Re: Salem 'Trumpeter Swan'

[october at ida dot net]

Lu,

I'll do my best to address your arguments individually below.  I'll be
back in Island Park tomorrow and will try to take some photos of juvenile
Trumpeters for comparison.


>1. According to Sibley, juvenile trumpeter swans have a bill that is
> "always
> black at base" whereas tundra swans have a bill that is "pink at base,
> becoming black."


Since the Salem bird has a black bill base and both Tundra and Trumpeter
also have a black bill base I'm not sure this is relevent.  Although the
cygnet in the photo you referenced at
http://www.eimagesite.net/s1/gst/run.cgi?action=imagen&prid=310 shows a
similar bill pattern it still has less extensive pink than the Salem bird.
 Also it's a very young Trumpeter that hasn't fully developed yet.  I know
the date is Oct 10th but it appears to be a captive bred bird which
presumably would make it possible for it to be much younger in Oct than
wild Trumpeters would be.  Regardless of date the Salem bird has very
white wing coverts (back) which Trumpeters won't show until late next
summer, when they're more than one year old, at which time the bill will
be entirely black.  Considering the extent of white on the back the Salem
bird would have to have some kind of pigment anomoly to be a Trumpeter
with this extent of pink in the bill.  You also made reference to a photo
on Bill Schmoker's site as follows:
"http://www.schmoker.org/BirdPics/Photos/Waterfowl/TRUS_TUSWcomp1.jpg. In
> this
> respect these birds appear similar to the bird illustrated to Sibleys and
> also
> to the Salem swan.

In it's original context that photo is actually being used to illustrate
the difference in head shape and width of bare lores between Trumpeter and
Tundra Swans.  Here's what the photo caption says "Head comparison of
juvenile Tundra (right- note very narrow lores) and adult Trumpeter
Swans...."  The URL for this page is
http://www.schmoker.org/BirdPics/TRUSs.html, fourth photo down.  Just to
be clear, the bird on the right is a juvenile Tundra Swan, not a Trumpeter
as it came up on a google search.


> 2. The head shape of trumpeter swans differs from that of tundra swans. In
> this I refer to the "Identification of Swans" item in Sibleys, and also to
> an
> online article authored by Kevin McGowan entitled "Swan Identification in
> upstate New York" found at http://www.birds.cornell.edu/crows/SwanID.htm.
> Dr.
> McGowan, ....
>articulates the differences in head shapes in the following words:
"Trumpeters >have a longer, flatter bill, and a more flattened profile
and head shape (somewhat >Canvasback-like).  Tundras have more rounded
heads and slightly concave bills."

I agree that the Salem bird has a flat culmen/bill shape.  While the
differences mentioned by Kevin and drawm by Sibley are generally true
there is variation in these characters in both species.  I've seen adult
Tundras (yellow spot on lores and all) with very flat bills and obvious
Trumpeters with concave bills.  Regardless of bill shape the head of
Tundra is slightly domed above the eye, as it is in the Salem bird, while
Trumpeters have a very flat head essentially continuing the line of the
bill all the way to the back of the head where there is a slight peak. 
Nikcy Davis has added two photos I took last week to the page at
http://www.wildutah.us/h_swan_trumpeter.html.  Look at how flat the head
is and where the head peaks (far to the rear on Trumpeter) and compare it
to the slightly domed appearance of the head on the Salem bird.


> 3. In adult birds, according again to Dr. McGowan, "the eye of a Trumpeter
> looks contained within the black mask of the face, while the eye of a
> Tundra
> looks nearly separate, connected only by a small area directly in front of
> the
> eye.  (This connection can look even narrower because of the yellow
> lores.)


Very young Trumpeters on which the feathering is not fully developed would
have the eye seperate from the bill as on Tundra.  However, as stated
above, for a Trumpeter to have this much white in the back it would be
over one year old.  Even on juvenile Trumpeters, born in 2005, the
feathering would be fully developed by January and the eye would not
appear seperate from the bill and connected by a thin black line as in the
Salem bird.  Compare this in the photos on Nicky Davis's page referenced
above.  You can also see this in one of the photos I referenced in my last
post (top photo at http://www.octoberweb.com/birds/whooper/), although not
very well.  Again I'll try to get some better photos tomorrow.


> 4. I'm not familiar with your observation that begins "edge of
> feathering,"
> although I do not doubt its correctness.

Again, this is hard to explain.  What I'm referring to is where the
feathers on the head and face meet the unfeathered bill.  If you start
near the chin on the bottom of the bill, where the bill meets the
feathered throat, if you follow the edge of the feathers upward and it
curves back and eventually goes all the way to the eye (and if you
contiune around the eye and across the forehead, etc).  The shape of this
edge differs between species.  Sibley draws this difference in the heads
of the swans at the right edge of page 73 (Field Guide to North America,
not one of the regional guides).  On the Trumpeter that's second down from
the top, there's a line pointing to the base of the bill that says
"straighter edge".  On the Tundra directly below that one a line points to
the same place and says "curve at gape".  This "curve at gape" is clearly
visible in the photos of the Salem bird.



> 5. As for the matter of flat backs versus arched backs, Sibley states that
> in
> trumpeter swans "back tends to be more evenly rounded than Tundra
> [swans]."
> McGowan does not comment on this attribute. I have no doubt that you have
> seen
> far more of each specie than I have, Cliff, but to me this extent of
> roundness
> versus flatness seems to be rather a subjective identifier, i.e., one
> subject
> to the interpretation of the observer. In looking at the images sited
> above
> and on McGowan's page, I have to confess that I would find myself
> extremely
> hard-pressed to differentiate between the species shown on his page based
> solely on the extent of back-arch. In addition, I find myself wondering if
> this is always consistent, even within the same bird. Primate postures can
> change, depending on how animal is carrying itself. One simply has to
> watch
> men on a beach, trying to impress women, to see this changing of postures
> at
> work. Is this also possible in birds? If so, how ultimately reliable is
> back
> shape in swan species differentiation?

Your primate posture analogy isn't a good example in my opinion.  Apples
and oranges.  Birds aren't primates and posture varies in different ways. 
That said the shape of the back is subject to posture to some extent, but
the difference is real.  Look at the the difference between the Tundra on
the left and the Trumpeters on the right in these photos:
http://www.muskoka.com/~sinclair/archives/tundtrum.jpg



>
> 6. Coloration seems to indicate that the bird is a juvenile bird, but how
> far
> can this be taken? If the Salem bird was born a few weeks earlier or later
> than the Island Park birds you observed, is it not possible that its
> coloration would be somewhat out of phase with those birds?

No.  As I mentioned above the timing of obtaining white wing coverts is
dramatically different between species.  We're talking months, like eight
months, not weeks.

I question the
> value
> of coloration in juvenile as an objective identification tool in
> differentiating the species.

Obviously there is variation as in most, or all, characteristics but the
difference is striking and is very useful in first winter juvenile
Trumpeter/Tundra identification.

There is one more point that I neglected to mention in my last post to
Utahbirds.  Leg color of juveniles varies between species.  Tundras have
black legs, Trumpeters have grayish/yellowish legs.  The Salem bid clearly
has black legs, visible in Nicky Davis's photos at
http://www.wildutah.us/h_swan_trumpeter.html.  While I'm on the subject of
leg color there is one more consideration.  Trumpeters have a rare but
regular leucistic color morph.  These birds appear white as juveniles but
have very obviously yellow legs which the Salem bird does not show.

I hope all this is helpful.  If you still have doubts I recommend you post
a query on ID Frontiers.  You'll likely get opinions from people with far
more experience and knowledge than I have.  That's probably your best bet
for nailing down the ID.

Cheers,
Cliff

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