The post-fledging period, extending from fledging to independence, is a crucial life stage characterized by high mortality due to fledglings' limited mobility and inexperience. During this stage, fledglings gradua...The post-fledging period, extending from fledging to independence, is a crucial life stage characterized by high mortality due to fledglings' limited mobility and inexperience. During this stage, fledglings gradually increase their mobility, leave their parents, disperse from their natal site, and respond to the challenges of new environments. Characterizing these post-fledging movements and space use is essential for understanding juvenile survival strategies and devising targeted conservation measures. The Crested Ibis (Nipponia nippon), an endangered species and a highly protected animals at the national level in China, has seen limited research on its post-fledging movements and space use. From 2015 to 2023, we utilized biologgers, combined with field surveys, to study the movement and space use characteristics of 37 fledglings in Hanzhong City, Shaanxi Province, China, over a two-month post-fledging period. We quantified changes in activity levels (based on overall dynamic body acceleration), independence timing, onset of post-fledging dispersal, habitat selection, and daily activity rhythms after independence. Our results revealed individuals began independent living 26.23 ± 2.34 days post-fledging and onset of dispersal at 25.58 ± 2.33 days, with a range area at the natal of 2.08 ± 0.56 km^(2). The initial 30 days post-fledging are characterized as an ontogenetic phase marked by a rapid increase in body activity level. Fledglings preferred paddy fields during the independent period rather than the forests they relied on before independence. Interestingly, the daily activity rhythm, particularly foraging behavior, peaked at noon—contrasting with the expected morning and evening activity peaks—likely as an adaptation to avoid periods of peak human activity. Additionally, drowning, collisions, and predation in paddy fields are noteworthy causes of fledgling mortality. Consequently, we recommend protecting a 2-km^(2) area around the nest site for at least two-month post-fledging, implementing safety measures around power lines and cesspools. Additionally, reducing human disturbances near foraging habitats and expanding space within paddy fields would help mitigate survival pressures on fledglings.展开更多
The concept of foraging niche provides an insight into habitat use and dietary information of animals.Knowing intraspecific variation in foraging niche and trophic level is critical to the understanding of the species...The concept of foraging niche provides an insight into habitat use and dietary information of animals.Knowing intraspecific variation in foraging niche and trophic level is critical to the understanding of the species response to environmental changes during the process of range expansion,as well as the habitat management for conservation of threatened species.Using stable isotopic values of eggshell membranes(δ;C andδ;N),we examined whether there are differences in habitat use,trophic level,foraging niche width between the new and old breeding habitats(plains vs.mountains)of wild Crested Ibis(Nipponia nippon)in the early breeding season.Crested Ibis exhibited high variability in bothδ;C andδ;N values,δ;C andδ;N varied as a function of habitat types.Birds breeding in plains had significantly higherδ;C but lowerδ;N values compared to the birds breeding in mountains.Higherδ;N suggested that individuals in mountains consumed a great proportion of higher trophic level prey species in the early breeding season.Moreover,the isotopic niches were distinctly different in positions and showed small overlap between the two habitat types.The niche width was wider in old habitat than in the expanded new habitat.Our results demonstrated that the wild Crested Ibis had a high intraspecific variation in habitat uses and trophic levels in the early breeding season,and they could be divided into mountain and plain groups based on their different foraging niches.The difference inδ;N and niche width revealed that high trophic level food resources might be insufficient in plains.These findings stressed the importance of protecting foraging grounds in mountains and the necessity of improving foraging grounds in plains during winter and spring.Our study highlights the feasibility of investigating intraspecific variation in foraging ecology of birds through non-invasive isotopes of eggshell membranes.Understanding foraging niche variation gives us an insight into the food resource diversity in local areas and provides important information regarding particular foraging habitats that require protection.展开更多
基金funded by the National Natural Science Foundation of China(No.32270554,32400400).
文摘The post-fledging period, extending from fledging to independence, is a crucial life stage characterized by high mortality due to fledglings' limited mobility and inexperience. During this stage, fledglings gradually increase their mobility, leave their parents, disperse from their natal site, and respond to the challenges of new environments. Characterizing these post-fledging movements and space use is essential for understanding juvenile survival strategies and devising targeted conservation measures. The Crested Ibis (Nipponia nippon), an endangered species and a highly protected animals at the national level in China, has seen limited research on its post-fledging movements and space use. From 2015 to 2023, we utilized biologgers, combined with field surveys, to study the movement and space use characteristics of 37 fledglings in Hanzhong City, Shaanxi Province, China, over a two-month post-fledging period. We quantified changes in activity levels (based on overall dynamic body acceleration), independence timing, onset of post-fledging dispersal, habitat selection, and daily activity rhythms after independence. Our results revealed individuals began independent living 26.23 ± 2.34 days post-fledging and onset of dispersal at 25.58 ± 2.33 days, with a range area at the natal of 2.08 ± 0.56 km^(2). The initial 30 days post-fledging are characterized as an ontogenetic phase marked by a rapid increase in body activity level. Fledglings preferred paddy fields during the independent period rather than the forests they relied on before independence. Interestingly, the daily activity rhythm, particularly foraging behavior, peaked at noon—contrasting with the expected morning and evening activity peaks—likely as an adaptation to avoid periods of peak human activity. Additionally, drowning, collisions, and predation in paddy fields are noteworthy causes of fledgling mortality. Consequently, we recommend protecting a 2-km^(2) area around the nest site for at least two-month post-fledging, implementing safety measures around power lines and cesspools. Additionally, reducing human disturbances near foraging habitats and expanding space within paddy fields would help mitigate survival pressures on fledglings.
基金funded by the National Natural Science Foundation of China(No.31772483,31900371)the Biodiversity Survey,Monitoring and Assessment Project of Ministry of Ecology and Environment,China(No.2019HB2096001006)。
文摘The concept of foraging niche provides an insight into habitat use and dietary information of animals.Knowing intraspecific variation in foraging niche and trophic level is critical to the understanding of the species response to environmental changes during the process of range expansion,as well as the habitat management for conservation of threatened species.Using stable isotopic values of eggshell membranes(δ;C andδ;N),we examined whether there are differences in habitat use,trophic level,foraging niche width between the new and old breeding habitats(plains vs.mountains)of wild Crested Ibis(Nipponia nippon)in the early breeding season.Crested Ibis exhibited high variability in bothδ;C andδ;N values,δ;C andδ;N varied as a function of habitat types.Birds breeding in plains had significantly higherδ;C but lowerδ;N values compared to the birds breeding in mountains.Higherδ;N suggested that individuals in mountains consumed a great proportion of higher trophic level prey species in the early breeding season.Moreover,the isotopic niches were distinctly different in positions and showed small overlap between the two habitat types.The niche width was wider in old habitat than in the expanded new habitat.Our results demonstrated that the wild Crested Ibis had a high intraspecific variation in habitat uses and trophic levels in the early breeding season,and they could be divided into mountain and plain groups based on their different foraging niches.The difference inδ;N and niche width revealed that high trophic level food resources might be insufficient in plains.These findings stressed the importance of protecting foraging grounds in mountains and the necessity of improving foraging grounds in plains during winter and spring.Our study highlights the feasibility of investigating intraspecific variation in foraging ecology of birds through non-invasive isotopes of eggshell membranes.Understanding foraging niche variation gives us an insight into the food resource diversity in local areas and provides important information regarding particular foraging habitats that require protection.
