Lesser Nighthawk
Chordeiles acutipennis
The
Lesser Nighthawk is San Diego County’s most easily seen nightjar, often
flying at sunset and sometimes active at midday.
Nesting on bare ground, it inhabits sparsely vegetated areas: open
desert scrub or sage scrub, broken chaparral (as among vernal pools or
along ridge tops), and even disturbed areas if these are not thickly grown
to weeds. Mainly a summer visitor,
it is generally uncommon and patchily distributed even in the Anza–Borrego
Desert, its stronghold within the county.
In the coastal lowland it has been greatly reduced by urbanization.
Breeding
distribution:
The Lesser Nighthawk is most numerous in the Anza–Borrego Desert, but
even there we found it to be quite local.
It is frequent in the Borrego Valley, though the largest concentration
there, of 100 on 27 April 2000 (G24; P. D. Ache) may have included migrants. Another large concentration was of 48 at the
northeastern corner of San Diego County (C29) 1 August 1998 (R. Theriault). The birds
had roosted by day in the undisturbed desert within Anza–Borrego Desert
State Park then at dusk flew toward the Salton
Sea and irrigated agriculture of the Coachella Valley where flying insects
abound. Generally, however, daily counts numbered 10
or fewer. The nighthawk tends to
be more frequent in flatter desert and absent from rocky or rugged regions,
but there are exceptions, such as the nine on the northeast slope of the
Santa Rosa Mountains (C28) 3 May 2000 (R. Thériault). Probably the abundance of flying insects is
more important than the nature of the terrain.
In the coastal lowland the Lesser Nighthawk
is now found mainly in Marine Corps Air Station Miramar and nearby areas
remaining undeveloped north into eastern Poway. This region still has the dry cobbly washes and mesa tops studded with vernal pools that
constitute ideal Lesser Nighthawk habitat.
Numbers in this area still range as high as 12 in Goodan
Ranch County Park (N12) 28 April and
At higher elevations the Lesser Nighthawk
is lacking over most of San Diego County but scattered over the Campo
Plateau (up to six just east of Old George Mountain, U27, 7 May 1997,
F. L. Unmack). It also occurs
sparsely in central northern San Diego County, even up to 5800 feet on
the south slope of Hot Springs Mountain (F20; four on 14 July 2000, K.
L. Weaver) and 4600 feet elevation in Lost Valley (D21; two on 26 June
1999, L. J. Hargrove; male with moderately enlarged testes collected 24
June 1998, SDNHM 50059). The only
other record from a high elevation is of one at 5500 feet in the Laguna
Mountains (O23) 9 or 10 June 2001 (C. G. Edwards).
Nesting: The Lesser Nighthawk lays
its eggs on the bare ground, perhaps in a slight scrape, often in full
sun. One nest in Murphy Canyon
(P10) 3 June 1998 was in sand and gravel remaining on the foundation of
a demolished building (G. L. Rogers).
Our egg dates ranged from 24 April to 17 June, practically the
same interval attested by early egg collections.
Chicks at
Migration: The Lesser Nighthawk arrives
consistently in late March. From
1997 to 2001 our earliest spring dates ranged from 20 March to 1 April,
except for one at 2000 feet elevation on the east slope of Otay
Mountain 8 March 2001 (K. J. Winter), possibly a bird that had wintered. In the past, flocks of postbreeding
birds had been seen in the coastal lowland, up to 40 in the Tijuana River
valley 20 September 1977 (J. L. Dunn), but there are no recent reports
of such numbers. The species decreases
in abundance in October and is only rarely reported in November.
Winter: The Lesser Nighthawk is
very rare in winter, with all 14 records being from the coastal lowland,
mainly in southern San Diego County. The
only winter occurrence during the atlas period was of two at Poway (M12)
11 February 1998 (P. von Hendy). This
is also the northernmost winter record for the county.
All winter records are of single birds except this and another
of two at Lower Otay Lake (U13/U14) 5 January 1991 (K. A. Radamaker, AB 45:321, 1991).
Conservation: The historical record is
meager, but clearly the Lesser Nighthawk is much scarcer than formerly. Emerson (1887), misidentifying it as the Common
Nighthawk, reported it as “common” at Poway. Stephens (1919a) considered it a “rather common
summer resident of the coast region and foothills.” Egg collections attest to former nesting at
Escondido, La Mesa, and National City.
Nesting on the ground, the Lesser Nighthawk is highly susceptible
to disturbance and predation. Most
of the flat mesas and floodplains that constitute the best Lesser Nighthawk
habitat have already been developed. Lovio (1996) identified the Lesser Nighthawk, along with the
Sage Sparrow, as the species most sensitive to habitat fragmentation on
the east edge of metropolitan San Diego.
He found it remaining only in blocks of appropriate habitat greater
than 100 hectares. Air Station
Miramar is currently serving as a refuge for the species, but shifting
military priorities could change this.
The Lesser Nighthawk is under less pressure in the Anza–Borrego
Desert, though off-road vehicles could pose a threat.
Wildlife rehabilitators have encountered at least two instances
of Lesser Nighthawks nesting in San Diego County on flat gravel-topped
roofs, as the Common Nighthawk does commonly in parts of its range.
But in the Lesser such a habit must be rare, because over most
of the developed areas of San Diego County the Lesser Nighthawk is never
seen.
Taxonomy: Chordeiles
a. texensis Lawrence, 1858, is the only
subspecies of Lesser Nighthawk occurring in California.
Common
Nighthawk
Chordeiles minor
In
spite of its name, the Common Nighthawk is extremely rare in San Diego
County. Though it breeds as close
as the San Bernardino Mountains, its migration swings to the east, and
the species is seldom seen at low elevations anywhere in southern California. The Common Nighthawk resembles the Lesser closely
and is best distinguished by its loud call, like an alarm buzzer.
Migration: There are four records
of the Common Nighthawk in San Diego County, of one heard at Cabrillo National Monument, Point Loma, 5 June 1975 (J. L.
Dunn), one seen in the Tijuana River valley 25 September 1976 (AB 31:233,
1977), one seen and heard at Escondido 11 July 1981 (K. L. Weaver), and
one seen and heard at El Cajon 6 July
1988 (G. and R. Levin, AB 42:1341, 1988).
Common
Poorwill Phalaenoptilus
nuttallii
The
Common Poorwill rests quietly on the ground
during the day, hidden under chaparral or camouflaged on rocky desert
slopes. After dark it forages for flying insects and
advertises its territory with its eponymous trisyllabic
call, “poor-will,” or, more accurately, “poor Philip.” The poorwill is fairly
common at least locally but seldom found except by voice. Thus apparent variations in its abundance could
be due more to weather conditions that affect the birds’ calling—and human
listeners’ ability to hear—than to variations in the birds’ numbers by
habitat.
Breeding
distribution:
The poorwill is perhaps the bird most poorly
sampled by our atlas protocol. Because
we had no standards for nocturnal coverage, some atlas squares were covered
at night much better than others, and the poorwill
was undoubtedly missed in dozens of squares where it occurs.
Nevertheless, the species is widespread in San Diego County, though
lacking from developed and forested areas.
It may avoid the coast, or the dearth of coastal records during
the breeding season may be a by-product of urbanization. In the Anza–Borrego Desert the poorwill inhabits rocky hills, alluvial slopes, and badlands
but probably not flat valley floors. The
few records from flat sandy areas (latest, one near Peg Leg Road in the
Borrego Valley, F25, 7 May 1998, P. D. Ache) may be of migrants, not locally
breeding birds. On the coastal
slope the largest numbers are in areas of extensive chaparral, as in
Nesting: The poorwill
lays its eggs on the bare ground with the benefit of no nest whatsoever. Even if the species were diurnal its nesting
would be difficult to track, as it
carries
no nest material and feeds its young by regurgitation. As a result, we confirmed breeding only a few
times, finding just five nests with eggs (15 April–25 June), two broods
of young chicks three or four days old (about 1 May 2001, Mission Trails
Regional Park, P11, D. C. Bostock; 29 May 1999,
near Jamacha, R14, W. E. Haas), and fledglings twice, plus the
broken eggshells in the Laguna Mountains.
Migration: Specimens of the inland
subspecies on the coastal slope attest to the poorwill’s
migrating through San Diego County in both spring and fall (see Taxonomy). Furthermore, the poorwill
has been found repeatedly if rarely in both spring and fall in areas and
habitats where it does not breed, especially at Point Loma. The local population may be largely resident,
the birds going torpid rather than migrating when the supply of night-flying
insects is low.
Winter:
One
surprising result of the atlas study was the number of poorwills
found in winter and how that number was related to rainfall. Before 1984 there was only one record of the
poorwill in San Diego County in December or January; from
1997 to 2002 we noted it 35 times in those two months. The detections of the poorwill
in winter (February included) were concentrated strongly in the wet year
1997–98, which yielded 32 reports totaling 59 individuals. The next winter the figures dropped to 17 reports
totaling 29 individuals, and in the drought-plagued final three winters
of the study they stabilized at 6 to 9 reports and 11 to 18 individuals
per year. Though the nights during
El Niño were often cool and wet, the rain clearly stimulated the birds
to call and feed. The largest numbers
found per night were greatest at this time (up to six near De Luz, B6,
Though we found poorwills
in winter in a few places where we did not find them in the breeding season,
these were all most likely locations where the species is resident.
Conservation: No adequate data exist
from which trends in poorwill numbers in San
Diego County can be judged. Nevertheless,
as a bird that roosts and nests on the ground, the poorwill
is ill adapted to the habitat loss, human disturbance, and cats that accompany
urbanization. It appears absent
from urban canyons, though still inhabiting areas on the urban fringe
such as Marine Corps Air Station Miramar, Mission Trails Regional Park,
and the Otay–Sweetwater unit of San Diego National Wildlife Refuge.
Poorwills often use the openings in chaparral
provided by roads as launch pads for their nocturnal foraging.
As a result, they are particularly susceptible to being killed
by moving cars; the San Diego Natural History Museum has received many
specimens as a result. As the human population of San Diego County’s
back country increases, so does the number of roads and traffic on them,
increasing the toll on the poorwill.
Taxonomy: San Diego County is an
area of contact and intergradation between the
dark brownish subspecies P. n. californicus
Ridgway, 1887, and the pale nominate P. n. nuttallii (Audubon, 1844), in which the pale areas on
the upperparts are silvery gray, making the black spots and triangles
stand out in bolder contrast. Subspecies
californicus matches leaf litter; nuttallii
matches granite. A small minority
of the 45 specimens from the coastal slope of San Diego County are as
dark as californicus from northern California, such as a male
from Dulzura (T16) 15 May 1917 (SDNHM 31432)
and a female that had recently ovulated from Lakeside (P14) 23 July 1992
(SDNHM 48121). Most, however, are
slightly paler, intermediate toward nuttallii,
including the one winter specimen, from Mission Trails Park (P11) 31 December
1991 (SDNHM 47868), and two specimens from slightly east of the mountain
crest, from San Felipe Valley near Paroli Spring
(I21) 10 October 1983 (SDNHM 42604) and Boulevard (T26) 12 September 1981
(SDNHM 41585).
Fourteen specimens from the coastal
slope are typical of nuttallii or closest
to it. Some of these are probably
migrants from the north or northeast; nuttallii
definitely migrates through southeastern California (Rea 1983, Patten
et al. 2003). But some of the specimens
of nuttallii from the coastal slope represent the breeding
population, especially one from Mission Valley 19 May 1922 (SDNHM 31460)
and one still in molt from Pamo Valley 8 miles
north of Ramona (I15) 10 August 1992 (SDNHM 48118). The situation of the poorwill
thus resembles that of the Great Horned Owl, in which the population of
San Diego County’s coastal slope is heterogeneous, covering all variations
between the coastal and desert subspecies.
Of the ten specimens of the poorwill
from the lower elevations of the Anza–Borrego Desert most are typical
of nuttallii. These
very likely represent the local breeding population; some of those collected
in April had moderately enlarged gonads, though none was in full breeding
condition. The breeding range of
nuttallii thus extends south of that
mapped by Grinnell and Miller (1944).
One specimen from 0.25 mile west of San Felipe Narrows (I25) 6
May 1966 (SDNHM 36000) is closer to californicus,
resembling most specimens from the coastal slope.
Two specimens from the Anza–Borrego Desert (SDNHM 17937, 40974)
have the black spots on the upperparts more or less reduced and are thus
somewhat intermediate toward P. n. hueyi
Dickey, 1928. Their color, though,
is still the silver gray of nuttallii;
true hueyi, pinkish and finely patterned, appears narrowly
restricted to the lower Colorado River valley, being unrecorded even in
the Salton Sink.
Whip-poor-will Caprimulgus
vociferus
The
Whip-poor-will has colonized some of southern California’s higher mountain
ranges, though its breeding there remains unconfirmed. But it is still a casual vagrant to San Diego
County, where there are only three records.
Migration: One was captured and released
at Point Loma 14 November 1970 (Craig 1971). Another was seen roosting daily in Coronado
from late December 1971 to 25 March 1972 (AB 26:655, 1972). One was heard calling near Julian 8 July 1971
(AB 25:907, 1971).
Taxonomy: Two subspecies of the Whip-poor-will
occur in the United States, nominate C. v. vociferus Wilson, 1812, in the East and C. v. arizonae (Brewster, 1881) in the mountains of Arizona.
The two are well differentiated by voice and in juvenile plumage
(Ridgway 1914) but weakly in adult plumage (Hubbard
and Crossin 1974).
The bird near Julian was undoubtedly arizonae
because summering Whip-poor-wills elsewhere in southern California sing
the song of this subspecies. Craig
(1971) reported the bird at Point Loma as vociferus
on the basis of its short wings and entirely black rictal
bristles, but Hubbard and Crossin (1974) questioned
this identification.