The stunning Baikal Teal (Sibirionetta formosa) is a firm favourite for many, but it's only a generation or 2 since it was considered difficult to breed and so commanded a high price. The rare occurrence of a wild visitor to the UK was often viewed with suspicion. In 1956, Jean Delacour considered that all European records were escapees.
By 2005, we had the technology, ability and will for tissue sampling to question historic records. The results of a stable-hydrogen isotope analysis of feathers from a specimen of a Baikal Teal shot at Tillingham, Essex, in January 1906 suggested that the bird had not been hatched in western Europe, and this record was duly accepted by the British Ornithologists’ Union Records Committee (BOURC) as the first for Britain. The bird's feather sample had very low hydrogen-isotope values consistent with an origin in Siberia (Votier et al. 2009).