Previous studies of avian nest predation have focused on how human‐induced changes in the landsca... more Previous studies of avian nest predation have focused on how human‐induced changes in the landscape influence the frequency of predation However, natural variation in the abundance of predators due to their choice of habitat can also influence predation rate To determine if predation on artificial nests was influenced by forest stand type, we placed ground and shrub nests containing quail and plasticine eggs in contiguous coniferous, mixedwood and deciduous stands in the southern boreal mixedwood forest of central Canada Nest predators were identified using remotely triggered cameras and marks left in plasticine eggs, while the relative abundance of nest predators such as squirrels and corvids were estimated using acoustic‐visual surveys Using the fate of quail eggs to calculate predation rate, we found that predation was significantly higher in coniferous (67%) than in deciduous (17%) or mixedwood (25%) forest, with similar predation on ground (37%) and shrub (29%) nests Using plasticine eggs to calculate predation rate, nests in coniferous forest still suffered higher rates of predation, although predation rates were 15–20% higher, and ground nests suffered significantly higher rates of predation than shrub nests Quail eggs seemed to suffer lower rates of predation because small mammals were unable to penetrate the shell, but could leave marks on plasticine eggs The higher predation rate in coniferous forest was likely caused by higher abundance of red squirrels Tamiasciurus hudsonicus, the presence of fishers Martes pennanti and a simplified understory which may have made it easier for predators to find nests relative to the deciduous and mixedwood forest Plasucine eggs provide new insights into nest predation by identifying predation events by smaller predators such as mice that are missed when using quail eggs
Habitat suitability models allow for predictive modeling of the supply of wildlife habitat throug... more Habitat suitability models allow for predictive modeling of the supply of wildlife habitat through time under various forest harvesting scenarios. These models often rely on remotely sensed data in a forest resource inventory (FRI). However, the level of detail and (or) the accuracy of a FRI may be insufficient to accurately predict habitat suitability for forest birds. We tested if detailed vegetation measurements created habitat suitability models with better predictive power than models that used FRI data alone and if rough estimates of shrub cover were sufficient to supplement FRI data to create models with similar predictive power. For 28 species of forest birds, we found that less of the variation in abundance and (or) occurrence (% deviance explained) could be explained by models using FRI data alone (34% ± 2%) than by models using detailed vegetation information (40% ± 2%). However, when shrub density rank was included with FRI data, we found no difference in the deviance explained by the two model sets (39% ± 2% vs. 40% ± 2%). The best-fitting models containing the same vegetation parameters but using different methods of vegetation sampling were similar. These results suggest that coarse habitat classification schemes may be as effective in describing the major variance in bird community structure in the boreal forest as detailed vegetation inventory data.
Conventional management of shoreline forest in harvested boreal landscapes involves retention of ... more Conventional management of shoreline forest in harvested boreal landscapes involves retention of treed buffer strips to provide habitat for wildlife species and protect aquatic habitats from deleterious effects of harvesting. With shoreline forests being considered for harvest in several jurisdictions, it is important to determine the potential impacts of this disturbance on birds. In this study, responses of riparian- and upland-nesting birds to three levels of harvest (0%–50%, 50%–75%, and 75%–100% within 100 m of the water) in shoreline forests around boreal wetlands were assessed 1 year before and each year for 4 years after harvest relative to unharvested reference sites. Upland-nesting species showed variable responses to harvest, with greatest declines in abundance of interior forest nesting species (e.g., Ovenbird, Seiurus aurocapillus L.) with the highest levels of harvest. Shrub-nesting and generalist species increased in abundance in harvest treatments relative to reference sites. Riparian birds showed little response to harvest, suggesting that shoreline forest harvest has little effect on their abundance up to 4 years after harvest. Retention of small buffers may not be an effective management strategy for conservation of birds occupying shoreline forests, particularly interior forest nesting species. We suggest that alternatives to conventional buffer management be explored.
... ERIN M. BAYNE, Department of Biology, University of Saskatchewan, 112 Science Place, Saskatoo... more ... ERIN M. BAYNE, Department of Biology, University of Saskatchewan, 112 Science Place, Saskatoon, SK ... The Watson-William test showed significant differences in the temporal distribution of predation events ... ROBBINS, CS, J. R. SAUER, RS GREENBERG, AND S. DROEGE. ...
Adult long-tailed ducks (Clangula hyemalis) were collected from nine locations across their breed... more Adult long-tailed ducks (Clangula hyemalis) were collected from nine locations across their breeding grounds in northern Canada and measurements of stable isotopes of carbon (delta(13)C), nitrogen (delta(15)N) and sulfur (delta(34)S) in bone collagen were used to investigate if relative use of freshwater habitats such as the Great Lakes (with expected depleted stable isotope profiles) compared with coastal marine environments (with expected enriched stable isotope foodweb profiles) could explain tissue trace element profiles. Contrary to expectation, all three stable isotopes did not covary in our sample, suggesting that mechanisms other than simple freshwater vs. marine isotopic gradients were involved among populations. All three stable isotopes varied significantly with collection location and both delta(15)N and delta(13)C values varied significantly between sexes suggesting that males exploit either a different food base or occur in different geographic areas than females for at least part of the year. The delta(34)S data, in particular, suggested that many of the birds breeding in the western Canadian Arctic probably overwinter in the Great Lakes along with many of the birds breeding in Hudson Bay. Males at the majority of collection locations had higher concentrations of hepatic Hg (1.1-8 microg/g dw), Cu (25-40 mug/g dw), Se (7.3-27 mug/g dw) and renal Cd (33-129 microg/g dw) than females. Concentrations of Hg, Cu and Cd were well below toxicological threshold levels found in the literature. However, hepatic Se concentrations in 64% of the females exceeded 10 mug/g dw and concentrations in 8% of the birds measured exceeded 33 microg/g dw suggesting levels of potential concern.
Previous studies of avian nest predation have focused on how human‐induced changes in the landsca... more Previous studies of avian nest predation have focused on how human‐induced changes in the landscape influence the frequency of predation However, natural variation in the abundance of predators due to their choice of habitat can also influence predation rate To determine if predation on artificial nests was influenced by forest stand type, we placed ground and shrub nests containing quail and plasticine eggs in contiguous coniferous, mixedwood and deciduous stands in the southern boreal mixedwood forest of central Canada Nest predators were identified using remotely triggered cameras and marks left in plasticine eggs, while the relative abundance of nest predators such as squirrels and corvids were estimated using acoustic‐visual surveys Using the fate of quail eggs to calculate predation rate, we found that predation was significantly higher in coniferous (67%) than in deciduous (17%) or mixedwood (25%) forest, with similar predation on ground (37%) and shrub (29%) nests Using plasticine eggs to calculate predation rate, nests in coniferous forest still suffered higher rates of predation, although predation rates were 15–20% higher, and ground nests suffered significantly higher rates of predation than shrub nests Quail eggs seemed to suffer lower rates of predation because small mammals were unable to penetrate the shell, but could leave marks on plasticine eggs The higher predation rate in coniferous forest was likely caused by higher abundance of red squirrels Tamiasciurus hudsonicus, the presence of fishers Martes pennanti and a simplified understory which may have made it easier for predators to find nests relative to the deciduous and mixedwood forest Plasucine eggs provide new insights into nest predation by identifying predation events by smaller predators such as mice that are missed when using quail eggs
Habitat suitability models allow for predictive modeling of the supply of wildlife habitat throug... more Habitat suitability models allow for predictive modeling of the supply of wildlife habitat through time under various forest harvesting scenarios. These models often rely on remotely sensed data in a forest resource inventory (FRI). However, the level of detail and (or) the accuracy of a FRI may be insufficient to accurately predict habitat suitability for forest birds. We tested if detailed vegetation measurements created habitat suitability models with better predictive power than models that used FRI data alone and if rough estimates of shrub cover were sufficient to supplement FRI data to create models with similar predictive power. For 28 species of forest birds, we found that less of the variation in abundance and (or) occurrence (% deviance explained) could be explained by models using FRI data alone (34% ± 2%) than by models using detailed vegetation information (40% ± 2%). However, when shrub density rank was included with FRI data, we found no difference in the deviance explained by the two model sets (39% ± 2% vs. 40% ± 2%). The best-fitting models containing the same vegetation parameters but using different methods of vegetation sampling were similar. These results suggest that coarse habitat classification schemes may be as effective in describing the major variance in bird community structure in the boreal forest as detailed vegetation inventory data.
Conventional management of shoreline forest in harvested boreal landscapes involves retention of ... more Conventional management of shoreline forest in harvested boreal landscapes involves retention of treed buffer strips to provide habitat for wildlife species and protect aquatic habitats from deleterious effects of harvesting. With shoreline forests being considered for harvest in several jurisdictions, it is important to determine the potential impacts of this disturbance on birds. In this study, responses of riparian- and upland-nesting birds to three levels of harvest (0%–50%, 50%–75%, and 75%–100% within 100 m of the water) in shoreline forests around boreal wetlands were assessed 1 year before and each year for 4 years after harvest relative to unharvested reference sites. Upland-nesting species showed variable responses to harvest, with greatest declines in abundance of interior forest nesting species (e.g., Ovenbird, Seiurus aurocapillus L.) with the highest levels of harvest. Shrub-nesting and generalist species increased in abundance in harvest treatments relative to reference sites. Riparian birds showed little response to harvest, suggesting that shoreline forest harvest has little effect on their abundance up to 4 years after harvest. Retention of small buffers may not be an effective management strategy for conservation of birds occupying shoreline forests, particularly interior forest nesting species. We suggest that alternatives to conventional buffer management be explored.
... ERIN M. BAYNE, Department of Biology, University of Saskatchewan, 112 Science Place, Saskatoo... more ... ERIN M. BAYNE, Department of Biology, University of Saskatchewan, 112 Science Place, Saskatoon, SK ... The Watson-William test showed significant differences in the temporal distribution of predation events ... ROBBINS, CS, J. R. SAUER, RS GREENBERG, AND S. DROEGE. ...
Adult long-tailed ducks (Clangula hyemalis) were collected from nine locations across their breed... more Adult long-tailed ducks (Clangula hyemalis) were collected from nine locations across their breeding grounds in northern Canada and measurements of stable isotopes of carbon (delta(13)C), nitrogen (delta(15)N) and sulfur (delta(34)S) in bone collagen were used to investigate if relative use of freshwater habitats such as the Great Lakes (with expected depleted stable isotope profiles) compared with coastal marine environments (with expected enriched stable isotope foodweb profiles) could explain tissue trace element profiles. Contrary to expectation, all three stable isotopes did not covary in our sample, suggesting that mechanisms other than simple freshwater vs. marine isotopic gradients were involved among populations. All three stable isotopes varied significantly with collection location and both delta(15)N and delta(13)C values varied significantly between sexes suggesting that males exploit either a different food base or occur in different geographic areas than females for at least part of the year. The delta(34)S data, in particular, suggested that many of the birds breeding in the western Canadian Arctic probably overwinter in the Great Lakes along with many of the birds breeding in Hudson Bay. Males at the majority of collection locations had higher concentrations of hepatic Hg (1.1-8 microg/g dw), Cu (25-40 mug/g dw), Se (7.3-27 mug/g dw) and renal Cd (33-129 microg/g dw) than females. Concentrations of Hg, Cu and Cd were well below toxicological threshold levels found in the literature. However, hepatic Se concentrations in 64% of the females exceeded 10 mug/g dw and concentrations in 8% of the birds measured exceeded 33 microg/g dw suggesting levels of potential concern.
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