We have been tagging Henslow’s Sparrows this summer using Lotek tags and leg loop harnesses. These are the smallest birds we have tagged so far (juncos are a breeze after working with Henslow’s). We have been using sizes as recommended but birds have been getting out of the leg loops - sometimes it takes a few weeks. We are color banding birds so we have re-sighted birds that lost their nanotags. We think the tags may be getting hung up in the grass as they run through and are pulled down the back just enough for them to get the loops off. We have been able to recover the tags with tracking and digging through the grass. The tags seem to fit fine and pass the flip test. We hate to go smaller as these birds should put on fat for migration. Any suggestions?
We have tagged Golden-winged Warblers (+/- 9g) with high success. We use black 0.5 Stretch Magic harnesses and make harness size based on each individual’s weight and wing, sometimes varying only 2mm and this does seem to make a difference. In addition to the “flip-test” I would certainly test by pulling back on the tag by the antenna and it should not slip at all.
could you please explain what you mean with the flip-test? Maybe this is a naïve question or maybe we just use a different term for that in Europe and that’s why I don’t recognize it. Anyway I thought I ask and maybe I am not the only one wondering J
Thanks. Now I understand what you mean by flip-test.
Coming back to your original question/problem: I always adjust the harness to an individual bird and never use “pre-assigned” harness sizes (as seen also in the video-link you sent).
We always have a non-fixed harness that I adjust to the right fit when tagging a bird. We have done that on different species (from 30 g to 200 g) and many birds have had their tags for 1 year or longer. To me it feels more comfortable that way compared to using fixed harness sizes depending on wing length or any other structural size. The latter I had to do in one collaborative project and sometimes tags seem to sit just a little too lose (or too tight), even though it “should” be the right harness size for that bird. Of course, adjusting harness sizes to individual birds is not error-free either but according to my personal experience it works better. Maybe this could help you mimising tag loss?
We have been using premade loops but select a size based on the bird’s wing. We are going to adjust sizing down 1-2mm and see if we can get them on. So much easier with larger birds where you can use crimp beads.
Hola Arne, the “flip test” involves holding the tag by the antenna and pulling it over the back towards the head. If the harness size is right it should flip over with ease (at least with Lotek Nanotags and glued-on harnesses).
Ernesto