Grassland Bird Species Research Articles

Cost, risk, landscape context, and potential treatments vary with biological value for conservation of declining grassland birds

AbstractSpatially explicit models are an important component of systematic conservation planning, enabling the depiction of biodiversity metrics across landscapes and objective evaluation of candidate sites for conservation delivery. However, sites considered “best” for conservation are typically viewed from the standpoint of biological value and may not be the most effective or efficient when risk of habitat loss, cost of conservation, intended conservation treatments, and overall conservation strategy are considered. We evaluated risk of habitat loss, land cost, and landscape context for geographic areas harboring most‐dense to least‐dense population quartiles for 16 species of grassland birds in the US northern Great Plains. Differences in land cost, risk of grassland conversion, and landscape context among quartiles and species indicated that a minimum‐area strategy may be inefficient and even ineffective. Priority zones for western species were generally associated with lower agricultural land cost, more protected land, and landscape characteristics associated with intact grasslands; eastern species were generally associated with higher agricultural land cost, tillage probability, grass loss, cropland, development, forest, Conservation Reserve Program grasslands, and distance to grass. Our results indicate that addressing areas outside of population cores increases conservation options and may provide substantial benefits to portions of populations that are most vulnerable to habitat loss or other stressors.

The LTAR Grazing Land Common Experiment at the Central Plains Experimental Range: Collaborative adaptive rangeland management.

Semiarid rangelands throughout the western Great Plains support livestock production and many other ecosystem services. The degree to which adaptive multi-paddock (AMP) grazing management approaches can help achieve desired ecosystem services remains unclear. At the Central Plains Experimental Range in northeastern Colorado, a management-science partnership with a diverse stakeholder group is comparing collaborative adaptive rangeland management (CARM), designed to incorporate AMP principles, to traditional rangeland management (TRM), consisting of season-long grazing during the growing season. Each treatment was implemented on a set of 10, 130-ha pastures paired by soils, topography, and plant communities to evaluate how CARM affects vegetation (composition and production), livestock production (steer weight gain), and wildlife habitat (vegetation structure for grassland birds). For the first 5 years of the experiment, CARM cattle were managed as a single herd using AMP grazing with planned year-long rest in 20% of the pastures. Relative to TRM, CARM enhanced heterogeneity in vegetation structure across the landscape, benefiting two grassland bird species. However, this came at the cost of 12%-16% lower steer weight gains in CARM versus TRM and declining populations of a third bird species of conservation concern in both treatments. Here we discuss how increased understanding of ecological and social processes during the experiment's first 5 years led to changes in the CARM treatment and management objectives during the next 5 years. We also discuss how innovations in remote sensing, environmental sensors, ecosystem modeling, social learning, and economic analyses are being integrated into and supported by the CARM experiment.

Conservation of Threatened Grassland Birds in the Mediterranean Region: Going up or Giving Up?

Grassland bird populations in the Mediterranean lowlands have declined dramatically over the past few decades. This decline is due to a combination of factors, including changes in land use and farming practices as well as the impacts of climate change. In particular, more intensive agricultural methods have played a significant role in this reduction. However, in the higher-altitude uplands of the region, traditional practices like pastoralism and rotational low-intensity farming are still common, and these areas continue to support substantial populations of several threatened grassland bird species. In this viewpoint, we discuss the challenges that the uplands are facing and suggest rethinking regional development to better balance the needs of people and nature.

Traditional paddy field-supported bird diversity ignored by forest-focused protection of ecosystems in tropical China.

Biodiversity in tropical regions is facing threats from agricultural expansion and intensification. Therefore, a promising future for local ecosystem conservation depends not only on traditional protected areas but also on well-managed agricultural landscapes. In this study, we compared the ecological traits of bird species in paddy fields outside of protected areas and natural forests within the protected areas of Xishuangbanna, southern China. There were 148 species in total, of which 98 were in forests and 55 in paddy fields. The abundance of birds in paddy fields was 176 per kilometer, which was much higher than the 60 per kilometer in forests. There were 26 law-protected species observed, half of which were found in each habitat. The main functional groups living in nature reserves are invertivores and frugivores, whereas paddy fields provide habitats for aquatic predator and granivore bird species. Our results indicate that paddy fields act as a refuge for wetland and grassland bird species when natural wetlands disappear, highlighting the urgent need to focus more on wetland protection and eco-friendly agricultural schemes at the landscape scale in future conservation policies.

Evaluation of an autonomous acoustic surveying technique for grassland bird communities in Nebraska.

Monitoring trends in wildlife communities is integral to making informed land management decisions and applying conservation strategies. Birds inhabit most niches in every environment and because of this they are widely accepted as an indicator species for environmental health. Traditionally, point counts are the common method to survey bird populations, however, passive acoustic monitoring approaches using autonomous recording units have been shown to be cost-effective alternatives to point count surveys. Advancements in automatic acoustic classification technologies, such as BirdNET, can aid in these efforts by quickly processing large volumes of acoustic recordings to identify bird species. While the utility of BirdNET has been demonstrated in several applications, there is little understanding of its effectiveness in surveying declining grassland birds. We conducted a study to evaluate the performance of BirdNET to survey grassland bird communities in Nebraska by comparing this automated approach to point count surveys. We deployed ten autonomous recording units from March through September 2022: five recorders in row-crop fields and five recorders in perennial grassland fields. During this study period, we visited each site three times to conduct point count surveys. We compared focal grassland bird species richness between point count surveys and the autonomous recording units at two different temporal scales and at six different confidence thresholds. Total species richness (focal and non-focal) for both methods was also compared at five different confidence thresholds using species accumulation curves. The results from this study demonstrate the usefulness of BirdNET at estimating long-term grassland bird species richness at default confidence scores, however, obtaining accurate abundance estimates for uncommon bird species may require validation with traditional methods.

The Influence of Grazing Systems on Bird Species Richness and Density in the Nebraska Sandhills

Grazing is the de facto method of habitat management used in much of the Nebraska Sandhills. Ranchers use a variety of grazing systems, and our goal was to evaluate the effects of systems on grassland birds. We estimated the species richness and density of grassland birds for three grazing systems used on private ranches: long, medium, and short duration grazing systems. We observed sixty species, and the grazing system with pastures utilizing long duration grazing periods had the highest estimates of species richness as well as the most heterogeneous habitat structure. Differences in species richness among systems were most pronounced in years of limited precipitation. Together, grasshopper sparrows (Ammodramus savannarum), western meadowlarks (Sturnella neglecta), and brown-headed cowbirds (Molothrus ater) accounted for 72% of our observations. We used a model comparison approach to determine the effects of habitat on the densities of six species. Densities of grasshopper sparrows and mourning doves showed effects of the grazing system. More species had higher densities in short duration, rotational systems than other grazing systems. However, species of grassland birds showed responses to a variety of cover types and habitat structures depending on life history needs. Regardless of the grazing system used, managers can use grazing and other tools such as prescribed burning to maintain habitat heterogeneity to support diverse bird communities.

Managing Grass Height for Birds and Livestock: Insights from the Río de la Plata Grasslands

Success in conserving biodiversity in rangelands depends on effectively managing the systems to achieve positive economic outcomes while preserving biodiversity. In the native grasslands of the Río de la Plata region, livestock production often falls below its potential due to low forage availability. Cattle management strategies that promote taller grass height can increase forage mass without replacing native vegetation, enhancing cattle dry matter intake and potentially boosting production. Nonetheless, the impact of such changes on grassland bird populations remains unclear. In this study, we implemented management changes to increase grass height across six ranches and evaluated the responses of grassland bird specialists. Initially, the average grass height was 6 cm, but after the management changes, it increased to an average of 12 cm. This also increased grass heterogeneity, which is desirable for supporting a higher richness of grassland birds. We found that both the abundances of individual grassland bird species and richness did not vary after the management changes. Moreover, threatened grassland bird species that rely strictly on taller grasses did not colonize the paddocks following the alterations. Therefore, we conclude that maintaining the abundance of seven grassland bird specialists and potentially increasing livestock production is feasible, as the attained grass height coincided with levels known to maximize cattle dry matter intake rate. However, achieved average grass height was not sufficiently tall to support endangered tall grass specialists. It is possible that longer time frames allow tussocks to grow taller and provide such habitat conditions. Most previous research on rangelands biodiversity has focused on assessing faunal responses in either ungrazed or heavily grazed areas. Therefore, our findings contribute to a better understanding of faunal responses within this spectrum and align with a win-win production-conservation approach, which can aid in safeguarding biodiversity across large geographic scales.

Climate-induced shifts in grassland bird nesting phenology have implications for grassland management

Grasslands are among the most impacted ecosystems globally. In the midcontinent of North America, a > 80% loss of grasslands has made their conservation a major priority for resource managers. Grassland ecosystems evolved under periodic disturbances; consequently, grassland management often involves regular actions such as grazing, haying, or burning to maintain ecosystem integrity. The timing of such practices has direct implications on grassland ecology, agricultural economics, and survival and fecundity of grassland nesting birds (hereafter grassland birds). We conducted a meta-analysis on the nesting phenology of grassland birds throughout North America, focusing on nest-survival literature. We constructed a well-fitting model to predict median date of expected nest departure (hereafter fledge date) for grassland birds across the midcontinent. Predictions from our model demonstrate considerable spatial variation in median nesting phenology that is predictable using a spatially explicit spring phenology index. Median fledge dates were 8 or 13 days earlier in years of extreme weather conditions (dry or wet, respectively) than in years of average conditions. Species that generally nest in taller vegetation tended to have later median nest phenologies than those using shorter vegetation. Our results incorporate the most rigorous information available in the literature on nesting phenology of 36 grassland bird species and improve information available to managers about nesting phenology of grassland birds in the midcontinent of North America. Our predictions approximate the day when one-half of the nesting efforts would be complete for a given area within the midcontinent grasslands and can inform management and conservation decisions about the timing of management actions in grassland ecosystems.

An efficient acoustic classifier for high‐priority avian species in the southern Great Plains using convolutional neural networks

AbstractPassive acoustic monitoring is a valuable ecological and conservation tool that allows researchers to collect data from vocal species across large geographic areas and temporal spans. Grassland bird populations, many of which are indicators of ecosystem health, have experienced precipitous declines over the past several decades. Acoustic monitoring of grassland bird populations provides opportunities to monitor declines and focus conservation practices, yet the ability to identify species efficiently and accurately from acoustic data is challenging. Therefore, development of automated classifiers such as convolutional neural networks (CNNs) are at the forefront of streamlining detection and identification of individual species. Here, we present a CNN classifier for 5 key grassland bird species across southcentral Oklahoma, a part of the southern Great Plains: northern bobwhite (Colinus virginianus), painted bunting (Passerina ciris), dickcissel (Spiza americana), eastern meadowlark (Sturnella magna), and Bell's vireo (Vireo bellii). We compiled a high‐quality training dataset consisting of 6,933 calls, built semiautonomously using template matching that can be expanded easily to any bird species of interest. Our trained multilabel CNN achieved a high level of classification accuracy (≥98%) for the 5 species using the library of test calls and field recordings played using a programmable game caller. The ability to conduct acoustic wildlife surveys across large spatial extents will allow for more efficient monitoring of wildlife to determine key population parameters and trends and effects of biotic and abiotic factors (e.g., vegetation, disturbance, weather) on these key species.

Potential impacts of land‐management schedules on grassland bird nests and fledglings

AbstractTrade‐offs exist between timing of grassland habitat management activities (e.g., weed and brush control) while also ensuring other conservation objectives (e.g., grassland bird reproductive success) are met. On land set aside for grassland conservation (e.g., lands enrolled in the U.S. Department of Agriculture Conservation Reserve Program and some state and federal wildlife management areas), federal and state agencies set time frames for land management based on avoiding disturbance of grassland bird nests. However, recent calls for considering the needs of dependent fledglings in conservation plans imply a need to evaluate whether current time frames are adequate. We used initiation and end dates for 3,257 nests of 8 obligate grassland bird species in Illinois and Wisconsin and a simulation approach for fledgling survival to estimate the potential proportion of active nests at risk when management (e.g., mowing, fire) occurred on the 1st and 15th day of May, June, July, and August during the breeding season. Management during June had the potential to impact 24–61% of nests, depending on the species. Management during July had the potential to impact 4–52% of nests, depending on the species. If disturbance occurred during August, proportionately few active nests were at risk for any species (0–9% of nests on 1 August, 0–<0.5% on 15 August). Potential proportions of fledglings at risk from management were greatest in July for 7 of the 8 species (7–18%). Our study suggests that on lands where a primary conservation objective is to increase or ensure survival of grassland birds, delaying management activities until August could be beneficial for protecting both grassland bird nests and fledglings.

Patch Area Cannot Predict Species Richness of Grassland Birds in Colorado’s Front Range

Birds breeding in grassland have declined steeply over the last 50 years, and green-space systems in Colorado’s urbanizing Front Range have not maintained all grassland bird species the area originally supported. Patch area affects the species richness of urban green spaces, and researchers have suggested that protecting or enlarging green spaces should be effective ways to maximize richness and mitigate species loss. In the Front Range, protection of urban green space is expensive, conservation budgets are limited, and tools are needed to guide strategic protection decisions. Front Range planners use patch area as a criterion to prioritize grassland conservation, but the explanatory and predictive powers of patch area have not been comprehensively assessed. Using eBird community science data, I found that log-transformed grassland patch area was positively associated with the species richness of grassland birds and explained a large portion of its variance. However, 95% simultaneous prediction intervals for species richness were wide, and those of the smallest and largest patches examined overlapped. Thus the model cannot precisely predict a number of species, and it should not be used to quantitatively evaluate the expected return on investment from financial allocations to protect or enlarge grassland patches. Nonetheless, the model’s explanatory power supports the use of grassland patch area as a general principle guiding conservation of grassland birds. Planners should consider it among a suite of other habitat characteristics and prioritize large, regularly shaped grassland patches situated close to other grassland patches and with limited nearby forest cover and urban development.

Trending against the grain: Bird population responses to expanding energy portfolios in the US Northern Great Plains.

Future global energy demand may be met through increased extraction of fossil fuels and production of renewable energy such as biofuels. Renewable energy from biofuels is often proposed as an environmentally friendly alternative to fossil fuels; however, impacts of renewable energy sources on wildlife populations have rarely been evaluated in working landscapes. We used North American Breeding Bird Survey data (1998 to 2021) to assess whether the joint effects of oil and gas and biofuel crop production explained grassland bird population declines. We modeled location-specific effects of land use on grassland bird habitat use for four grassland bird species (bobolink [Dolichonyx oryzivorus], grasshopper sparrow [Ammodramus savannarum], Savannah sparrow [Passerculus sandwichensis], and western meadowlark [Sturnella neglecta]) in North Dakota, a state experiencing rapid growth in both energy sectors. Our analysis showed that grassland birds responded more negatively to biofuel feedstocks (i.e., corn and soybeans) on the landscape compared with oil and gas development. Furthermore, we found that the effect of feedstocks was not generalizable to other forms of agricultural land use. When combined, these land use changes resulted in distributional shifts of grassland birds, with use by birds being lower in regions dominated by biofuel production, which appears partially responsible for observed abundance trends at the state level. Our results indicate that expansion of oil and gas development has negatively affected habitat use by some grassland birds, but this impact was more localized when compared to biofuel crops. Conservation practitioners may need to adapt their conservation strategies to account for widespread and rapid land use change driven by United States energy policies.

A new analytical framework for Maxent species distribution models unveils complex spatiotemporal suitability patterns for two migratory seedeaters (Aves: Sporophila) of conservation concern

Maxent species distribution models (SDMs) for rare, migratory taxa can be hindered by methodological and analytical issues. To overcome these problems, we developed an analytical framework to build SDMs for key stages of the annual lifecycle of the Marsh Seedeater and the Black-bellied Seedeater, two Neotropical grassland bird species of conservation concern. Occurrence data were compiled from multiple sources and ten environmental variables were used as predictors. We built SDMs with different spatial partitions, feature classes, and regularization multipliers, and devised a procedure to select models with high discrimination ability, low overfitting, statistically significant performance metrics, and high biological realism. From a total of 992 SDMs, 22 fully met the selection criteria for both species. These selected SDMs were equally or less overfit than non-selected ones and were mostly trained with the checkerboard 2 and n − 1 jackknife partitions. For each modeling scenario, we projected and interpreted composite models that emphasized areas of both consensus and divergence across individual predictions, rather than choosing a single model from the set of final SDMs. In the breeding season, areas of highest suitability occurred in restricted, disjunct sectors of the Campos and Pampas grasslands for the Marsh Seedeater and the highland grasslands of southern Brazil for the Black-bellied Seedeater. In the winter, high suitability for the Marsh Seedeater occurred in the western and northern Cerrado and the Pantanal, while in the spring migration, high suitability for the Black-bellied Seedeater was mostly concentrated in the southeastern portion of the Cerrado. The restricted breeding distribution of the Black-bellied Seedeater suggests that its conservation status should be reviewed. Both species shift their climatic niches and track their habitats throughout the year, responding to a few topographic, land-use, and climatic variables that represent different niche components. By addressing major modeling issues in a three-step model selection procedure, we were able to project precise and biologically interpretable SDMs with the level of complexity required for each modeling scenario. Our framework is readily replicable and can be used to unravel intricate spatial suitability patterns of organisms whose distribution undergoes temporal shifts throughout the year.

Three grassland bird species’ responses to fire and habitat structure in southern Illinois, USA suggest broad benefits of grassland size and plant diversity

Grassland birds are the most rapidly declining bird guild in North America, largely due to extensive habitat loss and fragmentation. Because many grassland bird species have different habitat preferences, managing grasslands to provide habitat for a range of species can be a challenge. We used four years of data from southern Illinois, USA grasslands to estimate the influence of prescribed fire and habitat structure on nest survival, nest density, and abundance of three grassland bird species with different habitat preferences: Dickcissel (<em>Spiza americana</em>), Field Sparrow (<em>Spizella pusilla</em>), and Common Yellowthroat (<em>Geothlypis trichas</em>). We found that Dickcissels exhibited the strongest response to prescribed fire, as nest density and nest survival both increased after previously undisturbed grasslands were burned. Fire may have also benefitted Common Yellowthroats and Field Sparrows by reducing woody cover and increasing bare ground, both of which were characteristics associated with nest survival for these birds. Dickcissel abundance was positively related to plant diversity within a grassland and agriculture in the surrounding landscape (within 400 m of a grassland patch), and negatively related to edge-interior ratio. Field Sparrows demonstrated a positive association with woody cover and proximity to forests. Common Yellowthroats were associated with tall vegetation and agriculture in the surrounding landscape. Both Field Sparrows and Common Yellowthroats associated positively with habitat characteristics that reduced nest survival, suggesting potential adaptive mismatches. Our results suggest that periodic prescribed fire, increased plant diversity, and larger patch size may simultaneously benefit a broad variety of grassland bird species with different habitat preferences.

Diversity in selection patterns of five grassland songbirds in dry-mixed grasslands of Alberta

Declining grassland bird populations across North America continue to be a concern. Understanding local relationships between grassland bird abundance and vegetative and landscape characteristics will enable more prescriptive recommendations to be made to land managers. We used point count survey data collected by the MULTISAR (Multiple Species At Risk) program along with field measurements of habitat and landscape characteristics on 15 ranches in the Dry Mixed-grass Subregion in southern Alberta to improve our understandings of habitat relationships for five grassland bird species: Baird’s Sparrow (<em>Centronyx bairdii</em>), Sprague’s Pipit (<em>Anthus spragueii</em>), Thick-billed Longspur (<em>Rhynchophanes mccownii</em>), Chestnut-collared Longspur (<em>Calcarius ornatus</em>), and Grasshopper Sparrow (<em>Ammodramus savannarum</em>). We used generalized linear mixed models to examine the relationship between the predicted abundance of a species and covariates that represented vegetative structure (e.g., litter), management (e.g., range health), and anthropogenic features (e.g., energy development) of habitat site selection. Model results demonstrate four vegetation structure covariates were of most importance for predicting abundance, including litter, vegetation height, bare soil, and shrub cover. Quadratic relationships were found with litter amounts for the predicted abundance of Baird’s Sparrow, Chestnut-collared Longspur, and Grasshopper Sparrow. Contrastingly, higher amounts of litter reduced the predicted abundance of Thick-billed Longspur. The relationship of vegetation height was quadratic for Sprague’s Pipit and was positive for Baird’s Sparrow, but negative for Thick-billed Longspur. As bare soil percentage increased, the predicted abundance of Baird’s Sparrow and Chestnut-collared Longspur decreased, with Sprague’s Pipit showing a quadratic association. Negative relationships were found with increased amounts of shrub cover for Chestnut-collared Longspur, Sprague’s Pipit, and Thick-billed Longspur. Our results help to further understand individual grassland bird species’ habitat requirements, enabling us to provide land management recommendations for maintaining, improving, or creating the heterogenic environments needed for a variety of grassland birds in the Dry Mixed-grass Subregion.

Balancing ecosystem service outcomes at the ranch-scale in shortgrass steppe: The role of grazing management

• Grazing management for providing multiple ecosystem services at the ranch scale requires balancing desired outcomes. • Abundant challenges involve matching the spatial heterogeneity in soils and associated plant community characteristics with the temporal variability in precipitation. • Prescriptive grazing (season-long continuous and time-controlled rotational grazing) removes the human experiential knowledge to adapt to changing conditions, whereas adaptive multipaddock (AMP) grazing often invokes high stock densities, which reduce livestock weight gain. • A “mix-and-match” or blending of both approaches for grazing management in the shortgrass steppe can result in reduced drought risk, enhanced breeding habitat availability for grassland bird species of concern, and sustained livestock production.

Effects of grazing strategy on facultative grassland bird nesting on native grassland pastures of the Mid-South USA.

Understanding how livestock grazing strategies of native warm season grasses (NWSG) can impact facultative grassland bird nesting can provide insight for conservation efforts. We compared pre and post treatment effects of rotational grazing (ROT) and patch-burn grazing (PBG) for facultative grassland bird species nest success and nest-site selection on NWSG pastures at three Mid-South research sites. We established 14, 9.7 ha NWSG pastures and randomly assigned each to either ROT or PBG and monitored avian nest-site selection and nest success, 2014–2016. We collected nesting and vegetation data in 2014, before treatment implementation, as an experimental pre-treatment. We implemented treatments across all research sites in spring 2015. We used a step-wise model selection framework to estimate treatment effect for ROT or PBG on avian nest daily survival rate (DSR) and resource selection function (RSF) at the temporal scale and within-field variables. Daily survival rates were 0.93% (SE = 0.006) for field sparrow (Spizella pusilla), 0.96% (SE = 0.008) for red-winged blackbird (Agelaius phoeniceus), and 0.92% (SE = 0.01) for indigo bunting (Passerina cyanea). Model support for PBG treatment and vegetation height were indicated as negative and positive influences for field sparrow DSR, respectively. Red-winged blackbirds’ DSR were negatively influenced by ROT while vegetation height positively affected DSR, and DSR for indigo bunting did not differ among treatments. Combined RSF models indicated nest-site selection for all species was positively related to vegetation height and only weakly associated with other within-field variables. We provide evidence that ROT and/or PBG effects vary by species for DSR for these three facultative grassland birds, and vegetation characteristics affected their nest-site selection in the Mid-South USA. A lack of disturbance in Mid-South grasslands can lead to higher successional stages (i.e., mix shrub-grassland), but some combination of ROT, PBG, and unburned/ungrazed areas can provide adequate nesting habitat on small pasture lands (∼1.8 –7.8 ha) for various facultative grassland birds and potentially offer the opportunity to simultaneously maintain livestock production and grassland bird nesting habitat.

Fine‐scale habitat associations of Oklahoma's longspurs

AbstractOverwintering is a key demographic stage for migratory birds but remains poorly understood, especially among multiple declining grassland bird species. The non‐breeding ranges all 4 species of longspur (i.e., chestnut‐collared [Calcarius ornatus], Smith's [C. pictus], Lapland [C. lapponicus], thick‐billed [Rhynchophanes mccownii]) overlap in Oklahoma and the Texas Panhandle, USA, making this region ideal to study their wintering ecology. We evaluated the relationship between wintering longspur occurrence and fine‐scale habitat characteristics using a combination of standardized bird surveys and vegetation plot sampling. Our study encompassed large, representative tracts of 3 prairie ecosystems (i.e., shortgrass, mixed‐grass, and tallgrass prairies) that intersect within the Southern Great Plains, during winters of 2018–2019 and 2019–2020. Using randomization tests and classification trees, we characterized longspur habitats and compared these associations across the 3 prairie ecosystems. Fine‐scale winter habitats (horizontal structure, vertical structure, and species compositions) varied among all 4 longspur species, varied at very fine scales, and differed between grassland types. Our findings can be applied to the management of grasslands such as decreasing vegetation height in mixed‐grass prairies for chestnut‐collared longspurs or removing woody vegetation in shortgrass prairies for thick‐billed longspurs to help develop full‐life cycle conservation for longspurs, which have experienced population declines.

Nesting biology of the Hudson´s Canastero (Asthenes hudsoni) and the Bearded Tachuri (Polystictus pectoralis), two threatened and poorly known birds of the Pampas grasslands

ABSTRACT The accelerated rate of grasslands transformation has led to noticeable population declines of many grassland bird species. Although several species of the Pampas grasslands are of conservation concern, the information on their nesting biology is generally sparse. During three consecutive breeding seasons (2018–2019 to 2020–2021), we studied nesting attempts of two of the most threatened grassland bird species in central-eastern Argentina: the Hudson’s Canastero (Asthenes hudsoni) and the Bearded Tachuri (Polystictus pectoralis). We found 16 nests of Hudson’s Canastero and seven nests of Bearded Tachuri in natural grasslands. In both species, the modal clutch size was three eggs, and predation was the main cause of nest failure. Incubation and nestling periods lasted 15 and 11.5 days for the Hudson’s Canastero and 14.3 and 12 days for the Bearded tachuri. Daily Survival Rates were 0.90 and 0.97, resulting in a cumulative survival of 4% for the Hudson’s Canastero and 39% for the Bearded Tachuri. We found that the breeding biology of the two threatened grassland bird species is strongly tied to tall native grasslands and suggest that both species could be sensitive to changes in breeding habitat, particularly in the grassland vegetation structure.

Winter space use and sex ratios of Chestnut-collared Longspurs (Calcarius ornatus) in Oklahoma

As grasslands have become the most threatened ecosystem in North America, so too have many migratory obligate grassland birds. Chestnut-collared Longspurs (Calcarius ornatus) are a great example, as they have experienced an 89% population decline during the last 5 decades. We captured and tracked individuals during the winters of 2018–2019 and 2019–2020 and calculated their home ranges as both minimum convex polygons (MCP) and fixed kernel density estimates (KDE). Across the 2 winters, we captured and banded 116 longspurs (∼75% males), fitting 90 of them with VHF radio-transmitters. The winter (5 Dec–8 Mar) mean home ranges defined by MCP were 128.8 ha, while the 95% KDE indicated a mean of 29.87 ha. Wintering longspurs used larger areas and displayed higher nomadism than reported for other grassland bird species. Therefore, management for the species scales up beyond the relatively small areas that longspurs aggregate into flocks within and will require landscape-level coordination to maintain habitat adequate for effective winter population.