Factors affecting the breeding ecology of the globally threatened Lesser Adjutant (Leptoptilos javanicus) in agricultural landscapes of Nepal

Abstract

Many threatened birds use the mosaic of agricultural landscapes for foraging and breeding. Despite the reliance of many species on these habitats, few studies have investigated factors influencing the breeding ecology of storks in agricultural landscapes. We assessed sitelevel variables (tree height and location of nest tree; human habitation or non-human habitation), colony-level variables (colony size and chicks per nest), and landscape-level variables (area of human habitation, wetland area, and distance to the nearest wetland) to understand the factors influencing the breeding ecology of the globally threatened Lesser Adjutant (Leptoptilos javanicus) across multiple locations in the agricultural landscape of lowland Nepal during 2019-2020. We monitored 65 active colonies that had 206 active nests in five study sites. Two hundred eighty chicks fledged from these colonies, with 13% (n = 41) chick mortality. Most colonies were in agricultural land (51%) and human habitation (28%). Lesser Adjutant colonies located on tall trees such as Bombax ceiba (57%), Haldina cordifolia (11%), and Ficus religiosa (11%); however, these tree species were used much more than their availability on the landscape. Tree height had a significant positive influence on colony site selection and colony size, whereas colony size positively influenced fledgling success. Measured landscape variables did not have significant relationships with breeding success metrics. The agricultural landscapes of lowland Nepal provided important breeding habitat for Lesser Adjutants, and the suitability of sites with colonies related more to site-level and colony-level than landscape-level variables. Increasing urban development of agricultural landscapes is likely the greatest threat to breeding Lesser Adjutants, with the decline of suitable nesting trees being a potential additional threat. Lowland Nepal's agricultural landscapes support significant breeding populations of Lesser Adjutants that had considerable breeding success, underscoring the urgent need to support traditional agriculture that favors large waterbirds. Facteurs affectant l'écologie de reproduction du marabout chevelu (Leptoptilos javanicus) menacé à l'échelle mondiale dans les paysages agricoles du NépalRÉSUMÉ. De nombreux oiseaux menacés utilisent la mosaïque des paysages agricoles pour chasser et se reproduire. Bien que de nombreuses espèces dépendent de ces habitats, rares sont les études portant sur les facteurs qui influencent l'écologie de reproduction des cigognes dans les paysages agricoles. Nous avons évalué les variables au niveau des sites (hauteur des arbres et emplacement des nids ; habitation humaine ou non-humaine), au niveau des colonies (taille de la colonie et nombre d'oisillons par nid) et au niveau des paysages (zone d'habitation humaine, zone humide et distance par rapport à la zone humide la plus proche) afin de comprendre les facteurs qui influencent l'écologie de reproduction du marabout chevelu (Leptoptilos javanicus) dans de multiples emplacements du paysage...

Breeding ecology of the Asian openbill in eastern Nepal: Larger trees support higher fledgling success

“…. Similarly, colony size also influenced the breeding success of the Asian openbill, as reported in other studies (Lesser Adjutant:Katuwal, Sundar, et al, 2022;Sundar et al, 2019 and Marabou Storks Leptoptilos crumeniferus:Monadjem, 2005);…”

“…We surveyed the selected area from early May 2020 through the end of November 2022, following the methods previously used in Nepal to study the breeding biology of the Lesser Adjutant and other large waterbirds (Katuwal, Sundar, et al., 2022 ; Koju et al., 2019 ; Sundar et al., 2016 ). In each grid, we traveled all the available motorable routes and enquired with local people to locate stork colonies within the study area (Koju et al., 2019 ).…”

“…These habitats provide abundant food, which enhances their breeding performance and productivity (Janiszewski et al., 2014 ; Sundar, 2006 ). Moreover, the presence of larger trees in these landscapes, which are maintained by farmers, is essential for various waterbird species (Hilaluddin et al., 2003 ; Katuwal, Sundar, et al., 2022 ; Koju et al., 2019 ). Specifically, these large trees, characterized by their tall height, substantial diameter at breast height (DBH), and expansive canopy cover, facilitate the establishment of larger colony sizes (Clancy & Ford, 2011 ; Ghimire et al., 2022 ; Katuwal, Sundar, et al., 2022 ).…”

“…Moreover, the presence of larger trees in these landscapes, which are maintained by farmers, is essential for various waterbird species (Hilaluddin et al., 2003 ; Katuwal, Sundar, et al., 2022 ; Koju et al., 2019 ). Specifically, these large trees, characterized by their tall height, substantial diameter at breast height (DBH), and expansive canopy cover, facilitate the establishment of larger colony sizes (Clancy & Ford, 2011 ; Ghimire et al., 2022 ; Katuwal, Sundar, et al., 2022 ). This, in turn, significantly impacts the breeding performances of colonial waterbirds, including storks such as the Asian openbills ( Anastomus oscitans ; Mohapatra et al., 2019 ; Rajković, 2021 ).…”

“…Lastly, there is a significant lack of information about where these storks' nest are in Nepal and what habitats they prefer for breeding, especially in the eastern region. This gap is especially concerning because of the ongoing unplanned urbanization in agricultural‐wetland landscapes (Bhattarai et al., 2023 ; Rimal et al., 2018 ), and tree felling is rapidly increasing (Katuwal et al., 2024 ; Katuwal, Sundar, et al., 2022 ), which could have a major impact on the breeding success of these storks.…”