BRN 9-2 (uncompressed) - Flipbook - Page 24
Science Advances, 23 July 2025,
Volume 11, Issue 30, DOI:10.1126/
sciadv.adw5857). As you might
gather from the title of the article,
various bird species were using the
the base color effect well before
Homo sapiens evolved. This is a well
conceived and well executed study.
The research article and the supplementary materials available at the link
to the article are well worth the time if
you have an interest in the topic or
wish to review an excellent
description of scientiÞc research.
In a rare case for scientiÞc reporting,
the abstract of this study is worthy of
repetition - in its entirety.
ÒBirds are renowned for their diverse
and colorful plumage. Here, we
demonstrate that vibrant plumage in
the tanager genus Tangara is
substantially intensiÞed by a ÔhiddenÕ
layer of achromatic (white or black)
plumage concealed beneath the
outermost colorful layer. Using
hyperspectral imaging, multispectral
photography, microspectrophotometry, reßectance spectrophotometry,
and optical modeling, we show that
hidden white and black feather layers
are systematically distributed on the
body to enhance the brightness and
saturation of carotenoid-pigmented
and structurally colored plumage,
respectively, by increasing or
decreasing the amount of backscattered light that interacts with
pigments or nanostructures. We
compare male and female coloration
and show that sexual dichromatism in
some Tangara carotenoid plumage
stems primarily from white layers in
males and black layers in females
rather than from differences in
carotenoid pigmentation. Last, we
Þnd that white and black hidden
feather layers are widespread in
colorful passerines. Hidden feather
layers likely play a previously
overlooked but critical role in colorful
plumage evolution in birds.Ó
In previous issues of this journal we
have discussed feathers, their
purposes, their structure, and how
they create color - either through
pigmentation or structure. (See
ÒFeathersÓ in Volume 5, Number 1,
January 3, 2022, as one example of
our fascination with this topic.)
Color and imaging? My fascination
with those topics crops up occasionally in this journal. (See ÒThe
Camera and Natural History - William
L. FinleyÓ, Volume 4, Number 4,
October 3, 2021, for starters.)
Consider that fascination and you will
understand why I believe this is such a
great abstract. Think Òhyperspectral
imaging, multispectral photography,
microspectrophotometry, reßectance
spectrophotometry, and optical
modelingÓ, golly gee whiz.
Although the subject study was
heavily focused on Thraupidae
(tanagers found south of the United
States border with Mexico), it also
explored the feather layering effect in
many non-tanager species. The
graphic at the bottom of the previous
23
page is from the study and
demonstrates the effect dramatically
in the House Finch and Northern
Cardinal, both of which are in my yard
as I write this. The top images show
feathered areas without the layered
effect while the bottom images show
areas with the effect. The luminescence of the feathers in the bottom
photographs is striking.
The Western Tanager (see image at
the top of the page), Piranga
ludoviciana, is not a Tanager. It, and
the other North American Tanagers,
were moved to the Family
Cardinalidae based on a 2007 study
which resulted in signiÞcant realignment in the traditional Cardinal and
Tanager taxonomic regimes.
Not only is the Western Tanager not a
tanager, or more precisely not
Thraupidae, it was not included in this
study. Although not certain, I would
wager that the head area of this
species has a layered feather
structure. The color of that area can
be breathtaking at times, especially in
the low level lighting of early
morning and late evening.
Our understanding of the amount we
do not know about the natural history
of the world increases with every new
research study. For some humans that
is a frightening thing. For the rest of
us it is an exciting and invigorating
thing. Makes you want to get up and
have a cup of coffee and one of tea.
