Navigation requires a compass, which indicates where is the North, and a map, for knowing your position relative to your destination. If a migratory bird follows a bearing for a determinate amount of distance and time it is using vector navigation. Meanwhile, if it uses a map, reliable cues, and a bi-coordinate system, it is using true navigation and can adjust its orientation to reach a determined destination in case of being displaced. There is evidence for true navigation in seasoned migratory songbirds, but the cues and sensory systems on which they rely are still unclear.
One possible cue for determining position is using magnetic parameters, and it is thought that birds may process such information using sensory sytems like the ophthalmic branch of the trigeminal nerve (V1). The goal of this study was to test if V1 plays a role in the navigation of migratory Eurasian reed warblers after being displaced 1,000 km toward the east from their breeding ranges during spring migration. With this purpose, the researchers performed a series of orientation tests with Emlen funnels at the capture site in Rybachy on intact birds, then sectioned the V1 of one group and performed sham-surgery on another as a control. Both groups were displaced to Zvenigorod where they were subjected to further orientation tests. The hypothesis was that V1-sectioned birds would use vector navigation and behave like intact birds in Rybachy, while sham-sectioned birds would readjust their orientation because an intact V1 plays a role in true navigation.
Also talk about the differences in magnetic field parameters between the two areas (done in discussion)
and talk about how the compass part of navigation is better understood than the map info, which is why they are doing this experiment
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