Understanding factors that influence the demography of grassland species in agricultural landscap... more Understanding factors that influence the demography of grassland species in agricultural landscapes is essential given the amount of land under agricultural production. Winter wheat is promoted by avian conservation organizations in North America because it provides cover early in the breeding season without much disturbance to nesting waterfowl. We conducted point-count surveys in fields of winter wheat, spring wheat, summerfallow, planted grassland and native grassland to determine: 1) the relative benefits of winter wheat to songbirds, 2) the extent to which cropland suitability changes over the breeding season, and 3) the extent to which the surrounding landscape influences songbird abundance. Horned lark (Eremophila alpestris), Savannah sparrow (Passerculus sandwichensis) and vesper sparrow (Pooecetes gramineus) were most commonly recorded in wheat and summerfallow fields, and their abundance varied over the breeding season and with the amount of native grassland in the surrounding landscape. Horned lark was more abundant in winter wheat early in the breeding season and its abundance increased with the amount of native grassland in the surrounding landscape. Savannah sparrow abundance increased in all field-types over the breeding season and decreased in cropland fields as the amount of native grassland in the surrounding landscape increased. Programs that encourage or incentivize winter wheat seeding in grassland-dominated landscapes will yield the greatest benefits for horned lark whereas Savannah sparrows would derive the greatest benefit in cropland-dominated landscapes. However, such programs must target cultivated fields to ensure that grassland obligate species are not compromised.
Mediterranean vegetation is characterized by high biodiversity and conservation value and grazing... more Mediterranean vegetation is characterized by high biodiversity and conservation value and grazing is controversial. We sampled woody and herbaceous plants on a limestone mountain with strong mesic-xeric gradients, ranked grazing pressure (on a scale of 1-4) and asked whether grazing had a significant effect on plant compositional abundance before and after controlling for environmental covariates. For woody species the shift in means among grazing classes was greater than for herbaceous species according to distance-based redundancy analysis (dbRDA). For herbaceous species differences in multivariate dispersion were greater among grazing classes. Both groups showed significant differences among grazing classes in multivariate location (permutational multivariate ANOVA), even after controlling for aspect. After taking into account biophysical covariates, grazing was not significant and the variation unique to grazing was small. According to best models in dbRDA, grazing was significa...
Mediterranean maquis vegetation is highly biodiverse, but widespread grazing poses a challenge fo... more Mediterranean maquis vegetation is highly biodiverse, but widespread grazing poses a challenge for management and conservation. We sampled woody and herbaceous plants separately on a limestone mountain with strong mesic-xeric gradients in Tunisia’s Parc National de L’Ichkeul, assessed grazing pressure (on a scale of 1–3), and asked whether grazing had a significant effect on plant compositional abundance before and after controlling for environmental covariates. Sites on the more mesic lakeside face of the mountain were most compositionally unique, and forbs contributed most to the herbaceous beta-diversity on the mountain. We used variance partitioning to separate the collective and individual effects of the abiotic environment, grazing, human activity, and space on herbaceous and woody beta-diversity. However, the individual effect of grazing on overall plant community composition was confounded with space, due to the spatially autocorrelated grazing pressure on the mountain. Impo...
The concept of the Anthropocene, that humans are now re-engineering global ecosystems, is in part... more The concept of the Anthropocene, that humans are now re-engineering global ecosystems, is in part evidenced by the pervasive pollution by persistent organic pollutants (POPs). Certain POPs are hormone mimics and can disrupt endocrine and hence reproductive processes, shown mainly by laboratory studies with model species. There are, in contrast, fewer confirmations of such disruption from eco-epidemiological studies of wild mammals. Here we used the American mink (Neovison vison) as a sentinel species for such a study. Over the period 1998-2006, 161 mink carcasses were obtained from commercial trappers in the Canadian provinces of British Columbia and Ontario. Mink were aged, sexed, measured, and body condition assessed. Livers were analyzed either individually or pooled for organochlorine (OC) pesticides, polychlorinated biphenyls (PCBs), and subsets for polybrominated diphenyl ethers (PBDEs). We primarily addressed whether contaminants affected male reproductive development by meas...
We studied the abundance of cavity-nesting birds in forestry-related habitats in a region of Acad... more We studied the abundance of cavity-nesting birds in forestry-related habitats in a region of Acadian forest in New Brunswick. We examined five reference stands of natural forest, a chronosequence of conifer plantations up to 19 years old (the oldest in the study area), two selectively harvested stands, and a 30-year-old naturally regenerated clear-cut. The species richness and abundance of cavity-nesting birds were higher in reference forest (average 10.0 species per stand; 5.3 territories per 10 ha) than in plantations (2.3/stand; 1.0/10 ha), selectively harvested stands (7.0/stand; 3.8/10 ha), or the naturally regenerated clear-cut (5.0/stand; 2.5/10 ha). A cluster analysis segregated the “community” of cavity-nesting birds of natural forest from those of other treatments. Of the various harvested stands and plantations, five with a relatively large number of residual snags clustered similarly in the cluster analysis, while those with no or very few snags also clustered together. ...
Strychnine is a neurotoxin and an active ingredient in some rodenticides which are placed in burr... more Strychnine is a neurotoxin and an active ingredient in some rodenticides which are placed in burrows to suppress pocket gopher (Thomomys talpoides) populations in range and crop land in western North America. The population level impact was modelled of the use of strychnine-based rodenticides on a non-target snake species, the Great Basin Gophersnake (Pituophis catenifer deserticola), which is a predator of pocket gopher and a Species at Risk in Canada. Using information on population density, demographics, and movement and habitat suitability for the Gophersnake living in an agricultural valley in BC, Canada, we estimated the impact of the poisoning of adult snakes on the long-term population size. To determine the area where Gophersnakes could be exposed to strychnine, we used vendor records of a rodenticide, and quantified the landcover areas of orchards and vineyards where the compound was most commonly applied. GIS analysis determined the areas of overlap between those agricult...
... DAVID A. KIRK,' ANTONY W. DIAMOND,2 ALAN R. SMITH,3 GEORGE E. HOLLAND,4 AND PAUL CHYTYK5... more ... DAVID A. KIRK,' ANTONY W. DIAMOND,2 ALAN R. SMITH,3 GEORGE E. HOLLAND,4 AND PAUL CHYTYK5 ... is a mature mixed stand of white birch (Betula papyrifera), trembling aspen (Populus tremuloides), and white spruce (Picea glauca) with a few balsam poplar (Populus ...
Understanding factors that influence the demography of grassland species in agricultural landscap... more Understanding factors that influence the demography of grassland species in agricultural landscapes is essential given the amount of land under agricultural production. Winter wheat is promoted by avian conservation organizations in North America because it provides cover early in the breeding season without much disturbance to nesting waterfowl. We conducted point-count surveys in fields of winter wheat, spring wheat, summerfallow, planted grassland and native grassland to determine: 1) the relative benefits of winter wheat to songbirds, 2) the extent to which cropland suitability changes over the breeding season, and 3) the extent to which the surrounding landscape influences songbird abundance. Horned lark (Eremophila alpestris), Savannah sparrow (Passerculus sandwichensis) and vesper sparrow (Pooecetes gramineus) were most commonly recorded in wheat and summerfallow fields, and their abundance varied over the breeding season and with the amount of native grassland in the surrounding landscape. Horned lark was more abundant in winter wheat early in the breeding season and its abundance increased with the amount of native grassland in the surrounding landscape. Savannah sparrow abundance increased in all field-types over the breeding season and decreased in cropland fields as the amount of native grassland in the surrounding landscape increased. Programs that encourage or incentivize winter wheat seeding in grassland-dominated landscapes will yield the greatest benefits for horned lark whereas Savannah sparrows would derive the greatest benefit in cropland-dominated landscapes. However, such programs must target cultivated fields to ensure that grassland obligate species are not compromised.
Mediterranean vegetation is characterized by high biodiversity and conservation value and grazing... more Mediterranean vegetation is characterized by high biodiversity and conservation value and grazing is controversial. We sampled woody and herbaceous plants on a limestone mountain with strong mesic-xeric gradients, ranked grazing pressure (on a scale of 1-4) and asked whether grazing had a significant effect on plant compositional abundance before and after controlling for environmental covariates. For woody species the shift in means among grazing classes was greater than for herbaceous species according to distance-based redundancy analysis (dbRDA). For herbaceous species differences in multivariate dispersion were greater among grazing classes. Both groups showed significant differences among grazing classes in multivariate location (permutational multivariate ANOVA), even after controlling for aspect. After taking into account biophysical covariates, grazing was not significant and the variation unique to grazing was small. According to best models in dbRDA, grazing was significa...
Mediterranean maquis vegetation is highly biodiverse, but widespread grazing poses a challenge fo... more Mediterranean maquis vegetation is highly biodiverse, but widespread grazing poses a challenge for management and conservation. We sampled woody and herbaceous plants separately on a limestone mountain with strong mesic-xeric gradients in Tunisia’s Parc National de L’Ichkeul, assessed grazing pressure (on a scale of 1–3), and asked whether grazing had a significant effect on plant compositional abundance before and after controlling for environmental covariates. Sites on the more mesic lakeside face of the mountain were most compositionally unique, and forbs contributed most to the herbaceous beta-diversity on the mountain. We used variance partitioning to separate the collective and individual effects of the abiotic environment, grazing, human activity, and space on herbaceous and woody beta-diversity. However, the individual effect of grazing on overall plant community composition was confounded with space, due to the spatially autocorrelated grazing pressure on the mountain. Impo...
The concept of the Anthropocene, that humans are now re-engineering global ecosystems, is in part... more The concept of the Anthropocene, that humans are now re-engineering global ecosystems, is in part evidenced by the pervasive pollution by persistent organic pollutants (POPs). Certain POPs are hormone mimics and can disrupt endocrine and hence reproductive processes, shown mainly by laboratory studies with model species. There are, in contrast, fewer confirmations of such disruption from eco-epidemiological studies of wild mammals. Here we used the American mink (Neovison vison) as a sentinel species for such a study. Over the period 1998-2006, 161 mink carcasses were obtained from commercial trappers in the Canadian provinces of British Columbia and Ontario. Mink were aged, sexed, measured, and body condition assessed. Livers were analyzed either individually or pooled for organochlorine (OC) pesticides, polychlorinated biphenyls (PCBs), and subsets for polybrominated diphenyl ethers (PBDEs). We primarily addressed whether contaminants affected male reproductive development by meas...
We studied the abundance of cavity-nesting birds in forestry-related habitats in a region of Acad... more We studied the abundance of cavity-nesting birds in forestry-related habitats in a region of Acadian forest in New Brunswick. We examined five reference stands of natural forest, a chronosequence of conifer plantations up to 19 years old (the oldest in the study area), two selectively harvested stands, and a 30-year-old naturally regenerated clear-cut. The species richness and abundance of cavity-nesting birds were higher in reference forest (average 10.0 species per stand; 5.3 territories per 10 ha) than in plantations (2.3/stand; 1.0/10 ha), selectively harvested stands (7.0/stand; 3.8/10 ha), or the naturally regenerated clear-cut (5.0/stand; 2.5/10 ha). A cluster analysis segregated the “community” of cavity-nesting birds of natural forest from those of other treatments. Of the various harvested stands and plantations, five with a relatively large number of residual snags clustered similarly in the cluster analysis, while those with no or very few snags also clustered together. ...
Strychnine is a neurotoxin and an active ingredient in some rodenticides which are placed in burr... more Strychnine is a neurotoxin and an active ingredient in some rodenticides which are placed in burrows to suppress pocket gopher (Thomomys talpoides) populations in range and crop land in western North America. The population level impact was modelled of the use of strychnine-based rodenticides on a non-target snake species, the Great Basin Gophersnake (Pituophis catenifer deserticola), which is a predator of pocket gopher and a Species at Risk in Canada. Using information on population density, demographics, and movement and habitat suitability for the Gophersnake living in an agricultural valley in BC, Canada, we estimated the impact of the poisoning of adult snakes on the long-term population size. To determine the area where Gophersnakes could be exposed to strychnine, we used vendor records of a rodenticide, and quantified the landcover areas of orchards and vineyards where the compound was most commonly applied. GIS analysis determined the areas of overlap between those agricult...
... DAVID A. KIRK,' ANTONY W. DIAMOND,2 ALAN R. SMITH,3 GEORGE E. HOLLAND,4 AND PAUL CHYTYK5... more ... DAVID A. KIRK,' ANTONY W. DIAMOND,2 ALAN R. SMITH,3 GEORGE E. HOLLAND,4 AND PAUL CHYTYK5 ... is a mature mixed stand of white birch (Betula papyrifera), trembling aspen (Populus tremuloides), and white spruce (Picea glauca) with a few balsam poplar (Populus ...
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