Feeding Habits Study On Marsh Grassbird

Feeding habits is one of important areas in the study of animal life history. It is one way to understand materials and energy flow in the ecosystem. It provides a basis to the study of animal food sources because the stable isotope ratio between the two trophic levels has regular changes. Marsh Grassbird is a rare species classed as Near Threatened by IUCN. Study on its feeding habits in the different seasons can better understand the survival strategies of Marsh Grassbird, that can better protect the species.We collected individual samples of Marsh Grassbirds which accidently died from different causes during the banding process at Nanji Wetland and Chongming Dongtan from2010-13. The samples from Nanji wetland, there are5at pre-breeding period,6in breeding period,7in fall and4during winters. There are8samples from Chongmingdongtan during winters. We also collected samplesof the other birds using the same habitat and samples of other arthropods, such as, insects, spiders, and dominant plants. All the samples are brought back to the laboratory for the analysis of Marsh Grassbirds stomach contents and the determination of stable isotope.By gastric examination of Marsh Grassbirds stomach contents, we analyzed, observed and identified marsh. We used stable isotope to show the tracks of their food sources. And we also did field observations at breeding period at Nanji wetland. According these three methods, we studied their diet composition and changes in different seasons.My study at Nanji wetlands shows:1) on the birds are insectivorous at pre-breeding and breeding periods.2) Autumn diet was composed of arthropods (insects, spiders), three groups of C4and C3plants. The diet was composed of70.2%of animal foods and29.8%of plant foods by stomach inspection, and it was composed of Insects of34.1%,34.4%of C4plants,31.5%of C3plants by stable isotope analysis.3) Winter diet was composed of arthropods and C3plants,57.0%of animal and43.0%of plant foods through stomach inspection, and it was composed of53.3%insects,46.8%C3plants though stable isotope analysis.4) The values of δ13C and δ15N from back muscles of the Marsh Grassbirds in pre-breeding were1.18‰and1.27‰higher than the value of the breeding season. This indicates that Marsh Grassbirds feed better food in pre-breeding.The diet of the Marsh Grassbirds at Chongming Dongtan in winter are made by animal (93.4%) and plant (6.6%) foods. Animal foods are mainly low benthic animals including small gastropod snails (possibly Bullacta exarata) and small crustacean animals; plant foods are mainly seeds. The diet compositions the Marsh Grassbird is different from that in Nanji wetland.This paper also studies the trophic level of different species of birds using the same habitat with Marsh Grassbird in Nanji wetland. There are some differences at nutritional levels among species. Research results show that the different trophic level have certain differences between birds, and phytophagous birds are low trophic level position than insectivorous birds.