We have now got information thanks to Adjan in Sweden who has explored the breeding area to search for clues to what has occurred during the breeding season.
Sadly Tag18 was predated and its tag well and truly broken up.
Tag24 has been broken off the bird, possibly by itself. Hopefully winter observations may confirm that it is still alive if we can identify its leg ring.
Tag27 has also has a broken collar and might lose it in the fullness of time. Another one to look out for this coming winter.