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Geolocator harness and light stalk

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Hello everyone!


I wonder if the quality of light data obtained by a geolocator tagged like in this picture, is good enough:



It is a tag without stalk, attached as leg-loop position. 


Thank you very much in advance!


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Yes, sorry!


the model of my tag is ML650 (Biotrack). My study species is the barn swallow, and my purpose is to determine the migratory routes and winter areas, as well as testing the effects of the tag on survival and posterior reproduction.


Thank you

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Thanks for the clarification. I haven't used GLS with songbirds, nor have I used Biotrack GLS.  I have used Migrate Technology tags with small seabirds and had great success using back-mounted GLS with a small light pipe/stalk.

If feathers shade the light sensor you will have interference with your light data which could impact your ability to determine position estimates when you retrieve the GLS.


From what I understand many folks who deploy back-mounted GLS onto songbirds tend to use devices with a light stalk.  


There is quite a lot of published literature on geolocators and swallows.   



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Thank you stormpetrel,


I know that it is recommended to use a light stalk when attaching as leg-loop. However, there are already studies that have tried a leg-loop position without any light stalk:



I put on the last year 64 tags with a small light stalk and I obtained nice results. However, I noticed a significant reduced survival rate of tagged compared to control birds. This year I wanted to test if I could increase the survival rate by eliminating the light stalk. This is because the body of the barn swallow is very aerodinamic.


I also made a trial at my office: I put a rectrix on the light sensor and I analyzed the data. The tag recorded light values normally, as the light sensor was saturated even under the feather. However I wonder if this could be extrapolated to a real migrating bird.


Thank you again

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