Subject: Re: Odd grebe in Ellensburg
Date: Oct 23 11:37:33 1997
From: Deb Beutler - dbeutler at wsunix.wsu.edu


I would try but I'm afraid that my note taking back then was rather
spotty. I do remember thinking that the juv. Western Grebes looked exactly
like adult Western Grebes except for the eyeline. The white on the face
extent to just above the eye. The eye was visible in the white face but not
as obvious as the eye of a Clark's Grebe adult. I remember the sides being
dark gray and the bill the same color as the adult Western.
I will confess: I don't remember ever seeing a juvenile Clark's
Grebe. The Clark's Grebes seem to pass through southern Idaho in large
numbers during the spring (I don't know where they are headed) but I know of
only one place where Clark's nest, Minidoka National Wildlife Refuge (I
think it is in Power and Cassia counties, Idaho). I haven't been there
during the breeding season so I don't recall ever seeing a juvenile Clark's.
I have heard reports of Western and Clark's hybridizing at Minidoka
NWR but I haven't seen it myself. Every time I've observed a Western trying
to court a Clark's, the Clark's ignores the Western as if it were a
completely different species so I find it hard to believe that hybridization
is a common occurrence.
I will try to find out what a juvenile Clark's looks like and report
back.
Generally, I try to use a group of characteristics to identify these
grebes. Side color seems to work very well (Clark's have light gray sides,
Westerns have dark gray sides only slightly lighter than the black back) and
can be seen from a long distance. Bill color is a second character that
seems to hold well in all ages (Clark's have an orange-yellow bill and the
Western has a darker, greenish-yellow bill) but can be affected by distance,
optics and lighting. The call of the two is very distinct. This works well
in the spring when members of pairs are calling back and forth to one
another. The Western has a two note call and the Clark's has a one note
call. This can carry well over the water so you can tell if you have a
Clark's pair in with all of the Westerns. Unfortunately, lone birds are
generally silent. The eyeline works well in the spring and early summer and
can be used in the fall if you pay special attention to the eye and where it
is in relationship to the division between white and black on the head. On
an adult Western, the eye is surrounded by black and is rarely visible
except at close quarters. On juv. Westerns, the eye is right on the border
between the black and white. On adult Clark's, the eye is really obvious
because it is surrounded by white. Now I just have to find out where the
eyeline is on a juv. Clark's Grebe. :)
Hope it helps

At 22:16 22/10/97 -0700, you wrote:
>Hi Tweets
>
>Deb Beutler writes:
>
>> It is possible that the grebe Michael Hobbs saw was a Western Grebe
>>that was hatched this year. (snip)
>
>Deb, this really fills in a piece of the 'intermediate' plumage puzzle that
>can be a headache here. Thanks! Would it be possible to give us a
>point-by-point description of juv Clark's and salient differences to
>Westerns? Is bill-color distinctively different from hatching or fledging on?
>
>Michael Price We aren't flying...we're falling with style!
>Vancouver BC Canada -Buzz Lightyear, Toy Story
>mprice at mindlink.net
>
>
>
>
>

Deb Beutler
Department of Zoology
P.O. Box 644236
Washington State Univerisity
Pullman, Whitman Co., WA
dbeutler at wsunix.wsu.edu