Displacement experiments have demonstrated that experienced migratory birds translocated thousands of kilometers away from their migratory corridor can orient toward and ultimately reach their intended destinations.1 This implies that they are capable of “true navigation,” commonly defined2–4 as the ability to return to a known destination after displacement to an unknown location without relying on familiar surroundings, cues that emanate from the destination, or information collected during the outward journey.5–13 In birds, true navigation appears to require previous migratory experience5–7,14,15 (but see Kishkinev et al.16 and Piersma et al.17). It is generally assumed that, to correct for displacements outside the familiar area, birds initially gather information within their year-round distribution range, learn predictable spatial gradients of environmental cues within it, and extrapolate from those to unfamiliar magnitudes—the gradient hypothesis.6,9,18–22 However, the nature of the cues and evidence for actual extrapolation remain elusive. Geomagnetic cues (inclination, declination, and total intensity) provide predictable spatial gradients across large parts of the globe and could serve for navigation. We tested the orientation of long-distance migrants, Eurasian reed warblers, exposing them to geomagnetic cues of unfamiliar magnitude encountered beyond their natural distribution range. The birds demonstrated re-orientation toward their migratory corridor as if they were translocated to the corresponding location but only when all naturally occurring magnetic cues were presented, not when declination was changed alone. This result represents direct evidence for migratory birds’ ability to navigate using geomagnetic cues extrapolated beyond their previous experience. It is still unclear how migratory birds navigate from outside their familiar range. By testing their orientation in a changed magnetic field at the capture site, Kishkinev et al. show that birds respond to these changes as if displaced to the simulated location, suggesting they can extrapolate beyond their previous experience of the magnetic field.
Предметные области Scopus
- Биохимия, генетика и молекулярная биология (все)
- Земледелие и биологические науки (все)