Photo Quiz #23 Answer

By Jim Burns

Birders generally understand that bird taxonomy (the grouping into orders, families, and genera) is based on structural similarities, but there is little in the layman’s literature about the fascinating subject of the taxonomic order itself and how it was derived.  Birds in the front of your field guide are more “primitive” than those in the back, passerines in general more structurally evolved than waterbirds, warblers, more “like us,: if you will, than shorebirds.

Our current quiz again features a family of birds in the from of your books, a family barely out of the primordial soup.  Though some are long distance migrants, these birds are weak fliers with no tails to speak of.  Their feet and legs, so close to the rear of the body as to make travel on land almost impossible, can be extended backward in flight to help with steering.  But, as you can see in the first photo, those feet are lobed making this family, like the loons before them, wonderfully evolved for their water world, and any human with a fear of the water may find the live of a grebe harder to fathom than that of an albatross or buteo.

A) Good photo, easy bird

Except for its remarkable bill, this grebe in black and white and shades of gray looks very similar to our second quiz bird in the January/February issue.  But the bill length here is indicative of overall size and the diver supporting this veritable spear is from the genus Aechmophorus which translates from Greed as “spear-bearer.”  The two large grebes of this genus are nearly twice the length and three times the weight of the Horned Grebe of our previous quiz and are further distinguished from their smaller family relatives in the Podiceps genus by proportionately longer, thinner necks.

In the field, of course, the real question lies in separating our large grebes, Western and Clark’s, from one another.  Bill color and facial pattern provide the answer.  Although bill color is much the more reliable of these a non-breeding bird bobbing around in the distance, here in black and white it is of no help.  However, in a close view such as this we can readily see dark facial feathering completely encompassing the eye.  This is diagnostic of Western Grebe.  In the color slide this grebe’s bill is the dull yellow-with-olive tones also indicative of Western.  Other useful, corroborative, but not clinching differences between the two Aechmophorus species are dorsal color and voice.  Westerns are typically more uniformly dark, which makes them appear darker overall, and they have a two syllable call, the second syllable higher or accented.  Clark’s call is an ascending single syllable.

This Western Grebe was photographed on McKellips Lake along the Scottsdale Greenbelt in November 2000.  In breeding plumage, roughly March through September, the dark feathering around this bird’s eye would be even darker, nearly matching the black of its crown, as would the lighter loral spot discernible in this photo.

B) Good photo, difficult bird

At first glance our second grebe shows the same long, thin neck and the same long, thin spear as our Western, but it has a decidedly different facial pattern, so it must be a Clark’s?  Perhaps, but we need to slow down a bit.  Ornithologists split Western and Clark’s grebes into separate species in the mid ‘80s/  A careful discussion of the field marks seen in our second photo will illuminate why that split is still debated and disputed by some avian researchers.

Older field guides treat the Aechmophorus grebes as color phases of the same species, Western the dark phase, Clark’s the light.  Newer books, after the split, show us the eyes of breeding adults, Western encompassed by dark, Clark’s by white.  The most recent guides such as Sibley and the third edition National Geo also show us winter adults…with a caveat.  In winter Westerns, the dark facial feathering fades somewhat like that in our first photo.  In winter Clark’s, the white facial feathering smudges and darkens…beginning to resemble that in our first photo.  If this were not enough to give us pause, not that our second bird is obviously much darker overall than our first bird.

We don’t yet have a date for the second photo.  Could this second bird be another winter Western of even be the same bird?  Since we cannot discern bill color, the short answer is “yes, it could be.”  Several times in this quiz we have spoken of sight angles and the play of light and shadow changing perceptions.  Sibley gives us a better reason-“Intermediate birds, seen regularly, especially during winter, are unidentifiable.  Some may be hybrids.”  So, if you see a large grebe reasonable close during breeding season you should be able to identify it by facial pattern, but remember that identification of large grebes out of breeding season should be based on bill color.  Facial patterns can be very similar at this time of year.

Our second photo bird is, indeed, a Clark’s Grebe photographed in November 1995 along the lower Colorado river. In the color slide this grebe’s bill is the deep, bright orange-with-tones of red indicative of Clark’s.  The bird’s back appears uniformly black because it is perfectly shadowed from the bright sunlight by the head and neck.  This photo seems identifiable as a Clark’s because there appears no hint of dark feathering below the eye or above the lores, but the point of this exercise has been twofold- don’t’ assume every large grebe you see in Maricopa County in winter is a Western, and don’t assume every large grebe you see in Maricopa County in winter can be positively identified.

C) Bad photo, easy bird

One of the many anomalies in bird photography is that a great slide does not always translate into a good print and, conversely, a crummy slide can sometimes be manipulated into something pleasing on paper.  Birders and photographers mumble the same foul letter words when a great bird appears backlit.  Our third grebe was photographed with the sun behind it, the bird’s nice color and sharp markings muddy and obscured against the bright water background.  Overexposure in Adobe Photoshop created this rather stunning black and white, but the color bring left much to be desired.

This grebe’s dark over light head pattern is similar to the Aechmophorus grebes, but both its bill and neck are shorter and thicker, lending a chunkier, less elegant jizz reminiscent of the Podeceps genus of medium sized grebes.  Although the head pattern does closely resemble our Horned Grebe in last winter’s quiz, note that this bill  is too long and too thick for a Horned, and there is that well defined line running under the cheek and up the side of the neck.  Any confusion at this point probably again arises from no knowing the date of the photograph and assuming this is yet another winter grebe.

This is a breeding plumaged Red-necked Grebe, the largest of our three Podeceps grebes, photographed in Alaska, July 1994.  This bird was presented in breeding plumage to illustrate again the intriguing seasonal reversals of the light and dark head patterns which this genus undergoes.  As much as this summer Red-necked seems to mimic a winter Horned, winter Red-neckeds are identified by dark cheeks delineated by a light stirrup running from below the base of the bill up to the back of the crown, a pattern not unlike that of winter Eared.

Red-necked Grebes, rare in Arizona in winter, could easily be overlooked or mistaken for larger or smaller relatives by birders unaccustomed to seeing them in the desert.  There were confirmed sightings in the ‘90s from Lake Powell and Lake Pleasant and several rumors from the lower Colorado, but Red-necked Grebe is by no means an annual occurrence in our state.

If, like most birders, you word associate “bird” with the medium of air and the marvel of flight, keep a closer watch for some of our “lower” species.  For those of us uncomfortable around water, grebe in the next life could be a wonderfully satisfying experience.