Hi Tweets

Deb Beutler writes:

(snip)
>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.

The juv Clark's--provisionally aged--at Point Grey a few weeks ago had that
face pattern but dark grey sides paling toward the rear to pale grey-white
finely spotted grey where the nearby Westerns had solid grey sides. No
discernible difference in wing color.

>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)

Any tweetsters know their destination? Suspect they're pretty similar to a
Basic adult but with a shorter bill, darker flanks and back.

>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.

Doesn't seem to be, Deb. Over the years I've seen a few wintering birds here
where the bill color is the golden-yellow of Clark's but the bills have a
complete dusky outlin as on Western; they have a Western's head pattern, and
paler sides than the Westerns around them.

>I will try to find out what a juvenile Clark's looks like and report
>back.

That'd be great, Deb. Is there anything in the literature on
aging-and-staging since Storer & Neuchterlein's 1985 study?

>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.

The few coastal *adult* Clark's I've seen have had clearly paler grey backs
and much paler flanks than the Westerns.

>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.

That's for sure! The worst are the longest-billed birds at distance in
slanting sunshine, especially if they sleek down their crown feathers. Then
you hear the mutters among the scopes at waterside 'Hey, ya think that
third-from-right bird could be a Clark's?'

>The call of the two is very distinct.
(snip)

Can attest to that with one exception to the 'lone bird is silent'. In May
for a few years in the mid-80's a pre-migration staging flock of Westerns
would come into English Bay in downtown Vancouver BC, calling and dancing,
really whooping it up. For a couple of years each evening for several days
one could hear--sometimes see--the Clark's in the flock as its more emphatic
and further-carrying voice (creeeenk!) soared above the Westerns
(creenk-creenk and cri-creenk) in the same way that the call of a male
Eurasian Wigeon does in a flock of Americans. As you pointed out, he
(assumed 'he' since calling loudly in a flock full of courting birds)
couldn't seem to attract any interest: was always alone in the flock (okay,
okay, say it: awww). In this context, the Westerns also had a 'cri-cri-crik'
call. Neat, too, how a bird on the side of the flock would begin calling and
each neighbor would take it up, until the whole flock was rockin'. Sometimes
you could hear how the calls literally rippled from one side of the flock to
the other.

>On adult Clark's, the eye is really obvious
>because it is surrounded by white.

As Alternate plumage, May to September at least.

>Now I just have to find out where the
>eyeline is on a juv. Clark's Grebe. :)

Going by the drift of some of these ID postings, it'll be somewhere in the
Yucatan Peninsula. '-)

>Hope it helps

Sure does!

Michael Price We aren't flying...we're falling with style!
Vancouver BC Canada -Buzz Lightyear, Toy Story
mprice at mindlink.net