Baird's Sparrow Research Articles

Integrating counts from rigorous surveys and participatory science to better understand spatiotemporal variation in population processes

Abstract Knowledge of variation in population processes (e.g. population growth) across broad spatiotemporal scales is fundamental to population ecology and critical for conservation decision‐making. Count data from rigorous surveys (e.g. surveys with probabilistic sampling design and distance sampling information) can inform population processes but are often limited in space and time. Participatory science data cover broader spatiotemporal extents but are prone to bias due to limited to no sampling design and lack of distance sampling information, hindering their capability of informing population processes. Here, we developed an integrated dynamic N‐mixture model that jointly analyses rigorous survey and participatory science data to inform population growth at broad spatiotemporal extents. The model contains a flexible scaling parameter that allows fixed and random effects to account for biases and errors in participatory science data. We conducted simulations to evaluate the inference performance of this model across a broad range of spatial and temporal overlap between rigorous survey and participatory science data. We also conducted a case study of Baird's Sparrow (Centronyx bairdii), a species of conservation concern, to illustrate the application of the integrated model with rigorous survey data from the Integrated Monitoring in Bird Conservation Regions programme and participatory science North American Breeding Bird Survey and eBird data. Simulations showed that the integrated model improved precision without biasing parameter estimates, in comparison with a model informed by rigorous survey data alone. The case study further demonstrated the utility of the integrated model for quantifying range‐wide, long‐term population processes and environmental drivers despite limited spatiotemporal extent of rigorous survey data. In particular, we found that population growth rate peaked under medium temperature, which were only apparent in the integrated model. The integrated model developed in this study is useful for understanding wildlife population processes at broad spatiotemporal scales with count data. The flexible structure of this model, in particular the scaling parameter, makes it highly adaptable to a broad range of ecological systems and survey procedures. These properties make this modelling approach highly relevant for both population ecology and conservation practice.

Nesting ecology and reproductive success of mixed-grass prairie songbirds

Vast areas of North American grasslands have been lost and degraded, resulting in unprecedented declines of biodiversity. For example, 82% of North American grassland songbird species are experiencing population declines. Basic natural history, life history, and demographic data from different regions and time periods are essential for modeling population dynamics and developing effective conservation strategies for grassland birds. We monitored 392 nests to provide information on nesting biology, quantify reproductive success, and gain insight into the extent to which predation and weather influence nest survival of 7 grassland songbird species in southwest Saskatchewan, during 2010 and 2011. Clutch sizes of all species were within the range reported previously and declined as the breeding season progressed, particularly for Chestnut-collared Longspur (Calcarius ornatus), Vesper (Pooecetes gramineus) and Baird's (Centronyx bairdii) sparrows, and Western Meadowlark (Sturnella neglecta). Overall, 32–69% of the nests we monitored were depredated, and predation accounted for 91% of all unsuccessful nesting attempts. Daily survival rates were lowest during the nestling stage for 5 species, and nest survival estimates ranged from 16% to 48%. Nest survival of 4 species was influenced by the temporal effects of age and date. Chestnut-collared Longspur and Western Meadowlark nest survival increased through early to mid-incubation and declined thereafter until ∼3 d prior to fledging before increasing again. Nest survival of these 2 species, along with Sprague's Pipit (Anthus spragueii) and Vesper Sparrow, were lowest in late June to early July. We found no support for a strong effect of precipitation on nest survival. However, nest survival rates declined with increasing ambient temperature for Chestnut-collared Longspur and Horned Lark (Eremophila alpestris), the 2 study species with the most exposed nests, and were highest for Western Meadowlark nests when ambient temperatures were between 15 and 24 °C.

Nesting ecology and reproductive success of mixed-grass prairie songbirds

Vast areas of North American grasslands have been lost and degraded, resulting in unprecedented declines of biodiversity. For example, 82% of North American grassland songbird species are experiencing population declines. Basic natural history, life history, and demographic data from different regions and time periods are essential for modeling population dynamics and developing effective conservation strategies for grassland birds. We monitored 392 nests to provide information on nesting biology, quantify reproductive success, and gain insight into the extent to which predation and weather influence nest survival of 7 grassland songbird species in southwest Saskatchewan, during 2010 and 2011. Clutch sizes of all species were within the range reported previously and declined as the breeding season progressed, particularly for Chestnut-collared Longspur (Calcarius ornatus), Vesper (Pooecetes gramineus) and Baird's (Centronyx bairdii) sparrows, and Western Meadowlark (Sturnella neglecta). Overall, 32–69% of the nests we monitored were depredated, and predation accounted for 91% of all unsuccessful nesting attempts. Daily survival rates were lowest during the nestling stage for 5 species, and nest survival estimates ranged from 16% to 48%. Nest survival of 4 species was influenced by the temporal effects of age and date. Chestnut-collared Longspur and Western Meadowlark nest survival increased through early to mid-incubation and declined thereafter until ∼3 d prior to fledging before increasing again. Nest survival of these 2 species, along with Sprague's Pipit (Anthus spragueii) and Vesper Sparrow, were lowest in late June to early July. We found no support for a strong effect of precipitation on nest survival. However, nest survival rates declined with increasing ambient temperature for Chestnut-collared Longspur and Horned Lark (Eremophila alpestris), the 2 study species with the most exposed nests, and were highest for Western Meadowlark nests when ambient temperatures were between 15 and 24 °C.

Conservation of Sage‐grouse Critical Habitat and Implications for Prairie Songbirds

ABSTRACTA popular approach for conserving multiple organisms in a given region is to identify one or more umbrella species. Identifying and managing for species that have a high degree of overlap in their habitat requirements with a broader suite of organisms is expected to enhance the effectiveness of conservation actions when resources are limited. The greater sage‐grouse (Centrocercus urophasianus) has received considerable attention as a potential umbrella species for shrub‐steppe flora and fauna in the core of its range. However, the extent to which conserving sage‐grouse habitat benefits mixed‐grass prairie songbirds in the northern portion of its range is unclear. We compared abundance of grassland songbirds within grasslands designated as sage‐grouse critical habitat by the Canadian federal government, and within a 1.6‐km buffer of adjacent habitat in southwestern Saskatchewan, Canada in 2016 and 2017. We also quantified relationships between bird abundance and gradients of vegetation structure. Lark bunting (Calamospiza melanocorys) abundance was 3 times greater within sage‐grouse critical habitat, whereas chestnut‐collared longspur (Calcarius ornatus), Baird's sparrow (Centronyx bairdii), and Sprague's pipit (Anthus spragueii) abundance was 1.6–1.8 times greater outside of these areas. The abundance of grassland specialists was negatively associated with total shrub and silver sagebrush (Artemisia cana) cover, both of which characterize sage‐grouse critical habitat in Canada at both landscape and local scales. Furthermore, characteristics of vegetation structure associated with grassland generalists overlapped with characteristics of vegetation structure that defined greater sage‐grouse critical habitat. Conservation of greater sage‐grouse critical habitat in Canada is likely to have a positive influence on shrub‐dependent or shrub‐tolerant species, such as lark bunting. The conservation of open, native grasslands within greater sage‐grouse critical habitat could benefit grassland specialists, however, any changes in the current management that increases the cover of exotic species, silver sagebrush, and other shrubs will negatively affect grassland specialists. We recommend that protection and management activities be targeted towards greater sage‐grouse, Sprague's pipit, and chestnut‐collared longspur to maximize the conservation of mixed‐grass prairie songbirds and minimize the number of focal umbrella species required. © 2021 The Wildlife Society.

DIFERENCIACIÓN DEL SEXO DEL GORRIÓN DE BAIRD (Centronyx bairdii) POR MEDIO DE REDES NEURONALES ARTIFICIALES Y DATOS MORFOMÉTRICOS

Las estimaciones indican que 148 especies de aves en Norteamérica enfrentan amenaza alta o severa, pues sus poblaciones están disminuyendo. El gorrión de Baird (Centronyx bairdii) es una de las especies con declive poblacional, presenta plumaje monomórfico y su sexo no se puede determinar a simple vista. La determinación del sexo de las aves permite conocer su comportamiento social y proporción en la dinámica de sus poblaciones. Un método de clasificación es el de redes neuronales artificiales y se ha utilizado en diversos campos, como la clasificación de plantas y semillas y la diferenciación de especies productoras de madera. En el ámbito de la ornitología se ha utilizado poco. Por lo tanto, el objetivo de este estudio fue desarrollar una red neuronal artificial para diferenciar el sexo de los gorriones de la especie Centronyx bairdii, con datos zoométricos obtenidos en campo. La hipótesis fue que las redes neuronales artificiales pueden predecir el sexo de las aves de la especie Centronyx bairdii. La red neuronal construida a partir de los datos de peso, cuerda alar, longitud de cola, culmen, ancho del pico y profundidad del pico de 111 aves, permitió diferenciar el sexo de la especie con grado de certeza de 92.3%.

Habitat Targets for Imperiled Grassland Birds in Northern Mixed-Grass Prairie

Grassland bird populations are declining faster than any other avian guild in North America, and promotion of favorable habitat conditions in rangeland breeding cores is important for their maintenance. There is much information on associations between breeding grassland songbirds and vegetation attributes. However, previous results have been difficult to translate into management practices due to mismatch between the scale and metrics used in biological sampling and those used in management. Here, we evaluate the response of imperiled grassland bird species to vegetation conditions using metrics and scales accessible to managers. We focus on four species that are experiencing particularly severe population declines: Baird's sparrow (Centronyx bairdii), chestnut-collared longspur (Calcarius ornatus), McCown's longspur (Rynchophanes mccownii), and Sprague's pipit (Anthus spragueii). In 2017 and 2018, we evaluated the abundances of these species within their core distributions in northern Montana. We used temporally replicated point-counts and hierarchical models to estimate abundance and associations with plot-level (9-ha) vegetation conditions while accounting for spatially and temporally variable detectability. Exotic grass encroachment and shrub cover had negative or neutral effects on all species. Birds responded strongly to biomass at this scale, with chestnut-collared longspurs and Sprague's pipit preferring a range of 1 100 kg ha−1 to 1 400 kg ha−1, and McCown's longspurs selecting for the lowest available. Residual grass and litter cover were important for Baird's sparrows. Variable results among species emphasize the need for heterogeneity in vegetation structure and composition at scales larger than the plot. Our results provide guidance for managers interested in improving habitat for these species.

Southward breeding range expansion of the Baird's Sparrow.

Southward breeding range expansion of the Baird's Sparrow.

Fall vegetative cover and summer precipitation predict abundance of wintering grassland birds across the Chihuahuan desert

Local winter abundance of grassland passerines is highly variable throughout the Chihuahuan Desert among years. The objective of this study is to determine if plant biomass in grasslands and precipitation are predictors of bird abundance in space and time through Chihuahuan Desert. We conducted avian surveys in 17 Grassland Priority Conservation Areas (GPCA) in northern Mexico and southwestern United States in the winters of 2007–2011. We used distance sampling on line transects to estimate annual winter bird density in all GPCAs. We used a hierarchical model of distance sampling to estimate the effect of summer precipitation and vegetative cover during the fall on bird density for 10 grassland species. We used the MODIS NDVI at a pixel resolution of 231.5 m as a measure of plant biomass. Grasshopper Sparrow, Baird's Sparrow, Savannah Sparrow, Vesper Sparrow, and Eastern Meadowlark showed a strict positive response to NDVI, while Horned Lark, Sprague's Pipit, Chestnut-collared Longspur and Lark Bunting did not show a strictly-positive response to NDVI. Our results provide a valuable tool for the conservation of declining migratory birds on their wintering grounds by identifying a wildlife-habitat relationship using a remotely-sensed and readily available index of vegetative growth.

Effects of conventional oil wells on grassland songbird abundance are caused by presence of infrastructure, not noise

Understanding the mechanisms that explain why oil infrastructure has an effect on wildlife, and comparing effects of different types of infrastructure, is necessary for determining how we may minimize or mitigate those effects. We compared the abundances of five grassland songbird species at oil well sites with different pump mechanisms and power sources, and determined the effects of exotic vegetation, perch sites, and road densities. We compared effects of wells that were active with effects of wells that were turned off to evaluate whether effects of wells were caused by noise or human activity at wells. We conducted 800-m abundance transects at 42 sites twice per year in 2013 and 2014 in Alberta, Canada. Two species at risk, Baird's sparrows (Ammodramus bairdii) and Sprague's pipits (Anthus spragueii), had significantly lower abundances at all sites that contained oil infrastructure. However, there was little evidence that noise, human activity, or traffic explained these effects. Effects of active and inactive wells were the same, and grid-powered wells had a greater effect than did generator-powered wells, although generator-powered wells are louder. Our research suggests that reducing noise, human activity or traffic would not reduce the effects of wells on grassland songbirds, and, therefore, mitigation must focus on minimizing the extent of above-ground infrastructure.

Molecular analysis of stomach contents reveals important grass seeds in the winter diet of Baird's and Grasshopper sparrows, two declining grassland bird species.

We analyzed the diet of Baird’s Sparrow (Ammodramus bairdii) and Grasshopper Sparrow (A. savannarum) in three different sites and sampling periods across the Chihuahuan Desert in northern Mexico. DNA from seeds in regurgitated stomach contents was sequenced using NGS technology and identified with a barcoding approach using the P6 loop of the trnL intron as genetic marker. During each sampling period, we collected random soil samples to estimate seed availability in the soil seed bank. Due to the variability and size of the genetic marker, the resolution was limited to a family level resolution for taxonomic classification of seeds, but in several cases a genus level was achieved. Diets contained a high diversity of seeds but were dominated by a limited number of genera/families. Seeds from Panicoideae (from the genera Panicum, Setaria, Eriochloa, Botriochloa, and Hackelochloa) contributed for the largest part to the diets (53 ± 19%), followed by Bouteloua (10 ± 12%). Depending on the site and sampling period, other important seeds in the diets were Eragrostideae, Pleuraphis, Asteraceae, Verbena, and Amaranthus. The most abundant seeds were not always preferred. Aristida and Chloris were common in the soil seed bank but these seeds were avoided by both bird species. Baird’s and Grasshopper sparrows did not differ in seed preferences. This work highlights the importance of range management practices that favor seed production of Panicoideae and Bouteloua grasses to enhance winter habitat use and survival of Baird’s and Grasshopper sparrows in the Chihuahuan Desert.

Winter survival of North American grassland birds is driven by weather and grassland condition in the Chihuahuan Desert

Populations of grassland birds that overwinter in the Chihuahuan Desert are declining more rapidly than other grassland birds, and survival during the non-breeding season may have a strong influence on population trends of these species. Habitat loss and deterioration due to desertification may be contributing to these declines, and the winter ecology of grassland birds under these changing environmental conditions remains relatively unexplored. To fill this information gap, we estimated the survival of two grassland-obligate sparrows, Baird's Sparrows (Ammodramus bairdii) and Grasshopper Sparrows (A. savannarum), on their wintering grounds in the Chihuahuan Desert, and investigated the role of habitat structure and weather on survival rates. We deployed radio-transmitters on Baird's (N = 49) and Grasshopper (N = 126) sparrows near Janos, Chihuahua, and tracked birds from November to March during the winters of 2012–2013 and 2013–2014. Causes of mortality included avian predators, mammals, and possibly weather. We estimated an overall weekly winter survival probability of ŝ = 92.73% (95% CI[s] = 88.63–95.44%) for Baird's Sparrows in 2012–2013. We estimated a weekly winter survival probability of ŝ = 93.48% (95% CI[s] = 90.29–96.67%) and ŝ = 98.78% (95% CI[s] = 97.88–99.68%) for Grasshopper Sparrow in 2012–2013 and 2013–2014, respectively. Weekly winter survival was lower with colder daily minimum temperatures for both species and in areas with taller shrubs for Grasshopper Sparrows, with the shrubs potentially increasing predation risk by providing perches for Loggerhead Shrikes (Lanius ludovicianus). Our results highlight the need to maintain healthy grass structure in wintering areas to provide birds with food, protection from predators, and adequate cover from inclement weather. Our results also demonstrate that the presence of shrubs can lower winter survival, and suggest that shrub encroachment into the winter habitat of these sparrows may be an important driver of their population declines. Shrub removal could increase survival of wintering sparrows in the Chihuahuan Desert by reducing availability of perches for avian predators, thus reducing predation risk.

Using the North American Breeding Bird Survey to assess broad-scale response of the continent's most imperiled avian community, grassland birds, to weather variability

ABSTRACT Avian populations can respond dramatically to extreme weather such as droughts and heat waves, yet patterns of response to weather at broad scales remain largely unknown. Our goal was to evaluate annual variation in abundance of 14 grassland bird species breeding in the northern mixed-grass prairie in relation to annual variation in precipitation and temperature. We modeled avian abundance during the breeding season using North American Breeding Bird Survey (BBS) data for the U.S. Badlands and Prairies Bird Conservation Region (BCR 17) from 1980 to 2012. We used hierarchical Bayesian methods to fit models and estimate the candidate weather parameters standardized precipitation index (SPI) and standardized temperature index (STI) for the same year and the previous year. Upland Sandpiper (Bartramia longicauda) responded positively to within-year STI (β = 0.101), and Baird's Sparrow (Ammodramus bairdii) responded negatively to within-year STI (β = −0.161) and positively to within-year SPI (β = 0.195...

Oil and natural gas development has mixed effects on the density and reproductive success of grassland songbirds

Oil and natural gas development has increased dramatically in native grasslands over the past 25 years. Some grassland songbirds are less abundant in areas with oil and gas development, but the effects vary among species and geographically within a species' range. The reproductive consequences of nesting in areas with oil and gas development are unknown. We assessed how the density and reproductive success of five species of grassland songbird in Alberta, Canada, varied with distance to oil and gas wells, gravel roads, and trails, and cover of crested wheatgrass (Agropyron cristatum), an aggressive alien plant that often becomes established following anthropogenic disturbance. Crested wheatgrass cover had the greatest impact on the grassland songbird community. Sprague's Pipit (Anthus spragueii) nest survival decreased as the amount of crested wheatgrass increased. As crested wheatgrass cover increased from 0% to 60%, density of Savannah Sparrows (Passerculus sandwichensis) declined by 50%, but they fledged 25% more young from successful nests. Density of Savannah Sparrows was twice as high near wells, and fledging success was 40% higher compared with 700 m away. Distance to gravel roads did not influence the density or reproductive success of any species. Sprague's Pipits and Baird's Sparrows (Ammodramus bairdii) avoided nesting within 100 m of trails, and both species fledged fewer young from successful nests near trails. In contrast, Vesper Sparrows (Pooecetes gramineus) nested close to trails and fledged more young from successful nests near trails. Western Meadowlarks (Sturnella neglecta) were not strongly affected by any variable. Brown-headed Cowbird (Molothrus ater) abundance was three times higher in study plots with wells, although we detected no associated increase in brood parasitism. Our results indicate that the introduction and spread of crested wheatgrass and the creation of access trails to well pads have negative reproductive consequences for primary endemic species such as Sprague's Pipit and Baird's Sparrow, although these results do not extend to other grassland birds. The spread of crested wheatgrass and the disturbance of access trails could be reduced by directional drilling of multiple wells from a single well pad.

Nesting ecology of grassland songbirds: effects of predation, parasitism, and weather

Understanding the breeding ecology of grassland birds is vital for understanding the mechanisms underlying their widespread population declines. We describe the breeding biology of Sprague's Pipit (Anthus spragueii), Vesper Sparrow (Pooecetes gramineus), Savannah Sparrow (Passerculus sandwichensis), Baird's Sparrow (Ammodramus bairdii), and Western Meadowlark (Sturnella neglecta) and quantify the effects of nest predation, brood parasitism, and weather on the nest survival of these species in southeastern Alberta. Nest predation was the primary cause of nest failure, accounting for 75% of all nest losses. Daily survival rates were higher during incubation than the nestling stage for the three sparrow species, and nest survival of Baird's Sparrows was highest at intermediate temperatures. For all five species, clutch size, hatching success, and fledging success were within the range of values previously reported for these species in other parts of their range. Brown-headed Cowbirds parasitized nests of all species except Sprague's Pipit, with 4–11% of nests containing cowbird eggs. Savannah Sparrow experienced the highest frequency of brood parasitism and was the only species to successfully fledge cowbird young. Parasitized nests of Savannah Sparrows had reduced clutch size and hatching success, and fledged fewer young compared to non-parasitized nests. The overall cost of parasitism to Savannah Sparrows was at least 1.7 young per successful nest.

Grassland songbirds exhibit variable responses to the proximity and density of natural gas wells

Cultivation of native prairie was likely the primary cause of historical declines of grassland bird populations in North America, but the increase in natural gas development may be exacerbating those declines through habitat loss and degradation. We quantified the abundance of grassland songbirds and vegetation structure across a gradient of natural gas well densities to determine the extent to which density and proximity of gas wells influence songbird abundance. In 2008 and 2009, we conducted 1,258 point counts on 105 native grassland parcels (1.6 km2/parcel) at varying distances from natural gas wells and with varying gas well densities (0–25 per 1.6 km2). We found that vegetation structure influenced bird abundance more strongly than natural gas well proximity or density for all but 1 species and that the response of grassland songbirds to natural gas well density and proximity varied among species and regions. Sprague's pipit (Anthus spragueii) and Baird's sparrow (Ammodramus bairdii) abundance was not influenced by natural gas well proximity or density. Grasshopper sparrow (Ammodramus savannarum), McCown's longspur (Rhynchophanes mccownii), and chestnut-collared longspur (Calcarius ornatus) abundance was lower near gas wells, but both longspur species were also more abundant in areas with greater densities of gas wells. Horned lark (Eremophilus alpestris) abundance increased with well density in our northern study site. Savannah sparrow (Passerculus sandwichensis) abundance was higher near gas wells, but only in areas where well density was ≤9 wells/1.6 km2. We suggest that land managers and industry implement remediation activities that encourage vegetative re-growth, thus reducing the potential interactive relationship between natural gas development and changes in vegetation structure. © 2014 The Wildlife Society.

Off-road sampling reveals a different grassland bird community than roadside sampling: implications for survey design and estimates to guide conservation

Grassland bird species continue to decline steeply across North America. Road-based surveys such as the North American Breeding Bird Survey (BBS) are often used to estimate trends and population sizes and to build species distribution models for grassland birds, although roadside survey counts may introduce bias in estimates because of differences in habitats along roadsides and in off-road surveys. We tested for differences in land cover composition and in the avian community on 21 roadside-based survey routes and in an equal number of adjacent off-road walking routes in the grasslands of southern Alberta, Canada. Off-road routes (n = 225 point counts) had more native grassland and short shrubs and less fallow land and road area than the roadside routes (n = 225 point counts). Consequently, 17 of the 39 bird species differed between the two route types in frequency of occurrence and relative abundance, measured using an indicator species analysis. Six species, including five obligate grassland species, were more prevalent at off-road sites; they included four species listed under the Canadian federal Species At Risk Act or listed by the Committee on the Status of Endangered Wildlife in Canada: Sprague's Pipit (Anthus spragueii), Baird's Sparrow (Ammodramus bairdii), the Chestnut-collared Longspur (Calcarius ornatus), and McCown's Longspur (Rhynchophanes mccownii). The six species were as much as four times more abundant on off-road sites. Species more prevalent along roadside routes included common species and those typical of farmland and other human-modified habitats, e.g., the European Starling (Sturnus vulgaris), the Black-billed Magpie (Pica hudsonia), and the House Sparrow (Passer domesticus). Differences in avian community composition between roadside and off-road surveys suggest that the use of BBS data when generating population estimates or distribution models may overestimate certain common species and underestimate others of conservation concern. Our results highlight the need to develop appropriate corrections for bias in estimates derived from roadside sampling, and the need to design surveys that sample bird communities across a more representative cross-section of the landscape, both near and far from roads.

Songbird abundance in native and planted grassland varies with type and amount of grassland in the surrounding landscape

Agriculture and wildlife conservation programs have converted vast amounts of cropland into grasslands planted with exotic species. Understanding how landscape context influences avian use of native and planted grasslands is essential for developing effective conservation strategies in agricultural landscapes. Our primary objective was to determine the extent to which the amount and type of grassland in the surrounding landscape influences the abundance of grassland songbird species on native and planted grassland parcels in southern Saskatchewan and Alberta, Canada. Bird abundance was more strongly influenced by the amount and type of grassland within 400 m of breeding parcels than at larger spatial scales. Grassland specialists responded similarly to habitat and landscape type over both years and provinces. Sprague's pipit (Anthus spragueii) and Baird's sparrow (Ammodramus bairdii) were most common in native grassland parcels surrounded by native grassland and were more likely to occur in planted grasslands surrounded by native grassland. Bobolinks (Dolichonyx oryzivorus) were most common in planted grassland parcels, but their abundance increased with the amount of native grassland surrounding these parcels. Our findings indicate that the suitability of planted grasslands for these species is influenced by their proximity to native grassland. Grassland generalists showed mixed responses to habitat and landscape type over the 2 years (Le Conte's sparrow (Ammodramus leconteii)) and between provinces (Savannah sparrow (Passerculus sand- wichensis) and western meadowlark (Sturnella neglecta)). Management to benefit grassland specialists should therefore consider the landscape context when seeding cultivated land to non-native grassland and conserve extant native grassland. 2013 The Wildlife Society.

Territory Size in Mixed-grass Prairie Songbirds

I estimated breeding territory size in mixed-grass prairie songbirds, and explored how it varied among bird species, time-of-season, and year. The study was conducted at Bowdoin National Wildlife Refuge in north-central Montana during 2007-2009. Across all species, months and years, mean breeding territory size was estimated at 0.43 ha (SE = 0.03, n = 129). Estimates were nearly identical across study species: Sprague's Pipits (Anthus spragueii), Grasshopper (Ammodramus savannarum), and Baird's (A. bairdii) sparrows. There was no significant variation in territory size across months, suggesting little to no dependence on nest phase. In contrast, I found significant variation in territory size among years (P = 0.034), that did not interact meaningfully with species (R2 = 0.02, P = 0.603). This suggests that factors that vary annually appear to be affecting all bird species in a similar manner, which could be related to differences in vegetation structure and/or site quality (perhaps as a function of weather) or less likely, variation in population density.

Reproductive Biology of a Grassland Songbird Community in Northcentral Montana

Abstract Successful conservation of grassland bird populations requires basic information on their breeding biology; in particular, information from undisturbed native prairie over an extended period of time. We present data collected at Bowdoin National Wildlife Refuge in northcentral Montana on the reproductive biology of six grassland bird species that breed in mixed-grass prairie: Sprague's Pipit (Anthus spragueii), Savannah (Passerculus sandwichensis), Grasshopper (Ammodramus savannarum), and Baird's (A. bairdii) sparrows, Chestnut-collared Longspur (Calcarius ornatus), and Western Meadowlark (Sturnella neglecta). Basic measures of reproductive biology are presented, including estimates of nest density, phenology, fecundity, parasitism rates, and nest success, and how these and other characteristics varied across years. Nests (n = 1,494) of the six focal species accounted for 98% of all passerine nests found during 1997–2007; Chestnut-collared Longspurs (51%) were the dominant breeding species. Tot...

Factors Associated with Arrival Densities of Grasshopper Sparrow (Ammodramus savannarum) and Baird's Sparrow (A. bairdii) in the Upper Great Plains

ABSTRACT. Although critical to habitat and population management, the proximate cues that birds use to establish territories are largely unknown. Understanding these cues is important for birds, such as many grassland birds, that exhibit high annual variability in population density and make new habitat-selection decisions annually. Identifying the actual cues used is difficult in the field, but the factors associated with the arrival densities of birds can help uncover variables that are involved in or correlated with cues used for selection. During the summers of 2002–2004, we investigated how weather and local vegetation factors were related to arrival densities of Grasshopper Sparrows (Ammodramus savannarum) and Baird's Sparrows (A. bairdii) at three locations across North Dakota and Saskatchewan. Spring densities of Grasshopper Sparrows were positively correlated with concurrent May precipitation, whereas densities of Baird's Sparrows were negatively correlated with the previous winter's snowfall. We...