Olfaction and topography, but not magnetic cues, control navigation in a pelagic seabird: displacements with shearwaters in the Mediterranean Sea

Abstract

Pelagic seabirds wander the open oceans then return accurately to their habitual nest-sites. We investigated the effects of sensory manipulation on oceanic navigation in Scopoli’s shearwaters (Calonectris diomedea) breeding at Pianosa island (Italy), by displacing them 400 km from their colony and tracking them. A recent experiment on Atlantic shearwaters (Cory’s shearwater, Calonectris borealis) breeding in the Azores indicated a crucial role of olfaction over the open ocean, but left open the question of whether birds might navigate by topographical landmark cues when available. Our experiment was conducted in the Mediterranean sea, where the availability of topographical cues may provide an alternative navigational mechanism for homing. Magnetically disturbed shearwaters and control birds oriented homeward even when the coast was not visible and rapidly homed. Anosmic shearwaters oriented in a direction significantly different from the home direction when in open sea. After having approached a coastline their flight path changed from convoluted to homeward oriented, so that most of them eventually reached home. Beside confirming that magnetic cues appear unimportant for oceanic navigation by seabirds, our results support the crucial role of olfactory cues for birds’ navigation and reveal that anosmic shearwaters are able to home eventually by following coastal features.

Acoustic activity across a seabird colony reflects patterns of within‐colony flight rather than nest density

“…While the temporal resolution of our tracking data was too coarse (4-to 12-min intervals between GPS locations) to identify fine-scale details of these flight paths, the highly consistent distribution of tracks across years suggests that persistent flight paths do occur. The literature suggests that social information exchange is most likely to be the driver of the consistency in the flight paths observed here; however, other factors such as avoidance of topographical features or olfactory cues may also influence these distributions (Pollonara et al 2015, Yonehara et al 2016. One other possible reason for increased flight through this area is that the west coast of the island faces the Atlantic Ocean.…”

Experienced migratory songbirds do not display goal-ward orientation after release following a cross-continental displacement: an automated telemetry study

“…Support for this hypothesis comes, in part, from displacement experiments on homing pigeons ( Colubma livia domestica ) and shearwaters (Procellariiformes) where olfactory deprivation led to reduced navigational ability27282930. A recent displacement study on lesser black-backed gulls ( Larus fuscus ) suggested that experimentally-induced anosmia led to impaired navigation performance in one of two release sites10.…”

Pigeon navigation: exposure to environmental odours prior release is sufficient for homeward orientation, but not for homing

“…Once at the release site, pigeons may be able to determine the direction of displacement simply by recognising the prevalent local odours and recalling from which direction these arrived at the home loft. Although recent tracking studies on wild birds supported the critical role of olfactory information in avian navigation Pollonara et al, 2015;Wikelski et al, 2015), evidence supporting olfactory navigation in homing pigeons comes almost exclusively from traditional experiments in which vanishing bearings and homing performance were recorded. In fact, the only exception is a tracking study (Gagliardo et al, 2011b) reporting that pigeons made temporarily anosmic by anaesthetising their olfactory mucosa displayed impaired navigational abilities, unless they had been allowed to smell local environmental odours during transportation and at the release site prior to the release.…”