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Mendez

plot_slopes_by_location

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Hi all,

 I have a few geolocator files that I have not been able to process ( The location estimates are scattered all across the specified grid) and I believe it has something to do with the plot_slopes_by_location function. I know that this function is just to determine whenever the bird leaves the study site, however, in the graph it revealed that there are no dusk estimates after September (see attached picture). All of the geolocators that I have been unable to analyze have this similar problem. I'm not sure if that's actually the root of my problems or if its something else, this is just my best guess. Is anybody aware if this could be the problem and if it is is there anyway to correct for this problem?

Thanks,

Devin

slope.JPG

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Hi Mendez,

how did you call dawn and dusk times before loading the data into FlightR. Have you used the BAStag package? If yes, were the missing dusk events correctly selected by the package for these tags?

Did you possibly subset the data before using plot_slopes_by_location? Maybe something went wrong there?

All the best and have a nice day!

Hendrik

 

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  Hi Devin,

 Absence of the slopes after start of migration is normal, so no worries here. But what I see in the graph is difference between slopes during dusk and dawn yo have in the summer. THis could happen because (1) the start coordianates are not correct, (2) bird moved to a new place (and thus you do not know where to calibrate you tag), (3) there is a specific bird behaviour, that makes this difference. 

 I would suggest you double check the calibration location and if it was correct try try with calibration extracted from a tag that worked. For Intigeo tags that works well.

     Eldar

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Hi Eldar,

I double checked the start coordinates and they are correct. I went ahead and used the calibration from a tag that worked and I was able to get consistent results. The geos that I was having trouble with were attached to females. I was thinking that since the females spend the majority of their time on their nests during the times that I was using for the calibration period that it may cause extreme shading resulting in the unit believing that it was in another location leading to the calibration of the unit being wrong. Is this a viable hypothesis for these birds?

Thanks again,

Devin

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  Hi Devin,

 Yes, this happens often. In many cases (e.g. swifts) calibration twilights could be completely missing due to behaviour.

  Eldar

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I am still having some difficulties analyzing some of the geolocators that have differences between slopes in dawn and dusk. I have tried using the find.stationary.location function, but it provides me with a location that is way different than the original coordinates. All of the geos i'm having difficulties with are females from 2012-2013 and i'm imagining the problem is a lot of shading events on the breeding site which I have been using for the calibration periods.  Even when plotting the slopes with the derived location from the find. stationary.location there is still a lot of differences between the slopes. In the tool help it says that it does not work well with shaded data which i believe is the case.

Eldar recommended above to use the calibration extracted from a tag that worked. Should I try using a calibration file that was extracted from the same year? Also while using the calibration file from another geo i'm still not confident that i'm doing it correctly. 

I took the proc.data from a working geo and calibrated it normally. I would then plug in the proc.data from the geo that did not possess a calibration period into make.prerun.object with the calibration file from the working geo. Is this the correct workflow? I used this method with one of the problem geos and it appeared to work, but upon closer observation the dates did not align at all with the units previously analyzed.

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  Hi Devin,

 Plug calibration from the working tag into 

all.in<-make.prerun.object(proc.data, Grid, Calibration=Calibration)

  Hope this helps,

   Eldar

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