Feeding ecology of migrating Red-necked Phalaropes (Phalaropus lobatus) in the Quoddy region, New Brunswick, Canada

Abstract

During the summers of 1981 and 1982, feeding ecology was studied in migrating populations of Red-necked Phalaropes (Phalaropus lobatus) at their late summer – early fall staging ground in the Quoddy region of the Bay of Fundy (44°55′ – 45°00′ N, 66°54′–66°59′ W). This species was particularly abundant during August 1982 when 5 000 to 20 000/km2 were present in the study area at the peak of occupation. Calanus finmarchicus was both the major prey item and the most plentiful zooplankton species in the area in which the phalaropes fed (mean density, 117 individuals/m2). The birds were consistently found in sectors of the study area corresponding to maximum C. finmarchicus concentrations, made readily available at the surface by upwelling activity. The phalaropes fed almost exclusively on this species, which made up 88.6% of the total number of prey items found in the stomachs; smaller copepods, seeds, and insects made up the rest, with a size limit for ingested prey of 6 mm. The birds fed by pecking constantly at the surface of the water while swimming in a sinusoidal pattern; this differs markedly from the spinning behavior observed near the breeding grounds.