This article focuses on monitoring and tracking seabirds from the mid-twentieth century to the present. It illustrates how seabirds have been reconfigured as environmental sentinels through their enrolment in scientific networks aiming to understand birds and to monitor changing marine environments. Drawing on historical and geographical literatures exploring changes in environmental monitoring, ocean science, and ornithology over the latter half of the twentieth century, the article outlines three ways in which seabirds have been enrolled in scientific projects — as populations, samplers, and digital animals. It attends to the development of seabird monitoring programmes from the 1960s, enabled partly by European occupation of remote territories in the Southern Ocean. It then shows how seabird scientists positioned data collected through these programmes as contributing to knowledge about an increasingly turbulent, depleted sea. Finally, it explores how this idea was reconfigured in the 1990s through new bird-borne sensors, creating novel connections between the science and politics of the ocean as a physical space and lively ecology. Through this case, the paper advances conversations concerning the shifting character of environmental sensing and science in the Anthropocene and contributes to the development of technonatural history as a theory and method in geographical research.