Prey items fed to chicks of eight individually-marked and known specialist Thick-billed Murres (Una lomvia) were watched over a 15–year period at Coats Island, Nunavut, and time-depth recorders attached to eight birds in two separate years. Two males were amphipod specialists, one male a cod specialist and another male a shanny specialist; two females were sculpin specialists and two capelin specialists. Although there was likely some gender-related component to diet, there were clear specializations within each gender. Specialization in diet was mirrored by specialization in foraging behavior: amphipod specialists made V-shaped dives and had short foraging ranges, shanny/cod specialists made many shallow dives, sculpin specialists made deep, U-shaped dives, while capelin specialists made V- or W-shaped dives to moderate depths. There was no clear pattern between specialties and age or reproductive success. The use of longitudinal studies in foraging behavior, as long-term studies of individuals can complement existing knowledge of the flexibility or specialization of waterbirds, is encouraged.