An important question for Human-Computer Interaction is to understand how and why visual search strategy is adapted to the demands imposed by the task of searching the results of a search engine. There is emerging evidence that a key part of the answer concerns the expected information gain of each of the set of available information gathering actions. We build on previous research to show that people are acutely sensitive to differences in the density and in the number of items returned by the search engine. These factors cause shifts in the efficiency of the available information gathering actions. We focus on an image browsing task, and show that, as a consequence of changes to the efficiency of available actions, people make small but significant changes to eye-movement strategy.