-PiffttiTy of

PORfRT GI1L

CALIFORNIA

BIRDS

Vol.2, No. 4 ,1971

CALIFORNIA BIRDS

Journal of California Field Ornithologists

Editors: Alan Baldridge, Virginia P. Johnson, Alan M. Craig,
Jean T. Craig, Pierre Devillers, Joseph Greenberg, Clif-
ford R. Lyons, Guy McCaskie, Thomas L. Rodgers

Membership Secretary: Thomas L. Taylor.

Volume 2, Number 4, 1971

EDITORIAL 109

Wood Warblers and Vireos in California: The Nature of

the Accidental Paul DeBendictis 1 1 1

Interbreeding of the Glaucous-winged Gull and Western

Gull in the Pacific Northwest J. Michael Scott 129

NOTES

Olivaceous Cormorant Record for California H. Lee Jones 134

The Wood Thrush in California Guy McCaskie 135

Tennessee Warbler Observations in Oregon Carroll D.

Littlefield and Walter L. Anderson 137

Roadrunner Captures Orchard Oriole in California

Laurence C. Binford 139

The Alleged Occurrence of Nutting’s Flycatcher in Baja
California Pierre Devillers

140

CALIFORNIA

BIRDS

Volume 2, Number 4, 1971

THE CALIFORNIA RARITIES COMMITTEE

Because of their migratory behavior and high mobility, birds
frequently appear in areas far outside their normal ranges. Essential
to understanding the significance of these extra limital individuals is
the accumulation of accurate data concerning their distribution and
status (wild or non-wild).

In the last three decades there has been a substantial increase in
the number of field observers. With the improvements in modem
field identification techniques (Griscom, Modern Bird Study, 1945)
much information concerning range extensions, population dynamics,
incursions, and extra limital occurrences of birds has accumulated.
Much of this data is based on sight records, but some on photo-
graphic evidence. The scientific acceptability of sight records,
particularly of extra limital birds, has long perplexed ornithologists
because such records usually lack substantiating documentation. Con-
sequently, most serious ornithologists ignore such records. Some sight
records are undoubtedly correct and, if properly documented, could
constitute a valuable source of distributional data. Erroneous records
appearing in print seriously confuse the problem and perpetuate the
accumulation of inaccurate data. The problem most distributional
workers face is differentiating the good from the bad.

The committee system of reviewing records has been in existence
in Europe for more than a decade. Wallace (British Birds,
63:113-128, 1970) recently reviewed the activities of the British
Birds Rarities Committee and concluded the system was working
successfully. The Rarities Committee of the California Field Ornitho-
logists (Calif. Birds, 1:2-3, 1970), has been established to help
researchers evaluate records of unusual birds occurring in California. It
is hoped that all records of rarities found in California will be
submitted to the committee, which will review each record individual-
ly. All records, along with editorial comments when deemed pertinent,
will appear in the Rarities Committee’s annual report to be published

109

in CALIFORNIA BIRDS. Researchers utilizing these records can be
assured that they have been thoroughly reviewed, and that the
documenting evidence is on file.

To properly document an observation a detailed description along
with other pertinent data should be submitted to the Rarities
Committee at the address listed on the inside cover of CALIFORNIA
BIRDS. The following information, preferably typewritten on SW’ x
11” white bond paper, should be included:

1. SPECIES (the name of the species and number of individuals
involved).

2. LOCALITY (the exact locality of the observation - “2 miles S.W.
of Olema, Marin Co. Calif.” not “near Olema, Calif.”).

3. DATE (include the time of day and the duration of the stay as
well as the date).

4. OBSERVERS (include the names of others seeing the bird).

5. OPTICAL EQUIPMENT (include the type of optical equipment
as well as power).

6. HABITAT (describe the habitat in which the bird was observed).

7. LENGTH OF TIME BIRD OBSERVED.

8. DESCRIPTION (include a detailed description of the bird’s
appearance with emphasis on the color and pattern of the
plumage, size and shape, behavior, voice, and other pertinent
diagnostic data).

9. CONCLUSIONS (reasons for identification).

10. EXPERIENCE (familiarity with the reported species and those
similar).

11. ADDITIONAL MATERIAL (attach drawing, photographs, tape
recordings etc. if available).

Enclosed in this issue of CALIFORNIA BIRDS is a field list of the
birds of California. Records of those species marked with an asterisk
will be accepted by the Rarities Committee for review and publica-
tion in CALIFORNIA BIRDS as will records of birds new to the
state list. The committee currently consists of nine members - Eugene
A. Cardiff, Theodore Chandik, Laurence C. Binford, Alan M. Craig,
David DeSante, Clifford R. Lyons, Guy McCaskie, G. Shumway
Suffel and Jon Winter (Secretary). We urge anyone interested in field
ornithology to submit their records of extra limital birds found in
California to the Rarities Committee. Hopefully the committee will
be able to prepare a report for 1972, but the success of this will
depend on the participation of the observers in California.

Jon Winter

no

WOOD WARBLERS AND VIREOS IN CALIFORNIA:

THE NATURE OF THE ACCIDENTAL.

Paul DeBenedictis

Joseph Grinnell (1922) wrote “it is only a matter of time
theoretically until the list of California birds will be identical with
that for North America as a whole.” This prediction is being rapidly
fulfilled. However, the many records of “accidentals” obtained in
California since 1922 suggest that we should reexamine the applica-
tion of that term, particularly as applied to such species in California.
Specifically we here ask whether the records of accidentals are
without pattern, or whether they are in general predictable on the
basis of zoogeographic and/or ecological characteristics of the species
involved.

The vireos (Vireonidae) and wood warblers (Parulidae) are especial-
ly satisfactory groups to consider, because the majority of North
American species have been recorded in California and because
numerous records of them are available. Records through 1970 have
been obtained from Grinnell and Miller (1944); from more recent
issues of the Auk, Audubon Field Notes, the Condor and the Wilson
Bulletin; from examination of specimens in the California Academy
of Sciences, the Museum of Vertebrate Zoology University of Califor-
nia at Berkeley, and the San Diego Natural History Museum; and
from personal records of R. Guy McCaskie (San Diego), Richard L.
Stallcup (Oakland) and the author. Ranges of species have been
derived from the A.O.U. Checklist (1957), Mexican checklist (Miller
et al, 1957), and from certain more recent regional publications.
Records for the fall season are considered in greater detail, as recent
work by Point Reyes Bird Observatory personnel on South Farallon
Island suggests that our present understanding of spring abundance of
eastern migrants is subject to considerable revision.

I use the term commonness to apply to the total population of a
species and the term abundance to apply to the frequency at which a
species occurs in California. I offer no explanation of the common-
ness of Western (as defined below) species, and only species that
breed north of Mexico are considered. Subspecies are neglected
except for those of the Solitary Vireo. Nomenclature follows the
A.O.U. Checklist, 5th Ed. (1957); Blue-headed, Plumbeous, and
Cassin’s Vireo are used for the subspecies solitarius, plumbeus, and
cassini respectively, of the Solitary Vireo.

Calif. Birds 2:111-128, 1971 HI

WARBLERS AND VIREOS IN CALIFORNIA

Enough records exist to allow rank-order statistical testing of
hypothesis concerning abundance in California. Rank categories are
given in Table 1 . Parametric statistics cannot be used since degrees of
freedom are a matter of speculation. Two non-parametric tests, the
Spearman Rank Correlation Coefficient (r§) and the Olmstead-Tukey
Corner Test of Association (Steel and Torrie, 1960), were used
exclusively. Probabilities stated are those of observing so strong a
correlation under the null hypothesis that no relationship exists
between the variables being tested; the square of a correlation
coefficient is indicative of the amount of variation in one variable
which is due to the other.

Records were treated as two samples, those obtained prior to 1962
and those obtained between 1962 and 1970 inclusively. The abun-
dance of species in the early sample is highly correlated with their
abundance in the later sample (r s = 0.751, P < 0.001), and, as the
latter sample appears more consistent from year to year and also
more reliable, all further statistical analyses are restricted to the more
recent observations.

Only one source of observer bias is considered. Parnell (1969) has
shown that migrants tend to select habitats similar to their breeding
habitats while on migration. Migrants also tend to select characteristic
strata in vegetation for foraging (personal observations) and foraging
habits of some species, e.g. the American Redstart, tend to make
them particularly conspicuous. Species were ranked as having foraging
habits that would make them inconspicuous (slow moving and ground

Table 1. Rank Categories Used in Statistical Analyses

Spring

Fall

Habitat

Rank

Records

Records

Commonness

Stability

Foraging Habits

0

0

0

—

_

_

1

1-2

1-2

Rare

Early sere

Ground

2

3-6

3-6

Low, skulking

3

7-13

6-14

Low, normal

4

14-19

15-30

Fairly common

Medium, normal

5

20-40

31-62

Med., conspicuous

6

41 +

63-126

Climax

High, normal

7

-

127-254

Abundant

—

High, conspicuous

8

-

255 +

_

—

— indicates rank not assigned
112

WARBLERS AND VIREOS IN CALIFORNIA

foraging) or conspicuous (fast moving and tree-top foraging). There is
a tendency for species ranked as inconspicuous to be infrequently
detected in California (rg = 0.421, 0.01 > P > 0.001), but this
correlation “explains” only about a fifth of the variation in abun-
dance of these species in California. The magnitude of this effect is
probably the result of observers favoring localities where migrants
have little choice as to the types of habitat they may select.

I first describe the zoogeographic relationships of these species,
then propose and test several hypotheses concerning their abundance
in California, and finally discuss the general implications of the
results.

ZOOGEOGRAPHY OF NORTH AMERICAN VIREOS AND WOOD
WARBLERS

I divide North America into four major zoogeographic regions
based on breeding avifaunas. These are a combination of traditional
biogeographic regions (Udvardy, 1963) and life zones. These regions
are the West, the North, the East and the Southwest (Fig. 1). The
Northern region is further divided along the east slope of the Rocky
Mountains into the Northwest and Northeast subregions. Species that
breed in more than one of these regions are referred to the region
closest to California in which they are regularly present.

The zoogeography of migratory species is incomplete unless their
winter ranges and migratory routes are also considered. The winter
ranges of many vireos and wood warblers are poorly known, but the
West Coast (including western Mexico), Middle America, the Carib-
bean (including the southeastern United States), and South America
appear to be distinct regions (Fig. 1). Species wintering in more than
one of these regions are referred to the region closest to California in
which they are regularly present.

Migration routes are not directly considered. As a first approxima-
tion it is assumed that species migrate along direct great circle routes
(i.e., paths of shortest possible distance) between their breeding and
wintering ranges. Indeed, most species wintering in the Caribbean and
in South America have more easterly migration routes than species
wintering in Middle America. Assuming direct migration, transient
individuals would be expected to occur only in the region directly
between their breeding and wintering grounds. Thus, the species
expected only as transients in California are Northwestern species

113

WARBLERS AND VIREOS IN CALIFORNIA

FIGURE 1. Faunal regions of North America. Regions based on breeding
avifaunas are separated by dashed lines and are written in capital letters.
Regions based on wintering avifaunas are separated by dotted lines and are
written in lower case letters; the South American region, beginning at Panama,
is not shown. Stippled area is above 5000 feet elevation.

114

WARBLERS AND VIREOS IN CALIFORNIA

wintering on the West Coast. Since many migratory species not
meeting this requirement have been recorded in California (Table 2),
the preliminary assumption of direct migration must be modified.

The zoogeographic relationships of Northern, Western and Eastern
species are indicated in Table 3, the species arranged according to
their breeding and wintering range. Values used in statistical analysis
of the abundance of Northern and Eastern species in California are
presented in Table 2. To avoid biasing the analyses that follow, I do
not include Myrtle and Townsend’s warbler, both of which winter in
California.

Records of the Northern and Eastern species are now numerous
enough to suggest some patterns of abundance. Northwestern species
wintering in the West Coast region include two species, Myrtle and
Townsend’s warbler, regular in California and the commonest of the
accidentals, the American Redstart (McCaskie, 1970). Species not yet
recorded in the state all fall in the lower right corner of Table 3, save
the Blue-headed Vireo, which is possibly overlooked among the
similar Cassin’s Vireo, a common California bird. Although some
Palm Warblers may winter in the West Coast region, I have assumed
the nearest regular wintering populations are in eastern Texas.

The fourteen Southwestern species of vireos and wood warblers
may be described briefly as follows: Hutton’s and Bell’s vireo have
extensive breeding ranges in California; Grey and Plumbeous vireo
and Virginia’s and Lucy’s warbler breed in the southeastern part of
the state. Olive, Grace’s and Red-faced warbler, and Painted Redstart
breed north into Arizona and New Mexico; Black-capped Vireo,
Colima and Golden-cheeked warbler breed primarily in Texas; and
Yellow-green Vireo and Olive-backed Warbler breed in extreme south-
ern Texas as well as Sonora, Mexico. Hutton’s Vireo is essentially
non-migratory; the Yellow-green Vireo winters in South America; the
Golden-cheeked Warbler in southern Mexico, and the other species in
western Mexico. Of the forms not breeding in California, only the
Yellow-green Vireo, Red-faced and Grace’s warblers and Painted
Redstart have been recorded in the state. The latter two species occur
sufficiently far northwestward (Johnson, 1965) that their occurrence
in California is not surprising, and the group is otherwise too poorly
represented to permit analysis.

115

WARBLERS AND VIREOS IN CALIFORNIA

Table 2. Characteristics of Northern and Eastern Warblers and Vireos.

eg

o c c o g

u o c- _ O

bO

t| -' e*

o S

c

° S

Abundance rank 1 *

'll

ID -p

e

o

Species

Spring

Fall

O.C

S 3 !

<

E

E

u

».SP

l-J g

Warbler, Black-and-

5

6

6

13

5

1875

white

Prothonotary

2

2

3

88

3

2125

Worm-eating

0

2

2

73

2

1925

Swainson’s

0

0

1

112

1

1550

Golden-winged

1

1

3

67

3

2550

Blue-winged

0

2

3

73

3

1925

Bachman’s

0

0

5

133

1

1420

Tennessee

4

6

5

38

7

2775

Parula

5

5

5

62

4

2300

Magnolia

5

5

3

29

5

2600

Cape May

0

3

6

54

4

3100

Black-throated

0

5

3

88

5

2150

Blue

Black-throated

2

4

7

25

7

2025

Green

Cerulean

0

1

5

102

4

2650

Blackburnian

1

4

6

58

6

2725

Yellow-throated

1

1

5

61

3

1975

Chestnut-sided

2

5

5

58

6

2825

Bay-breasted

1

3

5

59

6

3975

Blackpoll

4

8

5

23

7

5450

Pine

0

2

5

61

4

1200

Kirtland’s

0

0

4

100

1

1400

Prairie

0

4

4

102

4

1750

Palm

3

7

4

38

5

2225

Ovenbird

5

4

1

25

6

2825

Waterthrush, Northern

5

5

1

17

5

1650

Louisiana

0

0

1

26

2

1975

Warbler, Connecticut

2

2

2

59

3

1725

Mourning

1

1

2

50

3

2900

Kentucky

1

0

2

73

2

1925

Hooded

1

2

3

73

4

1925

Canada

2

3

3

65

5

3650

Redstart, American

6

8

7

13

7

1300

Vireo, Black-whiskered

0

0

3

120

6

2025

White-eyed

1

0

2

61

3

1200

Blue-headed

0

0

3

37

4

2200

Yellow-throated

2

1

4

67

3

2450

Red-eyed

4

4

4

44

7

3700

Philadelphia

0

2

4

25

3

2825

1 Records, 1962-1970.

^ Degrees from normal migration route needed to reach California in Fall.

^ Miles from breeding range to wintering range.

116

4

5

4

5

2

2

5

2

4

4

5

5

6

5

5

5

2

4

6

5

1

2

4

6

4

4

3

3

5

5

4

4

6

3

5

5

6

3

Habitat

stability

WARBLERS AND VIREOS IN CALIFORNIA

Table 3. Zoogeographic relationships of Northern, Western, and Eastern vireos
and warblers. Underlined species not recorded from California. Abbrevations:
bk - black; bl - blue; br - breasted; cr - crowned; sd - sided; thr - throated; V -
vireo; W - warbler; Wth - waterthrush.

117

WARBLERS AND VIREOS IN CALIFORNIA

FACTORS INFLUENCING ABUNDANCE OF “ACCIDENTALS” IN
CALIFORNIA.

It is difficult to determine the factors which influence the
occurrence of “accidentals” in California, because of interactions
between environmental factors and behavioral characteristics. It is not
especially satisfying to invoke specific hypotheses for each species, and
I consider only hypotheses that can be expected to apply to all
species. I first examine possible influence of the migratory path.

Experiments with caged birds are interpreted to indicate that
migratory birds can use certain (celestial) cues to maintain a “pre-
ferred direction” of flight, but variation of 30 or more degrees in the
preferred direction of different individuals of a species is also evident;
some birds do not orient at all (e.g., Emlen, 1967). Such variation
suggests the hypothesis that misoriented individuals constitute the
majority of vagrants; specifically, if birds do follow a preferred
direction, ignoring all other cues, and if some individuals have a
preferred direction that would lead them away from their “normal”
migratory routes, it would not be surprising to find some individuals
of almost any migratory species in California. Although such deviant
individuals might be expected to be predominantly immatures, the
predominance of immature birds in the fall samples of “accidentals”
is probably overstressed and is not likely to be indicative of the
numbers of adults of “accidentals” that appear in California. A
similar autumnal predominance of immatures has been found in
Northern and Eastern species on the Atlantic coast (Murray, 1966)
and in Western species on the Pacific coast (Ralph, 1971), and is
possibly a general phenomenon resulting from other behavioral dif-
ferences between these age classes.

The greater the deviation from the “normal” migratory route a
misoriented individual shows, the less likely it is to arrive at a locality
favorable for survival. The result of selection should be that most
individuals are able to orient correctly. Thus, all other factors being
equal, we anticipate that the greater the deviation from the orienta-
tion between the breeding and wintering range required to lead a bird
to California, the less likely that bird is to occur there. I calculated
an angle of deviation necessary to reach California in the fall as the
spherical angle between 1) a great circle arc from the western edge of
the breeding range to the northwestern edge of the wintering range,
and 2) a great circle arc from the western edge of the breeding range
to Bakersfield, California (35.5°N, 119°W), a locality approximately
118

WARBLERS AND VIREOS IN CALIFORNIA

central to localities from which most records have been obtained.
These angles were then ranked. The abundance of Northern and
Eastern species in California increases as the angle of deviation
decreases (Fig. 2), the relationship being highly significant (r<$ =
0.573, P < 0.001), but see below.

Corresponding calculations for the spring records give the same
trend but the correlation is not significant. Over half the species are
unreported or known from only one record, so this result is not
surprising. Because of the geometry of the Americas, most species
need deviate less (less than half as much for 16 of the 38 species)
from the original migration route to reach California in the spring
than they need deviate in the fall, so less variation in abundance due
to misorientation should be evident. I have not further analyzed spring
records other than to note that species common in the fall tend also
to be common in the spring (rjj = 0.678, P <0.001).

The above hypothesis assumes all other factors are equal. Not all
warblers and vireos are equally common, and one would anticipate
commoner species to occur more frequently in California. There is
essentially no quantitative information available, especially for the

511

255

127

63

31

15

7

3

1

O

• • • •

20 40 60 80 100 120

Angle of Deviation

FIGURE 2. Abundance (Log2 [Number of records + 1]) of warbler and vireo
species in California in the fall versus Angle of deviation (degrees) from normal
migration route needed to teach California by fall migrants. Larger dots
represent two species.

119

WARBLERS AND VIREOS IN CALIFORNIA

western parts of the ranges, but overall commonness can be esti-
mated. The relative commonness of species was taken from Robbins,
Bruun and Zim (1966), species ranked 1 to 7 according to the
abundance category specified therein, except that species characte-
ristic of the Eastern Region were placed one rank rarer since these
tend to be uncommon at the northern periphery of their breeding
range. As species become more common they occur more frequently
in California (Fig. 3, rg = 0.761, P <0.001). However, the overall
abundance ranks proved to be correlated with the angle of deviation
from normal migration routes needed to reach California (rg = 0.532,
P <0.001). To investigate the influence of angle of deviation when
corrected for commonness and of commonness when corrected for angle
of deviation I calculated partial rank correlation coefficients using the
standard formula (Steel and Torrie, 1960). Commonness remained
significantly correlated with abundance of these species in California,
but angle of deviation had almost no effect, the partial correlation
coefficient being about 0.25 (0.1 >P>0.05). The simplest explana-
tion for this result would be to assume misoriented birds occur
rarely, but given that a bird will be disoriented all degrees of
misorientation are equally likely.

Species also differ in their migratory tendencies. There is no direct
way to measure this, but an indirect measure might be the length of
the migratory route, under the assumption that species having short
routes are likely to be less migratory (and migrate over a shorter
period) than species with a long route. (A mo/e realistic explanation
is that species with short routes live in or near areas where winter

7

o o

6

5

4

3

2

D O

0 • •

□ 0

0 ■ •

1

0

0 1 o • o o o

1 2 3 4 5 6 7

Commi

FIGURE 3. Abundance (rank) of
warbler and vireo species in Cali-
fornia in the Fall versus common-
ness (rank) of species, in general.
Empty circles = 1 species; solid cir-
cles = 2 species; empty squares = 3
species; solid squares = 4 species.

120

WARBLERS AND VIREOS IN CALIFORNIA

FIGURE 4. Abundance (Log 2 [Number of records + 1]) of warbler and vireo
species in California in fall versus length of migration route (miles) from
breeding range to wintering range. Larger dot represents two species. Black-
whiskered Viieo is not shown.

survival is possible.) A weak positive correlation (Fig. 4, Corner Test
= 9, P = 0.1) exists between length of the migration route and
abundance of these species in California. However, it is likely that
this correlation is spurious and results from a tendency for species
with short migration routes to be less common everywhere.

An ecological parameter that might influence the frequency of
“accidentals” in California is the serai stage in which the species
breeds. Species breeding in early serai stages are likely to find the
areas in which they now breed unsuitable in coming years, whereas
species which inhabit mature stages can expect to find presently
suitable habitat unchanged for much longer periods of time. Corres-
pondingly, one might expect species inhabiting the earlier stages to be
subject to less selection for the more accurate navigational abilities
needed to return them to the same spot every year and, hence, more
prone to vagrancy. Breeding habitats of the species were ranked from
1 to 6 according to their approach to climax. There was no
significant correlation between habitat stability and abundance in
California.

121

WARBLERS AND VIREOS IN CALIFORNIA

Another ecological factor that might influence frequency of
“accidentals” is the rate of population turnover. The more rapid the
rate of population turnover, the more likely a bird breeding for the
first time will find an empty territory in the areas where it hatched.
The greater assurance of finding a breeding territory there should lead
to greater selection for navigational abilities. There are no data with
which to test this hypothesis.

The Cordilleras of western North America form a potential barrier
to east-west migrations of birds. In the fall the mean rank for
abundance in California is 4.25 for species which breed or winter in
and west of these ranges and 2.04 for species which occur entirely
east of them. In the spring the contrast is more striking; no species of
rank 4, 5 or 6 occurs entirely east of these mountains. Even in
California the influence of the mountains is suggested by the
concentration of “accidentals” east of the White and Panamint
mountains, in the southeastern deserts, and along the coast (Fig. 5).
The concentration of records along the coast is probably the result of
observer concentration and the influence of the ocean on individuals
which do cross the mountains. It is difficult to separate any effect of
the mountains from that produced by the more westward ranges for
species that breed in the Cordilleras, but a possible reason for such an
effect can be suggested. Measurements of the altitude of migrating
birds, admittedly in low-lying areas, indicates that over 90 per cent of

FIGURE 5. Major localities for “accidentals” in Cali-
fornia. Stippled area is above 5000 feet elevation. 1)
Oasis, Mono County; 2) Deep Springs, Inyo County; 3)
Death Valley National Monument, Inyo County; 4)
Morongo Valley, San Bernardino County; 5) Cottonwood
Springs, Riverside County; 6) Parker Dam, San Bernar-
dino County; 7) Salton Sea, Imperial County; 8) Imperial
Dam and Potholes, Imperial County; 9) Point Reyes,
Marin County; 10) Point Bonita, Marin County; 11)
South Farallon Island; 12) Pacific Grove, Monterey
County; 13) Carmel, Monterey County; 14) Santa
3 Barbara, Santa Barbara County; 15) Los Angeles,
Los Angeles County; 16) Dana Point, Orange
County; 17) Solana Beach, San Diego County;
18) Point Loma, San Diego County; 19) Im-
perial Beach, San Diego County. Localities
6 where “accidentals” are rarely found: A)
Yolo County; B) Lake Tahoe; C) Tilden
Park, near Berkeley, Contra Costa
County.

122

WARBLERS AND VIREOS IN CALIFORNIA

all migrants fly below 5000 feet altitude (Eastwood and Rider,
1965), whereas much of western North America is above 5000 feet
elevation (Fig. 1). Records in eastern California appear strikingly
limited by the 5000 foot contour (Fig. 5). Although most of the
western species migrate, especially in the fall, at higher elevations in
the mountains (e.g., Austin, 1970), there are also observations of
some migrants avoiding these higher elevations (L. Miller, 1957). It is
not inconceivable that Eastern and Northeastern species as a group
are less prone to cross the higher mountains than Western and
Northwestern species but more field work on this point is clearly
required.

Present data suggest that the pattern of abundance of these species
is largely the result of passive phenomena - the failure of organisms
to be perfect navigators and the size of the source populations. As
additional records become available it would be desirable to deter-
mine if the patterns of abundance are different in the San Francisco
Bay area and the San Diego areas, between coastal and interior
localities, and also between spring and fall.

DISCUSSION

A large part of the variation in abundance of these “accidentals”
in California can be attributed to differences in population size. The
influence of the other factors is minimal. Of other possible factors,
the amount of deviation from normal migration routes seems most
likely to be influential as the abundance of only a few species is
predicted poorly by this factor. In the spring exceptional species are
Louisiana Waterthrush and Yellow-throated Warbler, which are un-
accountably scarce; the former is exceptionally scarce in the fall as
well. In the fall two species, Black -throated Blue and Prairie Warbler,
are exceptionally numerous. [Subsequent to completing this manu-
script I have found reference to Black-throated Blue Warblers breed-
ing in central Sasketchewan. If correct, this would reduce the angle
of deviation from 88° to 58°, and the species would no longer be
exceptionally abundant by this criterion.] Palm Warbler might also be
considered overly abundant by this criterion, but there are now
enough records of wintering birds to suggest that it regularly winters
in California and is not “accidental” there.

Movement of air masses southwestward from central Canada or
northwestward from western Mexico may influence the incidence of
“accidentals” in California, but the great distance involved and the

123

WARBLERS AND VIREOS IN CALIFORNIA

complications introduced by topography and by continuously avail-
able resting areas in intervening areas make “wind drift” a factor very
difficult to analyze. It will prove particularly difficult to separate the
role of weather in bringing birds to an area where they do not
normally occur from that of grounding migrants that happen to be
present.

All of the hypotheses I have proposed should apply to other
groups of birds as well. Migratory Northern and Eastern species of
other passerine families do not form as clear-cut a pattern as do
vireos and wood warblers, although the same trends are evident. The
records of these species are difficult to evaluate because of bias in
their identification and discovery. Some of these species are not
easily identified in the field (e.g. Hylocichla thrushes and tyrannid
flycatchers); others are both distinctive and are attracted to feeders
(e.g. orioles, sparrows). The best potential source of data is probably
the records being accumulated on South Farallon Island, but approxi-
mately ten years of field work will be necessary to elucidate whatever
patterns exist, if past experience is indicative.

Grinnell (1922) pointed out that the “accidental” was “the regular
thing, to be expected.” He believed the role of the “accidental” was
that of the explorer, individuals by which “the species keeps aware of
the possibilities of areal expansion.” No ornithologist can reasonably
deny the first statement, but the second is not as straightforward.

Range expansion of highly vagile animals such as birds is possible
under two circumstances. One is through amelioration of environ-
mental conditions around the range occupied by the species of
evolved adaptations to these conditions and subsequent range expan-
sion of the species into these areas. The other method is through
movement of individuals across unsuitable areas to isolated regions of
suitable but unoccupied habitat. I assume vagrancy leading to range
expansion occurs primarily by the last method.

There is little indication of range expansion in the records of
“accidentals” in California. The only “accidental” proven to have
bred in California, and that but once, is the Parula Warbler, whose
continued rarity probably results from the scarcity of nesting habitat
rather than the scarcity of individuals in western North America.
Palm Warbler and American Redstart may be establishing new Pacific
coast wintering grounds and the other Northwestern species which
appear in small numbers in California may be establishing direct
western migration routes.

The rarity of range expansion from long range vagrancy probably
124

WARBLERS AND VIREOS IN CALIFORNIA

owes to the difficulty in meeting several basic requirements. Not only
must several individuals find an area ecologically similar to their
“normal” range, but the new area should not be occupied by a
potentially competing species, as the latter’s presence may prevent
establishment of the invading species even if the invader is com-
petitively superior (Slobodkin, 1962, ch. 11). The rare instance in
which a new population is established may have important evolu-
tionary consequences. It is unlikely that two isolated areas will be
identical and, particularly for populations which remain isolated in
summer and winter, environmental differences may lead to genetic
differentiation. The founder effect (Mayr, 1962) could certainly be
important. Also, as the number of populations of a species increases,
the likelihood of all simultaneously becoming extinct is reduced. This
is, however, a long term view of the role of the “accidental.”

The majority of “accidentals” clearly do not accomplish any
meaningful “pioneering.” As these individuals are leaving the region
to which they are adapted, they are in a sense reducing the
probability of their own survival. Their genetic survival may not be
any greater even if they do not disperse, however, as most species
probably consist of fairly completely saturated populations in which
more individuals are produced each breeding season than can breed in
the following season. Indeed, the low probability of finding new,
suitable habitat may mean a wandering individual can have a better
chance of reproducing than a sedentary individual. The function of
dispersal is uncertain, but its results are clear. Movements away from
centers of abundance may lead to the founding of new populations,
but this is a result of dispersal, not its function. It may be more
appropriate to regard the role of the “accidental” as a reminder of
the difficulty of defining the range of highly vagile organisms.

The usefulness of the term “accidental” remains to be considered.
The implication of accident seems misleading when one can detect
such a strong pattern of abundance as exhibited by wood warblers
and vireos in California. Only if idealized animals existed in fixed
geographic ranges would the idea of accident have much meaning.
The great variation exhibited in any trait of every species attests to
the non-reality of ideal animals, just as the many examples of range
expansion and contraction negate the idea of fixed geographic distribu-
tion. The term “accidental” appears not to indicate so much accident as
either ignorance of the true status or extreme rarity in a continuum
of abundances within a well understood distributional pattern. In the
latter case, the appropriate description of abundance is frequency of

125

WARBLERS AND VIREOS IN CALIFORNIA

occurrence with respect to the distributional pattern, such as “Very
rare migrant, not detected annually.” In cases when the pattern of
occurrence is unknown, a noncommittal way of describing abundance

should be employed, such as “One record: Either form of

description passes more accurate information than does “accidental.”

SUMMARY

Records of “accidental” vireos and wood warblers in California
form a pattern of species abundance which can be largely explained
by the size of source populations. Local distribution of records in
California seems to be related to topographic features of the state.
Most of the consequences of vagrancy are results but not functions of
dispersal processes, and the most important possible consequence is
the rare chance of establishment of new population centers with
potential for differentiation.

LITERATURE CITED

American Ornithologists Union. 1957. Checklist of North American Birds. Fifth
ed., Baltimore, Md.

Austin, G. T. 1970. Migration of warblers in southern Nevada. Southwestern
Nat. 15: 231-238.

Eastwood, E., and G. C. Rider, 1965. Some radar measurements of the altitude
of bird flight. Brit. Birds 58: 393-425.

Emlen, S. J. 1967. Migratory orientation in the Indigo Bunting, Passerina
cyanea. Part I: Evidence for use of celestial cues. Auk 84: 309-342.

Grinnell, J. 1922. The role of the “accidental.” Auk 39: 373-380.

Grinnell, J., and A. H. Miller, 1944. The distribution of the Birds of California.
Pacific Coast Avifauna no. 27: 1-608.

Johnson, N. K., 1965. The breeding avifaunas of the Sheep and Spring Ranges
in southern Nevada. Condor 67: 93-104.

McCaskie, G. 1970. The American Redstart in California. Calif. Birds 1: 41-46.

Mayr, E. 1963. Animal Species and Evolution. Cambridge, Mass. Belknap Press
of Harvard Univ.

Miller, A. H., H. Friedman, L. Griscom, and R. T. Moore, 1957. Distributional
check-list of the birds of Mexico. Part II. Pacific Coast Avifauna 33: 1-436.

Miller, L. 1957. Some avian fly ways of western North America. Wilson Bull.
69: 164-169.

Murray, B. G., Jr. 1966. Migration of age and sex classes of passerines on the
Atlantic Coast in autumn. Auk 83: 352-360.

126

WARBLERS AND VIREOS IN CALIFORNIA

Parnell, J. F. 1969. Habitat relations of the Pamlidae during spring migration.
Auk 86: 505-521.

Ralph, C. J. 1971. An age differential of migrants in coastal California. Condor
73: 243-246.

Robbins, C. H., B. Bruun, and H. S. Zimm. 1966. Birds of North America. A
guide to field identification. New York. Golden Press.

Slobodkin, L. B. 1962. Growth and Regulation of Animal Populations. New
York. Holt, Rinehart, and Winston.

Steel, R. G. D., and J. H. Torrie. 1960. Principles and procedures of statistics.
New York. McGraw-Hill.

Udvardy, M. D. F. 1963. Bird faunas of North America. Proc. XIII Intern.
Ornithol. Congr. : 1147-1167.

Department of Biology, Syracuse University, Syracuse, New York,
13210.

POSTSCRIPT

Austin (Condor 73: 455461, 1971) has recently published an
independent analysis of eastern wood warbler abundance in Cali-
fornia. He recognizes the possible influence of zoogeographic phe-
nomena in determining abundance of these species in the state, and
has additionally made the important contribution of comparing dates
of occurrence in California with dates of occurrence in eastern North
America. I believe his conclusions on the timing of records in
California are subject to some modification, particularly for species
with more southeasterly breeding ranges. For such species, dates of
appearance in California in the fall would seem to be more closely
comparable with dates of arrival on the wintering range, since the
distances traveled are comparable. He has not attempted such a
comparison, presumably for lack of suitable data. In the spring, dates
of occurrence should be related primarily to the phenology of the
populations supplying individuals to California and are not necessarily
related to those obtained in eastern North America. Moreover, it is
my distinct impression that the magnitude of movements in late May
and early June is considerably underestimated by eastern observers,
who frequently concentrate their efforts in the early spring when the
foliage is not fully developed. In both spring and fall, based on my

127

WARBLERS AND VIREOS IN CALIFORNIA

own experience in southern Michigan and central New York, the
numbers of “migrating” birds which may be found is not very
different from the numbers observed in California at the same time
of the year. What seems to be changed is that individuals observed
earlier in the season in the East are missing in California (and records
from South Farallon Island suggest that even this impression is
somewhat erroneous). Lastly, I believe Austin does not realize how
localized the records of many of these species are, particularly when
he suggests that some of the abundance patterns are recent develop-
ments (with implication of during the twentieth century.) Based on
my personal field experience it is not at all surprising that, for
example, the first records of the Blackpoll Warbler were not obtained
in the San Francisco Bay area until 1962, in spite of a hundred year’s
prior field work there. Records of these species are almost non-
existent from localities more than a quarter mile inland of the Pacific
ocean, even for observers who are successful at locating these species
coastally.

128

INTERBREEDING OF THE GLAUCOUS -WINGED GULL
AND WESTERN GULL IN THE PACIFIC NORTHWEST

J. Michael Scott

The fifth edition of the A.O.U. Check-list (1957) states that the
Glaucous-winged Gull (Lams glaucescens } breeds from western Alaska
south to Copalis Rocks, Washington. In the southern part of its
breeding range (Vancouver Island to Copalis Rocks) it is sympatric
with the northernmost populations of the Western Gull (L. occiden-
talis) (Pearse, 1946; Jewett et al., 1953). In the summers of
1969-1971 several pairs of Glaucous-winged Gulls nested on Yaquina
Head, Oregon (44°40’N, 124°05’W) 300 km south of the previously
reported southernmost breeding colony for this species. Approximate-
ly 60 ± 10 pairs of Western Gulls also nested on Yaquina Head. In
addition three L. glaucescens were paired with L. occidental is in the
colony (Fig. 1). In 1971, six known hybrids were banded from a
total of three nests.

In the summers of 1970 and 1971, breeding sites from Cape
Perpetua, Oregon, north to Destruction Island, Washington, were
surveyed for Glaucous-winged Gulls; the species was observed in both
pure and mixed pairs on Yaquina Head and Jocky Cap in Oregon,
and on Destruction Island, Washington (Fig. 2). Mixed pairs have also
been observed in southern British Columbia (R. H. Drent, pers.
comm.; Table 2). Adults which were morphologically intermediate
between Glaucous-winged and Western gulls were observed infrequent-
ly on Yaquina Head, but were common on Destruction Island.

Previous workers have suggested that interbreeding might occur
between L. galucescens and L. occidentals, but these suggestions
were based on educated guesses (Swarth, 1934, p38) or on observa-
tions of gulls which were intermediate in morphological characteris-
tics between the two species (Zella Schultz, pers. comm.) However,
Pearse (1946) reported an apparent mixed pair on Pachena Rock, off
Vancouver Island, B.C., in 1943, and saw several apparent adult
hybrids in 1944; and Dawson (1923; pi 383) saw a mixed pair with
young in Washington in 1910. Because the Glaucous-winged Gull is
steadily increasing in British Columbia (Veermer, 1963), it is likely
that the area of sympatry may expand even farther sound and
additional interbreeding may result.

The interbreeding between Glaucous-winged and Western gulls
presents an excellent field situation for approaching some of the
Calif. Birds 2:129-133, 1971 129

INTERBREEDING OF GULLS

Pair

Composition

Year

Eggs

Laid

Young

Hatched

Young

Fledged

Pure

1969

X

0

0

Pure

1970

X

X

1

Pure

1971

0

0

0

Pure

1971

X

X

3

Mixed

1969

X

0

0

Mixed

1969

X

X

0

Mixed

1969

X

X

3

Mixed

1970

X

X

0

Mixed

1970

X

X

0

Mixed

1970

X

X

2

Mixed

1971

X

X

1

Mixed

1971

X

X

3

Mixed

1971

X

X

3

Table 1. Summary of nesting data for Glaucous-winged Gulls nesting on
Yaquina Head, Oregon, 1969-71. Pure pairs were entirely Glaucous-winged; in
mixed pairs a Glaucous-winged paired with a Western Gull.

FIGURE 1. A Glaucous-winged-Western Gull pair nesting on Yaquina Head,
Oregon. The Glaucous-winged Gull mounted during the three observed instances
of copulation. This was one of three mixed pairs nesting on Yaquina Head in
1970. Photo by Fred L. Ramsey

130

INTERBREEDING OF GULLS

FIGURE 2. A mixed species pair incubating a nest with two eggs at Destruction
Island, Washington, June 1, 1971. The dark primaried gull may possibly be of
mixed parentage Larus glaucescens, X Lams occidentalis.

Photos by J. M. Scott
131

INTERBREEDING OF GULLS

questions posed by Short (1969) and others regarding the biological
significance of interbreeding between two closely related species. 1)
What is the situation with respect to the occurrence or lack of
occurrence of hybrids? 2) What are the distribution and habits of
parental forms and hybrids? 3) What are the relative frequencies of
hybrid and parental phenotypes in the area of hybridization? 4) What
type of backcrossing is occurring? 5) What are the population
dynamics of the forms involved? Studies which may provide some
information on these and other questions are in progress.

Pair

Composition

Location

Date

Comments

Observer

Mixed

Jocky Cap,
Clatsop Co., Ore.

July 3,
1971

Glaucous-winged
feeding one
young.

J. M. Scott

Glaucous-

winged

Jocky Cap,
Clatsop Co., Ore.

July 3,
1971

Single bird on
territory.

J. M. Scott

Western

Jocky Cap,
Clatsop Co., Ore.

July 3,
1971

Estimated 70
pairs nesting
on island.

F.M.

Zeillemaker

Mixed

Destruction Is.,
Washington

June

1-2

1971

Four mixed pairs
on nests. At
least one had
two eggs.

J. M. Scott

Glaucous-

Destruction Is.,

June

30 nesting pairs

Rex

winged

Washington

9-10

1971

on island.

VanWarmer

Western

Destruction Is.,
Washington

June

9-10

1971

195 nesting pairs
on island.

Rex

VanWarmer

Mixed

Sea Lion Rocks,
Wickanninnish
Bay, Long
Beach, B.C.

July 26, Western and
27, 1969 Glaucous-winged
with three young.
Approximately 1500

R. H. Drent

pairs of Glaucous-
winged Gulls nest
on this island.

Table 2. Summary of nesting data at sites in Oregon, Washington, and British
Columbia at which interbreeding between Glaucous-winged and Western gulls
has been observed.

132

INTERBREEDING OF GULLS

ACKNOWLEDGEMENTS

I wish to thank the personnel of the U. S. Sport Fisheries &
Wildlife Service and the U. S. Coast Guard for their cooperation in
making my trip to Destruction Island possible.

My wife Sharon, Thomas W. Haislip, Jr., John A. Wiens and
Joseph R. Jehl, Jr. read the manuscript and provided many helpful
suggestions. Support for this study was received from the Natural
History Museum at Oregon State University and from a grant from
the Frank M. Chapman Memorial Fund of the American Museum of
Natural History. This is contribution No. 18 of the behavioral
ecology laboratory, Oregon State University.

LITERATURE CITED

American Ornithologists’ Union. 1957. Check-list of North American birds.

Fifth ed. Amer. Omithol. Union, Baltimore.

Dawson, William Leon. 1923. The birds of California. South Moulton Co., San
Diego, Calif.

Jewett, S. G., Taylor, Walter P., Shaw, William T., and John W. Aldrich. 1953.

Birds of Washington State. Univ. Wash. Press, Seattle.

Peaise, T. 1946. Nesting of Western Gull off the coast of Vancouver Island,
British Columbia and possible hybridization with the Glaucous-winged Gull.
Murrelet, 27: 39-40.

Short, Lester. 1969. Taxonomic aspects of avian hybridization. Auk, 86:
84-105.

Swarth, A. S. 1934. Birds of Nunivak Island, Alaska. Pacific Coast Avifauna,
No. 22: 1-64.

Veermer, Kees. 1963. The breeding ecology of the Glaucous-winged Gull ( Larus
glaucescens) on Mandarte Island, B.C. Occ. Pap. British Columbia Prov.
Mus., Vol. 13.

Department of Zoology, Oregon State University , Corvallis,
Oregon 97331

133

NOTES

OLIVACEOUS CORMORANT RECORD FOR CALIFORNIA

On the morning of 13 April 1971 while looking at birds in the vicinity of
Imperial Dam with Bill Clow and Richard Macintosh, I found an Olivaceous
Cormorant Phalacrocorax olivaceus in breeding plumage. The bird was found
among Double-crested Cormorants P. auritus on West Pond, situated about one
quarter mile west of Imperial Dam on the California side of the Colorado
River. During the two hours we had the bird under observation it was perched
on a short snag in the pond with an adult and three immature Double-crested
Cormorants. The close proximity of the bird to the Double-crested Cormorants
enabled us to make a direct size comparison of the two species.

The following description was taken while observing the bird through a 25X
Bushnell spotting scope at 75 to 100 yards with the sun directly behind us:

Plumage: body color black; wing feathers were slightly paler with a faint
greenish irridescence. Soft parts: gular pouch fleshy pink (this was
especially noticeable when the bird “yawned,” and was probably due to
the sunlight shining through the thin, vascularized pouch tissue); pouch
bordered posteriorly by a conspicuous white line; iris green; bill, legs and
feet dull black.

The Olivaceous Cormorant was about three-fourths the length, and one half
the bulk, of the Double-crested Cormorants with which it was associated. It
had a long tail for a cormorant and a disproportionately small neck, head, and
bill.

This is the first observation of the Olivaceous Cormorant in California. It
breeds north to southern Sonora on the Pacific coast (van Rossem, 1945) and
to Louisiana on the Gulf of Mexico (Lowery, 1960). There are at least eight
records for Arizona (Phillips, et al., 1964; Audubon Field Notes, 15:348,
16:354, 18:476 & 527, 24:76 & 526, 25:87), seven records for Oklahoma
(Sutton, 1967; AFN, 24:694, 25:75) and five records for New Mexico
(Hubbard, 1970). Strays have been reported from Kansas, Illinois, and Colorado
(A.O.U., 1957); however, the Illinois record, originally reported by Ridgway
(1880), may be in error. I know of no records for Baja California.

LITERATURE CITED

American Ornithologists’ Union. 1957. Check-list of North American birds. 5th
ed. American Ornithologists’ Union, Baltimore.

Hubbard, J. P. 1970. Check-list of the birds of New Mexico. New Mexico
Ornithological Soc. Publ. no. 3:1-103.

Lowery, G. H., Jr. 1960. Louisiana birds. Louisiana State Univ. Press, Baton
Rouge.

Phillips, A., J. Marshall and G. Monson. 1964. The birds of Arizona. Univ. of
Arizona Press, Tucson.

Ridgway, R. 1880. On birds new to the fauna of Illinois. Bull. Nuttall Ornith.
Club, 5:31.

Sutton, G. M. 1967. Oklahoma birds. Univ. of Oklahoma Press. Norman,
van Rossem, A. J. 1945. A distributional survey of the birds of Sonora,
Mexico. Occasional Paper no. 21. Mus. of Zoology, Louisiana State Univ.,
Baton Rouge..

H. Lee Jones, Department of Zoology, University of California, Los Angeles,
California 90024.

134

Calif. Birds 2:134, 1971

NOTES

THE WOOD THRUSH IN CALIFORNIA

On 1 8 November 1967 a party of us, including Pierre Devillers, Alan Craig, and
Cliff Lyons, were spending the afternoon checking for birds in the Tijuana River
Valley to the south of Imperial Beach, San Diego County, California. At Windover
Ranch, a small but well-watered avocado orchard situated just north of the
Mexican border, I discovered a Wood Thrush Hylocichla mustelina. When first
noted, the bird was feeding on the ground under a tree with Robins Turdus
migratorius and Hermit Thrushes Hylocichla guttata. It was clearly larger than the
Hermit Thrushes, being nearly the size of the Robins, and was acting very much
like a Robin. The following description was taken:

Upperparts: forehead and crown, dark chestnut; nape, bright buffy-rufous;
upper back, bright rufous, only slightly darker than the nape; rump and
tail, olive-gray contrasting sharply with the back. Wings: upper wing
coverts, brown, the lesser wing coverts edged with rufous; primaries and
secondaries, dark brown. Face: ear coverts, dark brownish -gray contrasting

FIGURE 1. A Wood Thrush captured near Imperial Beach, California, on 18
November 1967. Photo by Alan M. Craig

Calif. Birds 2:135-136, 1971 135

NOTES

sharply with the nape; eye-ring, pale buffy-white. Underpaits: entire
underparts, white with slight buffy wash across breast; throat streaked,
breast and flanks boldly spotted with black.

After about half an hour we erected a mist-net and promptly captured the
bird. It was studied in the hand and thought to be in an emaciated condition, but
was photographed (fig. 1) and released. One free, it was clear the bird was too
weak to fly, so it was recaptured and retained as a specimen (San Diego Natural
History Museum #36355). It proved to be a male with skull fully ossified and
having testes measuring 1.5 mm; the bird weighed 51.3 grams.

Another Wood Thrush appeared in a Verdugo Hills yard located in the
northern part of Glendale, Los Angeles County, California, on about 1 August
1968, and was killed there by a cat ten days later (G. S. Suffel, pers. comm.). The
specimen was retreived, and is now deposited in the Los Angeles County Museum
(#77806). It was found to be an adult male, skull fully ossified, having very small
testes, no fat, and exhibiting distinct body molt.

The Wood Thrush breeds in the eastern half of the United States (A.O.U.,
1957), reaching Canada only in extreme southern Ontario and Quebec (Godfrey,
1966). It winters to the south of the United States in Mexico and Central
America. West of its normal range it is casual in both spring and fall in eastern
Colorado (Bailey and Niedrach, 1965); there are two fall records for New Mexico
(Hubbard, 1970), and the same number of fall records for Arizona (Monson, 1968
and Snider, 1968). The two records presented above are the only occurrences for
California.

LITERATURE CITED

American Ornithologists’ Union. 1957. Check-list of North American birds. Fifth
ed. Amer. Omithol. Union, Baltimore.

Bailey, A. M. and R. J. Niedrach. 1965. Birds of Colorado. Vol. II. Denver
Museum of Natural History, Denver.

Godfrey, W. E. 1966. The birds of Canada. Nat. Mus. of Canada Bull. 203. Biol.
Series 73.

Hubbard, J. P. 1970. Check-list of the birds of New Mexico. New Mexico
Ornithological Soc. Publ. no. 3:1-103.

Monson, G. 1968. The Arizona state bird-list, 1964-67. Journal of the Arizona
Academy of Sciences 5:34-35.

Snider, P. R. 1968. Fall migration. Southwest region. Audubon Field Notes
22:75-77.

Guy McCaskie, San Diego Natural History Museum, Balboa Park, San Diego,
California 92112.

136

NOTES

TENNESSEE WARBLER OBSERVATIONS IN OREGON

On 12 June 1963 Eugene Kridler (1965) collected an adult female (USNM
#479637) Tennessee Warbler (Vermivora peregrina) at Malheur National Wild-
life Refuge Headquarters, Harney County, Oregon. This represented the first
record of the species in the state. Kridler also banded and photographed (color
transparencies on file at refuge H.Q.) an immature on 15 October 1963 at the
same locality.

Since 1963, nine additional Tennessee Warblers have occurred in the state,
seven at Malheur National Wildlife Refuge H.Q. One was observed with
Orange-crowned Warblers (Vermivora celata), Wilson’s Warblers (Wilsonia
pusilla), and Warbling Vireos (Vireo gilvus) by Joseph Hicks on 11 September
1969 fifteen miles north of Medford, Jackson County (Harry Nehls, pers.
comm.). Another, associating with Audubon’s Warblers (Dendroica auduboni) in
a stand of Whitebark Pine and Engelmann Spruce near Mirror Lake in the
Willowa Mountains, was observed on 9 August 1971 (John Butler, pers.
comm.).

The Malheur records include two observed on 29 May 1964 by John
Crowell and Jim Olson (Scott, 1964), and banded by Fred Zeillemaker on 31
August 1965, and single birds banded by Walter L. Anderson on 24 August and
3 September 1966. On 31 May 1971, Carroll D. Littlefield captured an adult
female, and on 12 June 1971 Anderson captured an adult male; both were
banded and photographed.

Larrison and Sonnenberg (1968) list the Tennessee Warbler as a rare
straggler into eastern Washington and mention no spring records. The species is
considered a casual fall vagrant in western Nevada based on an observation east
of Lake Tahoe on 29 August 1969 by Robert P. Russell, Jr. (Scott, 1970). In
California the species is now recognized as a rare but regular fall migrant or
vagrant (Baldridge et. al., 1970 and McCaskie, 1971).

The species can now be considered an occasional spring and fall vagrant in
southeastern Oregon. Possible explanations for the occurrence of the Tennessee
Warbler and other typically “eastern” species in California have been advanced
by (1) Aaron M. Bagg (1970), who reasoned that such species might reach the
California Coast as drifted migrants by following easterly airflows from the
Gulf of Mexico to the Far West, and by (2) David DeSante whose orientation
studies led him to believe that the birds should be classified as “misguided
migrants,” flying directly from breeding territory to wintering areas along
routes atypical of the species as a whole (Chandik et. al. 1971). The latter
hypothesis would be strengthened by the observations of the species in the fall
in Oregon. A chronological comparison of observation dates in Oregon and
California suggests a logical migratory sequence between the nesting grounds in
Western Canada and the wintering areas in Mexico and Central America.
Whether the fairly regular sightings in recent years indicate a minor change in
the migratory patterns of a population or simply reflect an increased observa-
tional effort remains to be established. The use of mist nets at Malheur has
accounted for seven of the eleven known records in Oregon, and perhaps the
true extent of the migration of this species through Oregon still awaits
discovery.

ACKNOWLEDGEMENTS

We would like - to express thanks to Dr. Roger C. Hungerford, Bruce E.
Deuel and John P. Gray of the University of Arizona for editorial comments.
The senior author would also like to express his appreciation to the Bureau of

Calif. Birds 2:137-138, 1971

137

NOTES

Sports Fisheries and Wildlife for the opportunity to conduct research on

Malheur NWR.

LITERATURE CITED

Bagg, A. M. 1970. A summary of the 1969 fall migration season, with special
attention to eruptions of various boreal and montane species and analysis of
correlation between wind flows and migration. Aud. Field Notes 24:4-13.

Baldridge, A., T. Chandik and D. DeSante. 1970. Middle Pacific Coast Region.
Aud. Field Notes 24:88-95.

Chandik, T., D. DeSante and Eleanor A. Pugh. 1971. Middle Pacific Coast
Region. Amer. Birds 25:100-106.

Kridler, E. 1965. Records, obtained while banding, of birds unusual in
southeastern Oregon. Auk 82:496-497.

Larrison, E. J. Jr. and K. G. Sonnerberg. 1968. Washington birds, their location
and identification. Seattle Aud. Soc., Seattle.

McCaskie, G. 1971. Southern Pacific Coast Region. Amer. Birds 25:106-112.

Scott, O. K. 1964. Great Basin, Central Rocky Mountain Region. Aud. Field
Notes 18:474476.

Scott, O. K. 1970. Great Basin, Central Rocky Mountain Region. Aud. Field
Nptes 24:74-75.

Carroll D. Littlefield, Department of Biological Sciences, University of Arizona,

Tucson, Arizona 85721 and Walter L. Anderson, Malheur National Wildlife

Refuge, Burns, Oregon 97721.

138

NOTES

ROADRUNNER CAPTURES ORCHARD ORIOLE IN CALIFORNIA

Although the Roadnmner (Geococcyx califomianus) has long been known
for its bird-catching propensity, there are few well-documented accounts of
such behavior under natural conditions. Bent (U.S. Natl. Mus., Bull. 176:4445,
1940) summarizes a number of observations, mostly concerning pet Road-
runners or juvenile prey, and Zimmerman (Condor, 72:475476, 1970) details
the capture of several adult passerines near a feeding station in New Mexico.

Mesquite Spring is a desert oasis located at an elevation of about 1,800 feet
in the north end of Death Valley National Monument, Inyo Co., California.
Surrounding the spring, which has been impounded to form a tiny pool that
provides fresh water throughout the year, are several small cottonwoods and a
group of mature mesquites. A narrow paved road separates the mesquites into
two strips and allows access to campsites among the trees. The adjacent desert
is extremely arid and rocky, with widely scattered small shrubs and herbs.

On 24 October 1971, J. Greenberg, P. Phillips, and I discovered a female or
first-year male Orchard Oriole (Icterus spurius), a rare vagrant in California
(McCaskie, Stallcup and DeBenedictis, Condor, 68:595-597, 1966), feeding in
the mesquite at the edge of the pool. After several minutes the bird flew to the
ground at the edge of the desert and began feeding among the low herbaceous
growth. At this time a Roadrunner appeared over the crest of a small hill,
walked slowly toward the vegetation in which the oriole was concealed, and
then suddenly crouched on its tarsi and froze with neck outstretched. After
several seconds, it lunged forward, dashed some 10 feet, and disappeared into
the vegetation. Immediately we heard a loud, passerine distress screech, and a
second or two later the Roadrunner emerged with the oriole in its bill.

Wishing to examine the oriole in the hand, I gave chase. After about 30
yards and some 15 seconds of elapsed time since the capture, the Roadrunner
dropped the oriole and disappeared into the desert. The Roadrunner seemed to
have no difficulty in carrying its prey. When I reached the oriole, it was lying
on its back and panting heavily; it made no attempt to escape. Measurements
of the wing chord (72.5 mm), tail (66), and exposed culmen (15.5) confirmed
our original identification (Ridgway, U. S. Natl. Mus., Bull. 50, Pt. 2:275-276,
1902). When released, the oriole flew to the nearest mesquite and rested for
several minutes. Later that afternoon I relocated the oriole; although still
feeding on the ground, it was considerably warier than before. It was seen the
next morning by Greenberg and Phillips and thus apparently survived its
harrowing experience.

Eight other bird species that represent potential prey for Roadrunners were
noted at Mesquite Spring. Feeding on the ground at the edge of the desert were
a Mourning Dove (Zenaidura macroura), two Starlings (Sturnus vulgaris), a
Savannah Sparrow (Passerculus sandwichensis) , and a Lincoln’s Sparrow
(Melospiza lincolnii). On the goround under the trees were a Varied Thrush
(Ixoreus naevius), two Hermit Thrushes (Hylocichla guttata), an American
Redstart (Setophaga ruticilla), and a Fox Sparrow (Passerella iliaca). None of
these species breeds at Mesquite Spring but are probably attracted there by the
presence of fresh water, and thus constitute a source of possible prey
throughout the year. The presence of several lizards and a tarantula on the
same day at nearby Scotty’s Castle suggests that non-avian prey was also
available to the Roadrunner at Mesquite Spring. Laurence C. Binford, California
Academy of Sciences, Golden Gate Park, San Francisco, California 94118.

Calif. Birds 2:139, 1971

139

NOTES

THE ALLEGED OCCURRENCE OF NUTTING’S FLYCATCHERS
BAJA CALIFORNIA

In a recent editorial comment (Calif. Birds 1:80, 1970), I uncritically repeated
the Baja California record of a Nutting’s Flycatcher Myiarchus nuttingi inquientus
from Catavina on 6 October 1930, quoted both by the North American check-list
(A.O.U. Check-list of North American birds, 1957) and the Mexican check-list
(Miller in Miller et al., A distributional check-list of the birds of Mexico, Part II,
1957). The bird was originally reported by Huey (Auk 48:429-430, 1931).

I have now examined the specimen, San Diego Natural History Museum no.
13652, “male”; it is unquestionably an Ash-throated Flycatcher M. cinerascens.
The tail pattern corresponds to the “typical Af. cinerascens pattern,” category I.A,
of Lanyon’s key (Condor 63:424426, 1961). In all other plumage characters,
pale underparts, whitish edges of secondaries, nuchal band, and gray color of
auriculars, it is typical of cinerascens. The measurements (wing 88, tail 86.7,
exposed culmen 1 3 mm) fall outside the range of male Ash-throated Flycatchers
but inside the range of female Ash-throated Flycatchers, as well as of Nutting’s
Flycatchers. The wing formula is inconclusive.

Dr. Wesley E. Lanyon kindly examined the specimen and confirmed (in litt.J its
identification as cinerascens, presumably mis-sexed. This record of Nutting’s
Flycatcher was the only one for Baja California, and to my knowledge, the only
truly extralimital record of M, nuttingi inquietus. Indeed, in my opinion southern
Arizona is within a normal area of wandering and/or expansion for Sonoran
species, and I do not consider the record from there as extralimital. Pierre
Devillers, 11 av. de l ’Oiseau bleu, 1 1 50 Bruxelles, Belgium.

Membership dues and changes of address should be sent to Clifford R. Lyons,
Treasurer, Post Office Box 369, Del Mar, California 92014. Classes of member-
ship (all include subscription to California Birds): Patron, $1000; Life, $150;
Supporting, $20 annually; Contributing, $10 annually; Regular, $5 annually.
Make checks payable to California Birds.

Manuscripts should be sent to Guy McCaskie, San Diego Natural History
Museum, Box 1390, San Diego, California 92112. Use of the Style Manual for
Biological Journals is suggested as a guide in preparing manuscripts. Fifty re-
prints of each article are provided free of charge. Arrangements for additional
reprints may be made at the time manuscripts are submitted; the additional
cost will be borne by the contributor.

Rare bird reports should be sent to Jon Winter, Secretary, Rare Bird Commit-
tee, Point Reyes Bird Observatory, Mesa Rd., Bolinas, California 94924.

Layout and cover design by Virginia P. Johnson

140

Calif. Birds 2:140, 1971

‘P&Zazy of

Robert gill 1

TABLE OF CONTENTS
INDEX

CALIFORNIA BIRDS

VOLUME 2, 1971

TABLE OF CONTENTS
CALIFORNIA BIRDS VOLUME 2

Volume 2, Number 1, 1971

Identification of Northern and Louisiana

Waterthrushes L. C. Binford 1

The distribution of certain large gulls (Larus) in
southern California and Baja California

P. Devillers, G. McCaskie and J. R. Jehl, Jr. 1 1

A hybrid Glaucous X Herring Gull from San Diego

J. R. Jehl , Jr. 27

NOTES

The Whip-poor-will in California Lee Jones 33

Eastern Whip-poor-will in San Diego Jean T. Craig 37

Volume 2, Number 2, 1971

On the Field Identification of California Hummingbirds F.

Gary Stiles 41

Rusty Blackbirds in California and Western North

America Guy McCaskie 55

NOTES

Black Skimmers at the Salton Sea, California Guy

McCaskie and Shumway Suffel 69

First Record of Field Sparrow in California Henry Robert 72

The Lark Bunting in California Sanford R. Wilbur, W.

Dean Carrier, and Guy McCaskie

73

Volume 2, Number 3, 1971

Northern and Louisiana Waterthrushes in California Laurence

C. Binford 77

NOTES

Black-throated Blue Warbler Records for Southeastern

Oregon Carroll D. Littlefield and Eldon L. McLaury 93

First Record of White-eyed Vireo in California Henry Robert 94

A Prothonotary Warbler in Inyo County, California Mike San

Miguel 95

Red Phalarope Mortality in Southern California Suzanne I.

Bond 91

Roadside Distribution of the Common Raven in the Mohave

Desert George T. Austin 98

A Pyrrhuloxia Wanders West to California Guy McCaskie 99

A Probable Swift-Cactus Collision Charles T. Collins 101

Mallards Resting in Trees F. Russell Lockner, Douglas D.

Donaldson, and Judith L. Tartaglia 1 02

First Record for the Ruff in Washington State Laurence C.

Binford and Michael Perrone, Jr. 103

LETTERS TO THE EDITORS 105

BULLETIN BOARD 106

Volume 2, Number 4, 1971

EDITORIAL 109

Wood Warblers and Vireos in California: The Nature of

the Accidental Paul DeBendictis 1 1 1

ii

Interbreeding of the Glaucous-winged Gull and Western

Gull in the Pacific Northwest J. Michael Scott 129

NOTES

Olivaceous Cormorant Record for California H. Lee Jones 134

The Wood Thrush in California Guy McCaskie 1 35

Tennessee Warbler Observations in Oregon Carroll D.

Littlefield and Walter L. Anderson 137

Roadrunner Captures Orchard Oriole in California

Laurence C. Binford 139

The Alleged Occurrence of Nutting’s Flycatcher in Baja

California Pierre Devillers 140

INDEX 141

iii

INDEX TO CALIFORNIA BIRDS, VOLUME 2

Compiled by Virginia P. Johnson

Aberti, Pipilo, 99
Agelaius phoeniceus, 59-61
alexandri, Archilochus, 41-54
alpina, Erolia, 103
Anas platyrhynchos, 102
Anderson, Walter L., see Littlefield,
Carroll D., and -
anna, Calypte, 41-54
Archilochus alexandri, 41-54
argentatus, Larus, 14, 27-32
Arizonae, Caprimulgus vociferus, 33-36,
37-40

auduboni, Dendroica, 137
auritus, Phalacro corax, 134
aurocapillus, Seiurus, 93
Austin, George T., Roadside distribution
of the Common Raven in the Mojave
Desert, 98

barrovianus, Larus hyperboreus, 15
Binford, Laurence C., Identification of
Northern and Louisiana Waterthrushes,
1-10; Northern and Louisiana Water-
thrushes in California, 77-92; Road-
runner captures Orchard Oriole in
California, 1 39

Binford, Laurence C. and Michael Perrone,
Jr., First record for the Ruff in Wash-
ington State, 103-104
Blackbird, Brewer’s, 59-61
Red-winged, 59-61
Rusty, 55-68

Bond, Suzanne I., Red Phalarope mor-
tality in southern California, 97
brachyrhynchus, Larus canus, 11-26
Bunting, Lark, 73-76
caerulescens, Dendroica, 93
Calamospiza melanocorys, 73-76
californianus, Geococcyx, 139
califomicus, Larus, 22
calliope, Stellula, 41-54
Calypte anna, 41-54
Costae, 41-54

Caprimulgus vociferus arizonae, 33-36,
37-40

v. vociferus, 33-36, 37-40
Cardinal, 99
Cardinalis cardinalis, 99
sinuata, 99-100
$ fulvescens, 99
i peninsulae, 99

carolinus, Euphagus, 55-68
Carrier, Dean, see Wilbur, Sanford R., et
al.

celata, Vermivora, 137
Chaetura vauxi, 101
cinerascens, Myiarchus, 140
citrea, Prothonotaria, 95-96
citrina, Wilsonia, 88

Collins, Charles T., A probable swift-
cactus collision, 101
corax, Corvus, 98
Cormorant, Double-crested, 134
olivaceous, 134
Corvus corax, 98
cryptoleucus, 98
costae J Calypte, 41-54
Craig," Jean T., Eastern Whip-poor-will in
San Diego, 37-40
cryptoleucus, Corvus, 98
cyanocephalus, Euphagus, 59-61
DeBenedictis, Paul, Wood warblers and
vireos in California: the nature of the
accidental, 111-128; letter, 105
delawarensis, Larus, 22
Dendroica auduboni, 1 37
caerulescens, 93

Devillers, Pierre, The alleged occurrence of
Nutting’s Flycatcher in Baja California,
140

Devillers, Pierre, Guy McCaskie, and
Joseph R. Jehl, Jr.,

The distribution of certain large gulls
(Larus) in southern California and Baja
California, 11-26

Donaldson, Douglas D„ see Lockner, F.

Russell, et al.

Dove, Mourning, 1 39
Dunlin, 103
Empidonax griseus, 94
wrightii, 94
Erolia alpina, 103
Euphagus carolinus, 55-68
cyanocephalus, 59-61
Flycatcher, Ash-throated, 140
Gray, 94
Nutting’s, 140
fulicarius, Phalaropus, 97
Fulmar, 97
Fulmarus glacialis, 97
fulvescens, Cardinalis sinuata, 99

141

galbula. Icterus, 93
Geococcyx californianus, 1 39
gitvus, Vireo, 137
glacialis, Fulmarus, 97
glaucescens, Larus, 11-26, 28-29, 129-133
glaucoides, Larus, 14
griseus, Empidonax, 94
Puffinus, 97
Vireo, 94

Gull, California, 22

Glaucous, 11-26, 27-32
Glaucous-winged, 11-26, 28-29, 129-133
Heermann’s, 22
Herring, 27-32
Mew, 11-26
Ring-billed, 22
Thayer’s, 1 1-26, 28-29
Western, 11-26, 29, 129-133
Yellow-legged Western, 1 1-26
guttata, Hybcichla, 135, 139
heertnanni, Larue, 22
Hummingbird, Allen’s, 41-54
Anna’s, 41-54
Black-chinned, 41-54
Broad-tailed, 41-54
Calliope, 41-54
Costa’s, 41-54
Rufous, 41-54

Hylocichla guttata, 135, 139
mustelina, 135-136
hyperboreus, Larus, 11-26,27-32
Larus h., 15, 25
Icterus galbula, 93
spurius, 139
iliaca, Passerella, 139
inquientus, Myiarchus nuttingi, 140
International Ornithological Congress,
107-108

Ixoreus naevius, 1 39

Jehl, Joseph R., Jr., A hybrid Glaucous X
Herring Gull from San Diego, 27-32;
see also Devillers, Pierre, et al.

Jones, Lee, Olivaceous Cormorant record
for California, 1 34;

The Whip-poor-will in California, 33-36
Larus argentatus, 14, 27-32
a. smith sonianus, 31
a. vegae, 31
califomicus, 22
canus brachyrhynchus, 1 1-26
delawarensis, 22

glaucescens, 11-26, 28-29, 129-133
glaucoides, 14
heermanni, 22
hyperboreus, 11-26, 27-32

142

h. barrovianus, 15
h. hyperboreus, 15, 25
occidental is, 129-133
o, livens, 11-26
o. occidentals, 11-26, 29
o. wymani, 11-26
thayeri, 11-26, 28-29
leucophrys, Zonotrichia, 99
lincobiii, Mebspiza, 1 39
Littlefield, Carroll D. and Eldon L.
McLaury, Black-throated Blue Warbler
records for southeastern Oregon, 93
Littlefield, Carroll D. and Walter L.
Anderson, Tennessee Warbler
observations in Oregon, 137-138
livens, Larus occidentals, 11-26
Lockner, F. Russell, Douglas D. Donald-
son, and Judith L. Tartaglia, Mallards
resting in trees, 102

McCaskie, Guy, A Pyrrhuloxia wanders
west to California, 99-100; Rusty
Blackbirds in California and western
North America, 55-68; The Wood
Thrush in California, 135-136; see also
Devillers, Pierre, et al. and Wilbur,
Sanford R., et al.

McCaskie, Guy and Shumway Suffel,
Black Skimmers at the Salton Sea,
California, 69-71

McLaury, Eldon L., see Littlefield, Carroll
D., and -

macroura, Zenaidura, 139
melanocorys, Calamospiza, 73-76
Mebspiza lincolnii, 139
migratorius, Turdus, 135
Mnbtilta varia, 93
motacilla, Seiurus, 1-10, 77-92
mustelina, Hybcichla, 135-136
Myiarchus cinerascens, 140
nuttingi inquientus, 140
naevius, Ixoreus, 139
nigra, Rynchops, 69-71
noveboracensis, Seiurus, 1-10, 77-92
Vireo griseus, 94
occidentals, Larus, 129-133
Larus o., 1 1-26, 29
otivaceus, Phalacrocorax, 134
Oriole, Baltimore, 93
Orchard, 139
Ovenbird, 93

Passerculus sandwichensis, 1 39
Passerella iliaca, 1 39

Peakall, David B., Request for heronry
information, 106
peninsulae. Cardinals sinuata, 99

peregrine, Vermivora, 93, 137-138
Perrone, Michael, Jr., see Binfoid,
Laurence C., and -
Phalacrocorax auritus, 1 34
olivaceus, 134
Phalarope, Red, 97
Phalaropus fulicarius, 97
Philomachus pugnax, 103
phoeniceus, Agelaius, 59-61
Pipilo aberti, 99
platycercus, Selasphorus, 41-54
platyrhynchos, Anas, 102
Prothonotaria citrea, 95-96
Puffinus griseus, 97
pugnax , Philomachus, 103
pusilla, Spizella, 72
Wilsonia, 137
Pyrrhuloxia, 99-100
Raven, Common, 98
White-necked, 98
Redstart, American, 85, 139
Roadrunner, 139

Robert, Henry, First record of Field
Sparrow in California, 72; First record
of White-eyed Vireo in California, 94
Robin, 135
Ruff, 103

rufum, Toxostoma, 93
rufus, Selasphorus, 41-54
ruticilla, Setophaga, 85, 139
Rynchops nigra, 69-71
sandwichensis, Passerculus, 139
San Miguel, Mike, A Prothonotary Warbler
in Inyo County, California, 95-96
sasin, Selasphorus sasin, 41-54
Scott, J. Michael, Interbreeding of the
Glaucous-winged Gull and Western
Gull in the Pacific Northwest, 129-133
sedentarius, Selasphorus sasin, 41-54
Seiurus aurocapillus, 93
motacilla, 1-10, 77-92
noveboracensis, 1-10, 77-92
Selasphorus platycercus, 41-54
rufus, 41-54
sasin sasin, 41-54
s. sedentarius, 41-54
Setophaga ruticilla, 85, 139
Shearwater, Sooty, 97
sinuata, Cardinalis, 99-100
Skimmer, Black, 69-71
smithsonianus, Larus argentatus, 31
Sparrow, Field, 72
Fox, 139
Lincoln’s, 139

Savannah, 139
White-crowned, 99
Spizella pusilla, 72
spurius, Ictems, 139
Starling, 139
Stellula calliope, 41-54
Stiles, F. Gary, On the field identification
of California hummingbirds, 41-54
Sturnus vulgaris, 1 39

Suffel, Shumway, see McCaskie, Guy, and
Swift, Vaux’s, 101

Tartaglia, Judith L., see Lockner, F.
Russell, et aL

thayeri, Lams, 11-26, 28-29
Thrasher, Brown, 93
Thrush, Hermit, 135, 139
Varied, 139
Wood, 135-136
Towhee, Abert’s, 99
Toxostoma mfum, 93
Turdus migratorius, 135
U. S. Fish and Wildlife Service, Request
for Brown Pelican information, 106
varia, Mniotilta, 93
vauxi, Chaetura, 101
vegae, Lams argentatus, 31
Vermivora celata, 137
peregrina, 93, 137-138
Vireo gilvus, 137
griseus, 94
Vireo, Warbling, 137
White-eyed, 94

vocifems, Caprimulgus v., 33-36, 3740
vulgaris, Sturnus, 139
Warbler, Audubon’s, 137
Black and White, 93
Black-throated Blue, 93
Hooded, 88
Orange-crowned, 137
Prothonotary, 95-96
Tennessee, 93, 137-138
Wilson’s, 137

Waterthrush, Louisiana, 1-10, 77-92
Northern, 1-10, 77-92
Whip-poor-will, 33-36, 3740
Wilbur, Sanford R., W. Dean Carrier, and
Guy McCaskie, The Lark Bunting in
California, 73-76
Willis, Edwin O., letter, 105
Wilsonia citrina, 88
pusilla, 137

wrightii, Empidonax, 94
wymani, Lams occidentals, 1 1-26
Zenaidura macroura, 139
Zonotrichia leucophrys, 99

143