In the summer of 1902 two ships raced from opposite sides of the Pacific toward a reef-ringed atoll covered only in birds and birdshit. The rock was named Marcus Island (J: Minami-torishima), and despite its minuscule size it now threatened to provoke a diplomatic confrontation between the United States and Japan, two empires that in the previous years had expanded across the Pacific towards each other with startling rapidity. This chapter explores how booming demand for commodities such as plumage and guano fertiliser encouraged prospectors to stake claims to uninhabited or marginally inhabited bird islands. To do so they deployed the rhetoric of colonial boosterism, exploiting ambient cultures of imperialism to persuade their governments to assert territorial sovereignty over them. Yet international law was vague as to what constituted legitimate occupation of ‘uninhabited’ territory, setting the stage for confrontations over atolls such as Marcus in 1902.