Home ranges vary from one to ten acres or more and overlap greatly. Predators on the nesting ground include foxes, weasels, jaegers, gulls, and owls. Jaegers can capture and feed on phalaropes at sea. Occasionally there is mass mortality of phalaropes at sea due to starvation. Some phalaropes probably live for ten or more years.
Phalaropes are visual hunters.
During the summer, their diet is principally freshwater insects and other invertebrates. When feeding in deeper water, phalaropes sometimes swim rapidly in a small circle and create a vortex. As food items are raised from the depths, the birds peck from the center of the circle. At sea, these birds feed on zooplankton such as krill, copepods, arrow worms, and amphipods. Phalaropes sometimes associate with other animals, such as gray whales and oldsquaw ducks, which apparently stir up food from the bottom while feeding.