| Complex structure and assemble of animal community is determined by interspecific relationship,also as a result of resource utilizaiotn and partion by species groups(guilds).Research on community guilds could not only be useful for understanding the structure of the community,but also for sheding light on the process of community organization.Foraging guilds of waterbird communities are clustered by using the same resources,and guild structure analysis can be directly reflected on the response of waterbird communities to habitat changes.Wintering waterbirds highly rely on wetland habitats.Their ability of rapid adaptive response to habitat changes determines the complexity of the response mechanism of its community and guild structure.Therefore,the wintering waterbird community guild structure has become a key research field for the waterbird ecology.In this study,two river-connected lakes,Shengjin Lake and Caizi Lake in Anhui province were selected as the research areas about wintering waterbirds communities.The foraging habitat and foraging behavior of the wintering waterbirds were observed by the instantaneous scanning method,and the sample data of foraging behavior and foraging habitat were collected.Data matrixes were established by the observed feeding records.Based on these,we carried out the research by mutivariate analyse on the structure,temporal and spatial dynamics,guild structure characteristics and guild niche of the wintering waterbird community,and shed light on the response of feeding guild structure to habitat changes.The main results are as follows.1.The composition and spatial and temporal dynamics of the wintering waterbird community are determined by the spatial and temporal distribution of food resources in the two lakes with different landuse models.The wintering waterbirds adjusted the composition of community structure to adapt the habitat changes.The evenness and stability of the wintering waterbirds community at Caizi Lake were low,and the number of wintering waterbirds decreased month by month in the whole winter.The population peaked in December,decreased sharp by 53.74% in January,and by another 39.61% in February.The wintering waterbird community in Shengjin Lake showed a relatively stable characteristic in the whole winter.Number of the population in January was slightly higher than other two months.The results were consistent with the spatial and temporal distribution pattern of food resources on the two lakes.The lake-wide culture mode was implemented at Shengjin Lake with low anthropogenic interference.Water level decreased gradually throughout the winter,supplied larger area natural habitats,more suitable micro-habitats and higher habitat heterogeneity than Caizi Lake.Moreover,food resources at Shengjin Lake were gradually supplied and uniformly at spatiotemporal patterns.Conversely,enclosure culture at Caizi Lake with great human disturbance,and more breeding ponds with human control of water level resulted in an uneven spatial and temporal distribution food resources.Therefore,the composition and dynamic characteristics of wintering waterbirds are determined by the spatial and temporal distribution characteristics of their food resources in the two lakes.2.The foraging guild structure of the wintering waterbird community is not invariable but dynamically changing.The wintering waterbird community responded to the changes of wetland habitats in the two lakes by adjusting the foraging guild structure of the communities.The different fishery patterns at Shenjin and Caizi lakes caused different guild structures in the waterbird community.And the dynamic response of the foraging guild structure of waterbird community to the changes of lake wetland habitat could be divided into two levels.1)Due to the change of foraging habitat,moveout of some waterbirds resulted in species composition of each guild in the community,and even the changes of guild structure.Moving of wintering waterbirds between different lakes is beneficial for escaping adverse environmental conditions and choosing better foraging habitats.The results indicated that the food resource changes could lead to the moving in or out of some waterbird species.Moreover,it was also found that the presence of these moving birds might be primarily related to fluctuations in the abundance or availability of their food resources.Furthermore,due to the over-exploitation of enclosure culture at Caizi Lake,the food abundance and the diversity of foraging microhabitats were lower in the foraging habitat than at Shengjin Lake.Therefore,some species with more requirements for foraging habitat disappeared at Caizi Lake and appeared at Shengjin Lake.The results showed that there were four similar foraging guilds for the wintering waterbirds communities in both lakes,the number of species of the wintering waterbird communities at Caizi Lake were significantly less than that at Shengjin Lake.2)Shifts in the ecological niche of forager were caused by intra-guild shifts of species composition,in turn to resulting in the inter-guild shifts.According to this study,no changes of the foraging characteristic on the guild levels were found.However,the changes of the resource utilization patterns on species levels in different lakes were obvious,such as Anser albifrons belonged to the first guild,shallow pickers at Shengjin Lake,but the second guild,grassland pickers at Caizi Lake,A.cygnoidesand Tringa hypoleucos were the second guild at Shengjin Lake,but the first guild at Caizi Lake.The changes of A.albifrons,A.cygnoides and T.hypoleucos in different foraging habitats in lakes lead to the changes of the guilds which they belonged to.The changes of foraging patterns are influenced by several factors.Food resources and their availability affected the foraging patterns of waterbird species and thus the foraging guild structure of waterbird communities.Therefore,food resources and their availability were the important factors to maintain the stability of foraging guild structure in the wintering waterbird community.3.Wintering waterbirds took suitable width and overlap of foraging niche to face the habitat difference in between Shenjin and Caizi Lakes.There were significant differences in the niche charachateristic for the waterbirds in the two different landuse models of lakes.It was found that waterbirds preferred to wider niche to weaken competition effect,increase niche overlap in the lake with abundant food,and the spatial distribution of bird population showed a relatively clustered state.Oppositely in the food-deficient lake,the niche width was relatively wide,and the competition was enhanced,so the niche overlap was reduced,and the spatial distribution of bird population showed a relatively discrete state.The niche breadth and niche overlap of the waterbird communities at Shengjin Lake were significantly larger than that at Caizi Lake,which was related to the food abundance and availability between the two lakes.In general,Shengjin Lake had a better habitat,rich food resources,stable hydrological conditions and open water than Caizi Lake.Therefore,the food resources and their availability are the key factors affecting the niche width and overlap degree of the foraging guild structure of the wintering waterbird community.Overall,the wintering waterbird communitiy response the changes of foraging habitats in different lakes by regulating the species composition,foraging niche and foraging guild structure.Composition,foraging guild structure and foraging niche took adaptive variation for wintering waterbirds to face t to the habitat changes in different foraging sites.The spatial and temporal configuration of food resources may be responsible for these adaptive changes.This study provides a theoretical basis for the protection and management of wintering waterbird communities and their habitats. |
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