Biodiversity is declining rapidly, largely driven by intensive agricultural land-use and habitat loss (Díaz et al., 2019). In Europe roughly half of the land is devoted to agriculture (EEA, 2025), with diminishing biodiversity (Emmerson et al., 2016). In response, the European Union's Biodiversity Strategy and Nature Restoration Regulation (NRR) was developed to restore semi-natural habitats within agricultural landscapes, to help restore biodiversity and ecosystem functions, especially pollination (Hermoso et al., 2022). NRR has several measures to reverse the decline of pollinator groups. Such restoration interventions are more effective if they benefit further groups beyond pollinators, like birds. These interventions may also benefit rodent pests, which are important parts of the food web in agricultural systems. Establishment of wildflower plantings is a widely used intervention to counteract pollinator decline in agricultural landscapes, as it provides more flower resources for pollinating insects (e.g. Bihaly et al., 2024; Williams et al., 2015). A growing body of evidence has accumulated on the effects of wildflower plantings on non-target, but key farmland groups for example birds, as wildflower plantings provide nesting and foraging sites for birds. These studies found that the presence of wildflower plantings is consistently linked to higher breeding bird abundance and species number compared to intensively managed arable fields (Redhead et al., 2018; Rieger et al., 2022; Schmidt et al., 2022). Landscape heterogeneity in agricultural areas increases bird abundance and diversity (Bosco et al., 2024; Rösch et al., 2023). It was also found that larger wildflower plantings promote birds and pollinators more effectively (Bihaly et al., 2024; Meichtry-Stier et al., 2018). Both pollinators and birds contribute to agricultural yield via pollination and pest control services, as insectivorous birds may contribute to pest control (Garcia et al., 2020), and raptors may regulate rodent pest populations (Labuschagne et al., 2016; Paz et al., 2013).

Although the evidence on the effect of both wildflower planting area, and landscape structure on birds is well established, significant knowledge gaps remain. First, the interaction of these factors is rarely assessed, especially in a rigorous experimental design. For example, landscape context may interact with the effectiveness of local interventions (Batáry et al., 2011). Second, most evidence is from Western and Northern European biogeographic regions (e.g. Bosco et al., 2024; Redhead et al., 2018; Rösch et al., 2023; Staggenborg and Anthes, 2022), so it is geographically biased, with less knowledge from the Eastern parts of the EU with higher farmland biodiversity (Báldi and Batáry, 2011; Sutcliffe et al., 2015). Knowledge from less studied regions is essential to fully understand the relationships, and to reliably provide evidence for the NRR's national implementation plans. These have to be specific to local context, thus local information is badly needed. Third, most studies searched for biodiversity benefits of wildflower plantings, and associated increase in yield, but few addressed potential harms to yield in surrounding crops, like spillover of rodent pests (Briner et al., 2005). Wildflower plantings are non-tilled, therefore they provide undisturbed burrows and constant feed for rodent pests, like common voles (Microtus arvalis), which may seriously damage crops (Heroldová et al., 2018). Generally speaking, interventions on the one hand may significantly contribute to NRR targets, like increased ecosystem function, and pollinator and farmland bird populations, but on the other hand may reduce the net benefits of the intervention for farmers and thereby lower acceptance of restoration efforts.

We established a landscape-scale experiment to promote pollinators in 2020, by sowing wildflower plantings in the agricultural landscape of Central Hungary. Wildflowers were sown in two different configurations (larger, continuous field, or three smaller strips), but with the same cumulative area in both homogeneous (>90 % arable land) and heterogeneous (40 %–60 % semi-natural habitats) agricultural landscape plots (Báldi et al., 2022). We already showed that they promote insect pollinators (Bihaly et al., 2024), so in this paper, we aim to assess their effects on two different taxa that are important for farmland ecosystems, birds and rodents. Namely, our questions were: (1) How do different configurations of wildflower plantings in heterogeneous and homogeneous agricultural landscapes affect breeding bird species number, number of individuals and Shannon-diversity, and is there an interaction between landscape structure and spatial configuration of plantings? (2) Is the response of bird communities to treatment and landscape structure similar to patterns found in Western and Northern European biogeographic regions? (3) How do wildflower fields affect rodent populations in heterogeneous and homogeneous agricultural landscapes?

We recorded 24 bird species and 183 individuals, with skylark (Alauda arvensis; n=29) and stonechat (Saxicola rubicola; n=26) as the most abundant species. For bird species number, individual number and diversity we found significant effects of spatial configuration (species number: χ2=10.47, P=0.005; individual number: χ2=15.66, P < 0.001; diversity: χ2= 9.64, P = 0.008), landscape context (species number: χ2=18.34, P<0.001; individual number: χ2=23.0, P<0.001; diversity: χ2=18.42, P<0.001) and the interaction of spatial configuration and landscape context (species number: χ2=8.80, P=0.012; individual number: χ2=11.09, P<0.001; diversity: χ2=9.64, P=0.008) (Fig. 1). The sampling round had no significant effect on species number (χ2=2.59, P=0.11), marginal effect on individual number (χ2=2.84, P=0.092) and significant effect on Shannon-diversity (χ2=4.21, P=0.040), as diversity was higher in the second sampling round. Post-hoc analysis revealed that there were no significant differences between spatial configurations in heterogeneous landscape in birds species and individual number and diversity (species number: all P>0.44; individual number: all P>0.58; diversity: all P>0.11), while in homogeneous landscapes field plots had significantly higher number of species, individuals and diversity than strip plots (species number: z=2.52, P=0.031; individual number: z=2.93, P=0.0096; diversity: z=2.88, P=0.011) or control plots (species number: z=2.65, P=0.022; individual number: z=3.00, P=0.0079; diversity: z=3.76, P<0.001), and there was no difference between strip and control plots (species number: z=-0.44, P=0.90; individual number: z=-0.44, P=0.90; diversity z=-0.85, P=0.67) (Fig. 1). Also, we found that in heterogeneous landscapes there were significantly higher number of species, individuals and diversity than in homogeneous landscape plots in both strips (species number: z=2.74, P=0.006; individual number: z=3.53, P<0.001; diversity: z=2.92, P=0.0035) and control areas (species number: z=3.33, P<0.001; individual number: z=3.72, P<0.001; diversity: z=5.03, P<0.001), however, this difference was only present on field plots in terms of individual number (z=2.01, P=0.045), not in species number (z=1.18, P=0.24) or diversity (z=1.60, P=0.11) (Fig. 1).

There were significantly more active vole burrows in wildflower fields than in control areas (χ2=18.47, P<0.001; Fig. 2a). The number of active burrows was also higher in April than in October (χ2=6.63, P=0.010; Fig. 2b), while landscape context had no effect (χ2=0.002, P=0.964). Active burrows in control areas were recorded only in alfalfa (Medicago sativa) fields.

In this study, we examined how an experimental setup of pollinator-promoting wildflower plantings in agricultural landscapes of Central-Eastern Europe affects key groups of ecosystem functioning beyond pollinators. We found that these plantings have positive effects on two key vertebrate groups, birds and rodents, depending on planting spatial configuration and landscape context. In homogeneous agricultural landscapes, wildflower fields enhanced bird species number, abundance, and diversity, whereas strips offered no significant improvement over crop fields. Wildflower fields also created undisturbed soil conditions within otherwise intensively tilled landscapes, allowing burrowing rodent pests to persist, as indicated by the presence of vole burrows almost exclusively within these fields. Note that our burrow surveys were restricted to the wildflower fields and the crop fields; other uncultivated habitats in the landscape, such as tree rows and semi-natural grasslands, undoubtedly support voles as well, but were not sampled.

In homogeneous agricultural landscapes, where arable land exceeds 90 % of the area, only plots containing wildflower fields supported bird species number and diversity comparable to those observed in heterogeneous landscapes. In homogeneous landscapes strip plots had similarly low bird species number, individual numbers and diversity as control plots, indicating that they are less effective in attracting farmland birds than larger wildflower fields of at least 0.5 ha, which we used in this study. Bird communities in heterogeneous landscapes were similar to or richer than those recorded in wildflower fields within homogeneous landscapes, regardless of planting configuration. This is consistent with previous observations that habitat diversity and landscape heterogeneity increase bird numbers and diversity (Bosco et al., 2024; Rösch et al., 2023), but here we showed it using an experimental set-up. Our results suggest that the additional benefits of wildflower plantings may be limited in structurally diverse landscapes, where baseline habitat heterogeneity is already high. According to our results, wildflower plantings larger than those typically implemented (<0.5 ha area and at least 12–20 m width) are more effective at attracting birds, consistent with findings by Rieger et al. (2022) in Western Europe.

In the same study system, Bihaly et al. (2024) showed that both fields and strips increased pollinator species number and abundance in homogeneous landscapes, particularly in late summer. Thus, while pollinators benefit from both wildflower fields and strips, birds appear to respond primarily to fields. Based on this, we recommend promoting larger wildflower fields (like 50 m × 100 m, as in our study) in agri-environmental schemes. A drawback of wider, larger plantings is the loss of productive crop area, which may reduce farmer acceptance despite their ecological benefits, as they aim to maximize yield. Acceptance, however, can be improved by dedicated payments and outreach.

Wildflower fields support ecosystem services by providing habitat for pollinators that enhance crop pollination and for birds that contribute to pest control, but they may also promote ecosystem disservices by offering refuge to potential agricultural pests such as voles. Voles may have negative effects, as they consume entire plants, including seeds (Heroldová et al., 2021) and may reduce yield in neighbouring fields (Jacob and Tkadlec, 2010). In our study, common voles were present in all but one wildflower field, and absent in all but one control plot. This is consistent with their preference for undisturbed soil for burrowing (Heroldová et al., 2018), as the only control plots with active burrows were on alfalfa fields, which was only mown, not tilled. These observations suggest that, although wildflower fields can support vole populations, their impact on crops may be limited. Briner et al. (2005) showed that voles in wildflower fields rarely venture into neighbouring crop fields, thereby not causing crop damage.

Most studies find that vole density increases from spring to autumn, due to production of offspring (Aschwanden et al., 2007; Tkadlec et al., 2026). However, we found a decrease in active vole burrows from spring to autumn. We suspect that this may be the result of predation. Predation by raptors, like common kestrels (Falco tinnunculus) can decrease common vole population sizes in agricultural landscapes (for review, see Labuschagne et al., 2016). In our study area, raptors like common kestrels and marsh harriers (Circus aeruginosus) were recorded repeatedly during point counts flying over or outside of the 100 m radius and during other field surveys. Additionally, we put ca. 3 m tall posts on all corners of each field and strip plots when establishing the wildflower fields, to mark them for tractor drivers. These posts act as perches for birds, which can increase raptors' presence at the wildflower fields (Labuschagne et al., 2016; Paz et al., 2013). During the point counts, we recorded birds perching on posts on the majority of fields. Wildflower fields may provide food for raptors by attracting voles.

Our results should be interpreted with caution given the small scale of this pilot study. The design comprised only eight replicates (landscape triplets for birds and field–control pairs for voles), each surveyed in two rounds, and for birds three plots had to be excluded. Bird observations were limited (typically 3–5 individuals per visit), so some effects may reflect chance detection, while subtler ones – such as potential benefits of wildflower plantings in heterogeneous landscapes – may have remained undetected. Our landscape classification was also coarse: grasslands and wetlands were pooled as semi-natural habitat, although they may affect birds differently. Furthermore, we measured only alpha diversity, which does not capture changes in community composition, nor demographic parameters such as breeding success or foraging, on which wildflower fields may have effects beyond those detected here. Longer-term monitoring of these sites producing a larger dataset is needed to confirm these patterns and to assess finer-scale responses.

Pollinator promoting interventions can have positive effects on vertebrate groups, but these depend on both field size and landscape structure. Despite the limited sample size, our results provide evidence that farmland birds benefit from larger wildflower fields in homogeneous agricultural landscapes, in line with similar benefits for pollinators in the same system (Bihaly et al., 2024). In heterogeneous landscapes, where bird communities were already richer, we could not detect an additional effect within the scope of this study. Wildflower fields also provide refuge for potential agricultural pests such as voles; however, these species may simultaneously play a beneficial role as a key food source for raptors. Overall, our results demonstrate that well-designed wildflower plantings can deliver multiple biodiversity and ecosystem service benefits supporting the effective implementation of the Nature Restoration Regulation in Eastern European agricultural landscapes.