The effect of land-use on the diversity and mass-abundance relationships of understory avian insectivores in Sri Lanka and southern India

Self Cite

Selective logging dominates forested landscapes across the tropics. Despite the structural damage incurred, selectively logged forests typically retain more biodiversity than other forest disturbances. Most logging impact studies consider conventional metrics, like species richness, but these can conceal subtle biodiversity impacts. The mass–abundance relationship is an integral feature of ecological communities, describing the negative relationship between body mass and population abundance, where, in a system without anthropogenic influence, larger species are less abundant due to higher energy requirements. Changes in this relationship can indicate community structure and function changes. We investigated the impacts of selective logging on the mass–abundance scaling of avian communities by conducting a meta‐analysis to examine its pantropical trend. We divide our analysis between studies using mist netting, sampling the understory avian community, and point counts, sampling the entire community. Across 19 mist‐netting studies, we found no consistent effects of selective logging on mass–abundance scaling relative to primary forests, except for the omnivore guild where there were fewer larger‐bodied species after logging. In eleven point‐count studies, we found a more negative relationship in the whole community after logging, likely driven by the frugivore guild, showing a similar pattern. Limited effects of logging on mass–abundance scaling may suggest high species turnover in logged communities, with like‐for‐like replacement of lost species with similar‐sized species. The increased negative mass–abundance relationship found in some logged communities could result from resource depletion, density compensation, or increased hunting; potentially indicating downstream impacts on ecosystem functions. Synthesis and applications. Our results suggest that size distributions of avian communities in logged forests are relatively robust to disturbance, potentially maintaining ecosystem processes in these forests, thus underscoring the high conservation value of logged tropical forests, indicating an urgent need to focus on their protection from further degradation and deforestation.

Section: Discussionmentioning

confidence: 79%

Section: Discussionmentioning

confidence: 96%

Section: Discussionmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 91%

Section: Introductionmentioning

confidence: 99%

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Mass–abundance scaling in avian communities is maintained after tropical selective logging

Cosset

Gilroy

Srinivasan

et al. 2020

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Patterns and processes underlying understory songbird communities in southern China

Liu,

Yu,

Che

et al. 2024

Understory bird communities, especially those comprising insectivores, are highly sensitive to forest loss and fragmentation. Currently, there is little knowledge regarding the large‐scale diversity patterns of understory bird communities, particularly in Eastern Asia. Consequently, we aimed to identify the distribution patterns of understory birds in southern China and the factors underlying these patterns. We analysed the diversity distribution patterns of taxonomic and functional α and β diversity for understory Passeriformes birds in southern China utilising cluster and ordination analyses. Subsequently, we analysed the effects of geographic distance, annual mean temperature, annual temperature range, annual mean precipitation, and annual precipitation range on diversity distribution patterns. In total, 9282 individuals belonging to 11 orders, 48 families, and 297 species were captured over 98,544 net hours, with Alcippeidae being the most abundant family in southern China. The understory bird communities of the 25 sites were categorised into six sub‐regions of the Oriental Realm (Indo‐Malayan Realm). The pattern in the distribution of taxonomic and functional β‐diversity of understory birds in southern China was consistent with zoogeographical regionalisation. Three distinct geographical groups were identified: Group 1 was located in the Min‐Guang Coast and Hainan sub‐regions; Group 2 was located in the East Hilly Plain, Southwest Mountains, and Western Mountains and Plateaus sub‐regions; and Group 3 was located in the Southern Yunnan Mountain subregion. The most critical factors related to the distribution patterns of β‐diversity were geographical distance, annual mean temperature, and annual temperature range. Our results showed that the understory bird communities of the Southwest Mountain, East Hilly Plain, and Western Mountains, and Plateaus sub‐regions were similar, as were those of the Min‐Guang Coast and Hainan sub‐regions. Our results underscore the joint roles of distance, temperature, and historical evolution in understory bird communities.

Playback‐Aided Surveys and Acoustic Monitoring in the Detection of the Endangered Forest Owlet Athene blewitti

Rajan,

Neema,

Trivedi

et al. 2024

Monitoring rare and endangered species over the long term is challenging due to limited historical data and comparable methods. Climate and landscape changes can significantly impact species distributions, driving some to extinction. The Forest Owlet is an endangered bird considered extinct but rediscovered after 113 years in 1997. Since its rediscovery, followed by the description of its calls, there have been regular recent sightings of the species from newer locations, leading to its downlisting in the IUCN Red List from critically endangered to endangered. In the Dang region in Gujarat, India, there have been no historical records despite previous systematic ornithological studies over three decades, but have multiple sightings over the last few years. Although we now know a little more about the broad association of the species occurrence with habitat and climate variables, a major focus of this study is to estimate the reasons for the “appearance” of the Forest Owlet in Dangs. We revisited locations of past surveys to determine if the species is currently found in the study sites where it was previously unrecorded. We also examine whether new survey methods using playback of its call could enhance its detection. During resurveys, we located the Forest Owlet at new, previously unrecorded locations. Analyses of satellite imagery products revealed significant changes in the broader Dang landscape, including the loss of native forests, increased agriculture, and shifts in mean maximum temperature and rainfall. Our research suggests playback can enhance detection, although its effectiveness varies across landscapes. A detection strategy for long‐term monitoring was developed using different acoustic detectors. An effective detection distance of 300 m within the habitat was achieved using automated recording units (ARUs). Although the species responds to climate and habitat change, the cause of the increased reports of this endangered species remains undetermined. However, we found increased detections using newer survey techniques involving bioacoustics. We recommend using these techniques carefully for future baseline studies, which are urgently required.