The Nuttall's and Ladder-backed Woodpeckers are two
closely related similar species that are both residents of San
Diego County and occasionally confused. Our atlas effort has already
revealed unexpected new aspects of their distribution and ecology,
making them an ideal pair to "focus on" in Wrenderings. Over
much of their ranges, including San Diego County, their ranges
fit together almost like puzzle pieces, distributions called "parapatric" by
Both of these woodpeckers are readily distinguished from others
by their black-and-white barred "ladder" backs, black-and-white
patterned heads, and white or whitish underparts. Adult males sport
red patches on the head; adult females lack red, having the crown
largely or entirely black. Juveniles of both sexes, however, have
red on the crown and are the principal culprits in birders' confusing
the two species.
As happens so often with closely similar species, the voices are
the best clue to the birds' identification. Both species sometimes
give a single-noted call that could be confusing in isolation,
but usually the notes are run together in a pattern characteristic
of each species. Nuttall's makes a crisp, slightly metallic-sounding
rattle, "trrrrrrt." The pitch of the call ascends slightly toward
the end of the rattle, and the call ends abruptly with a definite "t" sound.
The call of the Ladder-backed, however, descends in pitch, sounding
more like a whinny than a rattle. The whinny trails off at the
end with no crisp conclusion. Interestingly, the calls of the Ladder-backed
and Downy Woodpeckers are almost identical.
The species can be identified by plumage as well, with careful
study. The underparts of the Nuttall's are pure white, with scattered,
variable black spots and bars on the sides and flanks. In the Ladder-backed
the underparts are lightly tinged smoky brown, though seeing the
difference from white in the field requires a good view. The upperparts
of the Ladder-backed have more white: the white bars on the back
of the Ladder-backed are broader than the black bars (equal to
or narrower than in Nuttall's), and the white spots on the wings
are larger. On the Ladder-backed the white bars on the back extend
to the base of the neck, while on Nuttall's the upper back is black
with little or no white barring. This difference is most obvious
in the males, where Nuttall's shows a distinct black patch between
the red nape and the barring of the back, the Ladder-backed little
Understanding the differences in head pattern between the two
species requires determining whether the bird is adult or juvenile.
The juvenile plumage in these woodpeckers is seen only from fledging
(midsummer) to about the first of September; later in the fall
the young birds have finished their molt and have assumed adult
plumage. In the adult male Nuttall's the hindcrown is red, the
forecrown black with some white streaking. In the adult male Ladder-backed
the red (mottled with black and white) extends forward almost to
the base of the bill. In the juveniles of both the Nuttall's and
Ladder-backed, however, the red extends to the forehead--when birds
in juvenile plumage are about, the pattern of red on the crown
cannot be used to distinguish the two species.
The black on the sides of the head and neck is more extensive
in the Nuttall's than the Ladder-backed, though this can often
be difficult to assess in the field. A distinct and contrasting
white patch in the lores and nasal tufts at the base of the bill
is a diagnostic feature of the Nuttall's; in the Ladder-backed
this area is black or just obscurely grizzled with white, not forming
a distinct patch. This difference is not well illustrated in the
National Geographic field guide but Ridgway used it as the key
difference distinguishing the species in his classic "Birds of
North and Middle America."
Nuttall's Woodpecker is very widespread on the coastal slope of
San Diego County, being fairly common in riparian, oak, and mixed
conifer woodland. An interesting event illustrated by our atlas
results is the species' recent spread into residential areas in
central San Diego. Before 1990 Nuttall's Woodpecker was absent
from this area, occurring even in well-wooded Balboa Park as a
rare visitor only. In the last decade the species has become widespread
in urban areas, being recorded during the breeding season as well
as winter in such squares as R10, R11, S9, S10, and S11 where it
was previously absent. Perhaps with the aging of the central city
and the maturing of "urban forest" in what was once treeless sage
scrub the stature and density of trees finally achieved a threshold
Nuttall's Woodpeckers consider suitable.
Nuttall's Woodpecker extends down the east side of the mountains
only in wooded canyons: Middle Willows in Coyote Creek Canyon in
C22, Borrego Palm Canyon in F23, and Sentenac Canyon in J23, where
Bob Thériault found a nest in a mesquite. There were at
least of a couple of records in the 1970s at Lower Willows on Coyote
Creek (D23) but the species does not occur there now, as attested
by both our atlas results and the surveys by Art Morley and Keith
Smeltzer for the recent book "Birds of the Anza-Borrego Desert." In
the southeastern corner of the county Nuttall's ranges east to
Jacumba (U28). It hardly ever disperses even a short distance out
of its breeding range in the winter. Our only records outside breeding
habitat represent dispersal of less than 3 miles, in Earthquake
Valley (K23), where Bob Thériault had a single bird in a
cottonwood on 17 January 1998, and on the north slope of Grapevine
Peak (I22), where Paul Jorgensen had one on 9 April 1998.
The Ladder-backed, conversely, is largely a desert species, uncommon
even in its preferred habitat, favoring slopes vegetated with thorny
shrubs of the genus Prunus and above all the desert agave.
The birds feed eagerly in agave flowers while using the easily
excavated flower stalks for nest sites. In the flatter areas of
the Anza-Borrego Desert the Ladder-backed is very sparse, as suggested
by how scattered our records are in these squares.
Interestingly, the Ladder-backed is evidently absent from the
floor of the Borrego Valley; some of our best-covered desert squares,
F24, G24, and G25, have no records for either winter or the breeding
season. Apparently, the mesquite thicket in the Borrego Valley
doesn't attract it, and it doesn't take to the urbanization of
Borrego Springs the way Nuttall's has to that of San Diego.
The Ladder-backed Woodpecker ranges up the east slope of the mountains
to at least 3200 feet elevation in places, being recorded west
to Alder Canyon (C22), the east slope of San Felipe Valley (H21
and I21), Oriflamme Canyon (L22), and the upper end of Carrizo
Creek (T28). Thus there is a narrow strip, perhaps no more than
5 miles wide, along the east slope where both the Ladder-backed
and Nuttall's occur. In this strip, the two species are separated
by habitat, Nuttall's in the riparian woodland in canyons, the
Ladder-backed on dry slopes with catclaw, cacti, yuccas, and Prunus.
Nowhere is the precise replacement of the two woodpeckers so dramatic
as in San Felipe Valley, where Nuttall's comes down Volcan Mt.
to the creek while the Ladder-backed lives just a 5-minute walk
away up the opposite slope of the valley.
Among the more remarkable discoveries revealed by our atlas effort
are two regions where the Ladder-backed occurs on the coastal slope.
In the drainage basin of the Santa Margarita River, Ken Weaver
has found the species in semidesert scrub in Dameron Valley in
squares C15 and C16, confirming breeding in C15. During our blockbuster
weekend in January, Mike Mathos and I found a pair in leafless
elderberry trees among cholla thickets in the extreme northwest
corner of square C17. As with the Black-throated Sparrows in the
same areas, reported on in the fall 1998 issue of Wrenderings,
this isolated population presumably extends into the Aguanga region
of southern Riverside County, where the desert habitat is even
better developed. Unfortunately, Ken reports that clearing of this
unique habitat is in progress.
The other new site for the Ladder-backed Woodpecker on the coastal
slope is in Miller Valley in square S24. Here Margaret and Bert
McIntosh first discovered the species on our blockbuster weekend,
21 February 1998. Covering the area again in the breeding season
on 2 May, they used a taped recording to search for the birds,
finding a single female about three quarters of a mile away from
the previous winter's site. As in Dameron Valley, the microclimate
in Miller Valley promotes a desert fauna--both areas have Cactus
Wrens and White-tailed Antelope Squirrels too.
Unitt, with sketches by Nicole Perretta, from the spring 1999 issue
Nuttall's male (left), female (right)
Ladder-backed male (left), female (right)
Sketches by Nicole Perretta
Nuttall's Woodpecker Breeding