Date: 3/11/17 8:51 pm
From: Joel Geier <joel.geier...>
Subject: [obol] Re: Swan ID
About using size to distinguish between Tundra Swans and Trumpeter
Swans, others have hinted at this (as in Lars' mention of accipiters)
but perhaps someone needs to state it more clearly:

Males of both species are usually noticeably larger than females. A
large Tundra Swan male can be as big as a Trumpeter Swan female.

The two species will occur side-by-side and sometimes intermingled in
daytime feeding situations, in the Willamette Valley. They sort
themselves out again at the end of the day as family groups fly off
together on their way to nocturnal roosts, but during the day they can
mix it up a bit.

They differ in their feeding preferences so there is usually some
segregation when you see them in grass fields (Tundras grazing on the
higher ground and Trumpeters rooting around in the swales.). However
when you're viewing a flock through a scope, foreshortening of the view
field can make them look much closer to each other than they really
area.

The best traits (other than voice if you're so lucky as to hear them
vocalize) are the relation of the eye to the bare skin just ahead of it
as Dan Heyerly described, and after that the angle that the bare
skin/feathered cheek border makes with the base of the lower jaw.

The Trumpeter Swan Society swan ID sheet (which someone else mentioned)
illustrates numerous other characteristics that can help in situations
where the facial details are hard to ascertain (distance, heads tucked,
etc.). Back shape, neck proportions, etc. I personally like to use
multiple characteristics rather than rely on any one thing.

Good birding,
Joel

--
Joel Geier
Camp Adair area north of Corvallis


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