Biology subjects

Madhu, N.

Publications and source records attributed to Madhu, N..

4 recordsLinked to original sources

bioRxiv2026

Hornbill abundance and habitat correlates in Kali Tiger Reserve, Western Ghats, India-Insights from collaborative monitoring

1.The future of species, particularly large-bodied birds, under climate threats, is increasingly unclear. Protected areas (PAs) can mitigate the impacts of global change, but are not completely immune. This makes it imperative to monitor populations even inside PAs. In the forests of the Western Ghats, three hornbill species are found--Malabar Grey Hornbill, Malabar Pied Hornbill and Great Hornbill. Kali Tiger Reserve, of Karnataka state, India, is known for its healthy hornbill populations, yet few systematic surveys have attempted to estimate their abundance, distributions and habitat affiliations. In this study, we documented the distributions of the three hornbills, estimated the density of Malabar Grey Hornbills and assessed correlates of hornbill encounter rates within the reserve. Malabar Grey Hornbills were the most abundant and widely distributed, found in all ranges of the reserve. Gund, Kadra and Phansoli had the most detections of Malabar Pied and Great Hornbills. Encounter rates of Malabar Grey Hornbill were positively correlated with food-tree stem density, those of Malabar Pied Hornbill negatively correlated with basal area, while those of Great Hornbill not significantly associated with any variable. Malabar Grey Hornbills had a density of 5.1 per km2 (mean flock size = 1.2). While encounter rates of Malabar Pied and Great Hornbills were low, these numbers track the breeding season, when vocal activity is low and females are inside nests. This survey represents a partnership between researchers and the Karnataka forest department, aimed towards inculcating the collaborative spirit of research and monitoring.

ecology↗

bioRxiv2025

Effects of forest cover, temperature and flower abundance on cashew pollinators in the northern Western Ghats, India

Global declines in pollinators pose serious risks for biodiversity, ecosystem functioning, and human well-being. Understanding how landscape structure and climate shape pollinator communities is critical, yet studies that jointly assess these factors in human-dominated tropical landscapes remain scarce. Here, we investigate how forest cover, distance to forest patches, flower abundance, and temperature influence pollinator communities in monoculture cashew plantations that are rapidly expanding in the northern Western Ghats, part of the Western Ghats-Sri Lanka global biodiversity hotspot. We conducted 210 half-hour observation sessions across 30 cashew orchards in Dodamarg, India. At the community level, flower abundance and forest cover positively influenced pollinator richness, number of pollinators, and number of visits. The number of visits showed a unimodal response to temperature, with peaks occurring within narrow, taxon-specific ranges, lower temperatures for birds and higher for insects, likely reflecting physiological constraints. At the species level, flower abundance and temperature emerged as key predictors of occurrence, while three butterfly species occurred more frequently near forest patches. Contrary to expectations, proximity to forest did not reduce ambient orchard temperatures, suggesting limited forest-mediated thermal buffering in our site. Together, these findings highlight the vulnerability of pollination services to both land-use change and rising temperatures. Ongoing conversion of natural forests to cashew monocultures, coupled with climate warming, may erode pollinator communities and jeopardize crop yields in tropical agroecosystems. More broadly, our results underscore the importance of conserving remnant forests and accounting for thermal sensitivity of pollinators to sustain ecosystem services in changing landscapes worldwide.

ecology↗

bioRxiv2025

Effects of land-use intensification on nectar resources, bird assemblages and bird-flower interaction networks in the Western Ghats, India

1.Agricultural expansion is a major driver of tropical forest loss globally, making it critical to determine factors that maintain key plant-animal interactions, such as nectarivory, in human-dominated landscapes. In the Paleotropics, which is experiencing rapid expansion of tree crop plantations, few studies have compared floral and nectar-feeding bird communities, their interactions, and network organisation along a tree crop intensification gradient. In a cashew agriculture-forest matrix of the northern Western Ghats of India, we compared forests, cashew agroforests, and cashew monocultures to assess, 1) the abundance, diversity, and composition of flowers and nectar-feeding birds, 2) diversity of bird-flower interactions, and 3) network organisation. Floral abundance declined most sharply in monocultures, followed by agroforests. The abundance and diversity of nectar-feeding birds peaked in agroforests. Forests had the highest floral diversity and bird-flower interactions. Nectivore community composition differed across land-use types, with agroforests harbouring both forest specialists and open-habitat species typically found in monocultures. We found that sunbirds dominated plant-flower interactions across land-use types. After rarefaction (to control for differences in network size), agroforests and monocultures showed higher connectance, specialisation, and modularity than the forest network. Our results suggest that plantations that retain native trees (agroforests) can partially offset the alterations caused in floral resource availability and nectar-feeding bird communities by cashew cultivation. Planting bird-pollinated native tree species along orchard edges can make cashew farming more suitable for nectar-feeding birds, and has the potential to benefit cashew production by attracting avian pollinators.

ecology↗

bioRxiv2024

Native trees within plantations and surrounding forest cover are essential for bird conservation in cashew-dominated landscapes within a biodiversity hotspot

O_LIAnnually, agriculture is responsible for about 60% of tropical forest loss globally. C_LIO_LIstrategies in agricultural landscapes range from enhancing farm-level habitat diversity to retaining forest cover within landscapes. A critical question is determining the relative influence of native trees within farms and forest cover around them on avian diversity, trait responses and species persistence in tree-based systems in landscapes where protected areas are often absent, often the case in lowland tropical forest ecosystems. C_LIO_LIBy sampling birds across gradients of cashew plantation intensification and varying levels of surrounding cashew and forest cover, we examined the relative influence of site- and landscape-level factors on species composition, taxonomic, functional, and phylogenetic diversity, as well as species- and trait-specific responses, and whether phylogenetic relationships among bird species influenced these responses. C_LIO_LIAt the community level, forests, cashew agroforests, and cashew monocultures hosted compositionally different bird communities. Site-level variables, specifically the proportion of native trees, influenced taxonomic and phylogenetic diversity, while landscape-level variables had no effect. None of the predictor variables accounted for the variation in functional diversity. C_LIO_LIAt the species level, site-level variables, specifically the proportion of native trees, and landscape-level variables, particularly cashew cover around plantations, had positive and negative impacts on species responses, respectively. At the trait level, evergreen forest specialists were associated positively with the proportion of native trees and negatively associated with cashew cover. Resident species had a positive association with forest cover. We found a phylogenetic signal in species responses to predictor variables, indicating that closely-related species responded similarly to predictor variables. C_LIO_LISynthesis and applications: To retain taxonomic and phylogenetic diversity and ensure persistence of evergreen forest specialists, it is essential to retain native trees within cashew plantations and maintain surrounding forest cover. Future policies should incentivise the retention and restoration of forest patches and restrict the felling of native trees within cashew plantations. C_LI

ecology↗