A Long-Tailed Tit without a tail

A pair of long-tailed tits ('tits' in general are similar to the small birds that Americans call 'chickadees' - the word used to be 'titmouse') in my parents' garden. This particular species generally feed in pairs. One of these has lost its tail, perhaps to some cat or fox or some accident. It doesn't seem to cause it any problems flying, that I can see.