By Jim Burns

 
Photo By Jim Burns

Because it is common yet shy and retiring within its relatively restricted range, and because it does not wear the flashy colors of many of Arizona’s other special species--species found only here or more easily here than in any other state—scant attention is paid to Abert’s Towhee and its uniquely restricted niche in our state’s avifauna.  What do the water drip in my backyard, Ramer Lake in California’s Coachella Valley, and San Simon Cienega on the east side of the Chiricahuas have in common?  These far flung sites are all part of the Colorado River watershed and thus they all have Abert’s Towhees.  Whitewater Draw in Arizona’s Sulphur Springs Valley is apparently the only site outside of the Gila-Colorado drainage where Abert’s have ever been found.

Another interesting aspect of the history of Pipilo aberti is the fact that the species is named for a U.S. Army surveyor who never reached Abert’s range, presumably never saw the species alive, and simply forwarded a specimen collected by someone else to Spencer Baird in Washington.  Indeed, Abert’s is probably heard more often than seen, the sharp, pinging metal-on-metal call notes the only evidence left behind as a pair, mated for life, flip away unseen through the dense understory that is their preferred habitat.

Life in that understory depends on insects and seeds gleaned by “double scratch” foraging in the soil and leaf litter.  The next time you come upon an Abert’s undetected, which is not an easy thing to accomplish, focus specifically and closely on the footwork taking place beneath the feeding bird’s body.  Abert’s, like all towhees and many sparrows, can leave the ground, extend their feet forward to the limits of their reach, rake them backwards, and then return them to their original position, all with almost no perceptible body movement.  The stout, conical emberizid family bill then captures the exposed food.

Abert’s are non-migratory and inhabit dense willow groves and mesquite bosques along watercourses.  Nests are large, open cups either low to the ground in bushes or high in mistletoe clumps, built by the female, of leaves and twigs.  Nesting begins after spring rains and may continue through September with two broods.  Females do all of the incubation, but both adults feed the nestlings.  Nests are sometimes parasitized by cowbirds, but host nestlings are large enough to outcompete the smaller interlopers.

The combination of bulky body and rounded wings make Abert’s and their Pipilo congeners weak fliers, so typically they stick very close to vegetative cover.  Nonetheless, they can be easy to both hear and see in popular central Arizona birding sites such as the Phoenix Desert Botanical Garden, Granite Reef Recreation Area along the Verde River and Boyce-Thompson Arboretum State Park where the accompanying photograph was taken in November, 2002.

Abert’s Towhee is one of 19 emberizid species on the conservation Watchlist.  Parts of its restricted range, primarily in southwestern Utah and along the lower Colorado, have been fragmented because cattle have trampled the riparian vegetation upon which this species depends in these areas.  Any population declines there seem to have been offset by expansion along the Santa Cruz River, Sonoita Creek, and Oak Creek, as well as into suburban areas around Tucson and Phoenix.  Abert’s can now be found in many city parks and backyards if there is water and ground cover where they can forage without fear of predators.

Like our Rufous-winged Sparrow which also inhabits a uniquely restricted niche in Arizona, Abert’s Towhee has shown resilience in repopulating its historical ranges such as the lower San Pedro riparian area once cattle have been excluded.  Abert’s Towhee perfectly illustrates the importance of tracking and studying all our special species if our state’s spectacular biogeographical diversity is to survive.

7

By Jim Burns

Say what you will about our state’s special breeding species and its chance vagrants from south of the border, long time resident birders look forward most to winter with its tantalizing possibilities of surprise snowbirds.  In this quiz we are exploring the Gaviidae, that most primitive of our bird families which epitomizes for many of us the essence of true wilderness and the far north.

 In this close-up profile, three structural features of our first bird stand out.  Especially in comparison with the loons in the other two photos, here we see a large head, a massive bill, and a thick neck.  These structural elements tell us this is one of our two large loons, immediately eliminating all species but Common and Yellow-billed.

A closer look at the bill reveals a slightly downcurved culmen (top edge), dark to the tip on an otherwise light upper mandible.  Plumage considerations show a dark head and nape which contrast sharply with the bird’s light chin and neck, and there appears to be a dark collar which almost encircles the lower half of that neck.  The eye is surrounded by white areas in sharp contrast with the dark head.  All these are characteristic of winter Common Loon.

Yellow-billed, by comparison, has a straight culmen, entirely pale along its outer half.  The head and nape of Yellow-billed in winter are much paler (brown rather than black) and without this apparent contrast with chin and neck, the collar less obvious and less extensive, and the face much paler, bearing larger areas of white.

This Common Loon was photographed at Site Six on Lake Havasu in February, ’02, foraging alongside the Yellow-billed which spectacularly spent the entire winter there.  Seeing the two side by side was fun and instructive, and Site Six is a virtual field lab which I would encourage loon enthusiasts to visit even in the absence of any loon species other than Common.

B)--Good photo, difficult bird

Though not quite as good as the full profile view shown in our first photo, the angled profile in this second shot presents three structural differences from Common Loon.  The head of this bird appears smaller relative to its neck and body, its bill appears smaller and thinner, and that bill, in addition to being held at an upward angle, appears slightly upturned near the tip as well.

Plumage differences are also apparent.  This loon shows more extensive white in its face, its neck is less clean and contrasty, and its back is more obviously speckled with white.  These comparative differences suggest the description of Yellow-billed four paragraphs above and beg the possibility that the relatively small head and bill in this photo might be functions of sight angle and angle of light.  Additionally, along the flanks of this bird just above the waterline is an extensive area of white.  Let’s discuss this field mark first.

When Arctic and Pacific Loon were split, it was well noted that the single most reliable distinguishing feature of the former was the bright white visible on the flanks above the waterline.  At rest on the water Pacifics do not reveal any white in this area.  In flight this difference between Arctic and Pacific is analogous to that between Violet-green and Tree Swallow, the former showing its more extensive white flanks as a saddle up and over the sides of the rump.  Pacific Loons and Tree Swallows do not have this white saddle.

Could this be an Arctic Loon?  There are several reasons why not, the most obvious being Arctic Loon has never been recorded in Arizona.  Nonetheless, don’t 

discount its appearance here in some future winter.  The first documented Colorado Arctic Loon occurred just this past winter!

There are, additionally, several structural and plumage related reasons why this loon is neither Arctic nor Pacific.  Neither of those will ever show this extensive white in the face, and both in winter plumage have a much cleaner white throat and much greater contrast between nape and throat manifest as a straight vertical border down the length of the neck.

So, could this be a Yellow-billed?  The lower mandible of Yellow-billeds does, after all, have a distinctive upturn which is rendered all the more noticeable because this species typically carries its bill tilted upward like the bird in our photo.  Also apparent in this photo is a small dark spot on the auriculars (behind and below the eye toward the nape) which is a field mark for juvenile Yellow-billeds.  Curious too is the anvil shaped head with its appearance of two peaks, one near the front and one at the rear of the crown, a feature often noted on our two large loon species.

The white speckling on this loon’s back tells us it is a juvenile bird.  Since it is diffuse and without pattern-- in short, speckling rather than barring-- it also tells us this is not a juvenile Yellow-billed.  This is the juvenile Red-throated Loon that was discovered on Palm Lake at the Hassayampa Preserve in November, 1996.  Red-throated is our smallest loon, head and neck so similar in circumference that the bird has been mistaken for a snake when its body is submerged beneath the surface.  The slender, upturned bill, the plain face, and the peaked crown are most useful field marks on winter birds.

C)—Bad photo, easy bird

Our third image is a photo documentation, a euphemism for “crummy photo.”  The Common Loon was photographed from almost within spitting distance, the Red-throated from about forty yards.  This image was taken from well over 100 yards, looking through a chain link fence.  Get the picture?  Well, just barely.  Nothing beats close, not even good light.  In blowing this image to a size comparable to the other two, it is obvious how much sharpness and contrast have been lost.

Nonetheless, we have enough field marks here to pin a label on this loon just from our discussion of the first two images, and the similarity in sight angle to the second photograph makes it a fascinating study.  We see a smoothly rounded head with no white around the eye.  We see a thin bill, light with a dark culmen which, if not actually downcurved, certainly is not upturned.  The contrast between the dark hindneck and light foreneck is so sharp it appears as a well defined line.  The small white patches on the bird’s back, which designate it as a juvenile bird, are arranged into neat, parallel rows.  And nary a hint of white along the flanks at the waterline.

This juvenile Pacific Loon was discovered by former Phoenix birder, Bob Norton, in the canal south of Granite Reef Dam in January, 1993 and lingered in the area for several weeks.  Winter is here.  Arizona is due for an Arctic Loon appearance.  The lakes along the Colorado, any big water impoundment, even Tempe Town Lake would be logical venues.  You’ve done your homework.  See you at Site Six.