Bruce Pollard - Academia.edu (original) (raw)
Papers by Bruce Pollard
Landscape Ecology, 2017
Context This study synthesizes evidence from three separate surveys of American Black Duck and Ma... more Context This study synthesizes evidence from three separate surveys of American Black Duck and Mallard breeding habitat usage to quantify the effects of agriculture at the landscape scale. Objectives To assess duck breeding activity in agricultural landscapes within the Canadian maritimes in order to measure the overall impact of agricultural land use, the response to particular agricultural activities, and the influence of landscape configuration. Methods Models, constructed using a long-term census (SURVEY1), were used to predict habitat selection for two other independent surveys (SUR-VEY2, SURVEY3). Predictions incorporated information about wetland area and diversity, as well as anthropogenic factors, allowing subsequent analyses to focus on the remaining residual error attributable to agricultural effects. Results SURVEY2 results demonstrated that the proportion of active agriculture is an important indicator of the severity of human disturbance, yielding threshold estimates of 39% for Mallards and Electronic supplementary material The online version of this article (
Canadian Journal of Zoology, 2006
By analyzing 20+ years of data, we found that the nesting colonies of double-crested cormorants (... more By analyzing 20+ years of data, we found that the nesting colonies of double-crested cormorants ( Phalacrocorax auritus (Lesson, 1831)) in the North Channel and Georgian Bay of Lake Huron exhibit density-dependent population regulation. This conclusion is based on four lines of evidence. First, a time series of nest counts at specific colonies (1979–2001) showed density-dependent growth based on randomization tests of the time series. Second, the per capita rate of change in colony size declined with increasing colony size over a 10-year period. Third, a Ricker model of aggregate nest counts showed that population growth of nesting double-crested cormorants stabilized in recent years (through 2003), with K, the carrying capacity parameter, being 11 445 nests in the North Channel and 10 815 nests in Georgian Bay. Fourth, a colony area index showed near complete coverage of coastal areas by adult nesters coinciding with overall declines in population growth. High rates of population i...
Wetlands, 1991
Preliminary observations indicated that the productivity of wetlands in the /nterlake region of M... more Preliminary observations indicated that the productivity of wetlands in the /nterlake region of Manitoba, Canada is low, resulting in limited use by waterfowl and other wildlife species. This study compared nutrient availability, algal biomass, and invertebrate abundance and biomass between two lnterlake wetlands. The Narcisse site was a typical Interlake wetland with no known source of external nutrient input. The Cruise Marsh site was a wetland similar to the Narcisse site except for the operation of a cattle feedlot on its shore. Total dissolved and suspended N and P levels were higher at the Cruise Marsh s ite throughout much of the year. Phytoplankton and epiphyfic periphyton biomass were also much higher at Cruise Marsh. The water chemis~y and biomass of these two algae groups found in the Narcisse site were similar to levels characteristic of oligotrophic lakes. The algae at Narcisse also showed severe N and P deficiency throughout the year, while no similar deficiency was observed at Cruise Marsh. Epipelon biomass in unvegetated Narcisse sites was higher than found in vegetated Narcisse sites or at Cruise Marsh. Invertebrate abundance and biomass were lower at Narcisse. Cruise Marsh invertebrate abundance and biomass approached levels found in the more eutrophic Delta Marsh. The Narcisse wetlands do appear to be nutrient limited, which in turn affects the algae and higherorder consumers like invertebrates. These low invertebrate levels likely play a role in the low use by waterfowl and other marsh birds in these wetlands.
The Journal of Wildlife Management, 2012
We report on a management experiment examining the effects of large-scale egg oiling on double-cr... more We report on a management experiment examining the effects of large-scale egg oiling on double-crested cormorant nest abundance and measures of seasonal cormorant density (bird-days/km 2) from 2000 to 2005. We employed the staircase design to distinguish transient responses to management treatments from site and year effects that generally contribute to variation in populations. The response to egg oiling in Georgian Bay was as expected with a decline in nest abundance attributable to egg oiling. In the North Channel, nest abundance did not decline because of egg oiling but increased, reflecting either retention of nesting adults or recruitment to colonies. This surprising outcome may stem from fish escapement from pen rearing facilities in the vicinity of the oiling experiment in the North Channel. We observed no effect of egg oiling on the July-August seasonal density of cormorants. The strongest effect size was associated with site effects followed by year effects for nest abundance and seasonal density. The effect size of egg oiling on variation in nest abundance did not exceed 5% for any year in both the North Channel and Georgian Bay. Fish pen culture appears to affect coastal distribution of cormorants.
Hydrobiologia, 1994
... Henry R. Murkin 2, J. Bruce Pollard 1, Michael P. Stainton 3, John A. Boughen 3 & RD ... more ... Henry R. Murkin 2, J. Bruce Pollard 1, Michael P. Stainton 3, John A. Boughen 3 & RD Titman2 1 The Institute for Wetland and ... Surface water pH ranges from 8.0-9.0, with specific conductance values of 400-500 .S. Based on phosphorus and chlorophyll data (Mur-kin et al., 1991 ...
Canadian Journal of Zoology, 1992
Exuviae of 37 species of dragonflies were collected from the emergent vegetation of 19 small (<... more Exuviae of 37 species of dragonflies were collected from the emergent vegetation of 19 small (<35 ha) lakes across a pH gradient (range 4.9–8.1) in south-central Ontario to assess the effect of low environmental pH on species richness and diversity. The number of species present in a lake was not significantly correlated with lake pH. Two measures of diversity (Keefe and Bergersen's TU and McIntosh's M) indicate an increase in species diversity with decreasing lake pH. Species shifts in the communities were also correlated with lake pH: five species were apparently excluded from lakes with a midsummer epilimnetic pH below 5.8, and seven species were apparently restricted to lakes with a pH of less than 6.2.
Frontiers in Ecology and the Environment, 2009
Journal of Wildlife Diseases, 2012
Frontiers in Ecology and the Environment, 2009
Landscape Ecology, 2017
Context This study synthesizes evidence from three separate surveys of American Black Duck and Ma... more Context This study synthesizes evidence from three separate surveys of American Black Duck and Mallard breeding habitat usage to quantify the effects of agriculture at the landscape scale. Objectives To assess duck breeding activity in agricultural landscapes within the Canadian maritimes in order to measure the overall impact of agricultural land use, the response to particular agricultural activities, and the influence of landscape configuration. Methods Models, constructed using a long-term census (SURVEY1), were used to predict habitat selection for two other independent surveys (SUR-VEY2, SURVEY3). Predictions incorporated information about wetland area and diversity, as well as anthropogenic factors, allowing subsequent analyses to focus on the remaining residual error attributable to agricultural effects. Results SURVEY2 results demonstrated that the proportion of active agriculture is an important indicator of the severity of human disturbance, yielding threshold estimates of 39% for Mallards and Electronic supplementary material The online version of this article (
Canadian Journal of Zoology, 2006
By analyzing 20+ years of data, we found that the nesting colonies of double-crested cormorants (... more By analyzing 20+ years of data, we found that the nesting colonies of double-crested cormorants ( Phalacrocorax auritus (Lesson, 1831)) in the North Channel and Georgian Bay of Lake Huron exhibit density-dependent population regulation. This conclusion is based on four lines of evidence. First, a time series of nest counts at specific colonies (1979–2001) showed density-dependent growth based on randomization tests of the time series. Second, the per capita rate of change in colony size declined with increasing colony size over a 10-year period. Third, a Ricker model of aggregate nest counts showed that population growth of nesting double-crested cormorants stabilized in recent years (through 2003), with K, the carrying capacity parameter, being 11 445 nests in the North Channel and 10 815 nests in Georgian Bay. Fourth, a colony area index showed near complete coverage of coastal areas by adult nesters coinciding with overall declines in population growth. High rates of population i...
Wetlands, 1991
Preliminary observations indicated that the productivity of wetlands in the /nterlake region of M... more Preliminary observations indicated that the productivity of wetlands in the /nterlake region of Manitoba, Canada is low, resulting in limited use by waterfowl and other wildlife species. This study compared nutrient availability, algal biomass, and invertebrate abundance and biomass between two lnterlake wetlands. The Narcisse site was a typical Interlake wetland with no known source of external nutrient input. The Cruise Marsh site was a wetland similar to the Narcisse site except for the operation of a cattle feedlot on its shore. Total dissolved and suspended N and P levels were higher at the Cruise Marsh s ite throughout much of the year. Phytoplankton and epiphyfic periphyton biomass were also much higher at Cruise Marsh. The water chemis~y and biomass of these two algae groups found in the Narcisse site were similar to levels characteristic of oligotrophic lakes. The algae at Narcisse also showed severe N and P deficiency throughout the year, while no similar deficiency was observed at Cruise Marsh. Epipelon biomass in unvegetated Narcisse sites was higher than found in vegetated Narcisse sites or at Cruise Marsh. Invertebrate abundance and biomass were lower at Narcisse. Cruise Marsh invertebrate abundance and biomass approached levels found in the more eutrophic Delta Marsh. The Narcisse wetlands do appear to be nutrient limited, which in turn affects the algae and higherorder consumers like invertebrates. These low invertebrate levels likely play a role in the low use by waterfowl and other marsh birds in these wetlands.
The Journal of Wildlife Management, 2012
We report on a management experiment examining the effects of large-scale egg oiling on double-cr... more We report on a management experiment examining the effects of large-scale egg oiling on double-crested cormorant nest abundance and measures of seasonal cormorant density (bird-days/km 2) from 2000 to 2005. We employed the staircase design to distinguish transient responses to management treatments from site and year effects that generally contribute to variation in populations. The response to egg oiling in Georgian Bay was as expected with a decline in nest abundance attributable to egg oiling. In the North Channel, nest abundance did not decline because of egg oiling but increased, reflecting either retention of nesting adults or recruitment to colonies. This surprising outcome may stem from fish escapement from pen rearing facilities in the vicinity of the oiling experiment in the North Channel. We observed no effect of egg oiling on the July-August seasonal density of cormorants. The strongest effect size was associated with site effects followed by year effects for nest abundance and seasonal density. The effect size of egg oiling on variation in nest abundance did not exceed 5% for any year in both the North Channel and Georgian Bay. Fish pen culture appears to affect coastal distribution of cormorants.
Hydrobiologia, 1994
... Henry R. Murkin 2, J. Bruce Pollard 1, Michael P. Stainton 3, John A. Boughen 3 & RD ... more ... Henry R. Murkin 2, J. Bruce Pollard 1, Michael P. Stainton 3, John A. Boughen 3 & RD Titman2 1 The Institute for Wetland and ... Surface water pH ranges from 8.0-9.0, with specific conductance values of 400-500 .S. Based on phosphorus and chlorophyll data (Mur-kin et al., 1991 ...
Canadian Journal of Zoology, 1992
Exuviae of 37 species of dragonflies were collected from the emergent vegetation of 19 small (<... more Exuviae of 37 species of dragonflies were collected from the emergent vegetation of 19 small (<35 ha) lakes across a pH gradient (range 4.9–8.1) in south-central Ontario to assess the effect of low environmental pH on species richness and diversity. The number of species present in a lake was not significantly correlated with lake pH. Two measures of diversity (Keefe and Bergersen's TU and McIntosh's M) indicate an increase in species diversity with decreasing lake pH. Species shifts in the communities were also correlated with lake pH: five species were apparently excluded from lakes with a midsummer epilimnetic pH below 5.8, and seven species were apparently restricted to lakes with a pH of less than 6.2.
Frontiers in Ecology and the Environment, 2009
Journal of Wildlife Diseases, 2012
Frontiers in Ecology and the Environment, 2009