Forest patches as important bird habitats in Malaysia's large-scale infrastructure development areas

177 Forest patches as important bird habitats in Malaysia's largescale infrastructure development areas Norfazliyana Nordin1, Fudzla Zulfa Khiruddin1, Nor Adibah Ismail2, Ummi Nur Syafiqah Daud2, Nurfatin Batrisyia Md Ali1, Saiful Hilmi Jamal Shuhaily1, Ahmad Khusaini Mohd Kharip Shah3, Aisah Shukor4, Shukor Md Nor5, Mohammad Saiful Mansor1 1 Department of Biological Sciences and Biotechnology, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, 43600 UKM Bangi, Selangor, Malaysia 2 Department of Earth Sciences and Environment, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, 43600 UKM Bangi, Selangor, Malaysia 3 Department of Wildlife and National Parks (PERHILITAN) Peninsular Malaysia, KM 10, Jalan Cheras, 56100 Kuala Lumpur, Malaysia 4 TNB Research, No. 1, Lorong Ayer Itam, Kawasan Institusi Penyelidikan, 43000 Kajang, Selangor, Malaysia 5 Pelan Urus Services, Bangi Gateway, Seksyen 15, 43650 Bandar Baru Bangi, Selangor, Malaysia Corresponding author: Mohammad Saiful Mansor ([email protected]) Copyright: © Norfazliyana Nordin et al. This is an open access article distributed under terms of the Creative Commons Attribution License (Attribution 4.0 International – CC BY 4.0). Research Article Abstract The high demand for hydroelectric power to support electricity in rural areas of Malaysia drives the construction of dams. The development of large-scale dams threatens forest-dependent avian species due to habitat loss and fragmentation. Although many recent dam projects incorporate sustainable concepts for monitoring and managing wildlife, there is a lack of studies conducted during the development phase. This study evaluated avian species diversity across various habitats along a dam construction gradient, including recently disturbed forests, agricultural-forest patches and mosaic habitats. We conducted surveys using point count observations and mist-netting across six sampling sites over a 24-month period. A total of 120 bird species representing 40 families were recorded across the study area. Species richness was highest in agricultural–forest patches (78 species), followed by recently disturbed forests (65 species) and mosaic habitats (57 species). Hill numbers analysis similarly showed that agricultural–forest patches had the greatest overall diversity and the highest number of forest-dependent species. Feeding-guild patterns showed that omnivores dominated agricultural–forest patches and recently disturbed forests, while insectivores formed the largest proportion of the community in mosaic habitats containing embedded forest patches. Such findings highlight the importance of maintaining forest patches within homogeneous or degraded habitats, including agricultural and mosaic landscapes, as these remnants can continue to support substantial bird communities when properly managed. By implementing such sustainable management practices, the negative impacts of large-scale development projects on forest-dependent avian populations can be mitigated. Key words: Agricultural, avifauna, hydrodam, mosaic habitats, recently disturbed forests, remnant forests Introduction The rising demand for hydroelectric power in Malaysia has driven the construction of new dams, including the large-scale Nenggiri hydroelectric dam, which is currently under construction in the State of Kelantan. While such projects Academic editor: Abhijeet Bayani Received: 4 August 2025 Accepted: 13 November 2025 Published: 18 December 2025 ZooBank: https://zoobank. org/1E9A696D-52DE-4F5E-88E57E5AD4A603A4 Citation: Nordin N, Khiruddin FZ, Ismail NA, Daud UNS, Ali NBM, Shuhaily SHJ, Shah AKMK, Shukor A, Md Nor S, Mansor MS (2025) Forest patches as important bird habitats in Malaysia's large-scale infrastructure development areas. Nature Conservation 60: 177–194. https://doi.org/10.3897/ natureconservation.60.167763 Nature Conservation 60: 177–194 (2025) DOI: 10.3897/natureconservation.60.167763 178 Nature Conservation 60: 177–194 (2025), DOI: 10.3897/natureconservation.60.167763 Norfazliyana Nordin et al.: Critical forest habitats for birds have benefits, such as preventing flooding, providing renewable energy and the potential to transform the socio-economic conditions of the population (Hossain et al. 2018), the opening of forest areas for the construction of dams and high rates of ensuing logging activity lead to the loss of wildlife (Irving et al. 2018; Zainol et al. 2020; Nasruddin-Roshidi et al. 2021). Dam construction has a significant environmental impact due to the decreases in forest cover that result from deforestation and habitat fragmentation (Tang et al. 2010; Andriolo et al. 2013). Therefore, it is important to identify the habitat surrounding the dam project and the species of wildlife within the dam area. The construction of dams can precipitate a cascade of environmental changes, including the establishment of logging road networks, indigenous settlements, construction zones and vast logged regions designated for reservoirs, all of which will inevitably fragment and isolate the available habitats within the landscape. Before the inundation phase of large hydroelectric reservoirs, there may be considerable effects on aquatic and terrestrial biodiversity due to habitat loss and fragmentation along with alterations in the physical and chemical characteristics of the environment (Brown et al. 2024). During the construction phase before flooding occurs, the development of large dams can obstruct feeding and reproductive habitats and interfere with the dispersal and movement patterns of vertebrate populations across the landscape (Fimbel et al. 2001; Kleinschroth and Healey 2017). The effects of habitat loss may diminish biodiversity by altering competitive and predator-prey dynamics; this often favours generalist species and, thus, can affect the long-term stability of natural communities (Brose et al. 2017). Numerous avian species are sensitive to habitat loss, resulting in decreases in abundance and species richness immediately after anthropogenic disturbances. Birds, as indicators of forest habitat quality, play an important role in maintaining ecological balance (Egwumah et al. 2017; Grande et al. 2018; Puan et al. 2020; Kour and Singh 2023). Therefore, it is crucial to conduct bird studies in the areas remaining after habitat fragmentation caused by the development of dams and the associated logging activities. Common approaches employed by researchers for studying bird communities include point count, mist-netting and analyses of how species exhibit geographical variation in response to changes in the nature and structure of habitats (Eglington et al. 2012; Gardali et al. 2017; Tripathy et al. 2023). In recently disturbed forests, larger forest areas with high ecosystem integrity provide ideal foraging niches and shelter for many bird species (Grantham et al. 2020; Mansor et al. 2020a; Khiruddin et al. 2025). Forested areas can maintain conditions in terms of adequate food resources, suitable habitat structure and diversity of vegetation. Studies of the remaining forests in Sarawak have shown that, for hornbills, the area should be at least 50,000 hectares and that this can either be a single block or a cluster of virtually contiguous blocks forming a forest complex (Jaafar et al. 2020; Wee et al. 2024). Meanwhile, forest–agricultural landscape habitat refers to forested areas situated next to agricultural lands, consisting of remnant patches of the original forest that were not fully cleared for cultivation. These habitats retain native tree species characteristic of the original ecosystem, although their structure and ecological conditions are influenced by surrounding agricultural activities. As a result, they may exhibit unique ecological dynamics shaped by their proximity to agricultural practices, which can influence soil quality, moisture levels and species interactions (Yahya et al. 2023). 179 Nature Conservation 60: 177–194 (2025), DOI: 10.3897/natureconservation.60.167763 Norfazliyana Nordin et al.: Critical forest habitats for birds Although recent dam projects in Malaysia have emphasised sustainability in monitoring and managing wildlife, limited research has been conducted on the impact on wildlife during the development phase. Detailed studies of bird communities within areas designated for hydroelectric dam construction, are particularly lacking. Habitats have been significantly altered in recently disturbed forests within dam development zones, leading to changes in biodiversity patterns. Understanding these impacts is essential to developing strategies for conservation and sustainable management within dam-affected ecosystems. Several previous studies have been conducted by our team in a dam development zone in Hulu Terengganu (Adyla et al. 2016; Mohd-Taib et al. 2018; Nasruddin-Roshidi et al. 2021; Ismail et al. 2022). However, no assessment has been carried out on how recently disturbed landscapes affect bird diversity during the pre-construction phase. Therefore, this study aimed to evaluate avian species diversity across habitats situated along a dam construction gradient, including recently disturbed forests, agricultural-forest patches and mosaic habitats, all of which have been fragmented by logging roads and land clearing. Specifically, we sought to: (1) compare species richness and abundance across habitat types; (2) assess variation in species composition amongst the three habitats and (3) identify species of conservation concern, particularly those vulnerable to disturbance. We hypothesised that larger and less disturbed forest patches would support greater diversity and abundance of forest-dependent and specialist species, whereas more modified habitats, such as mosaics or agroforestry zones, would support a higher proportion of generalist and edge-adapted species. We also expected that species of conservation concern to show greater sensitivity to habitat disturbance due to their ecological specialisations. Although some species may persist during the logging phase, we anticipated that ongoing habitat alteration would reduce overall diversity and abundance (Irving et al. 2018; Nasruddin-Roshidi et al. 2021; Ismail et al. 2022). Studying bird diversity during the active development phase is, therefore, critical for understanding community-level responses and providing baseline data to guide conservation planning near hydroelectric dam sites. Study area This study was conducted in the Nenggiri hydroelectric dam catchment area, located in Mukim Ulu Nenggiri, Gua Musang District, Kelantan, located in the central-eastern Peninsular Malaysia, within the southern part of Kelantan. This region is characterised by tropical rainforest, which supports a high diversity of plant and animal species. The catchment area features a heterogeneous landscape comprising various habitat types, ranging from pristine and recently disturbed forests to agricultural-forestry patches, mosaic habitats, orchards, oil palm plantations, rubber plantations, human settlements, work areas and barren land (Fig. 1). Six study sites comprising different habitats were selected to assess the pattern of avian species diversity along the dam construction gradient. The habitats were Recently Disturbed Forests (RD), Agricultural–Forest Patches (AFP) and Mosaic Habitats (MH). The RD represented a natural forest that had been fragmented due to dam-related development activity. These sites are adjacent to barren land where deforestation and logging began approximately in mid-2022. This fragmentation has reduced the overall forest size, increased the distances between 180 Nature Conservation 60: 177–194 (2025), DOI: 10.3897/natureconservation.60.167763 Norfazliyana Nordin et al.: Critical forest habitats for birds patches and altered the surrounding landscape. Fragmentation results in edge effects, where the conditions of the forest edges become significantly different from the interior. The AFP represented a transition zone between natural forest ecosystems and adjacent agricultural areas, particularly oil palm plantations (Elaeis guineensis). This patch was uniquely positioned as a buffer zone, blending the characteristics of both forest and agricultural landscapes. The MH comprised a mixture of natural forest, agricultural crops such as rubber (Hevea brasiliensis) and orchards containing fruit-bearing trees, such as durian (Durio zibethinus) and cocoa (Theobroma cacao). Site selection was guided by dominant tree composition, drone imagery for large-scale assessment, land-use maps and digitised 2024 Landsat imagery. All sampling sites were located within a 5 km radius of anthropogenic disturbance areas, including logging zones and construction sites. Field survey methods Two field survey methods were used: point counts and mist-netting. The data were collected from July 2022 until July 2024 during the early stages of dam development, encompassing both the dry season (May to September) and the wet season (October to April), typical of Malaysia’s tropical rainforest climate. For point counts, we recorded all birds detected visually or aurally. This method is suitable for habitats with dense vegetation and high canopy cover. Each habitat type was represented by two study sites and, at each site, five point-count stations were established, spaced by 200 m apart. Counts were conducted for 20 minutes between 0700–1000 h and 1600–1900 h, corresponding to peak activity periods. Each site was visited three times per sampling period, yielding a total sampling effort of 30 hours (MacKenzie et al. 2017). Surveys were avoided during adverse weather, such as rain and strong winds. Observations were made using binoculars (Minox BV 10x42) and species identifications followed Robson (2014). For mist-netting, ten nets (2.5 m × 9 m × 4 m; mesh size 36 mm) were set up at each study site from 0700 to 1900 h over five consecutive days per field session. Nets were monitored every two hours and captured birds were fitted with numbered aluminium rings on the tarsus to avoid double counting, photographed and released unharmed. The total mist-netting effort across all sessions amounted to 3,600 net-hours. Figure 1. Locations of the study sites in the Nenggiri Hydroelectric Dam area, Gua Musang, Kelantan. The inset map shows an aerial view of Recently Disturbed Forests (RD), Agricultural–Forest Patches (AFP) and Mosaic Habitat (MH). 181 Nature Conservation 60: 177–194 (2025), DOI: 10.3897/natureconservation.60.167763 Norfazliyana Nordin et al.: Critical forest habitats for birds Data analysis We implemented species rarefaction and extrapolation techniques for evaluating bird diversity by utilising Hill numbers, a collection of metrics that quantify several dimensions of diversity, distinguished by an order parameter q. At q = 0, the Hill number represents species richness, effectively counting the number of distinct species present. At q = 1, the Hill number assesses both species richness and evenness, examining not only the quantity of species present, but also the uniformity of their individual abundances. At q = 2, the Hill number corresponds to the Simpson diversity index, which quantifies variety by squaring the fraction of each species relative to the total number of individuals, thereby emphasising dominating species. As q expands, the impact of rarer species in the calculation diminishes (Jost 2006; Chao et al. 2014), hence assigning greater significance to abundant species. As q approaches infinity, the metric converges to the abundance of the predominant species (Hill 1973). The Chao 1 index yields an estimate of species richness if sampling is prolonged. We examined the diversity indices to assess the total number of bird species occurring across these habitats using the iNEXT online website (Chao et al. 2014) and the Chao 1 index analysis using PAST Software (Paleontological Statistics, Version 4.03, Hammer and Harper (2001)). The Shapiro-Wilks test for normality showed the data were not normally distributed. The differences in bird species abundance amongst the three habitats were analysed using Pearson’s Chi-squared test, followed by posthoc analyses to identify significant pairwise differences. Variation in bird species composition was assessed at each observation point using non-metric multidimensional scaling (NMDS) with the Bray–Curtis index in PAST software. Bar plots and box plot diagrams were used to illustrate total species richness and abundance for the three habitats along the dam construction gradient and bar plots were used to show the proportions of species by feeding guilds across the three habitat types. All plots were generated using the ggplot2 package for R Software (R Development Core Team 2020; Oksanen et al. 2023). Bird species were classified into forest-dependent, non-forest dependent and feeding guilds, based on trophic groups as suggested by Robson (2014), Nasruddin-Roshidi et al. (2021) and Razali et al. (2022). Results A total of 727 bird observations representing 120 species and 40 families were recorded across the study area. The AFP showed the highest diversity of bird species, followed by RD and MH (Fig. 2). The family Pycnonotidae had the highest number of recognised species (12 species) across the three habitats, followed by Muscicapidae (12 species), Cuculidae (eight species) and Cisticolidae (six species). Black-headed Bulbul (Microtarsus melanocephalos), Yellow-bellied Bulbul (Alophoixus phaeocephalus), Yellow-vented Bulbul (Pycnonotus goiavier), Red-eyed Bulbul (Pycnonotus brunneus) and Spectacled Bulbul (Rubigula erythropthalmos) were relatively common in the study area. The most abundant species recorded from mist-netting were Little Spiderhunter (Arachnothera longirostra), Asian Emerald Dove (Chalcophaps indica) and Yellow-bellied Bulbul (Alophoixus phaeocephalus). 182 Nature Conservation 60: 177–194 (2025), DOI: 10.3897/natureconservation.60.167763 Norfazliyana Nordin et al.: Critical forest habitats for birds According to habitat, a total of 78 species (39% of total species and the highest amongst all habitats) and 210 individuals (29% of total individuals) occurred in AFP, followed by 65 species (33%) and 279 individuals (38% of the total individuals and the highest amongst all habitats) in RD. The least species-rich was MH, with only 57 species (29%) and only 238 individuals (33%) being recorded (Fig. 2, Table 1). The Chao 1 richness estimator indicates that the estimated species richness was highest in AFP at 144 species, followed by RD at 132 species and lowest in MH at 84 species (Table 1). The boxplot (Fig. 3) illustrates the abundances of the species throughout the three study habitats. AFP and MH had higher median bird abundance compared to RD, although RD exhibited the most variability. The abundance of the habitat-specific avifauna is included as a supplementary file (Suppl. material 1). The study identified a total of 90 forest-dependent species and 30 non-forest-dependent species, indicating a strong reliance on forest habitats amongst the avian community surveyed. Amongst the habitat types, AFP supported the highest number of forest-dependent species (n = 62), whereas RD and MH each harboured 42 forest-dependent species, highlighting the variation in species distribution across different forest conditions. Overall, forest-dependent birds accounted for 75% of the total species richness, emphasising the critical role of Figure 2. Species richness for three habitat types. Table 1. Bird diversity indices from all sampling sites across three habitats. Habitat Abundance Species Chao 1 richness estimator Coverage estimates Coverage estimates for twice Estimated diversity at 95% coverage q = 0 q = 1 q = 2 AFP 210 78 144 0.801 0.888 109.92 58.32 31.05 RD 279 65 132 0.868 0.919 76.43 25.15 10.51 MH 238 57 84 0.891 0.953 56 22.23 8.9 183 Nature Conservation 60: 177–194 (2025), DOI: 10.3897/natureconservation.60.167763 Norfazliyana Nordin et al.: Critical forest habitats for birds forest ecosystems in sustaining avian biodiversity. A comprehensive list of forest-dependent and non-forest-dependent species is provided in Suppl. material 1. Amongst the recorded species, one, the Greater Green Leafbird (Chloropsis sonnerati), was categorised as an Endangered (EN) species in the IUCN Red List. Five species were categorised as Vulnerable (VU): Brown-chested Jungle Flycatcher (Cyornis brunneatus), Grey-cheeked Bulbul (Alophoixus tephrogenys), Javan Myna (Acridotheres javanicus), Rhinoceros Hornbill (Buceros rhinoceros) and Wreathed Hornbill (Rhyticeros undulatus). Another 18 species were categorised as Near Threatened (NT), while the remaining species were in the least concern (LC) category (IUCN 2025) (Suppl. material 1). The bird species diversity differed significantly amongst the three habitats sampled (Pearson’s Chi-squared test: X2 = 606.01, df = 238, p ≤ 0.05). Pairwise Bonferroni analysis showed that the bird species diversity of AFP was significantly different from that of MH (p ≤ 0.05). AFP exhibited the highest species richness (78 species; Chao 1 index = 144) and diversity estimates across all scales (q = 0: 109.92; q = 1: 58.32; q = 2: 31.05), despite lower sampling coverage (q = 0: 0.801). RD had the highest abundance (279 individuals), but fewer species (65; Chao 1 index = 132), with diversity estimates (q = 0: 76.43; q = 1: 25.15; q = 2: 10.51) indicating a community increasingly dominated by fewer species. MH showed the lowest species richness (57; Chao 1 index = 84) and diversity (q = 0: 56; q = 1: 22.23; q = 2: 8.9), with the highest sampling coverage (q = 0: 0.891). The coverage-based rarefaction curves for the three study habitats showed steady increases, indicating that more species are expected to be discovered in these areas (Fig. 4). Diversity estimates for orders q = 0 (Species richness), q = 1 Figure 3. Boxplots illustrating the observed abundance of birds across three habitat types. Each point represents an individual observation at a point count station. Boxes represent the interquartile range (IQR), showing the middle 50% of the data. The horizontal line within each box indicates the median. Whiskers extend to the minimum and maximum values within 1.5 times the IQR. Points beyond the whiskers represent outliers. 184 Nature Conservation 60: 177–194 (2025), DOI: 10.3897/natureconservation.60.167763 Norfazliyana Nordin et al.: Critical forest habitats for birds (Shannon diversity) and q = 2 (Simpson diversity), each plotted with 95% confidence intervals, indicated that AFP had the highest estimated diversity, while MH had the lowest. Interpolation at the site with the lowest species abundance (AFP) of 210 individuals showed that AFP had the highest number of species (78), followed by RD (55.22) and MH (53.79). The iNEXT analysis showed that the estimated coverage values for the reference samples were 0.801 for AFP, 0.868 for RD and 0.891 for MH (Fig. 4). Higher sample coverage numbers that approach 1.0 indicate that the sampling effort has successfully captured the majority of species, whereas lower values signal that numerous species remain unrepresented. Non-metric Multidimensional Scaling (NMDS) analysis showed that the composition of bird species varied significantly amongst the observation points (stress = 0.3875, R2 values for axis 1 = 0.7152 and for axis 2 = 0.0561) (Fig. 5). The NMDS plot visually presents the differences in species composition amongst the three habitats. The data were collected over two study sites for each habitat and each site has 5-point counts, providing a temporal Figure 4. Coverage-based rarefaction and extrapolation generated using iNEXT function for bird communities across the three habitat types. Figure 5. Non-parametric Multidimensional Scaling (NMDS) showing the difference in species composition across three habitats. 185 Nature Conservation 60: 177–194 (2025), DOI: 10.3897/natureconservation.60.167763 Norfazliyana Nordin et al.: Critical forest habitats for birds dimension to the analysis. AFP appeared more distinct from RD and MH, while the latter two appear more similar to each other, based on the relative distances in the plot (Fig. 5). The proportions of bird species in different feeding guilds across the three habitats showed that omnivorous birds dominated both AFP and RD, contributing the largest proportion of the community at over 40%. In contrast, insectivorous birds were the most prevalent in MH, comprising more than 50% of the community (Fig. 6). Discussion The results revealed that agricultural-forest patch habitats supported greater bird diversity than recently disturbed forests and mosaic habitats. These habitats encompassed a range of feeding guilds and forest-dependent species, including six species listed as threatened on the IUCN Red List. The higher diversity observed in agricultural-forest patches likely reflects their greater structural complexity and the wider availability of ecological niches, consistent with findings by Gregory and Strien (2010), who reported higher avian diversity in structurally complex environments. These findings highlight the ecological importance of remnant forests and habitat rehabilitation in maintaining biodiversity within large-scale development landscapes (Tuen et al. 2018; Nasruddin-Roshidi et al. 2021; Ismail et al. 2022). Remnant forest patches within modified tropical landscapes provide essential refuges for threatened bird species (Mansor et al. 2018; Martínez-Ruiz et al. 2024). Agricultural-forest patches are still able to support high species richness because the nearby forest patches are large in size and connected to other forest areas. Forest areas with diverse microhabitats and foraging niches provide abundant food resources and can sustain larger bird populations (Mansor et al. 2018; Hendershot et al. 2023). Sensitive bird species require extensive areas to meet their foraging and ranging needs (Mansor et al. 2018). The connectivity of forest patches plays an important role in maintaining bird population persistence within landscapes fragmented by agriculture and dam construction (Kang et al. 2015; Nasruddin-Roshidi et al. 2021). Connected or closely-situated forest patches allow birds to move between habitats and reduce the risk of population isolation (Mohd-Taib et al. 2014). Conversely, forest patches that are widely separated create severe fragmentation, trapping birds within small areas with limited resources, which ultimately reduces breeding success and increases the risk of local extinction (Coddington et al. 2023). Figure 6. Proportions of species by feeding guilds across three habitat types. 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Springer, 468–478. https://doi.org/10.1007/978981-15-1971-0_47 Supplementary material 1 Forest patches as critical habitats for birds in Malaysian hydroelectric project areas Authors: Norfazliyana Nordin, Fudzla Zulfa Khiruddin, Nor Adibah Ismail, Ummi Nur Syafiqah Daud, Nurfatin Batrisyia Md Ali, Saiful Hilmi Jamal Shuhaily, Ahmad Khusaini Mohd Kharip Shah, Aisah Shukor, Shukor Md Nor, Mohammad Saiful Mansor Data type: xlsx Explanation note: This dataset lists bird species observed across different habitat types in Malaysia, specifically in recently disturbed forests (RD), agricultural forest patches (AFP), and mosaic habitats (MH). It includes details such as the bird’s family, scientific and common names, the number of individuals recorded at six different sites, their forest dependency (whether they rely on forests or not), IUCN conservation status (e.g., Least Concern), and feeding guilds like carnivores. The data helps show which birds are present in each habitat and how they relate to forest conditions and conservation priorities. Copyright notice: This dataset is made available under the Open Database License (http://opendatacommons.org/licenses/odbl/1.0/). The Open Database License (ODbL) is a license agreement intended to allow users to freely share, modify, and use this Dataset while maintaining this same freedom for others, provided that the original source and author(s) are credited. Link: https://doi.org/10.3897/natureconservation.60.167763.suppl1