Subject: Re: RFI:Tundra vs. Trumpeter Swans - Reply
Date: Mar 17 11:43:33 1997
From: Rick Hudson - rhhudson at u.washington.edu


Denny,

Dennis Paulson and I noted that error in the Master Guide several years
ago! You're correct, it apparently is a mistake!

Rick
Seattle, WA

On Mon, 17 Mar 1997, Denny Granstrand wrote:

> Tweeters,
>
> I looked in the Audubon Master Guide to Birding after reading this
> description of Tundra and Trumpeter Swans. It appears to me that the guide
> has a picture of a Tundra without the yellow spot in the section on
> Trumpeters. I then looked in the Stokes Field Guide to Birds, as it also
> has photos, and their photo of a Trumpeter is completely different from the
> Master Guide adult Trumpeter. Please correct me if I am wrong.
>
> Denny Granstrand
> Yakima, WA
>
> At 01:24 AM 3/17/97 EST, you wrote:
> >Identification of these two swans can be tricky, especially for persons
> >unfamiliar with one or both of the species. Characteristics often overlap or
> >are subtle; even diagnostic characters can be difficult until experience is
> >gained observing both species.
> >
> >When perusing flocks of swans for trumpeters, I generally look at the eye. In
> >most tundra swans the eye is readily distinguishable from the the black
> leathery
> >extension of the bill (which meets the eye in a narrow point). This is further
> >enhanced on the tundras that have the characteristic yellow spot. On trumpeter
> >swans, the bill extension envelops the eye. If you were to look at the swan in
> >a one-dimensional flat black and white context, the trumpeter swan eye
> would be
> >barely discernible from the bill extension, if at all. In the tundra
> swan, the
> >eye would appear as a large button, nearly separate from the bill extension.
> >This works well even at a distance and will separate out most tundra swans
> >quickly (but not all). From here, other standard trumpeter identification
> >features need to be looked at and/or compared with obvious tundras. These
> >other morphological or behavioral features (such as bill "V" notch, bill slope,
> >neck kink, body size and posture) are too detailed to explain here.
> >
> >Tundra swans tend to hold there head (bill) on a horizontal plane with the neck
> >held vertical. Trumpeters tend to have the bill pointed downward at a slight
> >angle (for feeding or semi-alert birds only) and their necks are often
> curved or
> >bowed to some degree. While alert, tundras tend to nod their head or have a
> >quick stiff neck bob returning the bill to horizontal and neck to vertical.
> >Trumpeters exhibit a deeper head/neck bob resulting in a 'S' curved appearance
> >to the head/neck, not the angular profile of the tundra. These differences
> fall
> >apart quickly depending on the alertness of the trumpeter.
> >
> >Other trumpeter clues include: small flocks or family groups separate or
> on the
> >periphery of a large flock of swans; trumpeters are generally dominant in a
> >mixed flock, thus tundras tend to give way when a trumpeter approaches;
> tundras
> >prefer more open sites while trumpeters will use areas with enclosed vegetation
> >or more visual barriers. By mid-winter, most immature tundras have attained
> >their white plumage with only a scattering of light gray feathers remaining.
> >Trumpeter immatures can remain quite gray into the spring and are
> >near-diagnostic this time of year. Again all of these are clues of possible
> >trumpeters and are not diagnostic. They are based on observations of swans in
> >wetland situations and may not hold true for field-feeding birds such as in
> >Skagit County.
> >
> >The Trumpeter Swan Society has published an identification pamphlet for
> >distinguishing the two swan species. I published an article in UTAH BIRDS,
> >Volume 6, Number 1, March 1990 that attempted to explain some of the subtle and
> >distinguishing characteristics of the two swan species. While it needs some
> >improvement, it may be useful. Unfortunately, I do not have either of these in
> >a readily available electronic format but will send paper copies to interested
> >persons if they email an address to me.
> >
> >Joe Engler
> >US Fish and Wildlife Service
> >Ridgefield, WA
> >joe_engler at mail.fws.gov
> >
> >
> >
>
>