Investigations On The Seasonal And Spatial Variations In Feeding Behavior Of Typical Shorebirds In The Yellow River Delta,China

The Yellow River Delta?YRD?has become an important stopover site for migrant birds along the flyway of the East Asian-Australasian Flyway?EAAF?.Because of the natural wetland degradation and food shortage,population of many shorebird species is under decline.Shorebirds'population dynamics are strongly linked with available food sources,research focusing on feeding ecology is therefore vital for formulating policies that benefit population recovery of rare bird.However,few relative researches were conducted in the YRD.Two natural wetlands in the YRD were selected as the research areas.Field samplings were conducted in spring and autumn,2018.Shorebirds collected included Numenius madagascariensis,Limosa lapponica,Larus saundersi and Sterna hirundo in spring,and Charadrius alexandrines,Calidris alpine,Larus ridibundus and Larus crassirostri in autumn.Bird plasma was obtained for later analysis.Macrobenthos,fishes and plants were collected as potential food sources.?¹³C and?¹⁵N values in bulk tissues and?¹³C_EAAAA values in 6 amino acids?Val,Leu,Ile,Thr,Phe and Lys?were determined.Diet composition and trophic position of shorebirds were explored.Main results were proposed as follows,?1?Shorebirds fed mainly on macrobenthos on the mud flats but hardly ate plants and fishes.Their key food sources in spring were polychaetes and in autumn were gastropods.Shorebirds in spring took up low trophic level of 2.73±0.36,and shorebirds in autumn were in average trophic level of 3.65±0.37.The latter were significantly higher than the former,which indicated trophic structure of shorebirds was highily plastic.?2?There was significant seasonal variation in the food composition of shorebirds,and it may result from seasonal variation in availiable sources.In spring,due to the low epifauna resource,shorebirds adopted opportunistic feeding strategy and probed in the sediment to obtain polychaetes.In autumn,availiable sources in the mud flats were relatively abundant,shorebirds consequently exhibited omnivorous.