Leucocytozoonosis was found in three layer farms in chickens with suspected fatty liver or fatty liver hemorrhagic syndrome in Korea between 2009 and 2011.These layer chicken flocks showed both mortality and decreased...Leucocytozoonosis was found in three layer farms in chickens with suspected fatty liver or fatty liver hemorrhagic syndrome in Korea between 2009 and 2011.These layer chicken flocks showed both mortality and decreased egg production for one or two weeks when they were between 59 and 82 weeks old.At the necropsy,the most prominent gross lesions were found in the liver,which was enlarged,had a fragile texture,exhibited yellowish discolorations,and had various hemorrhagic lesions.Tissue reactions associated with megaloschizonts specific for Leucocytozoon caulleryi were prominent upon microscopic examination of the liver without significant lipidosis.In addition,the ovaries and uterus were the most affected organs for Leucocytozoon caulleryi multiplication,which led to decreased egg productions.Molecular studies with formalin-fixed,paraffin-embedded tissues were performed in search of a partial region of the cytochrome b gene for hemosporidian parasites.Based on these results,the causal agent was determined to be closely related to Leucocytozoon caulleryi reported in Japan and Malaysia.In this study,we describe recently re-occurring leucocytozoonosis in layer chickens,which required histopathology for disease diagnosis.To prevent outbreaks and maintain chicken health and egg production,layer chickens need to be monitored for symptoms of leucocytozoonosis.展开更多
Background:Mixed-species flocks(MSFs)have been well sampled in the South Asia,but there has been as yet surprisingly little work on MSFs of Nepal,despite a diverse and well-studied avifauna.We surveyed MSFs in two for...Background:Mixed-species flocks(MSFs)have been well sampled in the South Asia,but there has been as yet surprisingly little work on MSFs of Nepal,despite a diverse and well-studied avifauna.We surveyed MSFs in two forest types in and around the Important Bird Area of Chitwan National Park in Nepal,between 150 and 800 m a.s.l.,to provide a first description of the composition of MSFs in this area.We also aimed to understand which species should be considered‘nuclear species',important to forming MSFs or leading them forward.Results:In total,we collected records on 222 MSFs that included 100 species,and 6097 individuals.The MSFs were similar to worldwide patterns in being dominated by leaf-gleaning,non-terrestrial insectivores.However,the MSFs were more dominated by canopy species than usual,and did not have a clear gregarious,understory leading species.Rather drongos(Family Dicruridae)and minivets(Family Campephagidae,Genus Pericrocotus)acted as leaders,and a cluster analysis of composition showed one group of large body size MSFs particularly characterized by the presence of the Greater Racket-tailed Drongo(Dicrurus paradiseus).Conclusions:Drongos are known to provide both costs and benefits to other flock participants:they are aggressive birds that can steal food,and manipulate other species with their vocalizations,but at the same time they are‘sentinel species'that produce information about predation risk other species can use.This study demonstrates that drongos can be considered nuclear species for some types of MSFs,despite the potential costs of their presence.MSFs led by sentinel species thus may form in Asia,as well as in the Neotropics.展开更多
In this paper, we study the flocking behavior of a thermodynamic Cucker–Smale model with local velocity interactions. Using the spectral gap of a connected stochastic matrix, together with an elaborate estimate on pe...In this paper, we study the flocking behavior of a thermodynamic Cucker–Smale model with local velocity interactions. Using the spectral gap of a connected stochastic matrix, together with an elaborate estimate on perturbations of a linearized system, we provide a sufficient framework in terms of initial data and model parameters to guarantee flocking. Moreover, it is shown that the system achieves a consensus at an exponential rate.展开更多
This study proposes a method for uniformly revolving swarm robots to entrap multiple targets,which is based on a gene regulatory network,an adaptive decision mechanism,and an improved Vicsek-model.Using the gene regul...This study proposes a method for uniformly revolving swarm robots to entrap multiple targets,which is based on a gene regulatory network,an adaptive decision mechanism,and an improved Vicsek-model.Using the gene regulatory network method,the robots can generate entrapping patterns according to the environmental input,including the positions of the targets and obstacles.Next,an adaptive decision mechanism is proposed,allowing each robot to choose the most well-adapted capture point on the pattern,based on its environment.The robots employ an improved Vicsek-model to maneuver to the planned capture point smoothly,without colliding with other robots or obstacles.The proposed decision mechanism,combined with the improved Vicsek-model,can form a uniform entrapment shape and create a revolving effect around targets while entrapping them.This study also enables swarm robots,with an adaptive pattern formation,to entrap multiple targets in complex environments.Swarm robots can be deployed in the military field of unmanned aerial vehicles’(UAVs)entrapping multiple targets.Simulation experiments demonstrate the feasibility and superiority of the proposed gene regulatory network method.展开更多
There are rich emergent phase behaviors in non-equilibrium active systems.Flocking and clustering are two representative dynamic phases.The relationship between both the phases is still unclear.Herein,we numerically i...There are rich emergent phase behaviors in non-equilibrium active systems.Flocking and clustering are two representative dynamic phases.The relationship between both the phases is still unclear.Herein,we numerically investigate the evolution of flocking and clustering in a system consisting of self-propelled particles with active reorientation.We consider the interplay between flocking and clustering phases with different initial configurations,and observe a domain in steady state order parameter phase diagrams sensitive to the choice of initial configurations.Specifically,by tuning the initial degree of polar ordering,either a more ordered flocking or a disordered clustering state can be observed in the steady state.These results enlighten us to manipulate emergent behaviors and collective motions of an active system,and are qualitatively different from the emergence of a new bi-stable regime observed in aligned active particles due to an explicit attraction[New J.Phys.14073033(2012)].展开更多
Compliance with appropriate flock health program is vital for preventing introduction and minimizing impact of diseases in goat farms. Unfortunately, most goat farms in Uganda, especially in the Albertine Graben Zone ...Compliance with appropriate flock health program is vital for preventing introduction and minimizing impact of diseases in goat farms. Unfortunately, most goat farms in Uganda, especially in the Albertine Graben Zone lack flock health program. The associated frequent outbreaks slow down effort aimed at commercializing goat production. In this study, we documented flock dynamics, identified and prioritized pressing challenges experienced by goat farms during the year 2022 and generated appropriate flock health program and packaged it for dissemination to farmers. Materials and Methods: Using a cross-sectional design, semi-structured questionnaire, data were collected and analyzed with MS Excel 2013. The data included: location and socio-demographics of household, farming system, flock dynamics, housing, feeding system, health management, challenges encountered by goat farm and suggested solutions. Results: Beginning January 2022 to December 2022, the number of goats reared in all the 45 sample farms increased from 2128 to 2220 goats. Results showed that 884 kids were produced and 88 breeding goats were introduced into the farms. Three hundred ninety-nine goats died due to mainly diseases and 435 goats got withdrawn through nondeath. The average farm level and overall mortality rate were 21 goats per 1000 goatmonths and 15 goats per 1000 goatmonths respectively. The most pressing challenges encountered by sample farms were death of goats especially due to diseases, poor access to veterinary extension services, high cost of inputs and feed scarcity. Solutions suggested by sample farms were improved access to veterinary services, improved housing, enhanced vaccination of goats against diseases, and enhanced grazing land management and feed conservation, all of which were incorporated into the flock health program. Conclusion and Recommendations: An appropriate flock health program was generated based on flock dynamics and production constraints which reveal high mortality and limited access to veterinary services respectively. Actors are recommended to promote adoption and adherence to the flock health program so as to increase goat production and access to wider market.展开更多
Rangelands of Central Asia(referring to Kazakhstan, Kyrgyzstan, Tajikistan, Turkmenistan and Uzbekistan in this study), the largest contiguous area of grazed land in the world, serve as an important source of liveliho...Rangelands of Central Asia(referring to Kazakhstan, Kyrgyzstan, Tajikistan, Turkmenistan and Uzbekistan in this study), the largest contiguous area of grazed land in the world, serve as an important source of livelihood for pastoral and agro-pastoral communities in this region. They also play an important role in absorbing CO2 as a global carbon sink. However, unsustainable management of rangelands has led to their degradation hugely by downgrading their potential agro-ecological, environmental and socio-economical roles. This paper reviewed the rangeland degradation in Central Asia, a topic which so far has received only scant coverage in the international scientific literature. It also provided examples of successful experiences and outlined possible options that land managers can adopt to enhance the sustainable management of these vast degraded rangelands. The experiences and lessons described in this paper may also be relevant for other degraded rangeland areas, especially in the developing countries. The causes of rangeland degradation within the Central Asian region are numerous, complex and inter-related. Therefore, while addressing the factors associated with improper rangeland management may shed some light on the causes of rangeland degradation, the scope of this paper would not be all-encompassing for the major causes of degradation. There is a need to develop and widely apply the viable and locally accepted and adapted packages of technical, institutional and policy options for sustainable rangeland management. Incentivizing the collective action of small-scale pastoralists who group together to facilitate access to remote pastures can reduce the degree of overgrazing within community pastures, such as those near the settlements. We also found that migratory grazing through pooling of resources among small-scale pastoralists can increase household income. After their independence, most Central Asian countries adopted various rangeland tenure arrangements. However, the building of enhanced capacities of pasture management and effective local rangeland governance structures can increase the likelihood, which will be sustainable and equitable. Finally, this paper presented several promising technical options, aiming at reversing the trend of rangeland degradation in Central Asia.展开更多
We consider the problem of controlling a group of mobile agents to form a designated formation while flocking within a constrained environment. We first propose a potential field based method to drive the agents to mo...We consider the problem of controlling a group of mobile agents to form a designated formation while flocking within a constrained environment. We first propose a potential field based method to drive the agents to move in connection with their neighbors, and regulate their relative positions to achieve the specific formation. The communication topology is preserved during the motion. We then extend the method to flocking with environmental constraints. Stability properties are analyzed to guarantee that all agents eventually form the desired formation while flocking, and flock safely without collision with the environment boundary. We verify our algorithm through simulations on a group of agents performing maximum coverage flocking and traveling through an unknown constrained environment.展开更多
Background:Food abundance and availability affect flock patterns of foraging birds.Cost and risk tradeoffs are especially critical for flocks of wintering waterbirds foraging in lake wetlands.Waterbirds losing suitabl...Background:Food abundance and availability affect flock patterns of foraging birds.Cost and risk tradeoffs are especially critical for flocks of wintering waterbirds foraging in lake wetlands.Waterbirds losing suitable habitats face insufficient food supplies and high levels of disturbance,affecting their foraging activities.Our objective was to study the effects of food abundance and disturbances on flock size and the structure of Hooded Crane flocks wintering at Shengjin Lake and,as well,to understand the response of wintering waterbirds to habitat degradation for future management decisions and protection of the population.Methods:We investigated food abundance,disturbances and flock foraging activities of the wintering Hooded Crane in several foraging habitats of Shengjin Lake from November 2013 to April 2014.Flock size and structure were observed by scan sampling.Data on food abundance and disturbances were collected by sampling.Flock size and structure were compared among three wintering stages.The relationship between food resources,disturbances and flock size were illustrated using a generalized linear model.Results:In the early and middle wintering periods,the Hooded Crane used paddy fields as its major foraging habitat,where the number of foraging birds and flocks were the highest.During the late period,the cranes took to meadows as their major foraging habitat.The variation among foraging flock was mainly embodied in the size of the flocks,while the age composition of these flocks did not change perceptibly.Family flocks were notably different from flock groups in size and age composition.The results of a generalized linear model showed that the food abundance had a marked effect on foraging flock size and age composition,while disturbances had a significant effect only on flock size.From our analysis,it appeared that the combined effect of the two variables was significant on the size of the foraging flock,but had less impact on age composition.Conclusions:Food abundance and disturbances affected the flock size of the Hooded Crane.With abundant food and high disturbances,flock sizes increased owing to cooperation in foraging.To avoid competition and maximize foraging benefits,flock size reduces with an abundance of food but low disturbance.By trading off risks and costs,the cranes showed flexible flock distributions and a variety of foraging strategies to maximize benefits and to improve their fitness.展开更多
We study the existence and uniqueness problem for the nonhomogeneous pressureless Euler system with the initial density being a Radon measure. Our uniqueness result is obtained in the same space as the existence theor...We study the existence and uniqueness problem for the nonhomogeneous pressureless Euler system with the initial density being a Radon measure. Our uniqueness result is obtained in the same space as the existence theorem. Besides, by counterexample we prove that Huang-Wang's energy condition is also necessary for our nonhomogeneous system.展开更多
Background: The foraging and diving behavior of waterfowl are affected by a number of important factors. Hence, learning more about these major factors is of great concern in order to protect endangered species. In th...Background: The foraging and diving behavior of waterfowl are affected by a number of important factors. Hence, learning more about these major factors is of great concern in order to protect endangered species. In this study, we verified the effect of sex, temperature, time and flock size on the diving behavior of the Scaly-sided Merganser(Mergus squamatus).Methods: The study was conducted by means of focal animal sampling in the Wuyuan section of the Poyang Lake watershed in Jiangxi Province, China from December 2015 to March 2016. We used one-way ANOVA and LSD tests to investigate the differences among these factors. Pearson correlations were used to test the relation between pause duration and the previous or subsequent dive duration. The relations between these factors and dive/pause duration are illustrated using Spearman correlations.Results: Mean dive duration and mean time on the pause of males were significantly higher than those of females. With an increase in temperature, dive duration significantly increased. Along with the passage of time of year and daytime, dive duration significantly increased, while dive duration decreased significantly with the increase in flock size.Conclusions: Sex, temperature, time and flock size have an effect on the diving behavior of the wintering Scalysided Merganser. The difference of diving behavior between males and females is related to differences in body mass. The difference of diving behavior among various temperatures and time periods may be related to a low minimum rate of oxygen consumption, while the difference among various flock sizes may be caused by rising intraspecific competition.展开更多
This paper investigates the flocking problem in multi-agent system with time-varying delay and a virtual leader. Each agent here is subject to nonlinear dynamics. For the system, the corresponding algorithm with time-...This paper investigates the flocking problem in multi-agent system with time-varying delay and a virtual leader. Each agent here is subject to nonlinear dynamics. For the system, the corresponding algorithm with time-varying delay is proposed. Under the assumption that the initial network is connected, it is proved that the distance between agents is in the desired distance. The theoretical deduction shows that the stable flocking motion is achieved.展开更多
This paper reports observations of flocking behavior of birds in a well-protected secondary forest in Tai Po Kau Nature Reserve,Hong Kong Special Administrative Region,China.A total of 1025 flocks including 5255 birds...This paper reports observations of flocking behavior of birds in a well-protected secondary forest in Tai Po Kau Nature Reserve,Hong Kong Special Administrative Region,China.A total of 1025 flocks including 5255 birds and 48 species were observed between October 2002 and November 2003.Most flocks consisted of only one species.The observed flocks averaged 1.79 ± 0.05(SE) species and 5.13 ± 0.18(SE) birds.The Japanese White-eye was the most numerous species and was present in 21.6% of the observed flocks.Seasonal trends in both flock size and number of species were similar to those in overall bird density and species richness in the study area reported in a previous study.展开更多
基金provided by the project of National Institute of Environment Research(No.2015080777)
文摘Leucocytozoonosis was found in three layer farms in chickens with suspected fatty liver or fatty liver hemorrhagic syndrome in Korea between 2009 and 2011.These layer chicken flocks showed both mortality and decreased egg production for one or two weeks when they were between 59 and 82 weeks old.At the necropsy,the most prominent gross lesions were found in the liver,which was enlarged,had a fragile texture,exhibited yellowish discolorations,and had various hemorrhagic lesions.Tissue reactions associated with megaloschizonts specific for Leucocytozoon caulleryi were prominent upon microscopic examination of the liver without significant lipidosis.In addition,the ovaries and uterus were the most affected organs for Leucocytozoon caulleryi multiplication,which led to decreased egg productions.Molecular studies with formalin-fixed,paraffin-embedded tissues were performed in search of a partial region of the cytochrome b gene for hemosporidian parasites.Based on these results,the causal agent was determined to be closely related to Leucocytozoon caulleryi reported in Japan and Malaysia.In this study,we describe recently re-occurring leucocytozoonosis in layer chickens,which required histopathology for disease diagnosis.To prevent outbreaks and maintain chicken health and egg production,layer chickens need to be monitored for symptoms of leucocytozoonosis.
基金supported by a Special Talent Recruitment grant from Guangxi University to EGa Chinese Government Scholarship to KRG。
文摘Background:Mixed-species flocks(MSFs)have been well sampled in the South Asia,but there has been as yet surprisingly little work on MSFs of Nepal,despite a diverse and well-studied avifauna.We surveyed MSFs in two forest types in and around the Important Bird Area of Chitwan National Park in Nepal,between 150 and 800 m a.s.l.,to provide a first description of the composition of MSFs in this area.We also aimed to understand which species should be considered‘nuclear species',important to forming MSFs or leading them forward.Results:In total,we collected records on 222 MSFs that included 100 species,and 6097 individuals.The MSFs were similar to worldwide patterns in being dominated by leaf-gleaning,non-terrestrial insectivores.However,the MSFs were more dominated by canopy species than usual,and did not have a clear gregarious,understory leading species.Rather drongos(Family Dicruridae)and minivets(Family Campephagidae,Genus Pericrocotus)acted as leaders,and a cluster analysis of composition showed one group of large body size MSFs particularly characterized by the presence of the Greater Racket-tailed Drongo(Dicrurus paradiseus).Conclusions:Drongos are known to provide both costs and benefits to other flock participants:they are aggressive birds that can steal food,and manipulate other species with their vocalizations,but at the same time they are‘sentinel species'that produce information about predation risk other species can use.This study demonstrates that drongos can be considered nuclear species for some types of MSFs,despite the potential costs of their presence.MSFs led by sentinel species thus may form in Asia,as well as in the Neotropics.
文摘In this paper, we study the flocking behavior of a thermodynamic Cucker–Smale model with local velocity interactions. Using the spectral gap of a connected stochastic matrix, together with an elaborate estimate on perturbations of a linearized system, we provide a sufficient framework in terms of initial data and model parameters to guarantee flocking. Moreover, it is shown that the system achieves a consensus at an exponential rate.
基金funded by the National Natural Science Foundation of China(62176147)the Science and Technology Planning Project of Guangdong Province of China,the State Key Lab of Digital Manufacturing Equipment and Technology(DMETKF2019020)the National Defense Technology Innovation Special Zone Project(193-A14-226-01-01)。
文摘This study proposes a method for uniformly revolving swarm robots to entrap multiple targets,which is based on a gene regulatory network,an adaptive decision mechanism,and an improved Vicsek-model.Using the gene regulatory network method,the robots can generate entrapping patterns according to the environmental input,including the positions of the targets and obstacles.Next,an adaptive decision mechanism is proposed,allowing each robot to choose the most well-adapted capture point on the pattern,based on its environment.The robots employ an improved Vicsek-model to maneuver to the planned capture point smoothly,without colliding with other robots or obstacles.The proposed decision mechanism,combined with the improved Vicsek-model,can form a uniform entrapment shape and create a revolving effect around targets while entrapping them.This study also enables swarm robots,with an adaptive pattern formation,to entrap multiple targets in complex environments.Swarm robots can be deployed in the military field of unmanned aerial vehicles’(UAVs)entrapping multiple targets.Simulation experiments demonstrate the feasibility and superiority of the proposed gene regulatory network method.
基金support from the Beijing Computational Science Research Centersupported by the National Natural Science Foundation of China(Grant Nos.U2230402,11975050,11735005,and 11904320)。
文摘There are rich emergent phase behaviors in non-equilibrium active systems.Flocking and clustering are two representative dynamic phases.The relationship between both the phases is still unclear.Herein,we numerically investigate the evolution of flocking and clustering in a system consisting of self-propelled particles with active reorientation.We consider the interplay between flocking and clustering phases with different initial configurations,and observe a domain in steady state order parameter phase diagrams sensitive to the choice of initial configurations.Specifically,by tuning the initial degree of polar ordering,either a more ordered flocking or a disordered clustering state can be observed in the steady state.These results enlighten us to manipulate emergent behaviors and collective motions of an active system,and are qualitatively different from the emergence of a new bi-stable regime observed in aligned active particles due to an explicit attraction[New J.Phys.14073033(2012)].
文摘Compliance with appropriate flock health program is vital for preventing introduction and minimizing impact of diseases in goat farms. Unfortunately, most goat farms in Uganda, especially in the Albertine Graben Zone lack flock health program. The associated frequent outbreaks slow down effort aimed at commercializing goat production. In this study, we documented flock dynamics, identified and prioritized pressing challenges experienced by goat farms during the year 2022 and generated appropriate flock health program and packaged it for dissemination to farmers. Materials and Methods: Using a cross-sectional design, semi-structured questionnaire, data were collected and analyzed with MS Excel 2013. The data included: location and socio-demographics of household, farming system, flock dynamics, housing, feeding system, health management, challenges encountered by goat farm and suggested solutions. Results: Beginning January 2022 to December 2022, the number of goats reared in all the 45 sample farms increased from 2128 to 2220 goats. Results showed that 884 kids were produced and 88 breeding goats were introduced into the farms. Three hundred ninety-nine goats died due to mainly diseases and 435 goats got withdrawn through nondeath. The average farm level and overall mortality rate were 21 goats per 1000 goatmonths and 15 goats per 1000 goatmonths respectively. The most pressing challenges encountered by sample farms were death of goats especially due to diseases, poor access to veterinary extension services, high cost of inputs and feed scarcity. Solutions suggested by sample farms were improved access to veterinary services, improved housing, enhanced vaccination of goats against diseases, and enhanced grazing land management and feed conservation, all of which were incorporated into the flock health program. Conclusion and Recommendations: An appropriate flock health program was generated based on flock dynamics and production constraints which reveal high mortality and limited access to veterinary services respectively. Actors are recommended to promote adoption and adherence to the flock health program so as to increase goat production and access to wider market.
基金the Asian Development Bank,the International Center for Agricultural Research in the Dry Areas,Russian Scientific Fund(14-38-00023)the CGIAR Research Program on Dryland Systems for their support and funding
文摘Rangelands of Central Asia(referring to Kazakhstan, Kyrgyzstan, Tajikistan, Turkmenistan and Uzbekistan in this study), the largest contiguous area of grazed land in the world, serve as an important source of livelihood for pastoral and agro-pastoral communities in this region. They also play an important role in absorbing CO2 as a global carbon sink. However, unsustainable management of rangelands has led to their degradation hugely by downgrading their potential agro-ecological, environmental and socio-economical roles. This paper reviewed the rangeland degradation in Central Asia, a topic which so far has received only scant coverage in the international scientific literature. It also provided examples of successful experiences and outlined possible options that land managers can adopt to enhance the sustainable management of these vast degraded rangelands. The experiences and lessons described in this paper may also be relevant for other degraded rangeland areas, especially in the developing countries. The causes of rangeland degradation within the Central Asian region are numerous, complex and inter-related. Therefore, while addressing the factors associated with improper rangeland management may shed some light on the causes of rangeland degradation, the scope of this paper would not be all-encompassing for the major causes of degradation. There is a need to develop and widely apply the viable and locally accepted and adapted packages of technical, institutional and policy options for sustainable rangeland management. Incentivizing the collective action of small-scale pastoralists who group together to facilitate access to remote pastures can reduce the degree of overgrazing within community pastures, such as those near the settlements. We also found that migratory grazing through pooling of resources among small-scale pastoralists can increase household income. After their independence, most Central Asian countries adopted various rangeland tenure arrangements. However, the building of enhanced capacities of pasture management and effective local rangeland governance structures can increase the likelihood, which will be sustainable and equitable. Finally, this paper presented several promising technical options, aiming at reversing the trend of rangeland degradation in Central Asia.
文摘We consider the problem of controlling a group of mobile agents to form a designated formation while flocking within a constrained environment. We first propose a potential field based method to drive the agents to move in connection with their neighbors, and regulate their relative positions to achieve the specific formation. The communication topology is preserved during the motion. We then extend the method to flocking with environmental constraints. Stability properties are analyzed to guarantee that all agents eventually form the desired formation while flocking, and flock safely without collision with the environment boundary. We verify our algorithm through simulations on a group of agents performing maximum coverage flocking and traveling through an unknown constrained environment.
基金supported by the staff of the Shengjin Lake National Nature Reservethe National Natural Science Foundation of China(Grant no.31172117,31472020)the Graduate Student Innovation Research Projects of Anhui University(YQH100270)for financial support
文摘Background:Food abundance and availability affect flock patterns of foraging birds.Cost and risk tradeoffs are especially critical for flocks of wintering waterbirds foraging in lake wetlands.Waterbirds losing suitable habitats face insufficient food supplies and high levels of disturbance,affecting their foraging activities.Our objective was to study the effects of food abundance and disturbances on flock size and the structure of Hooded Crane flocks wintering at Shengjin Lake and,as well,to understand the response of wintering waterbirds to habitat degradation for future management decisions and protection of the population.Methods:We investigated food abundance,disturbances and flock foraging activities of the wintering Hooded Crane in several foraging habitats of Shengjin Lake from November 2013 to April 2014.Flock size and structure were observed by scan sampling.Data on food abundance and disturbances were collected by sampling.Flock size and structure were compared among three wintering stages.The relationship between food resources,disturbances and flock size were illustrated using a generalized linear model.Results:In the early and middle wintering periods,the Hooded Crane used paddy fields as its major foraging habitat,where the number of foraging birds and flocks were the highest.During the late period,the cranes took to meadows as their major foraging habitat.The variation among foraging flock was mainly embodied in the size of the flocks,while the age composition of these flocks did not change perceptibly.Family flocks were notably different from flock groups in size and age composition.The results of a generalized linear model showed that the food abundance had a marked effect on foraging flock size and age composition,while disturbances had a significant effect only on flock size.From our analysis,it appeared that the combined effect of the two variables was significant on the size of the foraging flock,but had less impact on age composition.Conclusions:Food abundance and disturbances affected the flock size of the Hooded Crane.With abundant food and high disturbances,flock sizes increased owing to cooperation in foraging.To avoid competition and maximize foraging benefits,flock size reduces with an abundance of food but low disturbance.By trading off risks and costs,the cranes showed flexible flock distributions and a variety of foraging strategies to maximize benefits and to improve their fitness.
文摘We study the existence and uniqueness problem for the nonhomogeneous pressureless Euler system with the initial density being a Radon measure. Our uniqueness result is obtained in the same space as the existence theorem. Besides, by counterexample we prove that Huang-Wang's energy condition is also necessary for our nonhomogeneous system.
基金supported by the National Natural Science Foundation of China(Grant No.31560597)
文摘Background: The foraging and diving behavior of waterfowl are affected by a number of important factors. Hence, learning more about these major factors is of great concern in order to protect endangered species. In this study, we verified the effect of sex, temperature, time and flock size on the diving behavior of the Scaly-sided Merganser(Mergus squamatus).Methods: The study was conducted by means of focal animal sampling in the Wuyuan section of the Poyang Lake watershed in Jiangxi Province, China from December 2015 to March 2016. We used one-way ANOVA and LSD tests to investigate the differences among these factors. Pearson correlations were used to test the relation between pause duration and the previous or subsequent dive duration. The relations between these factors and dive/pause duration are illustrated using Spearman correlations.Results: Mean dive duration and mean time on the pause of males were significantly higher than those of females. With an increase in temperature, dive duration significantly increased. Along with the passage of time of year and daytime, dive duration significantly increased, while dive duration decreased significantly with the increase in flock size.Conclusions: Sex, temperature, time and flock size have an effect on the diving behavior of the wintering Scalysided Merganser. The difference of diving behavior between males and females is related to differences in body mass. The difference of diving behavior among various temperatures and time periods may be related to a low minimum rate of oxygen consumption, while the difference among various flock sizes may be caused by rising intraspecific competition.
文摘This paper investigates the flocking problem in multi-agent system with time-varying delay and a virtual leader. Each agent here is subject to nonlinear dynamics. For the system, the corresponding algorithm with time-varying delay is proposed. Under the assumption that the initial network is connected, it is proved that the distance between agents is in the desired distance. The theoretical deduction shows that the stable flocking motion is achieved.
文摘This paper reports observations of flocking behavior of birds in a well-protected secondary forest in Tai Po Kau Nature Reserve,Hong Kong Special Administrative Region,China.A total of 1025 flocks including 5255 birds and 48 species were observed between October 2002 and November 2003.Most flocks consisted of only one species.The observed flocks averaged 1.79 ± 0.05(SE) species and 5.13 ± 0.18(SE) birds.The Japanese White-eye was the most numerous species and was present in 21.6% of the observed flocks.Seasonal trends in both flock size and number of species were similar to those in overall bird density and species richness in the study area reported in a previous study.