To meet the above requirement, seabirds rely on prey being distributed in patches (Gaston 2004). Oceanography has a profound impact on the distribution of marine life (Miller 2004), and top predators frequently congregate in areas with a high prey biomass (Boyd & Arnbom 1991, Hunt et al. 1999). However, the impact of ocean physics on top-predator foraging behaviour is poorly understood, largely because of the complex trophic linkages involved. In particular, a detailed understanding of the interaction between seabirds and their prey is lacking. Two main methods are currently available to quantify seabird behaviour: animal-borne instrumentation and at-sea observations (see Box 12.1). In this chapter, we examine the impacts of oceanography on the foraging dynamics of North Sea seabirds during the breeding season. The seabirds of the North Sea are primarily piscivorous, with the majority wholly or largely dependent on the lesser sandeel Ammodytes marinus in summer (Furness & Tasker 2000). Using three seabird species with contrasting foraging strategies and dependence on sandeels, we test three specific predictions from the hypothesis that oceanography determines seabird foraging location and behaviour, using data from animal-borne instrumentation, oceanography and primary production collected concurrently. We interpret our findings in the context of the behaviour of seabirds' prey.