Turning to the identification of migrants, including birds of the year, there are difficulties
in the identification of at least a proportion of adults and probably of even
more young birds, further confused by moult into adult plumage in winter quarters.
Most discussions, including that of Vaurie (1951), are carefully worded suggesting
that the descriptions available have not been sufficiently carefully related to both type
specimens and specimens taken at or near their nests. In addition we have mentioned
the variability in the colour of the under-parts in this species, which are said to vary in
colour due to wear as well as individually. Incidentally, the recognition of saturata
tends to leave a more homogeneous gutturalis, which Vaurie (1954) characterised as
“usually whitish” below.