| Summary: | Compass orientation is central to the control of animal movement from the scale of local food-caching movements around a familiar area in parids [1] and corvids [2, 3] to the first autumn vector navigation of songbirds embarking on long-distance migration [4, 5, 6]. In the study of diurnal birds, where the homing pigeon, Columba livia, has been the main model, a time-compensated sun compass [7] is central to the two-step map-and-compass process of navigation from unfamiliar places, as well as guiding movement via a representation of familiar area landmarks [8, 9, 10, 11, 12]. However, its use by an actively navigating wild bird is yet to be shown. By phase shifting an animal’s endogenous clock, known as clock-shifting [13, 14, 15], sun-compass use can be demonstrated when the animal incorrectly consults the sun’s azimuthal position while homing after experimental displacement [15, 16, 17]. By applying clock-shift techniques at the nest of a wild bird during natural incubation, we show here that an oceanic navigator—the Manx shearwater, Puffinus puffinus—incorporates information from a time-compensated sun compass during homeward guidance to the breeding colony after displacement. Consistently with homing pigeons navigating within their familiar area [8, 9, 11, 18], we find that the effect of clock shift, while statistically robust, is partial in nature, possibly indicating the incorporation of guidance from landmarks into movement decisions.
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