The Chinese Egret(Egretta eulophotes)is a globally threatened bird species living on the coast and islands of Liaoning,northeastern China,mainly in summer.To further protect the breeding population of Chinese Egrets,i...The Chinese Egret(Egretta eulophotes)is a globally threatened bird species living on the coast and islands of Liaoning,northeastern China,mainly in summer.To further protect the breeding population of Chinese Egrets,it is important to understand the current protection status of their distribution sites at pre-migration period and migration routes.Thirty-three individuals were tagged with satellite transmitters at Fantuo Island in Changhai and Xingren Island in Zhuanghe,Liaoning Province,northeastern China,in July of 2016,2017,and 2018,to identify important distribution sites during the pre-migration period,as well as detailed migration routes.The results showed that coastal mudflats in Liaoning and the west coast of North Korea were important feeding and roosting sites for fledgling Chinese Egrets from August to September.The home range sizes in August were significantly larger than in September.The eastern coast from Shandong to Guangdong,as well as Taiwan,China,and Manila Bay and Galileo Islands in the Philippines,were important stopover sites during fall migration.Specifically,we found that the egrets’autumn migration could be divided into four routes,i.e.,sea-crossing migration(SCM),coastal migration(CM),inland migration(IM),and mixed migration(MM).The migration distance,timing,speed,and straightness of the four routes also differed.The SCM routes were the straightest,and had the fastest migration speed and shortest travel time,while the IM routes had the lowest straightness and speed,and the longest duration.Manila Bay and Bohol Island in the Philippines,the west coast of Tanintharyi in Myanmar,and the Zengwun River Estuary in Taiwan,China,were wintering sites.Our findings on the key distribution sites along pre-migration and fall migration routes,including some stopover sites,have important implications for the conservation of and global action plan development for the vulnerable Chinese Egret.展开更多
A longstanding suggestion posits that parents prefer to match nest volume and clutch size （clutch volume）, but few studies have tested this in colonial seabirds that nest in the open. Here, we demonstrate the effect...A longstanding suggestion posits that parents prefer to match nest volume and clutch size （clutch volume）, but few studies have tested this in colonial seabirds that nest in the open. Here, we demonstrate the effects of nest-clutch volume matching on egg survival, hatching, and fledgling success in black-tailed gulls Larus crassirostris on Hongdo Island, Korea. We show that the volume mismatch, defined as the difference between nest volume and total egg volume （the sum of all eggs＇ volume in the clutch）, was positively related to egg and chick mortality caused by predation, but was not significantly related to hatching success incurred by insulation during the incubation period. Although nest volume was negatively related to laying date, we found that the mismatch was positively related to laying date. Our results support the claim that well-matched nest-clutch volume may contribute to survival of eggs and chicks, and ultimately breeding success.展开更多
Many bird species use social information to guide territory selection.Different species in different habitats may use both pre-breeding and post-breeding conspecific cues.Abandoned agricultural fields are of particula...Many bird species use social information to guide territory selection.Different species in different habitats may use both pre-breeding and post-breeding conspecific cues.Abandoned agricultural fields are of particular interest for studies of conspecific attraction because the ephemeral nature of the habitat suggests territory search just before breeding,but high predation pressure suggests the use of performance-based conspecific cues.We investigated whether post-breeding or pre-breeding social cues affect Whinchat(Saxicola rubetra)abundance at the territorial scale during a two-year experiment in abandoned fields.We assigned 27 experimental plots(3.14 ha)to one of three treatments:post-breeding treatment,pre-breeding treatment and silent control.We conducted playback experiments with fledgling calls(evidence of past reproductive success)during the post-breeding period and male songs(evidence of conspecific presence)during the pre-breeding period.We estimated the difference in Whinchat abundance in two consecutive years and tested whether this value differed between treatment and control plots.We observed a slight increase(0.67±0.29 pairs per plot)in Whinchat abundance in the post-breeding treatment plots and no significant changes in the pre-breeding(-0.22±0.32 pairs per plot)and control(-0.22±0.22 pairs per plot)plots.Our results suggest that Whinchats do not use conspecific acoustic cues during the pre-breeding period and provide limited evidence for the use of fledgling calls as conspecific cues in the post-breeding period.展开更多
Juveniles of interspecific avian brood parasites need to locate and recognize conspecifics to continue their life cycle after being reared by individuals of another species.However,little is known about the recognitio...Juveniles of interspecific avian brood parasites need to locate and recognize conspecifics to continue their life cycle after being reared by individuals of another species.However,little is known about the recognition mechanisms and cues involved in this critical stage of their lives.It has been proposed that adult parasites could show some kind of parental behavior by actively searching and interacting with conspecific young,which in turn could serve the juveniles to learn and/or reinforce the learning of conspecific characteristics.Since acoustic communication is one of the main channels used by birds,if such form of parental behavior by adult avian brood parasites does exist,adult cowbirds should recognize and respond positively to vocalizations of conspecific juveniles.We experimentally tested whether adult shiny Molothrus bonariensis and screaming M.rufoaxillaris cowbirds respond positively towards acoustic signals of conspecific juveniles using two playback experiments,one conducted in semi-captivity and the other in the field.In both cases,we presented 3 types of playbacks to adults of both cowbird species:vocalizations of shiny cowbird juveniles,vocalizations of screaming cowbird juveniles,and white noise as a control.In the experiment in semi-captivity,no significant differences were found between treatments.In the field experiment,no conspecifics approached the playback area,but hosts of the species whose playback was played were attracted to the loudspeaker.In conclusion,our results do not support the predictions we tested from the parental behavior hypothesis and indicate that adult shiny and screaming cowbirds do not respond positively to acoustic signals of conspecific juveniles,at least not to the type of signals used in our experiments.展开更多
基金supported by the National Key Research and Development Program of China (No. 2019YFA0607103)Program of National Forestry and Grassland Administration (No.213023721203)
文摘The Chinese Egret(Egretta eulophotes)is a globally threatened bird species living on the coast and islands of Liaoning,northeastern China,mainly in summer.To further protect the breeding population of Chinese Egrets,it is important to understand the current protection status of their distribution sites at pre-migration period and migration routes.Thirty-three individuals were tagged with satellite transmitters at Fantuo Island in Changhai and Xingren Island in Zhuanghe,Liaoning Province,northeastern China,in July of 2016,2017,and 2018,to identify important distribution sites during the pre-migration period,as well as detailed migration routes.The results showed that coastal mudflats in Liaoning and the west coast of North Korea were important feeding and roosting sites for fledgling Chinese Egrets from August to September.The home range sizes in August were significantly larger than in September.The eastern coast from Shandong to Guangdong,as well as Taiwan,China,and Manila Bay and Galileo Islands in the Philippines,were important stopover sites during fall migration.Specifically,we found that the egrets’autumn migration could be divided into four routes,i.e.,sea-crossing migration(SCM),coastal migration(CM),inland migration(IM),and mixed migration(MM).The migration distance,timing,speed,and straightness of the four routes also differed.The SCM routes were the straightest,and had the fastest migration speed and shortest travel time,while the IM routes had the lowest straightness and speed,and the longest duration.Manila Bay and Bohol Island in the Philippines,the west coast of Tanintharyi in Myanmar,and the Zengwun River Estuary in Taiwan,China,were wintering sites.Our findings on the key distribution sites along pre-migration and fall migration routes,including some stopover sites,have important implications for the conservation of and global action plan development for the vulnerable Chinese Egret.
文摘A longstanding suggestion posits that parents prefer to match nest volume and clutch size （clutch volume）, but few studies have tested this in colonial seabirds that nest in the open. Here, we demonstrate the effects of nest-clutch volume matching on egg survival, hatching, and fledgling success in black-tailed gulls Larus crassirostris on Hongdo Island, Korea. We show that the volume mismatch, defined as the difference between nest volume and total egg volume （the sum of all eggs＇ volume in the clutch）, was positively related to egg and chick mortality caused by predation, but was not significantly related to hatching success incurred by insulation during the incubation period. Although nest volume was negatively related to laying date, we found that the mismatch was positively related to laying date. Our results support the claim that well-matched nest-clutch volume may contribute to survival of eggs and chicks, and ultimately breeding success.
基金supported by the Russian Science Foundation(grant number 23-24-00042).
文摘Many bird species use social information to guide territory selection.Different species in different habitats may use both pre-breeding and post-breeding conspecific cues.Abandoned agricultural fields are of particular interest for studies of conspecific attraction because the ephemeral nature of the habitat suggests territory search just before breeding,but high predation pressure suggests the use of performance-based conspecific cues.We investigated whether post-breeding or pre-breeding social cues affect Whinchat(Saxicola rubetra)abundance at the territorial scale during a two-year experiment in abandoned fields.We assigned 27 experimental plots(3.14 ha)to one of three treatments:post-breeding treatment,pre-breeding treatment and silent control.We conducted playback experiments with fledgling calls(evidence of past reproductive success)during the post-breeding period and male songs(evidence of conspecific presence)during the pre-breeding period.We estimated the difference in Whinchat abundance in two consecutive years and tested whether this value differed between treatment and control plots.We observed a slight increase(0.67±0.29 pairs per plot)in Whinchat abundance in the post-breeding treatment plots and no significant changes in the pre-breeding(-0.22±0.32 pairs per plot)and control(-0.22±0.22 pairs per plot)plots.Our results suggest that Whinchats do not use conspecific acoustic cues during the pre-breeding period and provide limited evidence for the use of fledgling calls as conspecific cues in the post-breeding period.
基金supported by grants PICT 2015-1628 from Agencia Nacional de Promoción Científica y Tecnológica and UBACYT 20020170100521BA from Universidad de Buenos Aires to J.C.R.
文摘Juveniles of interspecific avian brood parasites need to locate and recognize conspecifics to continue their life cycle after being reared by individuals of another species.However,little is known about the recognition mechanisms and cues involved in this critical stage of their lives.It has been proposed that adult parasites could show some kind of parental behavior by actively searching and interacting with conspecific young,which in turn could serve the juveniles to learn and/or reinforce the learning of conspecific characteristics.Since acoustic communication is one of the main channels used by birds,if such form of parental behavior by adult avian brood parasites does exist,adult cowbirds should recognize and respond positively to vocalizations of conspecific juveniles.We experimentally tested whether adult shiny Molothrus bonariensis and screaming M.rufoaxillaris cowbirds respond positively towards acoustic signals of conspecific juveniles using two playback experiments,one conducted in semi-captivity and the other in the field.In both cases,we presented 3 types of playbacks to adults of both cowbird species:vocalizations of shiny cowbird juveniles,vocalizations of screaming cowbird juveniles,and white noise as a control.In the experiment in semi-captivity,no significant differences were found between treatments.In the field experiment,no conspecifics approached the playback area,but hosts of the species whose playback was played were attracted to the loudspeaker.In conclusion,our results do not support the predictions we tested from the parental behavior hypothesis and indicate that adult shiny and screaming cowbirds do not respond positively to acoustic signals of conspecific juveniles,at least not to the type of signals used in our experiments.
