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Louise de Raad

Locations around autumn equinox - real or artifact?

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Hi, I'm at the stage of interpreting my results (after now having produced the beautiful maps). One thing that slightly troubles me is that, for most birds, the locations in Africa either side of the autumn equinox differ. I am wondering if this is real, or an artefact of the equinox. Most of the locations after the equinox are further S, but a couple are N. There is a similar effect for some birds in spring. I tried to insert some examples (lat-lon plot & map), but seem unable to insert pictures (unless they have a URL?) and I am unsure how to upload files (to my "media library") to attach. What are people's thoughts on such findings? Is this a common artefact of the equinox, or might this be a real shift in location? Thanks for your feedback. Louise

 

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  Hi Louise,

 I do not think this is common, as I have seen many birds wintering around equator where geolocator inferred positions did not do jump. At the same time I have also seen many migrations within Africa during wintering from gps data, so it is common. 

The only suspicious thing is symmetrical movements in relation to autumn and spring equinoxes, if you have those - send me the lat-lon plots, please.

   Cheers,

  Eldar

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