Comparative nesting strategies of birds in high versus low vegetation areas

Introduction

Birds, in particular, are closely tied to the structure and condition of farmland. Fields with substantial vegetation cover often provide birds with more than just space-they offer shelter, concealment, and access to food. Dense crop growth, field margins, hedgerows, and cover crops can create microhabitats that protect nests from predators and buffer them from extreme temperatures. Such structural diversity not only reduces disturbance but also tends to support higher insect abundance, which is critical during the breeding season (Bas et al., 2009a; Best et al., 1997; Edo et al., 2024) [1,3,8] . As a result, these more complex agricultural settings frequently sustain greater nesting densities, higher species richness, and improved reproductive outcomes compared to simplified fields. Intensively managed fields are characterized by bare soil or uniform monocultures often leave birds exposed. In such environments, nests may be more visible to predators and more vulnerable to weather extremes. Ground-nesting species are particularly at risk because they depend heavily on vegetation for camouflage and thermoregulation (Lauck et al., 2023a Blosch et al., 2023a) [13,5] . Across different regions of the world, studies consistently demonstrate that habitat heterogeneity and vegetation structure are central to avian reproductive success. Fallow lands and structurally diverse crop fields tend to support more nests and a wider variety of species than intensively cultivated row crops (Tilgar et al., 2024) [22] . Moreover, nesting strategy strongly influences how birds respond to agricultural practices: species that nest on the ground are generally more sensitive to habitat simplification than those nesting in shrubs or trees (Li et al., 2023a) [15] . Despite this growing global understanding, region-specific research in South Asia remains limited. In the Indo-Gangetic Plains, particularly in Punjab, agricultural intensification has reshaped the rural landscape. Mechanization, widespread monocropping, removal of noncrop vegetation, and increasing input use have simplified field structure and reduced habitat diversity. Yet studies from nearby regions suggest that agricultural fields and surrounding heterogeneous elements-such as fallow patches, field margins, and rural infrastructurestill play an important role in maintaining avifaunal communities International Journal of Agriculture and Food Science https://www.agriculturaljournals.com (Mukhtar et al., 2025; Kumar & Sahu, 2016) [19,12] . Punjab's dominant rice-wheat rotation further influences seasonal vegetation patterns, often leaving fields with limited ground cover during critical breeding periods. Practices such as stubble burning and repeated tillage can intensify this effect, potentially threatening ground-nesting and low-vegetation-dependent species. Emerging evidence from neighboring areas also indicates that bird communities are shaped not only by crop type but by finer habitat features, including vegetation structure, field configuration, and even nearby cattle sheds (Grewal et al., 2023) [9] .

In one of India's most productive yet ecologically strained agroecosystems, understanding these dynamics is increasingly important. Exploring how birds select nesting sites in vegetated versus bare agricultural settings can provide valuable insights for balancing agricultural productivity with biodiversity conservation.

Methodology 2.1 Study area

The study was conducted in the agricultural landscapes by selecting fields in three villages namely Dhaipai (L1), Sahauli (L2) and Jodhan (L3) of district Ludhiana in Punjab, India, a region having intensive rice-wheat cropping systems. Mechanical and monoculture practices along with deforestation in agriculture in this region has created varying levels of vegetation structure across fields, ranging from densely or highly vegetated (HV) field area to low vegetated (LV) field area with minimal ground cover. To assess how vegetation influences avian nesting and breeding ecology, fields were categorized into two primary habitat types: (1) vegetated fields with substantial crop growth, field margins, or residual cover, and (2) simplified or bare fields with limited structural complexity or low vegetation. Surrounding habitat features like building structures were also noted.

Study design and nest searching

Fields were selected randomly at each location having representation of both high and low vegetation while maintaining spatial independence to reduce pseudo replication. Surveys were conducted during the primary breeding season (March to July), coinciding with peak Nesting activity of farmland birds in northern India in 2022-23 and 2023-24. Nest searches were performed using line transect method; observers walked parallel transects spaced approximately 5-10 meters apart, carefully scanning for nesting activity in vegetated fields (Verner 1985) [23] . In low vegetation field areas, nests were located by visual observations. This combination of systematic searching and observation is widely used in farmland bird studies to maximize detection probability while minimizing disturbance (Best et al., 1997; Bas et al., 2009b) [3,2] . Each nest was located and observed by minimizing disturbances; nests were approached cautiously for species identification and the nesting parameters like number of nests, nest height were recorded. Tree types preferred by birds for nesting sites were identified in studied fields.

Nest monitoring and breeding observations

Nests were monitored at intervals of five to seven days at studied locations. [14,5] . Nesting strategy (ground, shrub, or tree nesting) was documented for each species, given that ground-nesting birds are generally more sensitive to habitat features and agricultural intensification (Li et al., 2023b) [16] .

Results and Discussion

A total of 21 bird species were recorded nesting in agricultural fields with five species common to both high and low vegetation areas (Table 1 and2 Asian Koel

International Journal of Agriculture and Food Science https://www.agriculturaljournals.com

12.

High Vegetation denoted as HV The comparative analysis of nesting and reproductive parameters at all the locations during 2023-2025 revealed noticeable variations in species distribution, nesting characteristics, and breeding success. Among the three study sites, L2 exhibited comparatively higher species richness and nesting activity, followed by L1, whereas L3 showed relatively moderate nesting density. Nest height variation was largely species-specific rather than strictly locationdependent; however, L2 recorded slightly greater average nest heights in canopy-nesting species such as House Crow and Pariah Kite, indicating the presence of relatively taller trees (Table 3). At all sites, tree-nesting species generally built nests at heights ranging from 3-5 m above ground level. In

Discussion

The data has shown that agricultural fields with high vegetation and structural diversity supported higher number of avian species as compared to the low-vegetation fields at all the locations. It has indicated dependence of bird species on vegetation structures for nesting sites. Xu et al (2022) [25] observed that the tree diversity significantly affected bird diversity in urban mountain parks. Liu (2025) [17] had observed that the vegetation structural complexity especially the dense tree canopy is an important deciding factor that influences the selection of nesting sites by birds. Structural heterogeneity in vegetation in different habitats often affects the abundance, distribution, diversity and richness of the bird community (Kukreti 2020) [11] . A positive correlation between plant species diversity, foliage high density and bird species diversity has been reported by many workers (Joshi et al., 2012) [10] . Spatial variation in nesting activity and species richness among the three locations can be attributed to differences in habitat heterogeneity and resource availability. Ecologically complex habitats with greater vegetation stratification are widely known to support higher avian diversity and breeding densities, as they provide a variety of nesting substrates and foraging opportunities (Tews et al, 2004) [21] . Studies have consistently shown that areas with higher structural diversity promote niche differentiation and reduce interspecific competition, thereby enhancing species coexistence and reproductive activity. An ideal nesting site is a high-quality, strategic location that offers enhanced safety from predators, provides durable and stable materials for constructing a secure nest, and is in close proximity to abundant, nutrient-rich foraging habitats that facilitate successful rearing of the brood. The present study conclusively demonstrated that vegetation structure is the single most critical determinant of avian nesting diversity within agricultural landscapes of the Ludhiana region. Xu et al (2024) [24] also highlighted the critical role of dense canopy structure, including its horizontal and vertical distribution and variation, in predicting avian diversity. A comprehensive study by Ding et al (2023) [6] revealed no significant preference for specific tree species, but the height of tree and tree coverage appeared as the important factors influencing nest site selection. Variation in nest height, particularly among canopy-nesting species, reflects adaptive strategies to minimize predation risk and environmental stress. Elevated nesting in taller trees has been associated with reduced predation pressure and increased breeding success, especially in urban and semiurban habitats. Douini et al (2023) [7] reported maximum number of nesting species belonging to order Passeriformes in the study area having dense vegetation, and the results are aligned with our findings in present study. Reproductive success in birds is heavily determined by the selection of safe nesting site, and several birds have been reported to choose those sites for nesting which reduce the risk of predation (Mainwaring et al., 2014) [18] . Consequently, nesting strategy plays a critical role in determining reproductive success, with arboreal and cavity nesters generally exhibiting higher survival rates than ground nesters. Environmental conditions may influence survival rates of offspring, but clutch size itself tends to remain relatively stable unless extreme ecological pressures are present. Differences in hatching and fledgling success among locations highlight the role of habitat quality in determining reproductive outcomes. Higher reproductive success in favourable habitats is often linked to increased food availability, better nesting cover, and lower disturbance levels. The observed patterns reinforce the role of habitat structure and resource availability as key drivers influencing breeding outcomes across different landscapes.

Conclusion

Overall, the collective comparison indicates that L2 provided relatively more suitable breeding conditions in terms of vegetation diversity and habitat heterogeneity, followed by L1, while L3 showed comparatively moderate reproductive performance. Tree cavity nesters and colonial nesting species demonstrated greater reproductive stability across all sites, whereas ground-nesting birds remained more susceptible to environmental pressures. These findings underscore the significant influence of habitat structure and protection status on nesting success and reproductive output of avian species in the study region.

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