nests of radiotagged hen Pheasants collected from six sites between 1990 and 2003 and present results on the fate and survival rates of Pheasant nests in relation to habitat, predation control and other covariates. Survival rates during the laying stage and incubation stage were 28 and 37%, respectively, and overall nest survival was 10%. Nest predation rates were significantly lower on two sites where intensive predation control was undertaken than on four sites with only low levels of predation control. Red Foxes Vulpes vulpes and corvids were the most important nest predators, accounting for at least half of all predation events. We assess these results in the context of other ground-nesting farmland birds.
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effects of spring supplementary feeding on population density and breeding success of released Pheasants phasianus colchicus in britain
Wildlife Biology, 2005Co-Authors: Roger A. H. Draycott, Maureen I. A. Woodburn, John P. Carroll, Rufus B. SageAbstract:Abstract The release of hand-reared ring-necked Pheasants Phasianus colchicus in summer is a common practice in Britain to increase the number of birds available to hunters in winter. The breeding success of the birds which survive the shooting season is poor. Traditionally, birds are provided with supplementary wheat grain from release until the end of the shooting season (1 February) to maintain body condition and to help hold birds in areas for hunting. During 1997–2000 we assessed the effect of continuing supplementary feeding into spring on pheasant density and breeding success on seven private shooting estates. On each estate we randomly selected two distinct 1-km2 plots and provided wheat grain via feed hoppers for birds in breeding territories in one of the plots on each estate while the other plot acted as an untreated control. Food was provided from mid-February to mid-May. We crossed-over the treatment and control plot on each estate each year. We conducted pre- and post-breeding pheasant count...
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lead exposure in ring necked Pheasants on shooting estates in great britain
Wildlife Society Bulletin, 2005Co-Authors: David A Butler, Rufus B. Sage, Roger A. H. Draycott, John P. Carroll, Dick PottsAbstract:Abstract Although a few isolated incidences of lead shot ingestion have been reported in ring-necked Pheasants (Phasianus colchicus) in Great Britain, no studies have investigated the prevalence of shot ingestion in this species. In this study we investigated the extent of lead exposure in ring-necked Pheasants on shooting estates in Great Britain from the ingestion of shot and other sources through gizzard examinations and analysis of wing bones. We examined 437 ring-necked pheasant gizzards collected from birds shot on 32 shooting estates during spring 1996 and 1997 and during the hunting seasons of 1999–2000 and 2001–2002. We determined wing-bone-lead concentrations in 98 female birds collected in 1997. Gizzard examinations showed an overall ingestion incidence rate of 3.0%. We found no differences in ingestion rates among years, seasons, and sexes. Female Pheasants had bone-lead levels ranging from 7–445 ppm (x =48.8± 8.8) dry weight. The birds that had lead in their gizzards in 1997 also had high co...
Simon R. Leather - One of the best experts on this subject based on the ideXlab platform.
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body condition is negatively associated with infection with syngamus trachea in the ring necked pheasant phasianus colchicus
Veterinary Parasitology, 2016Co-Authors: Owen J Gethings, R B Sage, Eric R Morgan, Simon R. LeatherAbstract:The role that parasites play in regulating animal populations is debated, however recent research hints at their pervasiveness among free-living animal populations. Parasites exert both direct and indirect effects on host populations, and can act to regulate populations. The Ring-necked pheasant is an important game-bird species in the UK, and large numbers of birds are released annually. The impact of the ubiquitous tracheal nematode, Syngamus trachea on pheasant populations through effects on host condition was assessed on two pheasant estates in the south west of England. Pheasants infected with S. trachea demonstrated a significant reduction in host condition compared with uninfected controls, with as few as one pair of worms per bird. Although there was no difference in worm burden between sexes, analysis of regression slopes revealed there was a significant difference between sexes in the magnitude of the effect of increasing worm burden on host condition, with detectable effects observed in hosts with one and three pairs of worms for males and females respectively. The observed reductions in host condition in birds with even sub-clinical infections could be the cause of poor reproductive success and survival of Pheasants post-release.
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density dependent regulation of fecundity in syngamus trachea infrapopulations in semi naturally occurring ring necked Pheasants phasianus colchicus and wild carrion crows corvus corone
Parasitology, 2016Co-Authors: Owen J Gethings, R B Sage, Simon R. LeatherAbstract:Previous work has highlighted increased opportunities for the transmission of Syngamus trachea within pheasant release pens, due in part to high levels of environmental contamination around communal areas. Despite this, the distribution of adult worms within their definitive hosts is not significantly different from predicted distributions under Taylor's power law. Therefore, density-dependent processes are probably acting to regulate S. trachea population dynamics. Patterns of nematode fecundity were investigated in a semi-naturally occurring population of ring-necked Pheasants (Phasianus colchicus) and a wild population of carrion crows (Corvus carone). Worm length was a reliable indicator of nematode fecundity, and a negative association between mean worm length and mean worm burden was identified within both the species. The stunting of worms at greater parasite densities was present in both immunologically naive and previously exposed Pheasants, so is unlikely to be a function of age-dependent acquired immunity. Interestingly, the effect of parasite crowding in the crow population explained more of the variation in mean worm length, apparently driven by a greater mean worm burden when compared with Pheasants. The findings of the present study suggest that fecundity is a function of parasite density, i.e. parasite-mediated competition and not host-mediated heterogeneities in immunocompetence.
Andrew N. Hoodless - One of the best experts on this subject based on the ideXlab platform.
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Predation of released Pheasants Phasianus colchicus on lowland farmland in the UK and the effect of predator control
European Journal of Wildlife Research, 2018Co-Authors: Rufus B. Sage, Clare V. Turner, Maureen I. A. Woodburn, Roger A. H. Draycott, Andrew N. Hoodless, Nicolas W. SothertonAbstract:We present data accumulated over the last 25 years on predation of radio-tracked released Pheasants. In studies of birds during the autumn/winter at six pheasant shoots with high-density releases managed by full-time gamekeepers, predation of released Pheasants by foxes before the shooting season began (July–September) averaged 19.2 ± 4.0% per site, and during the shooting season (October 1st–February 1st), a further 15.9 ± 1.9% were predated. The range in 3-year average predation rates between sites before shooting began was 8.6 to 42.4%. At seven different sites during the spring and summer, between 20 and 71% of released or wild hens that survived the shooting season were predated, mainly by foxes, between mid-March and mid-July. Predation was significantly higher at sites with low-level predator control (59 ± 4.7%) compared to those with high-level control (30 ± 5.3%). At three of the four sites with low predator control between 5 and 22% of nest failures were caused by incubating hens being predated by foxes. Our data quantify for the first time highly variable predation rates of released Pheasants before and during the winter shooting season which we suggest was influenced by a range of site and management factors. During the spring and summer, our data provide evidence that predation of adult hen Pheasants as well as nest predation can suppress breeding success and that predator control can reduce these losses.
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releasing of Pheasants for shooting in the uk alters woodland invertebrate communities
Biological Conservation, 2015Co-Authors: Jessica L Neumann, Rufus B. Sage, Graham J Holloway, Andrew N. HoodlessAbstract:Abstract The management of Pheasants ( Phasianus colchicus ) in pens and their subsequent release within woodland for game shoots is widely practised in Britain. With the exception of ground flora and songbirds, the impacts on other taxa have not been well documented. We investigated the effects of Pheasants on invertebrate abundance and community composition, using pitfall trapping. We compared release pens with control plots located in the same woods and in woods where no pheasant releasing had occurred for at least 25 years. Conditions for invertebrates within release pens were altered, with more annual plants and disturbance-tolerant perennials and a reduced leaf litter layer. No major differences in invertebrate abundance, or Carabidae or Staphylinidae richness, were found in spring at either the pen scale or the wood scale. However, pheasant release pens resulted in significant changes in the species composition of Carabidae, with shifts towards species typical of arable fields and grassland. Carabid species active in spring and those that are very large (> 17.0 mm) declined at pheasant release densities higher than 1000 birds/ha. Both effects are likely to be due to predation by Pheasants at the peak of release in July–August, operating separately on larvae and adults respectively. There was an overall increase in the abundance of detritivores, including Diplopoda, Oniscoidea, Gastropoda (snails), at higher release densities. Mean release density in our study was 1489 ± 126 birds/ha (range 174–3409, n = 37 pens) and we suggest that detrimental effects on specialist woodland invertebrates would be minimized if releasing was conducted at the recommended density of 700 birds/ha.
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nest predation of common Pheasants phasianus colchicus
Ibis, 2008Co-Authors: Roger A. H. Draycott, Maureen I. A. Woodburn, Andrew N. Hoodless, Rufus B. SageAbstract:The Common Pheasant Phasianus colchicus is currently the most abundant, widespread and economically important gamebird in Europe. The Game and Wildlife Conservation Trust has undertaken several recent studies of Pheasant breeding ecology to improve the management of this species. Although predation is often the most important cause of nest failure in declining ground-nesting birds in agricultural landscapes, the causes of predation and the identity of predators are often unknown. In this paper, we analyse data from approximately 450 nests of radiotagged hen Pheasants collected from six sites between 1990 and 2003 and present results on the fate and survival rates of Pheasant nests in relation to habitat, predation control and other covariates. Survival rates during the laying stage and incubation stage were 28 and 37%, respectively, and overall nest survival was 10%. Nest predation rates were significantly lower on two sites where intensive predation control was undertaken than on four sites with only low levels of predation control. Red Foxes Vulpes vulpes and corvids were the most important nest predators, accounting for at least half of all predation events. We assess these results in the context of other ground-nesting farmland birds.
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effects of tick ixodes ricinus infestation on pheasant phasianus colchicus breeding success and survival
Wildlife Biology, 2003Co-Authors: Andrew N. Hoodless, Klaus Kurtenbach, Patricia A Nuttall, Sarah E RandolphAbstract:In some parts of Britain, Pheasants Phasianus colchicus are infested by Ixodes ricinus ticks in the spring and summer. The effects of experimental reduction of tick infestation levels on the breeding success and survival of reared female Pheasants were studied on two estates in southern England during 1995–1997. Females were radio-tagged and half of the birds, selected at random, were fitted with a slow-release acaricide, which substantially reduced their tick burdens. Clutch survival was significantly higher for treated females throughout the three-year study period, and hence more chicks were hatched by treated females (3.30 ± 0.86) than by control females (0.70 ± 0.36), even though treated and control birds produced the same numbers of clutches and eggs. During April-July, the female survival rate was significantly higher for acaricide-treated birds, showing an improvement of 10–15% over that of control birds each year. While these impacts will be of minor importance where annual pheasant releasing takes place to supplement autumn stocks for shooting, they might reduce the potential harvest on estates with wild Pheasants or on those aiming to re-establish self-sustaining naturalised populations.
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effects of supplementary feeding on territoriality breeding success and survival of Pheasants
Journal of Applied Ecology, 1999Co-Authors: Andrew N. Hoodless, Roger A. H. Draycott, M N Ludiman, Peter A RobertsonAbstract:1. The effects of supplementary food in spring on subsequent pheasant breeding in an intensively farmed area in southern England were assessed by a large-scale, replicated field experiment. 2. Territorial cock Pheasants were counted in April, and the breeding success and survival of radio-tagged hens were monitored in six 1-km2 plots during 1994 and 1995. Total numbers of young reared and post-breeding pheasant densities were found by August counts. In 1994, three randomly selected plots were supplied with wheat grains via hoppers along woodland edges and hedgerows. The other three plots acted as controls and the treatments were reversed in 1995. 3. The density of cock territories increased significantly in food-supplemented plots (44 ± 8 km−2) in relation to control plots (29 ± 8 km−2), and the presence of hoppers significantly affected the locations of territories. However, similar proportions of territorial males acquired harems in the control and food-supplemented plots. Hen density did not increase and, consequently, the mean harem size was significantly lower with supplementary feeding. 4. Hens given supplementary food did not nest earlier and the number of nests initiated, clutch sizes and the proportion of successful nests did not differ significantly from those of controls. However, hens supplied with supplementary food re-nested significantly more quickly following the loss of a nest or brood. 5. Radio-tagged hens did not rear significantly more young with supplementary feeding. Hen survival was unchanged and post-breeding pheasant densities were no higher. 6. On present evidence, spring feeding cannot be advocated as a management technique to improve the breeding success of Pheasants surviving the winter.
Roger A. H. Draycott - One of the best experts on this subject based on the ideXlab platform.
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Predation of released Pheasants Phasianus colchicus on lowland farmland in the UK and the effect of predator control
European Journal of Wildlife Research, 2018Co-Authors: Rufus B. Sage, Clare V. Turner, Maureen I. A. Woodburn, Roger A. H. Draycott, Andrew N. Hoodless, Nicolas W. SothertonAbstract:We present data accumulated over the last 25 years on predation of radio-tracked released Pheasants. In studies of birds during the autumn/winter at six pheasant shoots with high-density releases managed by full-time gamekeepers, predation of released Pheasants by foxes before the shooting season began (July–September) averaged 19.2 ± 4.0% per site, and during the shooting season (October 1st–February 1st), a further 15.9 ± 1.9% were predated. The range in 3-year average predation rates between sites before shooting began was 8.6 to 42.4%. At seven different sites during the spring and summer, between 20 and 71% of released or wild hens that survived the shooting season were predated, mainly by foxes, between mid-March and mid-July. Predation was significantly higher at sites with low-level predator control (59 ± 4.7%) compared to those with high-level control (30 ± 5.3%). At three of the four sites with low predator control between 5 and 22% of nest failures were caused by incubating hens being predated by foxes. Our data quantify for the first time highly variable predation rates of released Pheasants before and during the winter shooting season which we suggest was influenced by a range of site and management factors. During the spring and summer, our data provide evidence that predation of adult hen Pheasants as well as nest predation can suppress breeding success and that predator control can reduce these losses.
-
nest predation of common Pheasants phasianus colchicus
Ibis, 2008Co-Authors: Roger A. H. Draycott, Maureen I. A. Woodburn, Andrew N. Hoodless, Rufus B. SageAbstract:The Common Pheasant Phasianus colchicus is currently the most abundant, widespread and economically important gamebird in Europe. The Game and Wildlife Conservation Trust has undertaken several recent studies of Pheasant breeding ecology to improve the management of this species. Although predation is often the most important cause of nest failure in declining ground-nesting birds in agricultural landscapes, the causes of predation and the identity of predators are often unknown. In this paper, we analyse data from approximately 450 nests of radiotagged hen Pheasants collected from six sites between 1990 and 2003 and present results on the fate and survival rates of Pheasant nests in relation to habitat, predation control and other covariates. Survival rates during the laying stage and incubation stage were 28 and 37%, respectively, and overall nest survival was 10%. Nest predation rates were significantly lower on two sites where intensive predation control was undertaken than on four sites with only low levels of predation control. Red Foxes Vulpes vulpes and corvids were the most important nest predators, accounting for at least half of all predation events. We assess these results in the context of other ground-nesting farmland birds.
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effects of spring supplementary feeding on population density and breeding success of released Pheasants phasianus colchicus in britain
Wildlife Biology, 2005Co-Authors: Roger A. H. Draycott, Maureen I. A. Woodburn, John P. Carroll, Rufus B. SageAbstract:Abstract The release of hand-reared ring-necked Pheasants Phasianus colchicus in summer is a common practice in Britain to increase the number of birds available to hunters in winter. The breeding success of the birds which survive the shooting season is poor. Traditionally, birds are provided with supplementary wheat grain from release until the end of the shooting season (1 February) to maintain body condition and to help hold birds in areas for hunting. During 1997–2000 we assessed the effect of continuing supplementary feeding into spring on pheasant density and breeding success on seven private shooting estates. On each estate we randomly selected two distinct 1-km2 plots and provided wheat grain via feed hoppers for birds in breeding territories in one of the plots on each estate while the other plot acted as an untreated control. Food was provided from mid-February to mid-May. We crossed-over the treatment and control plot on each estate each year. We conducted pre- and post-breeding pheasant count...
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lead exposure in ring necked Pheasants on shooting estates in great britain
Wildlife Society Bulletin, 2005Co-Authors: David A Butler, Rufus B. Sage, Roger A. H. Draycott, John P. Carroll, Dick PottsAbstract:Abstract Although a few isolated incidences of lead shot ingestion have been reported in ring-necked Pheasants (Phasianus colchicus) in Great Britain, no studies have investigated the prevalence of shot ingestion in this species. In this study we investigated the extent of lead exposure in ring-necked Pheasants on shooting estates in Great Britain from the ingestion of shot and other sources through gizzard examinations and analysis of wing bones. We examined 437 ring-necked pheasant gizzards collected from birds shot on 32 shooting estates during spring 1996 and 1997 and during the hunting seasons of 1999–2000 and 2001–2002. We determined wing-bone-lead concentrations in 98 female birds collected in 1997. Gizzard examinations showed an overall ingestion incidence rate of 3.0%. We found no differences in ingestion rates among years, seasons, and sexes. Female Pheasants had bone-lead levels ranging from 7–445 ppm (x =48.8± 8.8) dry weight. The birds that had lead in their gizzards in 1997 also had high co...
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effects of supplementary feeding on territoriality breeding success and survival of Pheasants
Journal of Applied Ecology, 1999Co-Authors: Andrew N. Hoodless, Roger A. H. Draycott, M N Ludiman, Peter A RobertsonAbstract:1. The effects of supplementary food in spring on subsequent pheasant breeding in an intensively farmed area in southern England were assessed by a large-scale, replicated field experiment. 2. Territorial cock Pheasants were counted in April, and the breeding success and survival of radio-tagged hens were monitored in six 1-km2 plots during 1994 and 1995. Total numbers of young reared and post-breeding pheasant densities were found by August counts. In 1994, three randomly selected plots were supplied with wheat grains via hoppers along woodland edges and hedgerows. The other three plots acted as controls and the treatments were reversed in 1995. 3. The density of cock territories increased significantly in food-supplemented plots (44 ± 8 km−2) in relation to control plots (29 ± 8 km−2), and the presence of hoppers significantly affected the locations of territories. However, similar proportions of territorial males acquired harems in the control and food-supplemented plots. Hen density did not increase and, consequently, the mean harem size was significantly lower with supplementary feeding. 4. Hens given supplementary food did not nest earlier and the number of nests initiated, clutch sizes and the proportion of successful nests did not differ significantly from those of controls. However, hens supplied with supplementary food re-nested significantly more quickly following the loss of a nest or brood. 5. Radio-tagged hens did not rear significantly more young with supplementary feeding. Hen survival was unchanged and post-breeding pheasant densities were no higher. 6. On present evidence, spring feeding cannot be advocated as a management technique to improve the breeding success of Pheasants surviving the winter.
Owen J Gethings - One of the best experts on this subject based on the ideXlab platform.
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the influence of syngamus trachea on pheasant populations
2018Co-Authors: Owen J GethingsAbstract:Syngamus trachea is a highly pathogenic parasite affecting managed pheasant populations within the U.K. Morbidity and mortality rates are high, particularly when birds are managed at high densities, however very little is known about its disease dynamics and direct effects on Pheasants. This study sought to determine the spatio-temporal factors influencing disease occurrence on pheasant estates, and to determine what direct effect, if any, S. trachea is having on pheasant populations. Several factors influenced within and between-year disease transmission; the most important being pen age, average stocking density and soil moisture. Both stocking density and pen age were positively correlated with the number of eggs per gram of soil, whereas soil moisture was best modelled by means of polynomial regression. Larval recovery was both moisture and temperature dependent, with increased movement and abundance of hatched larvae on herbage, which in turn, facilitated transmission. Infection status, i.e. positive faecal egg counts, was associated with larval abundance. The infectious stages of S. trachea were highly spatially aggregated, with feeders acting as a spatial focus for disease transmission in release pens. This relationship was highly linear, with a steep decline in the number of eggs per gram of soil within the first 2 m’s from the feeder. Syngamus trachea was previously thought to be relatively benign, however it was demonstrated that even sub-clinical infections were sufficient to reduce body condition in managed Pheasants. It is clear that S. trachea is pervasive among managed pheasant populations, and the implications for survival and reproduction are likely to be significant in the absence of anthelmintic treatment. The finding of spatial foci upon estates provides a simple, low-cost solution to managing environmental contamination that should be incorporated into gamekeeper’s disease management plans.
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body condition is negatively associated with infection with syngamus trachea in the ring necked pheasant phasianus colchicus
Veterinary Parasitology, 2016Co-Authors: Owen J Gethings, R B Sage, Eric R Morgan, Simon R. LeatherAbstract:The role that parasites play in regulating animal populations is debated, however recent research hints at their pervasiveness among free-living animal populations. Parasites exert both direct and indirect effects on host populations, and can act to regulate populations. The Ring-necked pheasant is an important game-bird species in the UK, and large numbers of birds are released annually. The impact of the ubiquitous tracheal nematode, Syngamus trachea on pheasant populations through effects on host condition was assessed on two pheasant estates in the south west of England. Pheasants infected with S. trachea demonstrated a significant reduction in host condition compared with uninfected controls, with as few as one pair of worms per bird. Although there was no difference in worm burden between sexes, analysis of regression slopes revealed there was a significant difference between sexes in the magnitude of the effect of increasing worm burden on host condition, with detectable effects observed in hosts with one and three pairs of worms for males and females respectively. The observed reductions in host condition in birds with even sub-clinical infections could be the cause of poor reproductive success and survival of Pheasants post-release.
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density dependent regulation of fecundity in syngamus trachea infrapopulations in semi naturally occurring ring necked Pheasants phasianus colchicus and wild carrion crows corvus corone
Parasitology, 2016Co-Authors: Owen J Gethings, R B Sage, Simon R. LeatherAbstract:Previous work has highlighted increased opportunities for the transmission of Syngamus trachea within pheasant release pens, due in part to high levels of environmental contamination around communal areas. Despite this, the distribution of adult worms within their definitive hosts is not significantly different from predicted distributions under Taylor's power law. Therefore, density-dependent processes are probably acting to regulate S. trachea population dynamics. Patterns of nematode fecundity were investigated in a semi-naturally occurring population of ring-necked Pheasants (Phasianus colchicus) and a wild population of carrion crows (Corvus carone). Worm length was a reliable indicator of nematode fecundity, and a negative association between mean worm length and mean worm burden was identified within both the species. The stunting of worms at greater parasite densities was present in both immunologically naive and previously exposed Pheasants, so is unlikely to be a function of age-dependent acquired immunity. Interestingly, the effect of parasite crowding in the crow population explained more of the variation in mean worm length, apparently driven by a greater mean worm burden when compared with Pheasants. The findings of the present study suggest that fecundity is a function of parasite density, i.e. parasite-mediated competition and not host-mediated heterogeneities in immunocompetence.