The climatic variability hypothesis (CVH) posits that more flexible phenotypes should provide a f... more The climatic variability hypothesis (CVH) posits that more flexible phenotypes should provide a fitness advantage for organisms experiencing more variable climates. While typically applied across geographically separated populations, whether this principle applies across seasons or other conditions (e.g., open vs. sheltered habitats) which differ in climatic variability remains essentially unstudied. In north-temperate climates, climatic variability in winter usually exceeds that in summer, so extending the CVH to within-population seasonal variation predicts that winter phenotypes should be more flexible than summer phenotypes. We tested this prediction of the within-season extension of the CVH by acclimating summer and winter-collected house sparrows (Passer domesticus) to 24, 5, and À10 C and measuring basal metabolic rate (BMR) and summit metabolic rate (M sum ¼ maximum cold-induced metabolic rate) before and after acclimation (Accl). To examine mechanistic bases for metabolic variation, we measured flight muscle and heart masses and citrate synthase and b-hydroxyacyl coA-dehydrogenase activities. BMR and M sum were higher for cold-acclimated than for warm-acclimated birds, and BMR was higher in winter than in summer birds. Contrary to our hypothesis of greater responses to cold Accl in winter birds, metabolic rates generally decreased over the Accl period for winter birds at all temperatures but increased at cold temperatures for summer birds. Flight muscle and heart masses were not significantly correlated with season or Accl treatment, except for supracoracoideus mass, which was lower at À10 C in winter, but flight muscle and heart masses were positively correlated with BMR and flight muscle mass was positively correlated with M sum. Catabolic enzyme activities were not clearly related to metabolic variation. Thus, our data suggest that predictions of the CVH may not be relevant when extended to seasonal temperature variability at the within-population scale. Indeed, these data suggest that metabolic rates are more prominently upregulated in summer than in winter in response to cold. Metabolic rates tended to decrease during Accl at all temperatures in winter, suggesting that initial metabolic rates at capture (higher in winter) influence metabolic Accl for captive birds.
River regulation by dams on the Missouri River has modified riparian forest successional patterns... more River regulation by dams on the Missouri River has modified riparian forest successional patterns, with decreases in early and increases in later seral stages and higher occurrence of invasive tree species, including Russian olive (Elaeagnus angustifolia) and eastern red cedar (Juniperus virginiana). The effects of these altered successional trajectories on bird biodiversity are difficult to quantify because of limited data on bird-habitat associations. We surveyed riparian shrubland and forest bird species across a gradient of riparian forest ages along two segments of the regulated Missouri River in South Dakota and Nebraska, USA and explored relationships between bird abundance and patch-and landscape-scale vegetation characteristics for 46 bird species. Predicted abundances at sites assigned to five vegetation classes, estimated from Bayesian binomial N-mixture models, identified 11 early successional bird species and 19 forest bird species. Abundances of early successional bird species were similar at cottonwood-willow sites and Russian olive sites and were positively correlated with cottonwood (Populus deltoides) importance values for only one species, Willow Flycatcher (Empidonax traillii). Abundances of forest bird species were similar at sites in the three forest vegetation classes, although Ovenbird (Seiurus aurocapilla) and Baltimore Oriole (Icterus galbula) showed some affinity for mid-or late successional cottonwood sites over late-successional non-cottonwood sites. Abundances of three forest species, including Baltimore Oriole, were positively correlated with cottonwood or negatively correlated with eastern red cedar importance values. Fifteen species were positively correlated with shrubland land cover, whereas 21 species were positively correlated with forest land cover. For most bird species, correlations were strongest with land cover within a 200-m buffer compared to 400 or 1200 m. These data suggest that the trends in riparian forest change due to river regulation along the middle Missouri River may produce a mix of positive and negative effects on riparian bird species. While management plans to promote regeneration of early successional cottonwood-willow stands are likely to benefit conservation of early successional bird species, Russian olive may also provide suitable bird habitat for the majority those species. Associations végétales des oiseaux riverains dans les peuplements successionnels le long de la rivière Missouri
relatively little is known about the locations of North american landbirds' winter roosts (Skutch... more relatively little is known about the locations of North american landbirds' winter roosts (Skutch 1989, Dobbs and martin 2000). North american Piciformes and cavity-nesting passerines have frequently been documented using cavities and variations thereof for overnight roosts during the non-nesting season, but relatively little is known about where passerines that nest in cups or other open structures spend the night (Skutch 1989, Dobbs and martin 2000, antczak 2010). The rubycrowned Kinglet (Regulus calendula), an insectivorous cup-nesting species, has not been observed either nesting or roosting in cavities (Swanson et al. 2008).
Differences in straggling rates between two genera of dove lice (Insecta: Phthiraptera) reinforce... more Differences in straggling rates between two genera of dove lice (Insecta: Phthiraptera) reinforce population genetic and cophylogenetic patterns. International Journal for Parasitology, in press.
Finding ecologically relevant relationships between environmental covariates and response variabl... more Finding ecologically relevant relationships between environmental covariates and response variables requires determining appropriate scales of effect. While considering multiple spatial scales of effect in hierarchical models has been the focus of recent studies, the effect of spatiotemporal scales, and temporal resolution of data on habitat suitability and species abundance has received less attention. We investigated relationships between ringnecked pheasant rooster abundance and environmental covariates with the goal of identifying important variables and their scales of effect in South Dakota, U.S.A. Using a suite of remote sensing data, we examined whether seasonal environmental conditions influence pheasant relative abundance and how survey conditions might affect detectability of roosters. To select optimal scales of effect and the best subset of covariates simultaneously, we employed a Reversible-Jump Monte Carlo Markov Chain (RJMCMC) approach in a Bayesian framework. We explored sources of uncertainty in data and controlled them through consideration of random effects. The use of seasonal covariates in addition to annual covariates revealed differential effects on species abundance. The proportion of grasslands on the landscape was an important covariate in models in all years, with rooster abundance generally being highest at intermediate levels of grassland density at local scales of effect. Pheasant abundance was also positively related to the proportion of small grain crop cover on the landscape at >2 km scales. Spring gross primary productivity and percentage of herbaceous wetlands on the landscape, both at a large scale (8 km), were the most important covariates in the wet years of 2018 and 2019 and were positively related to pheasant abundance. Grasslands at intermediate levels of density explained variability of pheasant abundance. However, other variables important to pheasant relative abundance varied among years depending on prevailing weather and climate conditions. Our workflow to model relationships between relative abundance and habitat components for pheasants can also be employed to model count data for other species to inform management decisions.
Seasonal changes, such as alterations in food availability or type and cold conditions, present c... more Seasonal changes, such as alterations in food availability or type and cold conditions, present challenges to free-living birds living in highly seasonal climates. Small birds respond to such challenges through seasonal metabolic flexibility, which better matches seasonal metabolic phenotypes to environmental conditions and can improve fitness. To better understand the mechanistic basis of this metabolic flexibility, we conducted a large-scale metabolic profiling of pectoralis muscle in black-capped chickadees (Poecile atricapillus) and American goldfinches (Spinus tristis), which are small, year-round bird species of temperate-zones. We analyzed muscle samples using non-biased, global metabolomics profiling technology based on UHLC/MS/MS2 platforms. A total of 582 metabolites was characterized for summer and winter season samples. Chickadees showed greater seasonal separation of global metabolite profiles than goldfinches, which is consistent with previous transcriptomic studies of...
Ensemble of small models (ESMs) is a technique to overcome the problem of few occurrence points. ... more Ensemble of small models (ESMs) is a technique to overcome the problem of few occurrence points. Applying the ESMs in a spatially hierarchical framework could increase the accuracy of predictions and conclusions by restricting available habitat at sequentially finer spatial scales. Our objective was to show how applying ESMs in a hierarchical habitat selection framework could help to understand rare species’ niches at various scales. We compared the accuracy of ESMs made by committee averaging and weighted averaging methods. We also compared the predictive power of ESMs made by various modeling techniques for Virginia’s warbler (Leiothlypis virginiae) at its northeastern range limit. We defined biologically relevant hierarchical orders of habitat selection for Virginia’s warbler in the Black Hills, U.S.A. We modeled habitat suitabity at the broadest scale as a function of bioclimatic covariates and at finer scales as functions of landcover, soil group and landscape covariates. The performance of modeling techniques varied among scales. Using the committee averaging method led to more accurate results than weighted averaging. At the broadest order, Virginia’s warbler had a narrow climatic niche. The importance of covariates changed across finer orders, such that at broader orders many covariates were important whereas at finer orders certain covariates became more important than others. We conclude that applying ESMs within a hierarchical framework can lead to detailed information about rare species’ niches, limiting factors at each habitat selection order, and potential distribution, which could help inform multiscale management.
Migratory connectivity is the degree to which populations are linked in space and time across the... more Migratory connectivity is the degree to which populations are linked in space and time across the annual cycle. Low connectivity indicates mixing of populations while high connectivity indicates population separation in space or time. High migratory connectivity makes individual populations susceptible to local environmental conditions; therefore, evaluating migratory connectivity continuously across a species range is important for understanding differential population trends and revealing places and times contributing to these differences. The common nighthawk Chordeiles minor is a widespread, declining, long‐distance migratory bird. Variable population trends across the nighthawk breeding range suggest that knowledge of migratory connectivity is needed to direct conservation. We used GPS tags to track 52 individuals from 12 breeding populations. We estimated migratory connectivity as 0.29 (Mantel coefficient: 0 = no connectivity, 1 = full connectivity) between the breeding and wi...
Reversible phenotypic flexibility allows organisms to better match phenotypes to prevailing envir... more Reversible phenotypic flexibility allows organisms to better match phenotypes to prevailing environmental conditions and may produce fitness benefits. Costs and constraints of phenotypic flexibility may limit the capacity for flexible responses but are not well understood nor documented. Costs could include expenses associated with maintaining the flexible system or with generating the flexible response. One potential cost of maintaining a flexible system is an energetic cost reflected in the basal metabolic rate (BMR), with elevated BMR in individuals with more flexible metabolic responses. We accessed data from thermal acclimation studies of birds where BMR and/or Msum (maximum cold-induced metabolic rate) were measured before and after acclimation, as a measure of metabolic flexibility, to test the hypothesis that flexibility in BMR (ΔBMR), Msum (ΔMsum), or metabolic scope (Msum − BMR; ΔScope) is positively correlated with BMR. When temperature treatments lasted at least three we...
Context Ensemble of small models (ESMs) is a technique to overcome the problem of few occurrence ... more Context Ensemble of small models (ESMs) is a technique to overcome the problem of few occurrence points. Applying the ESMs in a spatially hierarchical framework could increase the accuracy of predictions and conclusions by restricting available habitat at sequentially finer spatial scales. Objectives Our objective was to show how applying ESMs in a hierarchical habitat selection framework could help to understand rare species' niches at various scales. We compared the accuracy of ESMs made by committee averaging and weighted averaging methods. We also compared the predictive power of ESMs made by various modeling techniques for Keywords Ensemble of small models Á ESMs Á Hierarchical habitat selection Á Rare species distribution model Á Virginia's Warbler Á Multi-scale Á Model performance Á Niche
Avian behavioral and physiological responses to challenging thermal environments and extreme weat... more Avian behavioral and physiological responses to challenging thermal environments and extreme weather events. Front. Ecol. Evol. :. doi: .
Flexible metabolic phenotypes allow animals to adjust physiology to better fit ecological or envi... more Flexible metabolic phenotypes allow animals to adjust physiology to better fit ecological or environmental demands, thereby influencing fitness. Summit metabolic rate (M sum = maximal thermogenic capacity) is one such flexible trait. Skeletal muscle and heart masses and myocyte metabolic intensity are potential drivers of M sum flexibility in birds. We examined correlations of skeletal muscle and heart masses and pectoralis muscle citrate synthase (CS) activity (an indicator of cellular metabolic intensity) with M sum in house sparrows (Passer domesticus) and dark-eyed juncos (Junco hyemalis) to determine whether these traits are associated with M sum variation. Pectoralis mass was positively correlated with M sum for both species, but no significant correlation remained for either species after accounting for body mass (M b) variation. Combined flight and leg muscle masses were also not significantly correlated with M sum for either species. In contrast, heart mass was significantly positively correlated with M sum for juncos and nearly so (P = 0.054) for sparrows. Mass-specific and total pectoralis CS activities were significantly positively correlated with M sum for sparrows, but not for juncos. Thus, myocyte metabolic intensity influences M sum variation in house sparrows, although the stronger correlation of total (r = 0.495) than mass-specific (r = 0.378) CS activity with M sum suggests that both pectoralis mass and metabolic intensity impact M sum. In contrast, neither skeletal muscle masses nor pectoralis metabolic intensity varied with M sum in juncos. However, heart mass was associated with M sum variation in both species. These data suggest that drivers of metabolic flexibility are not uniform among bird species.
Improved winter cold-tolerance is widespread among small birds from temperate climates and is usu... more Improved winter cold-tolerance is widespread among small birds from temperate climates and is usually associated with improved shivering endurance and elevated peak metabolic rate (Msum), although precise mechanisms of acclimatization are incompletely understood. Elevated Msum and improved cold-tolerance may be associated with greater metabolic intensity of thermogenic tissues, due to mass-specific increases in oxidative enzyme capacity, or to increases in the masses of metabolically active tissues. To examine mechanisms underlying winter increases in Msum, we captured wild, free-living individuals of three resident passerine species, White-breasted Nuthatch (Sitta carolinensis), Black-capped Chickadee (Poecile atricapillus), and House Sparrow (Passer domesticus). Each of these three species shows large seasonal variations in Msum, in excess of 35%. We investigated seasonal changes in the pectoralis and supracoracoideus muscles of mass-specific and total activities of key enzymes in...
Pine-juniper-shrub habitat with a shrubby understory of skunkbush sumac (Rhus aromatica) and moun... more Pine-juniper-shrub habitat with a shrubby understory of skunkbush sumac (Rhus aromatica) and mountain-mahogany (Cercocarpus montanus) and interspersed or adjacent Rocky Mountain juniper (Juniperus scopulorum) and ponderosa pine (Pinus ponderosa) is restricted in South Dakota to small areas in Custer and Fall River Counties in the southwestern Black Hills. These habitats have received very little ornithological investigation. We used fixed-width (25 m) line transect censuses and mist net sampling during the breeding season (25 May-9 July 1998) to document the abundance and breeding condition of birds in this habitat. Line transects yielded an overall raw density estimate of 411.7 birds km -2 and a mean (±SD) relative abundance (birds per kilometerlong transect) of 56.9 ± 12.8 birds/transect. Overall abundance increased significantly (P<0.01) over the study period from 43.7 birds/transect in late May to 68.2 birds/transect in early July. This probably results both from the recruitm...
Great-tailed grackles (Quiscalus mexicanus) formerly were present in North America only in southe... more Great-tailed grackles (Quiscalus mexicanus) formerly were present in North America only in southern Texas, but they have been expanding their range, primarily to the north and west, throughout the past century. Reports of this species have recently proliferated in the north central United States. Here we review the current status of the great-tailed grackle in South Dakota and report the first documented nesting of this species in the state. The first documented record of great-tailed grackle in South Dakota was a male that occurred on 14-15 May 1988 in Yankton County. No additional records of this species were documented for South Dakota until 1995, when birds from Charles Mix (6 April) and Clay (24 May-1 June) Counties were reported. Since that time, records of great-tailed grackles in South Dakota have occurred as far north as Brown and Deuel Counties and as far west as Lyman County, but no nests were documented until 1999. In 1999, we found three nests in a marsh lined with catt...
The climatic variability hypothesis (CVH) posits that more flexible phenotypes should provide a f... more The climatic variability hypothesis (CVH) posits that more flexible phenotypes should provide a fitness advantage for organisms experiencing more variable climates. While typically applied across geographically separated populations, whether this principle applies across seasons or other conditions (e.g., open vs. sheltered habitats) which differ in climatic variability remains essentially unstudied. In north-temperate climates, climatic variability in winter usually exceeds that in summer, so extending the CVH to within-population seasonal variation predicts that winter phenotypes should be more flexible than summer phenotypes. We tested this prediction of the within-season extension of the CVH by acclimating summer and winter-collected house sparrows (Passer domesticus) to 24, 5, and À10 C and measuring basal metabolic rate (BMR) and summit metabolic rate (M sum ¼ maximum cold-induced metabolic rate) before and after acclimation (Accl). To examine mechanistic bases for metabolic variation, we measured flight muscle and heart masses and citrate synthase and b-hydroxyacyl coA-dehydrogenase activities. BMR and M sum were higher for cold-acclimated than for warm-acclimated birds, and BMR was higher in winter than in summer birds. Contrary to our hypothesis of greater responses to cold Accl in winter birds, metabolic rates generally decreased over the Accl period for winter birds at all temperatures but increased at cold temperatures for summer birds. Flight muscle and heart masses were not significantly correlated with season or Accl treatment, except for supracoracoideus mass, which was lower at À10 C in winter, but flight muscle and heart masses were positively correlated with BMR and flight muscle mass was positively correlated with M sum. Catabolic enzyme activities were not clearly related to metabolic variation. Thus, our data suggest that predictions of the CVH may not be relevant when extended to seasonal temperature variability at the within-population scale. Indeed, these data suggest that metabolic rates are more prominently upregulated in summer than in winter in response to cold. Metabolic rates tended to decrease during Accl at all temperatures in winter, suggesting that initial metabolic rates at capture (higher in winter) influence metabolic Accl for captive birds.
River regulation by dams on the Missouri River has modified riparian forest successional patterns... more River regulation by dams on the Missouri River has modified riparian forest successional patterns, with decreases in early and increases in later seral stages and higher occurrence of invasive tree species, including Russian olive (Elaeagnus angustifolia) and eastern red cedar (Juniperus virginiana). The effects of these altered successional trajectories on bird biodiversity are difficult to quantify because of limited data on bird-habitat associations. We surveyed riparian shrubland and forest bird species across a gradient of riparian forest ages along two segments of the regulated Missouri River in South Dakota and Nebraska, USA and explored relationships between bird abundance and patch-and landscape-scale vegetation characteristics for 46 bird species. Predicted abundances at sites assigned to five vegetation classes, estimated from Bayesian binomial N-mixture models, identified 11 early successional bird species and 19 forest bird species. Abundances of early successional bird species were similar at cottonwood-willow sites and Russian olive sites and were positively correlated with cottonwood (Populus deltoides) importance values for only one species, Willow Flycatcher (Empidonax traillii). Abundances of forest bird species were similar at sites in the three forest vegetation classes, although Ovenbird (Seiurus aurocapilla) and Baltimore Oriole (Icterus galbula) showed some affinity for mid-or late successional cottonwood sites over late-successional non-cottonwood sites. Abundances of three forest species, including Baltimore Oriole, were positively correlated with cottonwood or negatively correlated with eastern red cedar importance values. Fifteen species were positively correlated with shrubland land cover, whereas 21 species were positively correlated with forest land cover. For most bird species, correlations were strongest with land cover within a 200-m buffer compared to 400 or 1200 m. These data suggest that the trends in riparian forest change due to river regulation along the middle Missouri River may produce a mix of positive and negative effects on riparian bird species. While management plans to promote regeneration of early successional cottonwood-willow stands are likely to benefit conservation of early successional bird species, Russian olive may also provide suitable bird habitat for the majority those species. Associations végétales des oiseaux riverains dans les peuplements successionnels le long de la rivière Missouri
relatively little is known about the locations of North american landbirds' winter roosts (Skutch... more relatively little is known about the locations of North american landbirds' winter roosts (Skutch 1989, Dobbs and martin 2000). North american Piciformes and cavity-nesting passerines have frequently been documented using cavities and variations thereof for overnight roosts during the non-nesting season, but relatively little is known about where passerines that nest in cups or other open structures spend the night (Skutch 1989, Dobbs and martin 2000, antczak 2010). The rubycrowned Kinglet (Regulus calendula), an insectivorous cup-nesting species, has not been observed either nesting or roosting in cavities (Swanson et al. 2008).
Differences in straggling rates between two genera of dove lice (Insecta: Phthiraptera) reinforce... more Differences in straggling rates between two genera of dove lice (Insecta: Phthiraptera) reinforce population genetic and cophylogenetic patterns. International Journal for Parasitology, in press.
Finding ecologically relevant relationships between environmental covariates and response variabl... more Finding ecologically relevant relationships between environmental covariates and response variables requires determining appropriate scales of effect. While considering multiple spatial scales of effect in hierarchical models has been the focus of recent studies, the effect of spatiotemporal scales, and temporal resolution of data on habitat suitability and species abundance has received less attention. We investigated relationships between ringnecked pheasant rooster abundance and environmental covariates with the goal of identifying important variables and their scales of effect in South Dakota, U.S.A. Using a suite of remote sensing data, we examined whether seasonal environmental conditions influence pheasant relative abundance and how survey conditions might affect detectability of roosters. To select optimal scales of effect and the best subset of covariates simultaneously, we employed a Reversible-Jump Monte Carlo Markov Chain (RJMCMC) approach in a Bayesian framework. We explored sources of uncertainty in data and controlled them through consideration of random effects. The use of seasonal covariates in addition to annual covariates revealed differential effects on species abundance. The proportion of grasslands on the landscape was an important covariate in models in all years, with rooster abundance generally being highest at intermediate levels of grassland density at local scales of effect. Pheasant abundance was also positively related to the proportion of small grain crop cover on the landscape at &gt;2 km scales. Spring gross primary productivity and percentage of herbaceous wetlands on the landscape, both at a large scale (8 km), were the most important covariates in the wet years of 2018 and 2019 and were positively related to pheasant abundance. Grasslands at intermediate levels of density explained variability of pheasant abundance. However, other variables important to pheasant relative abundance varied among years depending on prevailing weather and climate conditions. Our workflow to model relationships between relative abundance and habitat components for pheasants can also be employed to model count data for other species to inform management decisions.
Seasonal changes, such as alterations in food availability or type and cold conditions, present c... more Seasonal changes, such as alterations in food availability or type and cold conditions, present challenges to free-living birds living in highly seasonal climates. Small birds respond to such challenges through seasonal metabolic flexibility, which better matches seasonal metabolic phenotypes to environmental conditions and can improve fitness. To better understand the mechanistic basis of this metabolic flexibility, we conducted a large-scale metabolic profiling of pectoralis muscle in black-capped chickadees (Poecile atricapillus) and American goldfinches (Spinus tristis), which are small, year-round bird species of temperate-zones. We analyzed muscle samples using non-biased, global metabolomics profiling technology based on UHLC/MS/MS2 platforms. A total of 582 metabolites was characterized for summer and winter season samples. Chickadees showed greater seasonal separation of global metabolite profiles than goldfinches, which is consistent with previous transcriptomic studies of...
Ensemble of small models (ESMs) is a technique to overcome the problem of few occurrence points. ... more Ensemble of small models (ESMs) is a technique to overcome the problem of few occurrence points. Applying the ESMs in a spatially hierarchical framework could increase the accuracy of predictions and conclusions by restricting available habitat at sequentially finer spatial scales. Our objective was to show how applying ESMs in a hierarchical habitat selection framework could help to understand rare species’ niches at various scales. We compared the accuracy of ESMs made by committee averaging and weighted averaging methods. We also compared the predictive power of ESMs made by various modeling techniques for Virginia’s warbler (Leiothlypis virginiae) at its northeastern range limit. We defined biologically relevant hierarchical orders of habitat selection for Virginia’s warbler in the Black Hills, U.S.A. We modeled habitat suitabity at the broadest scale as a function of bioclimatic covariates and at finer scales as functions of landcover, soil group and landscape covariates. The performance of modeling techniques varied among scales. Using the committee averaging method led to more accurate results than weighted averaging. At the broadest order, Virginia’s warbler had a narrow climatic niche. The importance of covariates changed across finer orders, such that at broader orders many covariates were important whereas at finer orders certain covariates became more important than others. We conclude that applying ESMs within a hierarchical framework can lead to detailed information about rare species’ niches, limiting factors at each habitat selection order, and potential distribution, which could help inform multiscale management.
Migratory connectivity is the degree to which populations are linked in space and time across the... more Migratory connectivity is the degree to which populations are linked in space and time across the annual cycle. Low connectivity indicates mixing of populations while high connectivity indicates population separation in space or time. High migratory connectivity makes individual populations susceptible to local environmental conditions; therefore, evaluating migratory connectivity continuously across a species range is important for understanding differential population trends and revealing places and times contributing to these differences. The common nighthawk Chordeiles minor is a widespread, declining, long‐distance migratory bird. Variable population trends across the nighthawk breeding range suggest that knowledge of migratory connectivity is needed to direct conservation. We used GPS tags to track 52 individuals from 12 breeding populations. We estimated migratory connectivity as 0.29 (Mantel coefficient: 0 = no connectivity, 1 = full connectivity) between the breeding and wi...
Reversible phenotypic flexibility allows organisms to better match phenotypes to prevailing envir... more Reversible phenotypic flexibility allows organisms to better match phenotypes to prevailing environmental conditions and may produce fitness benefits. Costs and constraints of phenotypic flexibility may limit the capacity for flexible responses but are not well understood nor documented. Costs could include expenses associated with maintaining the flexible system or with generating the flexible response. One potential cost of maintaining a flexible system is an energetic cost reflected in the basal metabolic rate (BMR), with elevated BMR in individuals with more flexible metabolic responses. We accessed data from thermal acclimation studies of birds where BMR and/or Msum (maximum cold-induced metabolic rate) were measured before and after acclimation, as a measure of metabolic flexibility, to test the hypothesis that flexibility in BMR (ΔBMR), Msum (ΔMsum), or metabolic scope (Msum − BMR; ΔScope) is positively correlated with BMR. When temperature treatments lasted at least three we...
Context Ensemble of small models (ESMs) is a technique to overcome the problem of few occurrence ... more Context Ensemble of small models (ESMs) is a technique to overcome the problem of few occurrence points. Applying the ESMs in a spatially hierarchical framework could increase the accuracy of predictions and conclusions by restricting available habitat at sequentially finer spatial scales. Objectives Our objective was to show how applying ESMs in a hierarchical habitat selection framework could help to understand rare species' niches at various scales. We compared the accuracy of ESMs made by committee averaging and weighted averaging methods. We also compared the predictive power of ESMs made by various modeling techniques for Keywords Ensemble of small models Á ESMs Á Hierarchical habitat selection Á Rare species distribution model Á Virginia's Warbler Á Multi-scale Á Model performance Á Niche
Avian behavioral and physiological responses to challenging thermal environments and extreme weat... more Avian behavioral and physiological responses to challenging thermal environments and extreme weather events. Front. Ecol. Evol. :. doi: .
Flexible metabolic phenotypes allow animals to adjust physiology to better fit ecological or envi... more Flexible metabolic phenotypes allow animals to adjust physiology to better fit ecological or environmental demands, thereby influencing fitness. Summit metabolic rate (M sum = maximal thermogenic capacity) is one such flexible trait. Skeletal muscle and heart masses and myocyte metabolic intensity are potential drivers of M sum flexibility in birds. We examined correlations of skeletal muscle and heart masses and pectoralis muscle citrate synthase (CS) activity (an indicator of cellular metabolic intensity) with M sum in house sparrows (Passer domesticus) and dark-eyed juncos (Junco hyemalis) to determine whether these traits are associated with M sum variation. Pectoralis mass was positively correlated with M sum for both species, but no significant correlation remained for either species after accounting for body mass (M b) variation. Combined flight and leg muscle masses were also not significantly correlated with M sum for either species. In contrast, heart mass was significantly positively correlated with M sum for juncos and nearly so (P = 0.054) for sparrows. Mass-specific and total pectoralis CS activities were significantly positively correlated with M sum for sparrows, but not for juncos. Thus, myocyte metabolic intensity influences M sum variation in house sparrows, although the stronger correlation of total (r = 0.495) than mass-specific (r = 0.378) CS activity with M sum suggests that both pectoralis mass and metabolic intensity impact M sum. In contrast, neither skeletal muscle masses nor pectoralis metabolic intensity varied with M sum in juncos. However, heart mass was associated with M sum variation in both species. These data suggest that drivers of metabolic flexibility are not uniform among bird species.
Improved winter cold-tolerance is widespread among small birds from temperate climates and is usu... more Improved winter cold-tolerance is widespread among small birds from temperate climates and is usually associated with improved shivering endurance and elevated peak metabolic rate (Msum), although precise mechanisms of acclimatization are incompletely understood. Elevated Msum and improved cold-tolerance may be associated with greater metabolic intensity of thermogenic tissues, due to mass-specific increases in oxidative enzyme capacity, or to increases in the masses of metabolically active tissues. To examine mechanisms underlying winter increases in Msum, we captured wild, free-living individuals of three resident passerine species, White-breasted Nuthatch (Sitta carolinensis), Black-capped Chickadee (Poecile atricapillus), and House Sparrow (Passer domesticus). Each of these three species shows large seasonal variations in Msum, in excess of 35%. We investigated seasonal changes in the pectoralis and supracoracoideus muscles of mass-specific and total activities of key enzymes in...
Pine-juniper-shrub habitat with a shrubby understory of skunkbush sumac (Rhus aromatica) and moun... more Pine-juniper-shrub habitat with a shrubby understory of skunkbush sumac (Rhus aromatica) and mountain-mahogany (Cercocarpus montanus) and interspersed or adjacent Rocky Mountain juniper (Juniperus scopulorum) and ponderosa pine (Pinus ponderosa) is restricted in South Dakota to small areas in Custer and Fall River Counties in the southwestern Black Hills. These habitats have received very little ornithological investigation. We used fixed-width (25 m) line transect censuses and mist net sampling during the breeding season (25 May-9 July 1998) to document the abundance and breeding condition of birds in this habitat. Line transects yielded an overall raw density estimate of 411.7 birds km -2 and a mean (±SD) relative abundance (birds per kilometerlong transect) of 56.9 ± 12.8 birds/transect. Overall abundance increased significantly (P<0.01) over the study period from 43.7 birds/transect in late May to 68.2 birds/transect in early July. This probably results both from the recruitm...
Great-tailed grackles (Quiscalus mexicanus) formerly were present in North America only in southe... more Great-tailed grackles (Quiscalus mexicanus) formerly were present in North America only in southern Texas, but they have been expanding their range, primarily to the north and west, throughout the past century. Reports of this species have recently proliferated in the north central United States. Here we review the current status of the great-tailed grackle in South Dakota and report the first documented nesting of this species in the state. The first documented record of great-tailed grackle in South Dakota was a male that occurred on 14-15 May 1988 in Yankton County. No additional records of this species were documented for South Dakota until 1995, when birds from Charles Mix (6 April) and Clay (24 May-1 June) Counties were reported. Since that time, records of great-tailed grackles in South Dakota have occurred as far north as Brown and Deuel Counties and as far west as Lyman County, but no nests were documented until 1999. In 1999, we found three nests in a marsh lined with catt...
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Papers by David Swanson