This research employs ecological interface design to improve the human machine interface of an existing ground control station for the supervisory control of UAV swarms. As a case study, a general ground surveillance mission with four UAVs is envisioned. An analysis of the swarming work domain is performed to generate a reduced set of means-end relations. This analysis leads to a novel design that shows predicted coverage and range of the UAVs in the swarm. An evaluation study with 10 participants showed that the new interface successfully enables operators to control a swarm of four UAVs and mitigate problems during mission execution. The results of the evaluation study showed that operators had a better system understanding and that it promoted creative problem solving activities to scenarios that could not be solved by fixed procedures.