This is an open access article under the terms of the Creative Commons Attribution License, which... more This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
Fig. 1. Distribution of avian point-count samples used in density estimates derived from the Bore... more Fig. 1. Distribution of avian point-count samples used in density estimates derived from the Boreal Avian Modeling project (http://www.borealbirds.ca).
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
Background: Elucidating geographic locations from where migratory birds are recruited into adult ... more Background: Elucidating geographic locations from where migratory birds are recruited into adult breeding populations is a fundamental but largely elusive goal in conservation biology. This is especially true for species that breed in remote northern areas where field-based demographic assessments are logistically challenging. Methodology/Findings: Here we used hydrogen isotopes (dD) to determine natal origins of migrating hatch-year lesser scaup (Aythya affinis) harvested by hunters in the United States from all North American flyways during the hunting seasons of 1999-2000 (n = 412) and 2000-2001 (n = 455). We combined geospatial, observational, and analytical data sources, including known scaup breeding range, dD values of feathers from juveniles at natal sites, models of dD for growing-season precipitation, and scaup band-recovery data to generate probabilistic natal origin landscapes for individual scaup. We then used Monte Carlo integration to model assignment uncertainty from among individual dD variance estimates from birds of known molt origin and also from band-return data summarized at the flyway level. We compared the distribution of scaup natal origin with the distribution of breeding population counts obtained from systematic long-term surveys. Conclusions/Significance: Our analysis revealed that the proportion of young scaup produced in the northern (above 60uN) versus the southern boreal and Prairie-Parkland region was inversely related to the proportions of breeding adults using these regions, suggesting that despite having a higher relative abundance of breeding adults, the northern boreal region was less productive for scaup recruitment into the harvest than more southern biomes. Our approach for evaluating population declines of migratory birds (particularly game birds) synthesizes all available distributional data and exploits the advantages of intrinsic isotopic markers that link individuals to geography.
Eggs of glaucous gulls (Larus hyperboreus), black-legged kittiwakes (Rissa tridactyla), thick-bil... more Eggs of glaucous gulls (Larus hyperboreus), black-legged kittiwakes (Rissa tridactyla), thick-billed murres (Uria lomvia) and black guillemots (Cepphus grylle) were collected from several sites throughout the Canadian Arctic. Samples were analyzed for organochlorines as well as mercury and selenium. Glaucous gulls breeding at sites in the High Arctic showed higher levels of organochlorine contamination than those in the western Low Arctic. This was likely due to dietary differences among colonies as suggested by stable isotope data, although different overwintering areas may also play a role. Levels of AEPCB, AEDDT, AECHLOR, AECBz and dieldrin were significantly lower in thick-billed murres from Prince Leopold Island in the High Arctic compared with colonies in the eastern Low Arctic. This difference was likely due to the combined effects of different atmospheric deposition patterns in the High and Low Arctic and different overwintering areas since murres from Prince Leopold Island may winter farther north than murres from the other colonies sampled. Eggs from colonies at higher latitudes generally contained higher concentrations of mercury. The trophic and dietary differences/similarities suggested by stable-nitrogen and carbon isotope data in this study were useful in explaining the spatial patterns of contaminant concentrations observed among colonies of seabirds such as the glaucous gull and the black-legged kittiwake where variation in latitudinal atmospheric deposition patterns and different overwintering grounds did not appear to be confounding factors.
Populations of most North American aerial insectivores have undergone steep population declines o... more Populations of most North American aerial insectivores have undergone steep population declines over the past 40 years but the relative importance of factors operating on breeding, wintering, or stopover sites remains unknown. We used archival light-level geolocators to track the phenology, movements and winter locations of barn swallows (Hirdundo rustica; n = 27) from populations across North America to determine their migratory connectivity. We identified an east-west continental migratory divide for barn swallows with birds from western regions (Washington State, USA (n = 8) and Saskatchewan, Canada (n = 5)) traveling shorter distances to wintering areas ranging from Oregon to northern Colombia than eastern populations (Ontario (n = 3) and New Brunswick (n = 10), Canada) which wintered in South America south of the Amazon basin. A single swallow from a stable population in Alabama shared a similar migration route to eastern barn swallows but wintered farther north in northeast Brazil indicating a potential leap frog pattern migratory among eastern birds. Six of 9 (67%) birds from the two eastern populations and Alabama underwent a loop migration west of fall migration routes including around the Gulf of Mexico travelling a mean of 2,224 km and 722 km longer on spring migration, respectively. Longer migration distances, including the requirement to cross the Caribbean Sea and Gulf of Mexico and subsequent shorter sedentary wintering periods, may exacerbate declines for populations breeding in northeastern North America.
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.
Understanding movements of individual birds between breeding sites (breeding dispersal) or betwee... more Understanding movements of individual birds between breeding sites (breeding dispersal) or between natal sites and the site of first breeding (natal dispersal) is crucial to the modeling of population dynamics. Unfortunately, these aspects of demography are poorly understood for avian species in general, and for migratory songbirds in particular. This is because it is often impossible to sample broadly enough to relocate marked birds that have moved. We used stable-hydrogen (␦D) and carbon (␦ 13 C) isotope analyses of the feathers of 139 American Redstarts (Setophaga ruticilla) and 193 Ovenbirds (Seiurus aurocapillus) to evaluate evidence for individuals molting feathers at locations other than their breeding sites from the previous year. We sampled outer rectrices from breeding populations at three extensive boreal forest sites (Prince Albert National Park and Duck Mountain, Saskatchewan, and Lac La Biche, Alberta) and at three isolated forest tracts (Cypress Hills, and Moose Mountain, Saskatchewan, and Turtle Mountain, Manitoba) in western Canada. Based on outlier analysis of ␦D measurements, we found evidence for long-distance dispersal ranging from 0-29% of individuals. For both species, second-year birds had higher variance in ␦D values suggesting they had a higher probability of originating from elsewhere compared to after-second-year birds.
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.
Background: The ability to connect breeding, stopover and wintering locations of populations of m... more Background: The ability to connect breeding, stopover and wintering locations of populations of migratory birds greatly enhances our understanding of the phenomenon of migration and improves our chances of effectively conserving these species. Among Palearctic-Afrotropical migratory species, aerial insectivores like the house martin (Delichon urbicum) are sensitive to factors influencing the availability of flying insects, and have declined in recent decades. The strict aerial behaviour of martins severely limits ring recoveries on wintering grounds and so there is a dearth of information on where European breeding populations over-winter in Africa, and the relative effects of population regulation on breeding vs. wintering grounds. We used a newly developed multi-isotope (d 2 H, d 13 C, d 15 N) feather isoscape for Africa together with inferences from summarized ring return data based on longitude, to assign winter origins to birds captured at a breeding colony in The Netherlands.
... 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. ...
An enduring problem in avian ecology and conservation is linking breeding and wintering grounds o... more An enduring problem in avian ecology and conservation is linking breeding and wintering grounds of migratory species. As migratory species and populations vary in the degree to which individuals from distinct breeding locales mix on stopover sites and wintering grounds, establishing migratory connectivity informs our understanding of population demography and species management. We present a new Bayesian approach for inferring breeding grounds of wintering birds of unknown origins in North America. We incorporate prior information from analysis of genetic markers into geographic origin assignment based upon stable-hydrogen isotope analysis of feathers (d 2 H f), using the Loggerhead Shrike (Lanius ludovicianus). Likely geographic origins derived from analyses of DNA microsatellites were used as priors for Bayesian analyses in which birds were assigned to a breeding-ground origin using their d 2 H f values. As with most applications of Bayesian methods, our approach greatly improved the results (i.e. decreased the size of the potential area of origin). Area of origin decreased by 3 to 5-fold on average, but ranged up to a 10-fold improvement. We recommend this approach in future studies of migratory connectivity and suggest that our methodology could be applied more broadly to the study of dispersal, sources of productivity of migratory populations, and a range of evolutionary phenomena.
Globally and in Canada's boreal forest, extensive deforestation has occurred because of agricultu... more Globally and in Canada's boreal forest, extensive deforestation has occurred because of agricultural conversion. However, consequences of forest loss for bird assemblages associated with wetlands and their associated riparian areas and shoreline forests are poorly understood. Using the multivariate approach, Threshold Indicator Taxa Analysis (TITAN), we assessed the response of bird communities to an agricultural conversion gradient at two spatial scales: (1) locally within 500 m of a wetland, and (2) throughout a 5 × 5 km landscape. We compared results from a study area in Manitoba surrounded by agriculture (DMMB) to those from a landscape where agriculture is encroaching from the southern edge in east-central Alberta (ECAB). Both species-level and community-level changes tended to occur at lower levels of agricultural conversion in DMMB than in ECAB, particularly at the landscape scale. Community-level changes were more gradual and reached a single maximum at the wetland scale, whereas there were two to three distinct community-level change-points at the landscape scale. Species responding positively (15 in ECAB and 18 in DMMB) to agricultural conversion were typical of open-country ecoregions, while species that responded negatively (13 in each of ECAB and DMMB) tended to be those for which loss of forest cover represented direct loss of habitat. For species common to both regions, direction of response (+ or-) was typically consistent, but specific change-points differed. Where conversion of forest to agriculture is unavoidable in boreal forests, limiting the total amount of forest and wetland vegetation loss around wetlands and within the landscape matrix to ≤ 30%, along with wetland preservation, will have the greatest benefit to conserving bird communities typical of boreal wetlands and their adjacent riparian areas and forests. Variation régionale des communautés d'oiseaux associés aux milieux humides en réponse à la conversion de la forêt boréale en terres agricoles RÉSUMÉ. Partout sur la planète ainsi que dans la forêt boréale canadienne, on a défriché les forêts à grande échelle pour les convertir en terres agricoles. Toutefois, les conséquences de ces pertes de forêts sur les assemblages d'oiseaux associés aux milieux humides et leurs bandes riveraines et forestières adjacentes sont mal connues. Au moyen de l'approche multivariée TITAN (Threshold Indicator Taxa Analysis), nous avons évalué la réaction d'une communauté d'oiseaux en fonction d'un gradient de conversion agricole à deux échelles spatiales : 1) localement à l'intérieur de 500 m d'un milieu humide; et 2) dans un paysage de 5 × 5 km. Nous avons comparé les résultats provenant d'un site d'étude entouré de terres agricoles au Manitoba (DMMB) à ceux d'un paysage dans lequel l'agriculture empiète à la bordure sud dans le centre-est de l'Alberta (ECAB). Sur le plan des espèces comme sur celui des communautés, les changements ont eu tendance à se produire à des niveaux de conversion agricole plus faible dans DMMB que dans ECAB, particulièrement à l'échelle du paysage. Les changements au niveau de la communauté ont été plus graduels et ont atteint un unique maximum à l'échelle du milieu humide, tandis qu'il y a eu de 2 à 3 points de changements distincts de la communauté à l'échelle du paysage. Les espèces ayant réagi positivement aux conversions agricoles (15 dans ECAB et 18 dans DMMB) étaient typiques d'écorégions de milieux ouverts, alors que les espèces ayant réagi négativement (13 dans ECAB et 13 dans DMMB) avaient tendance à être celles pour lesquelles les pertes de forêts représentaient des pertes directes d'habitat. Pour les espèces communes aux deux régions, le sens de la réponse (+ ou-) était similaire, mais les points où se sont produits les changements spécifiques ont différé. En forêt boréale, là où les conversions de forêts en terres agricoles sont inévitables, le fait de limiter la perte de forêt et de végétation autour des milieux humides et dans le paysage à ≤ 30 %, combiné avec la préservation des milieux humides, offrira les bénéfices les plus importants pour conserver les communautés d'oiseaux caractéristiques des milieux humides boréaux et leurs bandes riveraines et forestières adjacentes.
Conventional acoustic surveys of avian communities require expert skills that are rare, particula... more Conventional acoustic surveys of avian communities require expert skills that are rare, particularly during the relatively short singing periods of most temperate North American species. We investigated the use of 2 newly developed omnidirectional microphones for field recordings of forest bird communities by comparing richness and abundance of species recorded by field experts and those inferred from simultaneous recordings and later analyzed by the same observers. For bird communities associated with the southern boreal mixedwoods of central Saskatchewan and western Ontario, the acoustic recording technique worked well. Similarity measures for both presence/absence and abundance data ranged from 83% to 97%. The acoustic recording technique, particularly when used in a stereo configuration, can be used to analyze species composition and relative abundance of forest bird communities. Moreover, this approach has numerous advantages including an archived record of point counts, the use of nonexpert field staff to collect recordings, and the standardization of field data through time.
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.
This is an open access article under the terms of the Creative Commons Attribution License, which... more This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
Fig. 1. Distribution of avian point-count samples used in density estimates derived from the Bore... more Fig. 1. Distribution of avian point-count samples used in density estimates derived from the Boreal Avian Modeling project (http://www.borealbirds.ca).
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
Background: Elucidating geographic locations from where migratory birds are recruited into adult ... more Background: Elucidating geographic locations from where migratory birds are recruited into adult breeding populations is a fundamental but largely elusive goal in conservation biology. This is especially true for species that breed in remote northern areas where field-based demographic assessments are logistically challenging. Methodology/Findings: Here we used hydrogen isotopes (dD) to determine natal origins of migrating hatch-year lesser scaup (Aythya affinis) harvested by hunters in the United States from all North American flyways during the hunting seasons of 1999-2000 (n = 412) and 2000-2001 (n = 455). We combined geospatial, observational, and analytical data sources, including known scaup breeding range, dD values of feathers from juveniles at natal sites, models of dD for growing-season precipitation, and scaup band-recovery data to generate probabilistic natal origin landscapes for individual scaup. We then used Monte Carlo integration to model assignment uncertainty from among individual dD variance estimates from birds of known molt origin and also from band-return data summarized at the flyway level. We compared the distribution of scaup natal origin with the distribution of breeding population counts obtained from systematic long-term surveys. Conclusions/Significance: Our analysis revealed that the proportion of young scaup produced in the northern (above 60uN) versus the southern boreal and Prairie-Parkland region was inversely related to the proportions of breeding adults using these regions, suggesting that despite having a higher relative abundance of breeding adults, the northern boreal region was less productive for scaup recruitment into the harvest than more southern biomes. Our approach for evaluating population declines of migratory birds (particularly game birds) synthesizes all available distributional data and exploits the advantages of intrinsic isotopic markers that link individuals to geography.
Eggs of glaucous gulls (Larus hyperboreus), black-legged kittiwakes (Rissa tridactyla), thick-bil... more Eggs of glaucous gulls (Larus hyperboreus), black-legged kittiwakes (Rissa tridactyla), thick-billed murres (Uria lomvia) and black guillemots (Cepphus grylle) were collected from several sites throughout the Canadian Arctic. Samples were analyzed for organochlorines as well as mercury and selenium. Glaucous gulls breeding at sites in the High Arctic showed higher levels of organochlorine contamination than those in the western Low Arctic. This was likely due to dietary differences among colonies as suggested by stable isotope data, although different overwintering areas may also play a role. Levels of AEPCB, AEDDT, AECHLOR, AECBz and dieldrin were significantly lower in thick-billed murres from Prince Leopold Island in the High Arctic compared with colonies in the eastern Low Arctic. This difference was likely due to the combined effects of different atmospheric deposition patterns in the High and Low Arctic and different overwintering areas since murres from Prince Leopold Island may winter farther north than murres from the other colonies sampled. Eggs from colonies at higher latitudes generally contained higher concentrations of mercury. The trophic and dietary differences/similarities suggested by stable-nitrogen and carbon isotope data in this study were useful in explaining the spatial patterns of contaminant concentrations observed among colonies of seabirds such as the glaucous gull and the black-legged kittiwake where variation in latitudinal atmospheric deposition patterns and different overwintering grounds did not appear to be confounding factors.
Populations of most North American aerial insectivores have undergone steep population declines o... more Populations of most North American aerial insectivores have undergone steep population declines over the past 40 years but the relative importance of factors operating on breeding, wintering, or stopover sites remains unknown. We used archival light-level geolocators to track the phenology, movements and winter locations of barn swallows (Hirdundo rustica; n = 27) from populations across North America to determine their migratory connectivity. We identified an east-west continental migratory divide for barn swallows with birds from western regions (Washington State, USA (n = 8) and Saskatchewan, Canada (n = 5)) traveling shorter distances to wintering areas ranging from Oregon to northern Colombia than eastern populations (Ontario (n = 3) and New Brunswick (n = 10), Canada) which wintered in South America south of the Amazon basin. A single swallow from a stable population in Alabama shared a similar migration route to eastern barn swallows but wintered farther north in northeast Brazil indicating a potential leap frog pattern migratory among eastern birds. Six of 9 (67%) birds from the two eastern populations and Alabama underwent a loop migration west of fall migration routes including around the Gulf of Mexico travelling a mean of 2,224 km and 722 km longer on spring migration, respectively. Longer migration distances, including the requirement to cross the Caribbean Sea and Gulf of Mexico and subsequent shorter sedentary wintering periods, may exacerbate declines for populations breeding in northeastern North America.
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.
Understanding movements of individual birds between breeding sites (breeding dispersal) or betwee... more Understanding movements of individual birds between breeding sites (breeding dispersal) or between natal sites and the site of first breeding (natal dispersal) is crucial to the modeling of population dynamics. Unfortunately, these aspects of demography are poorly understood for avian species in general, and for migratory songbirds in particular. This is because it is often impossible to sample broadly enough to relocate marked birds that have moved. We used stable-hydrogen (␦D) and carbon (␦ 13 C) isotope analyses of the feathers of 139 American Redstarts (Setophaga ruticilla) and 193 Ovenbirds (Seiurus aurocapillus) to evaluate evidence for individuals molting feathers at locations other than their breeding sites from the previous year. We sampled outer rectrices from breeding populations at three extensive boreal forest sites (Prince Albert National Park and Duck Mountain, Saskatchewan, and Lac La Biche, Alberta) and at three isolated forest tracts (Cypress Hills, and Moose Mountain, Saskatchewan, and Turtle Mountain, Manitoba) in western Canada. Based on outlier analysis of ␦D measurements, we found evidence for long-distance dispersal ranging from 0-29% of individuals. For both species, second-year birds had higher variance in ␦D values suggesting they had a higher probability of originating from elsewhere compared to after-second-year birds.
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.
Background: The ability to connect breeding, stopover and wintering locations of populations of m... more Background: The ability to connect breeding, stopover and wintering locations of populations of migratory birds greatly enhances our understanding of the phenomenon of migration and improves our chances of effectively conserving these species. Among Palearctic-Afrotropical migratory species, aerial insectivores like the house martin (Delichon urbicum) are sensitive to factors influencing the availability of flying insects, and have declined in recent decades. The strict aerial behaviour of martins severely limits ring recoveries on wintering grounds and so there is a dearth of information on where European breeding populations over-winter in Africa, and the relative effects of population regulation on breeding vs. wintering grounds. We used a newly developed multi-isotope (d 2 H, d 13 C, d 15 N) feather isoscape for Africa together with inferences from summarized ring return data based on longitude, to assign winter origins to birds captured at a breeding colony in The Netherlands.
... 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. ...
An enduring problem in avian ecology and conservation is linking breeding and wintering grounds o... more An enduring problem in avian ecology and conservation is linking breeding and wintering grounds of migratory species. As migratory species and populations vary in the degree to which individuals from distinct breeding locales mix on stopover sites and wintering grounds, establishing migratory connectivity informs our understanding of population demography and species management. We present a new Bayesian approach for inferring breeding grounds of wintering birds of unknown origins in North America. We incorporate prior information from analysis of genetic markers into geographic origin assignment based upon stable-hydrogen isotope analysis of feathers (d 2 H f), using the Loggerhead Shrike (Lanius ludovicianus). Likely geographic origins derived from analyses of DNA microsatellites were used as priors for Bayesian analyses in which birds were assigned to a breeding-ground origin using their d 2 H f values. As with most applications of Bayesian methods, our approach greatly improved the results (i.e. decreased the size of the potential area of origin). Area of origin decreased by 3 to 5-fold on average, but ranged up to a 10-fold improvement. We recommend this approach in future studies of migratory connectivity and suggest that our methodology could be applied more broadly to the study of dispersal, sources of productivity of migratory populations, and a range of evolutionary phenomena.
Globally and in Canada's boreal forest, extensive deforestation has occurred because of agricultu... more Globally and in Canada's boreal forest, extensive deforestation has occurred because of agricultural conversion. However, consequences of forest loss for bird assemblages associated with wetlands and their associated riparian areas and shoreline forests are poorly understood. Using the multivariate approach, Threshold Indicator Taxa Analysis (TITAN), we assessed the response of bird communities to an agricultural conversion gradient at two spatial scales: (1) locally within 500 m of a wetland, and (2) throughout a 5 × 5 km landscape. We compared results from a study area in Manitoba surrounded by agriculture (DMMB) to those from a landscape where agriculture is encroaching from the southern edge in east-central Alberta (ECAB). Both species-level and community-level changes tended to occur at lower levels of agricultural conversion in DMMB than in ECAB, particularly at the landscape scale. Community-level changes were more gradual and reached a single maximum at the wetland scale, whereas there were two to three distinct community-level change-points at the landscape scale. Species responding positively (15 in ECAB and 18 in DMMB) to agricultural conversion were typical of open-country ecoregions, while species that responded negatively (13 in each of ECAB and DMMB) tended to be those for which loss of forest cover represented direct loss of habitat. For species common to both regions, direction of response (+ or-) was typically consistent, but specific change-points differed. Where conversion of forest to agriculture is unavoidable in boreal forests, limiting the total amount of forest and wetland vegetation loss around wetlands and within the landscape matrix to ≤ 30%, along with wetland preservation, will have the greatest benefit to conserving bird communities typical of boreal wetlands and their adjacent riparian areas and forests. Variation régionale des communautés d'oiseaux associés aux milieux humides en réponse à la conversion de la forêt boréale en terres agricoles RÉSUMÉ. Partout sur la planète ainsi que dans la forêt boréale canadienne, on a défriché les forêts à grande échelle pour les convertir en terres agricoles. Toutefois, les conséquences de ces pertes de forêts sur les assemblages d'oiseaux associés aux milieux humides et leurs bandes riveraines et forestières adjacentes sont mal connues. Au moyen de l'approche multivariée TITAN (Threshold Indicator Taxa Analysis), nous avons évalué la réaction d'une communauté d'oiseaux en fonction d'un gradient de conversion agricole à deux échelles spatiales : 1) localement à l'intérieur de 500 m d'un milieu humide; et 2) dans un paysage de 5 × 5 km. Nous avons comparé les résultats provenant d'un site d'étude entouré de terres agricoles au Manitoba (DMMB) à ceux d'un paysage dans lequel l'agriculture empiète à la bordure sud dans le centre-est de l'Alberta (ECAB). Sur le plan des espèces comme sur celui des communautés, les changements ont eu tendance à se produire à des niveaux de conversion agricole plus faible dans DMMB que dans ECAB, particulièrement à l'échelle du paysage. Les changements au niveau de la communauté ont été plus graduels et ont atteint un unique maximum à l'échelle du milieu humide, tandis qu'il y a eu de 2 à 3 points de changements distincts de la communauté à l'échelle du paysage. Les espèces ayant réagi positivement aux conversions agricoles (15 dans ECAB et 18 dans DMMB) étaient typiques d'écorégions de milieux ouverts, alors que les espèces ayant réagi négativement (13 dans ECAB et 13 dans DMMB) avaient tendance à être celles pour lesquelles les pertes de forêts représentaient des pertes directes d'habitat. Pour les espèces communes aux deux régions, le sens de la réponse (+ ou-) était similaire, mais les points où se sont produits les changements spécifiques ont différé. En forêt boréale, là où les conversions de forêts en terres agricoles sont inévitables, le fait de limiter la perte de forêt et de végétation autour des milieux humides et dans le paysage à ≤ 30 %, combiné avec la préservation des milieux humides, offrira les bénéfices les plus importants pour conserver les communautés d'oiseaux caractéristiques des milieux humides boréaux et leurs bandes riveraines et forestières adjacentes.
Conventional acoustic surveys of avian communities require expert skills that are rare, particula... more Conventional acoustic surveys of avian communities require expert skills that are rare, particularly during the relatively short singing periods of most temperate North American species. We investigated the use of 2 newly developed omnidirectional microphones for field recordings of forest bird communities by comparing richness and abundance of species recorded by field experts and those inferred from simultaneous recordings and later analyzed by the same observers. For bird communities associated with the southern boreal mixedwoods of central Saskatchewan and western Ontario, the acoustic recording technique worked well. Similarity measures for both presence/absence and abundance data ranged from 83% to 97%. The acoustic recording technique, particularly when used in a stereo configuration, can be used to analyze species composition and relative abundance of forest bird communities. Moreover, this approach has numerous advantages including an archived record of point counts, the use of nonexpert field staff to collect recordings, and the standardization of field data through time.
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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