Foraging behaviour and diets of red-necked stints and curlew sandpipers in south-eastern Australia

Diet and feeding behaviour of red-necked stints (Calidris ruficollis) and curlew sandpipers (Calidris ferruginea) feeding in mixed flocks during the non-breeding season were investigated in Western Port in Victoria, south-eastern Australia. Surface pecking was the most common feeding action of both species, followed by jabbing for red-necked stints and probing for curlew sandpipers. Mean depths of substrate penetration were 3.4 mm (red-necked stints) and 14.0 mm (curlew sandpipers). The preferred feeding zone for red-necked stints was wet mud (86%) and for curlew sandpipers was shallow water (40%). Feeding rate did not vary between species but did vary between months and age classes for curlew sandpipers. Gastropods made up 68% of the sample volume for stints and two unidentified species in the families Hydrococcidae and Fossaridae occurred most frequently in terms of occurrence in the guts and total prey items. Curlew sandpipers took a wider variety of taxa (12) than did red-necked stints (8), with polychaete worms (Nereidae) being their most frequently recorded prey and comprising 63% of the volume of the gut samples. When prey taxa overlapped in the diets of the two species, some size differences of prey were apparent. Differences in bill morphology and feeding behaviour, including microhabitat use, corresponded with these differences in diets.