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Hi everyone.

Ken Tracey has circulated two interesting photographs of Reddish Egrets, and
speculated that one may be of an "intermediate" morph immature, and the other
an immature white-morph bird.

The notion that an "intermediate" morph exists surfaces occasionally because
some dark-morph birds (only adults, in my experience) show scattered white
feathers.  Usually these feathers are found in the tail or wing (primaries or
secondaries), and usually in a bilaterally symmetrical pattern.  Sometimes
there's a lot of white, and it's quite striking to see.  Occasionally too, white
contour feathers may be found on the body.  I suspect that on all such birds,
which I call "pied," a narrow fringe of white can be found at the gape and throat
if viewing conditions are good.

In the 1800s (until the 1880s), the white-morph Reddish was officially
regarded as a separate species:  the Peale's Egret.  Pied birds therefore were
considered hybrids.  The finding of mixed pairs at colonies, and even mixed broods
of nestlings, disproved the notion that there were two species.  Once the two
"species" were understood to be a single dimorphic species, the question of a
third "morph" arose.  Fortunately it never gained much credence.

The genetics of dimorphism in herons is very poorly known, but surely more
complex than a single Mendelian dominant/recessive locus.  With Reddish Egrets,
I've barely scratched the surface but in studies of marked nests in Texas
(where they often nest on the ground, and are much easier to see at nests than
here in Florida) I found that white-white pairs breed true.  That is, their young
are all white-morph.  Dark-white pairs produce mostly dark young, but some
are white.  Dark-dark pairs produce dark young, but you would expect that
"heterozygous" dark-dark pairs might occasionally produce a white young, and I did
find such a nest.  At no time did I find any nestling, fledgling, or fledged
immature that fit the description of an "intermediate" morph.

Additional uncertainty in genetic studies is caused by the fact that some
"extra-pair copulations" do occur.  It's likely that most of these are not
successful, but if any are, it complicates field work like mine that was done
without genetic analysis of blood samples of adults and offspring.

And you have to wonder just what is a "heterozygous" dark-morph adult, too.
Presumably a dark-morph birds can have 1, 2, or 3 white-morph grandparents,
for instance.  How this might affect the "phenotype" -- what we see -- is compl
etely unknown.

Immatures do exhibit some variation, though.  While most (dark-morph birds)
are a rather flat grayish-khaki color, a few in Texas were rather rufous.  I
suspect that all of them fade fairly quickly to look more or less like the bird
in Ken's photo.  Immature plumages are only recently included in field guides,
and they are still not widely known.  A bird that is pale gray or grayish-tan
throughout is a first-year or immature bird.  One that has acquired some
darker gray (same color as the adult, which really is neutral gray) back feathers
and wing coverts, plus a hint of occiputal and neck plumes (look for one or
two short scapular plumes too), is a yearling.  And in Florida, where nesting
can occur at almost any time of year, good luck.

The photo does appear to show a stripe of white on the back and neck, plus
some patches near the wings and tail.  It's hard to be certain from one photo,
but in my experience I frequently see such markings when the breeze parts the
feathers.  Perhaps the white stripe is a highlight.  Additional photos might
help clarify these characters.  We all want to say something definitive when
we're looking at photos (and I do too), but for now I have to say that I cannot
find a clear indication of "intermediate" or "pied" plumage in this photo.

Finally, I want to add that in looking at thousands of Reddish Egrets in the
field and in museum collections, I have seen no evidence (nor read of any,
either) indicating the validity of an "intermediate morph."  Yes, there are pied
plumages (in adults, at least) that represent a genetic intergrade, but that's
not the same thing.

On to the photo of the white-morph bird.  Aging white-morph birds can be
extremely difficult.  You have to look for the presence (and extent) or absense of
plumes, on the crown, neck, base of the neck, and back.  Soft-part colors
(bill, lores, legs) by themselves aren't enough.  Again, more than one photo
would help.  But I think there is a suggestion of a short back (=scapular) plume.
  My impression is that this may be a yearling bird.

Remember that for both morphs, the soft parts of breeding adults darken
following nesting.  By themselves, dark soft parts cannot be used to conclude that
a bird is an immature or a subadult.

Ken, thanks for submitting two provocative pictures.

Rich

Rich Paul
Tampa
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and
Manager, Florida Coastal Islands Sanctuaries
Audubon of Florida
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