Very creative and utilitarian post. You have selected those warblers with the most
dramatic plumage change between the archetypal breeding adults and the non-breeding
juvenile birds. Other species such as BT Green, Wilson's and N. Parula are less transformed,
although in a way there is no real metamorphic change since the shape and form of
the juvenile birds remains faithful to the species. After a while and with practice even the shape of the
bird's bill is an identifying feature that can be observed in the field irrespective of feather patterns.
Although the colours are muted, or present with a different tint, the juvenile warblers still mimic
the adult ... such as the yellow-green of a Chestnut-sided warblers crown, or the blush of rust on
a juvenile Bay-breasted warbler, or the flash of bright red and yellow on a juvenile male Am Redstart.
Of course, it helps to have a library of terrific images to illustrate your informative theme.
I thought of doing much the same theme but I have a dearth of photos of breeding adult
warblers beyond the most common migrants and that shortfall defeated my attempt.
The shots below transition from a juvenile (essentially female-like) Redstart, to a developing male to a breeding male.
