Abstract: Various environmental oceanic factors, such as ocean waves, affect seabird ecology; ocean waves are important, as most flying seabirds must land on ocean surfaces for foraging. However, the global ocean wave observation network is spatiotemporally poor compared to other parameters; fine-scale information on wave conditions is limited, and the influence of wave conditions on seabirds has not been quantitatively studied. In this study, a method was developed to estimate ocean waves from the fine-scale motions of seabirds floating on the sea surface, as recorded by a global positioning system (single-point positioning). Ocean wave parameters, estimated from streaked shearwater around the eastern ocean of Japan, strongly corresponded with the observation results of a buoy, with an accuracy of <0.3 m for wave heights of 1.0–2.5 m. Furthermore, wave height estimated from streaked shearwaters and wandering albatrosses around the southern Indian Ocean significantly correlated with hindcast-model values. Bird-based wave observation methods are valuable not only in seabird ecology but also in oceanography as an in-situ observation system. Based on the results of bird-based wave observations, the preferences of wandering albatrosses under various wave conditions were further examined. Anecdotal studies suggest that seabirds prefer low-wave conditions to forage in because of prey visibility; however, wandering albatrosses landed on the sea surface randomly, even on very high waves (5–6 m), revealing their tolerance to ocean surface conditions. Considering the effect of environmental factors on marine animals, increased inclusion of previously ignored parameters in analysis, such as ocean waves, is essential.