Research Paper

INTRODUCTION

In intensified agroecosystems, grassland birds show different habitat requirements where variation in resource availability is likely one of the primary forces structuring bird species distributions at a regional scale (Filloy and Bellocq 2007, Goijman et al. 2015). Additionally, the occurrence of grassland bird species is thought to be mediated by other factors, including nesting site availability, shelter, and matrix composition, where land use type and cover is predicted to affect foraging guilds differently (Blondel 2003, Sekercioglu 2006). Within each guild, birds exploit resources in a similar way, and thus species could respond similarly to habitat characteristics (Blondel 2003, Sekercioglu 2006). In particular, granivorous gleaners, ground insectivores, and omnivores are negatively affected by extensive areas of soybean cultivation because of the low availability of vegetated borders, although insectivorous gleaners and aerial foragers seem to be more tolerant (Goijman et al. 2015). Therefore, responses to environmental changes will likely be diverse and may vary according to each functional group.

During the breeding season, the availability of nesting sites is crucial in determining grassland bird distribution (Codesido et al. 2012). In Neotropical grasslands, individuals of grassland bird species search for suitable nesting habitats predominantly dominated by natural grasslands (Comparatore et al. 1996, Cozzani and Zalba 2009, Pretelli et al. 2013). The characteristics of these grasslands, such as vegetation structure, conspecific attraction, and breeding success are cues that birds use to establish territories (Winter and Faaborg 1999, Herkert et al. 2003, Askins et al. 2007). For these reasons, understanding the key role that natural grassland areas play in modulating habitat use of grassland birds during crucial moments of their life cycle is essential for predicting their fate in heavily fragmented ecosystems (Rahmig et al. 2009, Shahan et al. 2017).

In recent years, studies on grassland bird habitat use have focused their attention on entire habitat patches and the surrounding landscape in which these patches are embedded (Herse et al. 2017, Shahan et al. 2017, Cunningham and Johnson 2019). Although landscape-level effects may not be identical across all birds because of their foraging and breeding behavior (Ehrlich et al. 1988), previous studies have demonstrated that during the breeding season, grassland patch area, shape, and edge proportion modulate grassland bird occurrence (Winter and Faaborg 1999, Herkert et al. 2003, Askins et al. 2007). Grassland patches with a higher proportion of interior habitat relative to edge habitat (i.e., regular or circular patches) are more attractive to area-sensitive species (Davis 2004). For example, grassland birds may avoid edge habitats because of the increased density and activity of nest predators (Johnson and Temple 1990, Perkins et al. 2000), and changes in vegetation structure and composition (Davis and Duncan 1999, Ribic and Sample 2001).

The surrounding landscape in which grassland patches are embedded are particularly important because the land use matrix offers several elements that could be conditioning habitat use by grassland birds (Ribic et al. 2012, Pretelli et al. 2015). Some exotic perennial pastures can provide alternative habitats for some grassland bird species, acting as feeding and nesting sites (Calamari et al. 2016). Annual crop fields, groves, and human settlements are negatively associated with the abundance of many grassland bird species (Leston 2013, Dotta et al. 2016, Pretelli et al. 2018), where particularly woody vegetation and crops provide suitable habitats for nest parasites such as cowbirds (Molothrus spp.) and nest predators (Evans et al. 2004, Patten et al. 2006, Pietz et al. 2009, Vickery et al. 2009, Benítez-López et al. 2010, Ellison et al. 2013, Colombo and Segura 2021).

The Pampas ecoregion has undergone deep transformations, and the extensive original grasslands have been transformed, giving rise to lands currently covered by agricultural systems (Baldi et al. 2006, Baldi and Paruelo 2008). Native grasslands have been relegated to areas with soils unsuitable for agricultural practices and are currently fragmented and isolated in a matrix of annual crops and pastures (Bilenca and Miñarro 2004). This agriculturalization process has been coupled with the introduction of new elements to the landscape, such as human settlements, trees, and other woody plants that have invaded native grasslands, roadsides, and streams (Ghersa et al. 2002, Chaneton et al. 2012). These changes in landscape composition, particularly in land use types, influence the species richness, distribution, and abundance of the different trophic bird guilds in the Pampas grasslands (Codesido et al. 2008, Weyland et al. 2014).

Occupancy models assess how different variables affect occupancy while accounting for imperfect species detection (MacKenzie et al. 2018). Taking this approach into account is particularly important amongst grassland birds because many species are hard to identify or highly elusive (Maphisa et al. 2019). These models have been used in various grassland systems to evaluate how different landscape variables affect the habitat use probability of grassland birds (West et al. 2016, Green et al. 2019, Maphisa et al. 2019) They could, therefore, be incorporated into management and conservation plans for these species in the Pampas grasslands ecosystem (Hovick et al. 2014, Goijman et al. 2015).

The main goal of this study is to assess how grassland remnant characteristics influence breeding grassland bird habitat use in a fragmented grassland system of high conservation value within the Pampas ecoregion. Overall, we expect grassland remnant characteristics to be the main drivers of each species’ habitat use during the breeding season. Because grassland remnants provide foraging and nesting habitat for all grassland bird species, we tested the effect of their proximity, size, and shape on the breeding grassland bird habitat use. We predict that habitat use will be higher in sites associated with close, large, and regular remnants. Furthermore, we assess how other landscape variables such as land use and proximity to streams, groves, and human settlements could be influencing habitat use by increasing or reducing foraging and nesting habitat availability. In these cases we expect that habitat use will be higher in sites dominated by grassland and pastures and far from streams, groves, and settlements. We expect species habitat use to help understand patterns at the trophic guild level. Understanding how grassland bird habitat use is associated with these landscape characteristics will favor the design of effective conservation strategies.

METHODS

Study area

The Tandilia Mountains extend for 350 km across the Southern Pampas ecoregion within Buenos Aires Province of Argentina, covering an area of 12,314 km² and reaching a maximum elevation of 524 m a.s.l. (Dalla Salda et al. 2006, Valicenti et al. 2010). The predominant native vegetation persists within several highland grassland remnants of grass steppe, dominated by needlegrasses (Stipa spp.), shrubs, and ferns (De la Sota 1967, Cabrera 1971, Valicenti et al. 2010). Approximately 90% of the study area is cultivated by annual crops and perennial pastures. Because of steep slopes, shallow soils, and exposed bedrock, the surviving highland grassland remnants that have not yet been transformed into land used for agriculture or forestry represent less than 10% of the original ecosystem (Herrera et al. 2017).

Study design

We worked in an area of approximately 34,000 hectares within the Tandilia Mountains, where we established 126 sampling points (Fig. 1). We arranged these points along local and internal roads on different private properties with an average distance of 700 m between them (with a minimum of 250 m and a maximum of 4000 m). Using the QGIS software and a national crop map provided by the National Institute of Agricultural Technology from Argentina (de Abelleyra et al. 2020), we established an area of 100 meters radius surrounding each point (sampling unit), where we calculated the composition of the land use matrix. We grouped the existing categories into the following: (1) groves (i.e., planted and spontaneous trees), (2) crops (i.e., annual summer and winter crops), (3) pastures (i.e., perennial pastures), and (4) grasslands (i.e., natural grasslands). Furthermore, taking the sampling unit center as a starting point, we calculated the following distances (expressed in meters): (5) to the nearest stream, (6) to the nearest human settlement, (7) to the nearest grove, and (8) to the nearest grassland remnant. For the closest grassland remnant, we also calculated (9) the remnant area (expressed in ha) and (10) a remnant shape index (Shape = perimeter/[2√(π × area)]: Shake et al. 2012). A perfectly circular patch has a shape index of one, and the index value increases as the shape of a patch becomes more irregular.

Bird sampling

We visited each point seven times (once every month) between September 2020 and March 2021, covering the region’s entire austral grassland bird breeding season (Trofino-Falasco 2023). During each 5-minute visit, we recorded all birds detected (heard or seen actively using the sampled area) within a 100-m radius (sampling unit). This radius point count has been widely used in grassland bird surveys during the breeding season, as birds are more active during this time, ensuring both auditory and visual species detection (Davis 2004, Fontana et al. 2018).

Data analysis

We performed a descriptive analysis of the landscape variables associated with each sampling unit and explored variable correlations, obtaining a weak relationship between them. For each species detected during the sampling period, we calculated (1) the percentage of sites where it was detected (i.e., sites with detections), and (2) the percentage of sites located on grassland remnants where it was detected (i.e., sites on remnants with detections). We focused our interest on understanding species-level responses.

We analyzed the habitat variable’s effects on the use probability of grassland bird species with occupancy models (MacKenzie et al. 2018). Occupancy models jointly model the ecological process of species occurrence and the observation process of species detection but estimate these as separate processes. This modeling framework allows us to account for variations in detection probability when estimating species occurrence. Unlike other generalized linear models, occupancy models allow for the correction of imperfect detection, a crucial factor in biodiversity studies, where it is common for species not to be detected, even if they are present at a site (Comte and Grenouillet 2013). In these models, occupancy (ψ) is defined as the proportion of occupied sites, and detection (ρ) is defined as the probability that a species will be detected at the sampled site given that it is present (MacKenzie et al. 2018). We obtained the habitat use probabilities of each species from occupancy models and considered occupancy probability and use probability to be synonymous in this study.

We constructed detection histories that consisted of vectors of 1 or 0, indicating if the species was detected or not, from the information obtained during the seven visits and for each sampling unit (i.e., site). We excluded from modeling the species detected in less than 10% of the sampled sites (Cortelezzi et al. 2020). In the case of migratory species such as the Bearded Tachuri (Polystictus pectoralis) and the Double-collared Seedeater (Sporophila caerulescens), we worked with shorter detection histories, and only the months in which these species occupied the study area were considered. The season for the Bearded Tachuri was from October to March, while the season for the Double-collared Seedeater was from November to March (Collar and Wege 1995, Ortiz and Capllonch 2007).

First, we evaluated the constant model for each species, in which we assumed that detection and occupancy probabilities were constant across sites [indicated as ψ(.) ρ (.)]. Then, to evaluate the hypotheses, we developed a model set that incorporated site covariates through a logit link function for each grassland bird species. The set included all potential models with 2–9 parameters (including the intercept and detection probability), maintaining an approximate ratio of data to parameters > 10 (N = 126 sites; maximum number of parameters = 12; Burnham and Anderson 2002). Because the variables associated with land use area within the sampling unit are compositional, we included them one at a time in each model (van den Boogaart and Tolosana-Delgado 2013). We used the Akaike Information Criterion (AIC) to rank the obtained models (Burnham and Anderson 2002), and we eliminated those models that (a) did not converge, (b) the incorporation of another covariate did not improve their rank position, and (c) did not have any significant covariables.

Finally, we analyzed the models that ranked above the constant model for each species, selecting those that were within two AIC units (i.e., ΔAIC < 2) from the best model in the ranking (Burnham and Anderson 2002). From this best model list, we calculated the confidence interval of each parameter estimate (i.e., 1.96 x SE) for each model. Also, we calculated the estimates of its parameters (β) and its standard errors (SE) and analyzed whether the parameter differed significantly from zero (i.e., p ≤ 0.05; Burnham and Anderson 2002). For each species, and in cases where a covariate was present in more than one model from this list, we selected and graphed the parameter values with their confidence intervals from the best-ranked model. We performed all site-use modeling with the Unmarked package in R (Fiske and Chandler 2011).

Finally, to facilitate the search for common patterns among the species, we showed the results grouped in trophic guilds considering the main food component of their diet (Zotta 1940). We assigned grassland bird species to trophic guilds reported in Pampas grasslands (de la Peña 2011, Pretelli et al. 2018). The Grassland Sparrow (Ammodramus humeralis), the Rufous-collared Sparrow (Zonotrichia capensis), the Grassland Yellow-Finch (Sicalis luteola), and the Double-collared Seedeater were considered as granivores. The Red-winged Tinamou (Rhynchotus rufescens), the Spotted Nothura (Nothura maculosa), the Pampa Finch (Embernagra platensis), and the Long-tailed Reed Finch (Donacospiza albifrons) were considered omnivores. The Bearded Tachuri, the Spectacled Tyrant (Hymenops perspicillatus), the Grass Wren (Cistothorus platensis), the Short-billed Pipit (Anthus furcatus), the Pampas Pipit (Anthus chacoensis), the Correndera Pipit (Anthus correndera), the Hellmayr’s Pipit (Anthus hellmayri), the White-browed Blackbird (Leistes superciliaris), the Long-tailed Meadowlark (Leistes loyca), and the Brown-and-yellow Marshbird (Pseudoleistes virescens) were all considered insectivores.

RESULTS

Of the 126 sampled units, 55% (N = 69 sites) were on 23 natural grassland remnants with different characteristics, where 11 of these remnants were small (≤ 20 ha), six were medium (21–100 ha), and six were large (>100 ha; Table 1). The mean and SE of their areas were 8.19 ± 1.62 ha, 48.11 ± 3.69 ha, and 786.76 ± 32.20 ha, respectively. Small patches had shape index values of 1.66 ± 0.24, medium patches 2.89 ± 1.36, and large patches 5.57 ± 1.74, indicating that smaller patches were more circular.

We detected 18 grassland bird species, including 16 residents and two migratory species. Species detection in the 126 sites varied from 2% in the Short-billed Pipit and the Long-tailed Reed Finch to 84% in the Rufous-collared Sparrow. The Correndera Pipit, the Short-billed Pipit, and the Long-tailed Reed Finch were detected in less than 10% of the sites, so they were excluded from the habitat use probability modeling. We detected 56% of the 18 species in at least 30% of grassland remnants (N = 69 sites; Table 2). Hellmayr’s Pipit was the only grassland bird detected exclusively in grassland remnants.

The best-ranking habitat use models for the studied grassland bird species are summarized in Table 3. The distance and/or shape of the closest grassland remnant to the sampling unit were the grassland variables that affected the habitat use probability of most grassland birds (i.e., 12 of 15 modeled species), both having a negative effect (Fig. 2). Regarding the first variable, its effect was statistically significant for the Grassland Yellow-Finch (β = -0.68 ± 0.33), the Grassland Sparrow (β = -0.64 ± 0.28), the Long-tailed Meadowlark (β = -1.69 ± 0.61) and the Grass Wren (β = -4.67 ± 2.37), while grassland remnant shape was statistically significant for the Grassland Yellow-Finch (the only positively affected species; β = 5.03 ± 2.47), the Red-winged Tinamou (β = -0.59 ± 0.21), and the Long-tailed Meadowlark (β = -0.92 ± 0.36). The responses of the species’ habitat use to these remnant variables are shown in Figure 3. The closest grassland remnant area did not statistically affect any grassland bird species’ habitat use. In the grassland area within the sampling unit, we observed a statistically significant effect in three species, with different types of response: a positive effect in Hellmayr’s Pipit habitat use probability (β = 1.65 ± 0.61) and a negative effect for the Grassland Sparrow (β = -0.92 ± 0.28) and the White-browed Blackbird (β = -0.70 ± 0.32; Fig. 2).

Pasture area was the only land use type that significantly affected the use of almost half of the modeled species, having a positive effect on the Grassland Sparrow (β = 0.96 ± 0.33), Rufous-collared Sparrow (β = 0.71 ± 0.34), Spotted Nothura (β = 0.87 ± 0.40), and Brown-and-yellow Marshbird habitat use (β = 0.67 ± 0.26); and a negative effect on the Bearded Tachuri (β = -2.94 ± 1.44) and the Hellmayr’s Pipit (β = -1.89 ± 0.93; Fig. 2). Crop area only significantly affected the habitat use probabilities of the Pampa Finch (β = -0.57 ± 0.23) and the Brown-and-yellow Marshbird (β = -0.47 ± 0.23) in a negative way (Fig. 2).

The relationship between grove distance and species habitat use probability was always negative, with the opposite trend being observed for stream distance. In the first case, five grassland species showed a statistically significant effect: the Grassland Yellow-Finch (β = -0.87 ± 0.36), the Double-collared Seedeater (β = -0.41 ± 0.20), the Rufous-collared Sparrow (β = -0.74 ± 0.32), the Long-tailed Meadowlark (β = -0.84 ± 0.36), and the Spectacled Tyrant (β = -0.75 ± 0.33). The species that showed a statistically significant effect for the latter were the Grassland Sparrow (β = 0.70 ± 0.29), White-browed Blackbird (β = 0.67 ± 0.26), and Pampas Pipit (β = 1.40 ± 0.70).

DISCUSSION

This is the first study to evaluate which habitat variables are associated with the use probability of breeding grassland birds within the southern Pampas ecoregion. Habitat use probabilities in sites on natural grassland remnants were generally high (i.e., more than 40%), with more than half of the species being detected in at least 30% of these sites. This confirms the natural grassland habitat dependence of grassland birds because this habitat represents critical feeding and breeding sites for the studied species (Vickery et al. 1994, Guttery et al. 2017, Cunningham and Johnson 2019). Our results support the hypothesis that natural grassland remnants are the main drivers of grassland bird habitat use during the breeding season, whereas other landscape variables affect habitat use differently at a species and trophic guild level. Generally, bird species responded more strongly to the effects of proximity and shape of grassland remnants, as well as other land use types such as groves and perennial pastures. We highlight the variability in individual species’ responses within groups (Goijman et al. 2015), emphasizing the need to avoid the a priori grouping of species into guilds and the importance of accounting for the imperfect detection of individual species.

Individual species responses

During the breeding season, grassland birds all over the globe seek nesting habitats dominated by natural grasslands, as is observed in the Pampas ecoregion (Comparatore et al. 1996, Cozzani and Zalba 2009, Pretelli et al. 2013, Nugent et al. 2022, Wolcott et al. 2023). This coincides with our observations, in which even slight distances from grassland patches resulted in a rapid decrease in bird habitat use. Additionally, almost 80% of the studied grassland bird species used sites near more circular grassland patches, coinciding with several reports for grassland birds in other grassland systems (Vickery et al. 1994, Jacobs et al. 2012, Herse et al. 2017). An opposite trend was observed in the Grassland Yellow-Finch, which used sites associated with more irregular patches. This may be related to their habitat use plasticity and the fact that this species does not avoid nesting near grassland edges, unlike what is typically expected for many grassland passerines (Azpiroz et al. 2012, Colombo et al. 2024). Contrary to what was expected, the covered area by natural grasslands within sampling units only increased the habitat use probability of Hellmayr’s Pipit, a grassland specialist (Azpiroz et al. 2012).

Lands used for livestock grazing (under low to moderate regimes) can provide a wide range of opportunities for invertebrate and seed-eating birds (Perkins et al. 2000), as well as offering a certain vegetation structure that resembles natural grasslands in altered habitats (Codesido et al. 2013). This could explain the positive effect of perennial pastures on many of the studied species. However, this land cover decreased the habitat use probabilities of the Bearded Tachuri and the Hellmayr’s Pipit, as has been previously reported in other Pampas grasslands (Aldabe et al. 2024). The cultivated area negatively affected the habitat use probability of two grassland bird species (i.e., the Pampa Finch and the Brown-and-yellow Marshbird), suggesting that agriculture is more detrimental to the avian community than pasture farming during the breeding season, as was observed for other sites within the Pampas ecoregion (Filloy and Bellocq 2007).

Contrary to what was predicted, grove area did not affect the habitat use of grassland bird species, and approximately 30% of the species used sites near groves. This presents a different scenario compared to other grassland systems because, in North America, the occurrence probability of many grassland birds decreases as the cover of bushes, exotic shrubs, and trees increases (Grant et al. 2004, Ellison et al. 2013); meanwhile, in the Pampas grasslands of Uruguay, grassland specialist species were in general sensitive to tree cover and tended to respond positively to this land cover (Aldabe et al. 2024). In the Tandilia Mountains region, groves and other exotic woody vegetation were recently introduced by humans and are gradually replacing native xerophytic forest patches (Brea et al. 2020, Carabia-Sanz et al. 2024).

Unlike species response to groves, grassland birds used sites away from streams. This trend is contrary to what was observed in arid grassland ecosystems because riverine habitats are key breeding sites for passerine birds on account of the provision of a variety of resources absent in adjacent upland habitats and also because of the presence of standing water (Merritt and Bateman 2012). This is a different scenario from the Tandilia Mountains that have varied water sources, such as ephemeral wetlands, temporary ponds, and streams (Cortelezzi et al. 2015, Friedman et al. 2016). Along the northern slopes are the headwaters of many Pampean streams that drain in the NE direction and are characterized by the absence of riparian forest vegetation, the lack of a dry season or extreme temperatures (Feijoó et al. 2005, Cortelezzi et al. 2020). These Pampean streams have dynamic cycles, cross through grassy plains, and tend to waterlog grassland habitats (Cortelezzi et al. 2020), which can flood nests, causing bird species to avoid nesting near these water bodies (Colombo and Segura 2023). Additionally, although streams can provide shelter to many bird species, riverine habitats often harbor a greater abundance and density of predators (Shnack et al. 2000, Hilty and Merenlender 2004, Matos et al. 2009, Colombo and Segura 2023), which could also be related to the observed bird habitat use trends in the study region.

Trophic guild trends

Our results support the hypothesis that grassland birds are affected by the availability of food resources in agricultural landscapes in the Tandilia Mountains. Although many bird species within each trophic guild responded differently to landscape characteristics, agreeing with previous studies of individual species (Filloy and Bellocq 2007, Codesido et al. 2008, Goijman et al. 2015), we were able to identify some general trends for different trophic guilds.

As was mentioned for species-level responses regarding the effect of grassland remnant metrics, all the trophic guilds used sites near environments dominated by natural grasslands. As in other areas of the Pampas ecoregion, grassland fragmentation in the Tandilia Mountains has confined this habitat to smaller, isolated patches showing a greater edge effect (Saunders et al. 1991, Fahrig 2003, Herrera et al. 2017). The response of the trophic guilds in this study coincides with other reports because irregular patch shape and a greater proportion of patch edge negatively influence grassland remnant use by grassland birds (Winter and Faaborg 1999, Herkert et al. 2003, Askins et al. 2007).

Areas used for livestock production were primarily used by granivorous and omnivorous birds, which preferred sites with greater perennial pasture coverage. This trend is consistent with the hypothesis that in altered grassland ecosystems, perennial pastures can provide alternative habitats for these guilds, acting as feeding and nesting sites during the breeding season (Calamari et al. 2016). Many species within these groups are tolerant or benefit from this agricultural use, responding positively to perennial pastures, as was reported for other areas of the Pampas ecoregion and tallgrass prairies of North America (Rahmig et al. 2009, Goijman et al. 2015). However, the general trend observed in these two trophic guilds does not align with findings from grasslands in Uruguay, where, using a different scale of analysis, authors found that exotic perennial pastures had an overall negative impact on many grassland birds (Aldabe et al. 2024). Although these ground-foraging groups use perennial pastures, it is important to emphasize that different grazing intensities should be applied across the landscape at scales relevant to these birds to meet their habitat requirements, as reported for several agroecosystems worldwide (Temple et al. 1999, Perkins et al. 2000, Isacch et al. 2005, Howland et al. 2016).

As was anticipated in the species-level responses, granivorous and insectivorous birds used sites near groves. It is necessary to delve deeper into the effect of this landscape element, as it favors the presence of non-grassland bird species that are currently considered common in the Pampas ecoregion and are particularly abundant in the Tandilia Mountains (McKinney 2006, Codesido et al. 2011, Trofino-Falasco et al. 2023). These birds, such as the Chalk-browed Mockingbird (Mimus saturninus), the Great Kiskadee (Pitangus sulphuratus), and the Rufous-bellied Thrush (Turdus rufiventris), may be competing for resources, especially with grassland insectivorous species (Weyland et al. 2014). Furthermore, it has been reported that groves can offer shelter and perches for grassland bird predators (Calamari et al. 2016, Cunningham and Johnson 2019, Colombo and Segura 2021). This ecological interaction should be monitored because nesting predation is the leading cause of breeding failure in most grassland birds (Colombo and Segura 2023, Browne et al. 2023, Trofino-Falasco et al. 2024).

Some of the trends identified in this study could be confirmed with additional sampled data, especially those related to land use coverage within sampling units. For example, the grassland area did not reflect species habitat use, and this may be because the sampling unit size was relatively small, and some bird species could use larger territories. A possible solution could be to adjust this size according to the territories of each species (Di Giacomo et al. 2010). Grove area did not affect grassland birds either, as has been reported in other bird species, increasing their occurrence in the presence of these landscape elements (e.g., frugivores, nectarivores, etc.; McKinney 2006, Codesido et al. 2011). Additional studies should be carried out incorporating larger sampling unit sizes, increasing the number of sites, adding more breeding seasons and comparing with the non-breeding season to confirm or discard these trends.

In conclusion, the habitat variables that best explained the bird habitat use in this study were the metrics associated with natural grassland remnants near the sampled sites (i.e., distance and shape), perennial pasture cover area, and distances to other landscape elements (i.e., groves and streams). These results could be used to incorporate these variables into long-term monitoring studies of grassland bird species in the region and to design management actions related to these landscape elements, particularly those that are manageable, whether or not they are of natural or anthropogenic origin (Goijman et al. 2015, Brandolin et al. 2016, Pretelli et al. 2018, Pírez and Aldabe 2023). For example, it will be possible to identify thresholds for minimum distances to grassland remnants at which habitat use levels decrease for each grassland bird species.

Our study results confirm that grassland remnants were the main drivers of grassland bird habitat use during the breeding season in the Tandilia Mountains within the Pampas ecoregion. Therefore, it is essential to design management actions that support suitable conditions for grassland birds in fragmented landscapes, especially during the breeding season and in areas where the integrity of natural grasslands is protected.

LITERATURE CITED

Aldabe, J., T. Morán-López, P. Soca, O. Blumetto, and J. M. Morales. 2024. Bird species responses to rangeland management in relation to their traits: Rio de la Plata Grasslands as a case study. Ecological Applications 34:e2933. https://doi.org/10.1002/eap.2933

Askins, R. A., F. Chávez-Ramírez, B. C. Dale, C. A. Haas, J. R. Herkert, F. L. Knopf, and P. D. Vickery. 2007. Conservation of grassland birds in North America: understanding ecological processes in different regions. Ornithological Monographs 64:1-46. https://doi.org/10.2307/40166905

Azpiroz, A. B., J. P. Isacch, R. A. Dias, A. S. Di Giacomo, C. S. Fontana, and C. M. Palarea. 2012. Ecology and conservation of grassland birds in southeastern South America: a review. Journal of Field Ornithology 83:217-246. https://doi.org/10.1111/j.1557-9263.2012.00372.x

Baldi, G., J. P. Guerschman, and J. M. Paruelo. 2006. Characterizing fragmentation in temperate South America grasslands. Agriculture, Ecosystems & Environment 116:197-208. https://doi.org/10.1016/j.agee.2006.02.009

Baldi, G., and J. M. Paruelo. 2008. Land-use and land cover dynamics in South American temperate grasslands. Ecology and Society 13(2):6. https://doi.org/10.5751/ES-02481-130206

Benítez-López, A., R. Alkemade, and P. A. Verweij. 2010. The impacts of roads and other infrastructure on mammal and bird populations: a meta-analysis. Biological Conservation 143:1307-1316. https://doi.org/10.1016/j.biocon.2010.02.009

Bilenca, D., and F. Miñarro. 2004. Identificacion de Areas Valiosas de Pastizal en las pampas y campos de Argentina, Uruguay y sur de Brasil (AVPs). Fundación Vida Silvestre Argentina, Buenos Aires, Argentina.

Blondel, J. 2003. Guilds or functional groups: does it matter? Oikos 100:223-231. https://doi.org/10.1034/j.1600-0706.2003.12152.x

Brandolin, P. G., P. G. Blendinger, and J. J. Cantero. 2016. From relict saline wetlands to new ecosystems: changes in bird assemblages. Ardeola 63:329-348. https://doi.org/10.13157/arla.63.2.2016.ra7

Brea, M., D. Mazzanti, and G. A. Martínez. 2020. Xerophytic forest record of the Pleistocene/Holocene transition and use of wood resources by early human groups in the Eastern Tandilia Range, Argentina. PaleoAmerica 6:234-249. https://doi.org/10.1080/20555563.2019.1698189

Browne, M., C. Pasian, A. G. Di Giacomo, M. S. Di Bitetti, and A. S. Di Giacomo. 2023. Variation in mesopredator abundance and nest predation rate of the endangered Strange‐tailed Tyrant (Alectrurus risora). Ibis 165:1201-1216. https://doi.org/10.1111/ibi.13202

Burnham, K., and D. Anderson. 2002. Model selection and multimodel inference: a practical information-theoretic approach. Second edition. Springer, New York, New York, USA.

Cabrera, A. L. 1971. Fitogeografía de la república Argentina. Boletín de la Sociedad Argentina de Botánica 14:1-42.

Calamari, N. C., A. C. Blandón, S. B. Canavelli, S. Dardanelli, G. I. Gavier-Pizarro, and M. E. Zaccagnini. 2016. Asociación a Largo Plazo De La Densidad De Tyrannus savana y Sturnella superciliaris Con Variables De Cobertura De La Tierra Y climáticas En Agroecosistemas De Argentina. Hornero 31:97-112. https://doi.org/10.56178/eh.v31i2.556

Carabia-Sanz, I., M. V. Simoy, A. Cortelezzi, C. Trofino-Falasco, and I. Berkunsky. 2024. Spatial distribution and landscape impact analysis of quarrying in the highly fragmented ecosystem of Tandilia system (Province of Buenos Aires, Argentina). Environmental Earth Sciences 83:319. https://doi.org/10.1007/s12665-024-11657-4

Chaneton, E., N. Mazía, W. Batista, A. Rolhauser, and C. Ghersa. 2012. Woody plant invasions in Pampa grasslands: a biogeographical and community assembly perspective. Pages 115-146 in R. Myster, editor. Ecotones between forest and grassland. Springer, New York, New York, USA. https://doi.org/10.1007/978-1-4614-3797-0_5

Codesido, M., C. González-Fischer, and D. Bilenca. 2008. Asociaciones entre diferentes patrones de uso de la tierra y ensambles de aves en agroecosistemas de la Región Pampeana, Argentina. Ornitología Neotropical 19:575-585.

Codesido, M., C. González-Fischer, and D. Bilenca. 2011. Distributional changes of landbird species in agroecosystems of Central Argentina. Condor 113:266-273. https://doi.org/10.1525/cond.2011.090190

Codesido, M., C. González-Fischer, and D. Bilenca. 2012. Agricultural land-use, avian nesting and rarity in the Pampas of central Argentina. Emu - Austral Ornithology 112:46-54. https://doi.org/10.1071/MU11049

Codesido, M., C. M. González-Fischer, and D. N. Bilenca. 2013. Landbird assemblages in different agricultural landscapes: a case study in the Pampas of central Argentina. Condor 115:8-16. https://doi.org/10.1525/cond.2012.120011

Collar, N. J., and D. C. Wege. 1995. The distribution and conservation status of the Bearded Tachuri Polystictus pectoralis. Bird Conservation International 5:367-390. https://doi.org/10.1017/S0959270900001106

Colombo, M. A., K. M. Depot, and L. N. Segura. 2024. Selection for overhead concealment improves nest survival of a ground nesting bird in Argentinian rangelands. Rangeland Ecology & Management 96:47-55. https://doi.org/10.1016/j.rama.2024.05.004

Colombo, M. A., and L. N. Segura. 2021. Forest edges negatively influence daily nest survival rates of a grassland Tinamou, the Spotted Nothura (Nothura maculosa). Canadian Journal of Zoology 99:573-579. https://doi.org/10.1139/cjz-2020-0210

Colombo, M. A., and L. N. Segura. 2023. Nest‐site features influence nest survival of the Hellmayr’s pipit in extensive cattle‐grazed grasslands. Journal of Wildlife Management 87:e22396. https://doi.org/10.1002/jwmg.22396

Comparatore, V. M., M. M. Martínez, A. I. Vasallo, M. Barg, and J. P. Isacch. 1996. Abundancia y relaciones con el hábitat de aves y mamíferos en pastizales de paja colorada (Paspalum quadrifarium) manejados con fuego. Interciencia 21:228-237.

Comte, L., and G. Grenouillet. 2013. Species distribution modelling and imperfect detection: comparing occupancy versus consensus methods. Diversity and Distributions 19:996-1007. https://doi.org/10.1111/ddi.12078

Cortelezzi, A., I. Berkunsky, M. V. Simoy, R. E. Cepeda, C. B. Marinelli, and F. P. Kacoliris. 2015. Are breeding sites a limiting factor for the Tandilean redbelly toad (Bufonidae) in pampean highland grasslands? Neotropical Biology and Conservation 10:182-186. https://doi.org/10.4013/nbc.2015.103.09

Cortelezzi, A., M. V. Simoy, A. Siri, M. Donato, R. E. Cepeda, C. B. Marinelli, and I. Berkunsky. 2020. New insights on bioindicator value of Chironomids by using occupancy modelling. Ecological Indicators 117:106619. https://doi.org/10.1016/j.ecolind.2020.106619

Cozzani, N., and S. M. Zalba. 2009. Estructura de la vegetación y selección de hábitats reproductivos en aves del pastizal pampeano. Ecología Austral 19:35-44.

Cunningham, M. A., and D. H. Johnson. 2019. Narrowness of habitat selection in woodland and grassland birds. Avian Conservation and Ecology 14(1):14. https://doi.org/10.5751/ACE-01372-140114

Dalla Salda, L., L. Spalletti, D. Poiré, R. De Barrio, and H. Echeveste. 2006. Tandilia. Serie correlación geológica 21:17-46.

Davis, S. K. 2004. Area sensitivity in grassland passerines: effects of patch size, patch shape, and vegetation structure on bird abundance and occurrence in southern Saskatchewan. Auk 121:1130-1145. https://doi.org/10.1093/auk/121.4.1130

Davis, S. K., and D. C. Duncan. 1999. Grassland songbird occurrence in native and crested wheatgrass pastures of southern Saskatchewan. Studies in Avian Biology 19:211-218.

de Abelleyra, D., S. Banchero, S. Verón, J. Mosciaro, and J. Volante. 2020. Mapa Nacional de Cultivos campaña 2019/2020. Colección 1. Versión 1. Instituto Nacional de Tecnología Agropecuaria (INTA), Buenos Aires, Argentina.

de la Peña, M. 2011. Observaciones de campo en la alimentación de las aves. Biológica 13:1-88.

De la Sota, E. 1967. Composición, origen y vinculaciones de la flora pteridológica de las sierras de Buenos Aires (Argentina). Boletín de la Sociedad Argentina de Botánica 11:105-128.

Di Giacomo, A. S., P. D. Vickery, H. Casañas, O. A. Spitznagel, C. Ostrosky, S. Krapovickas, and A. J. Bosso. 2010. Landscape associations of globally threatened grassland birds in the Aguapey River important bird area, Corrientes, Argentina. Bird Conservation International 20:62-73. https://doi.org/10.1017/S0959270909990177

Dotta, G., B. Phalan, T. W. Silva, R. Green, and A. Balmford. 2016. Assessing strategies to reconcile agriculture and bird conservation in the temperate grasslands of South America. Conservation Biology 30:618-627. https://doi.org/10.1111/cobi.12635

Ehrlich, P. R., D. S. Dobkin, and D. Wheye. 1988. Birder’s handbook: a field guide to the natural history of North American birds. Simon & Schuster, New York, New York, USA.

Ellison, K. S., C. A. Ribic, D. W. Sample, M. J. Fawcett, and J. D. Dadisman. 2013. Impacts of tree rows on grassland birds and potential nest predators: a removal experiment. PLoS ONE 8:e59151. https://doi.org/10.1371/journal.pone.0059151

Evans, A., J. Vickery, and M. Shrubb. 2004. Importance of overwintered stubble for farmland bird recovery (and reply from G.R. (Dick) Potts). Bird Study 51:94-96. https://doi.org/10.1080/00063650409461339

Fahrig, L. 2003. Effects of habitat fragmentation on biodiversity. Annual Review of Ecology, Evolution, and Systematics 34:487-515. https://doi.org/10.1146/annurev.ecolsys.34.011802.132419

Feijoó, C., L. Rigacci, and S. Doyle. 2005. Ecological regionalization of pampean streams in Argentina. Internationale Vereinigung für theoretische und angewandte Limnologie: Verhandlungen 29:748-753. https://doi.org/10.1080/03680770.2005.11902778

Filloy, J., and M. I. Bellocq. 2007. Patterns of bird abundance along the agricultural gradient of the Pampean region. Agriculture, Ecosystems & Environment 120:291-298. https://doi.org/10.1016/j.agee.2006.09.013

Fiske, I., and R. Chandler. 2011. Unmarked: an R Package for fitting hierarchical models of wildlife occurrence and abundance. Journal of Statistical Software 43:1-23. https://doi.org/10.18637/jss.v043.i10

Fontana, C. S., E. Chiarani, L. da Silva Menezes, C. B. Andretti, and G. E. Overbeck. 2018. Bird surveys in grasslands: do different count methods present distinct results? Revista Brasileira de Ornitologia 26:116-122. https://doi.org/10.1007/BF03544422

Friedman, M., R. E. Cepeda, A. Cortelezzi, M. V Simoy, C. B. Marinelli, F. P. Kacoliris, J. E. Dopazo, and I. Berkunsky. 2016. Searching for an elusive anuran: a detection model based on weather forecasting for the tandilean red-belly toad. Herpetological Conservation and Biology 11:476-485.

Ghersa, C. M., E. de la Fuente, S. Suarez, and R. J. C. Leon. 2002. Woody species invasion in the Rolling Pampa grasslands, Argentina. Agriculture, Ecosystems & Environment 88:271-278. https://doi.org/10.1016/S0167-8809(01)00209-2

Goijman, A. P., M. J. Conroy, J. N. Bernardos, and E. Zaccagnini. 2015. Multi-season regional analysis of multi-species occupancy: implications for bird conservation in agricultural lands in east-central Argentina. PLoS ONE 10:e0130874. https://doi.org/10.1371/journal.pone.0130874

Grant, T. A., E. Madden, and G. B. Berkey. 2004. Tree and shrub invasion in northern mixed-grass prairie: implications for breeding grassland birds. Wildlife Society Bulletin 32:807-818. https://doi.org/10.2193/0091-7648(2004)032[0807:TASIIN]2.0.CO;2

Green, A. W., D. C. Pavlacky, and T. L. George. 2019. A dynamic multi-scale occupancy model to estimate temporal dynamics and hierarchical habitat use for nomadic species. Ecology and Evolution 9:793-803. https://doi.org/10.1002/ece3.4822

Guttery, M. R., C. A. Ribic, D. W. Sample, A. Paulios, C. Trosen, J. Dadisman, D. Schneider, and J. A. Horton. 2017. Scale-specific habitat relationships influence patch occupancy: defining neighborhoods to optimize the effectiveness of landscape-scale grassland bird conservation. Landscape Ecology 32:515-529. https://doi.org/10.1007/s10980-016-0462-y

Herkert, J. R., D. L. Reinking, D. A. Wiedenfeld, M. Winter, J. L. Zimmerman, W. E. Jensen, E. J. Finck, R. R. Koford, D. H. Wolfe, S. K. Sherrod, M. A. Jenkins, J. Faaborg, and S. K. Robinson. 2003. Effects of Prairie fragmentation on the nest success of breeding birds in the midcontinental United States. Conservation Biology 17:587-594. https://doi.org/10.1046/j.1523-1739.2003.01418.x

Herrera, L., M. C. Sabatino, F. R. Jaimes, and S. Saura. 2017. Landscape connectivity and the role of small habitat patches as stepping stones: an assessment of the grassland biome in South America. Biodiversity and Conservation 26:3465-3479. https://doi.org/10.1007/s10531-017-1416-7

Herse, M. R., M. E. Estey, P. J. Moore, B. K. Sandercock, and W. A. Boyle. 2017. Landscape context drives breeding habitat selection by an enigmatic grassland songbird. Landscape Ecology 32:2351-2364. https://doi.org/10.1007/s10980-017-0574-z

Hilty, J. A., and A. M. Merenlender. 2004. Use of riparian corridors and vineyards by mammalian predators in Northern California. Conservation Biology 18:126-135. https://doi.org/10.1111/j.1523-1739.2004.00225.x

Hovick, T. J., R. D. Elmore, and S. D. Fuhlendorf. 2014. Structural heterogeneity increases diversity of non-breeding grassland birds. Ecosphere 5:1-13. https://doi.org/10.1890/ES14-00062.1

Howland, B. W. A., D. Stojanovic, I. J. Gordon, J. Radford, A. D. Manning, and D. B. Lindenmayer. 2016. Birds of a feather flock together: using trait-groups to understand the effect of macropod grazing on birds in grassy habitats. Biological Conservation 194:89-99. https://doi.org/10.1016/j.biocon.2015.11.033

Isacch, J. P., N. O. Maceira, M. S. Bo, M. R. Demaría, and S. Peluc. 2005. Bird-habitat relationship in semi-arid natural grasslands and exotic pastures in the west pampas of Argentina. Journal of Arid Environments 62:267-283. https://doi.org/10.1016/j.jaridenv.2004.11.008

Jacobs, R. B., F. R. Thompson, R. R. Koford, F. A. La Sorte, H. D. Woodward, and J. A. Fitzgerald. 2012. Habitat and landscape effects on abundance of Missouri’s grassland birds. Journal of Wildlife Management 76:372-381. https://doi.org/10.1002/jwmg.264

Johnson, R. G., and S. A. Temple. 1990. Nest predation and brood parasitism of tallgrass prairie birds. Journal of Wildlife Management 54:106-111. https://doi.org/10.2307/3808909

Leston, L. 2013. Transmission lines as tall-grass prairie habitats: local mowing, spraying, and surrounding urbanization as determinants of wildlife richness and abundance. Dissertation. University of Manitoba, Winnipeg, Manitoba, Canada.

MacKenzie, D. I., J. D. Nichols, J. A. Royle, K. H. Pollock, L. L. Bailey, and J. E. Hines. 2018. Occupancy estimation and modeling: inferring patterns and dynamics of species occurrence. Second edition. Academic Press, London, UK. https://doi.org/10.1016/C2012-0-01164-7

Maphisa, D. H., H. Smit-Robinson, and R. Altwegg. 2019. Dynamic multi-species occupancy models reveal individualistic habitat preferences in a high-altitude grassland bird community. PeerJ 7:e6276. https://doi.org/10.7717/peerj.6276

Matos, H. M., M. J. Santos, F. Palomares, and M. Santos-Reis. 2009. Does riparian habitat condition influence mammalian carnivore abundance in Mediterranean ecosystems? Biodiversity and Conservation 18:373-386. https://doi.org/10.1007/s10531-008-9493-2

McKinney, M. L. 2006. Urbanization as a major cause of biotic homogenization. Biological Conservation 127:247-260. https://doi.org/10.1016/j.biocon.2005.09.005

Merritt, D. M., and H. L. Bateman. 2012. Linking stream flow and groundwater to avian habitat in a desert riparian system. Ecological Applications 22:1973-1988. https://doi.org/10.1890/12-0303.1

Nugent, D. T., D. J. Baker‐Gabb, P. Green, B. Ostendorf, F. Dawlings, R. H. Clarke, and J. W. Morgan. 2022. Multi‐scale habitat selection by a cryptic, critically endangered grassland bird—The Plains‐wanderer (Pedionomus torquatus): implications for habitat management and conservation. Austral Ecology 47:698-712. https://doi.org/10.1111/aec.13157

Ortiz, D., and P. Capllonch. 2007. Distribución y migración de Sporophila c. caerulescens en Sudamérica. Revista Brasileira de Ornitologia 15:377-385.

Patten, M., E. Shochat, D. Reinking, D. Wolfe, and S. Sherrod. 2006. Habitat edge, land management, and rates of brood parasitism in tallgrass prairie. Ecological Applications 16:687-695. https://doi.org/10.1890/1051-0761(2006)016[0687:HELMAR]2.0.CO;2

Perkins, A. J., M. J. Whittingham, R. B. Bradbury, J. D. Wilson, A. J. Morris, and P. R. Barnett. 2000. Habitat characteristics affecting use of lowland agricultural grassland by birds in winter. Biological Conservation 95:279-294. https://doi.org/10.1016/S0006-3207(00)00042-2

Pietz, P. J., D. A. Buhl, J. A. Shaffer, M. Winter, and D. H. Johnson. 2009. Influence of trees in the landscape on parasitism rates of grassland passerine nests in southeastern North Dakota. Condor 111:36-42. https://doi.org/10.1525/cond.2009.080012

Pírez, F., and J. Aldabe. 2023. Comparison of the bird community in livestock farms with continuous and rotational grazing in eastern Uruguay. Ornithology Research 31:41-50. https://doi.org/10.1007/s43388-022-00113-1

Pretelli, M. G., A. V. Baladrón, D. A. Cardoni, and J. P. Isacch. 2018. Bandadas otoño-invernales en agroecosistemas del sudeste de la región Pampeana, Argentina. Ornitologia Neotropical 29:259-269. https://doi.org/10.58843/ornneo.v29i1.396

Pretelli, M. G., J. P. Isacch, and D. A. Cardoni. 2013. Year-round abundance, richness and nesting of the bird assemblage of tall grasslands in the South-East Pampas Region, Argentina. Ardeola 60:327-343. https://doi.org/10.13157/arla.60.2.2013.327

Pretelli, M. G., J. P. Isacch, and D. A. Cardoni. 2015. Effects of fragmentation and landscape matrix on the nesting success of grassland birds in the Pampas grasslands of Argentina. Ibis 157:688-699. https://doi.org/10.1111/ibi.12292

Rahmig, C. J., W. E. Jensen, and K. A. With. 2009. Grassland bird responses to land management in the largest remaining tallgrass prairie. Conservation Biology 23:420-432. https://doi.org/10.1111/j.1523-1739.2008.01118.x

Ribic, C. A., M. J. Guzy, T. J. Anderson, D. W. Sample, and J. L. Nack. 2012. Bird productivity and nest predation in agricultural grasslands. Pages 119-134 in C. A. Ribic and F. R. Thompson III, editors. Video surveillance of nesting birds. University of California Press, Berkeley, California, USA. https://doi.org/10.1525/california/9780520273139.003.0010

Ribic, C. A., and D. W. Sample. 2001. Associations of grassland birds with landscape factors in southern Wisconsin. American Midland Naturalist 146:105-121. https://doi.org/10.1674/0003-0031(2001)146[0105:AOGBWL]2.0.CO;2

Saunders, D. A., R. J. Hobbs, and C. R. Margules. 1991. Biological consequences of ecosystem fragmentation: a review. Conservation Biology 5:18-32. https://doi.org/10.1111/j.1523-1739.1991.tb00384.x

Sekercioglu, C. 2006. Increasing awareness of avian ecological function. Trends in Ecology & Evolution 21:464-471. https://doi.org/10.1016/j.tree.2006.05.007

Shahan, J. L., B. J. Goodwin, and B. C. Rundquist. 2017. Grassland songbird occurrence on remnant prairie patches is primarily determined by landscape characteristics. Landscape Ecology 32:971-988. https://doi.org/10.1007/s10980-017-0500-4

Shake, C. S., C. E. Moorman, J. D. Riddle, and M. R. Burchell. 2012. Influence of patch size and shape on occupancy by shrubland birds. Condor 114:268-278. https://doi.org/10.1525/cond.2012.110107

Shnack, J., F. Francesco, U. Colado, M. Novoa, and E. Schnack. 2000. Humedales antrópicos: su contribución para la conservación de la biodiversidad en los dominios subtropical y pampásico de la Argentina. Ecología Austral 10:63-80.

Temple, S. A., B. M. Fevold, L. K. Paine, D. J. Undersander, and D. W. Sample. 1999. Nesting birds and grazing cattle: accommodating both on midwestern pastures. Studies in Avian Biology 19:196-202.

Trofino-Falasco, C. 2023. Efectos de la fragmentación y modificación del Pastizal Serrano del Sistema de Tandilia sobre las poblaciones de aves de pastizal. Dissertation. La Plata National University, La Plata, Buenos Aires, Argentina.

Trofino-Falasco, C., A. S. Di Giacomo, M. F. Aranguren, T. Martínez Aguirre, P. Grilli, E. L. Paz, M. G. Pizzarello, D. G. Vera, and I. Berkunsky. 2024. 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. Studies on Neotropical Fauna and Environment 59:74-83. https://doi.org/10.1080/01650521.2022.2052685

Trofino-Falasco, C., M. V. Simoy, M. F. Aranguren, M. G. Pizzarello, A. Cortelezzi, D. G. Vera, M. I. Simoy, C. B. Marinelli, R. E. Cepeda, A. S. Di Giacomo, and I. Berkunsky. 2023. How effective is camera trapping in monitoring grassland species in the southern Pampas ecoregion? Revista Mexicana de Biodiversidad 94:e945243. https://doi.org/10.22201/ib.20078706e.2023.94.5243

Valicenti, R., E. Fariña, R. Scaramuzzino, and C. D´Alfonso. 2010. Ordenación de la vegetación en el paisaje Boca de la Sierras (Azul, Sistema de Tandilia). Revista de la Sociedad Argentina de Ecología de Paisajes 1:111-122.

van den Boogaart, K. G., and R. Tolosana-Delgado. 2013. Analyzing compositional data with R. Springer, Berlin, Germany. https://doi.org/10.1007/978-3-642-36809-7

Vickery, J. A., R. E. Feber, and R. J. Fuller. 2009. Arable field margins managed for biodiversity conservation: a review of food resource provision for farmland birds. Agriculture, Ecosystems & Environment 133:1-13. https://doi.org/10.1016/j.agee.2009.05.012

Vickery, P. D., M. L. Hunter, and S. M. Melvint. 1994. Effects of habitat area on the distribution of grassland birds in Maine. Conservation Biology 8:1087-1097. https://doi.org/10.1046/j.1523-1739.1994.08041087.x

West, A. S., P. D. Keyser, C. M. Lituma, D. A. Buehler, R. D. Applegate, and J. Morgan. 2016. Grasslands bird occupancy of native warm-season grass. Journal of Wildlife Management 80:1081-1090. https://doi.org/10.1002/jwmg.21103

Weyland, F., J. Baudry, and C. M. Ghersa. 2014. Rolling Pampas agroecosystem: which landscape attributes are relevant for determining bird distributions? Revista Chilena de Historia Natural 87:1. https://doi.org/10.1186/0717-6317-87-1

Winter, M., and J. Faaborg. 1999. Patterns of area sensitivity in grassland-nesting birds. Conservation Biology 13:1424-1436. https://doi.org/10.1046/j.1523-1739.1999.98430.x

Wolcott, D. M., J. R. Herkert, C. A. Ribic, R. B. Renfrew, and D. W. Sample. 2023. Potential impacts of land‐management schedules on grassland bird nests and fledglings. Wildlife Society Bulletin 47:e1488. https://doi.org/10.1002/wsb.1488

Zotta, Á. 1940. Lista sobre el contenido estomacal de las aves argentinas. Hornero 7:402-411. https://doi.org/10.56178/eh.v7i3.353