until some day, for each bird, is discovered a happy solution that can
stand the great and final tests:—Does it describe the bird? Is it short
and pat? Is it a monosyllable? Or, if more than one syllable, is the
accent on the first? Is it different from other names? Is it easily
said? Does it tie up the bird with existing ideas? Can it be used in
writing verse? Does it win the popular attention and put both the bird
and name in the memories of the children and of the farmers? If it
does all these, it will have back of it all the power of the genius
of English to fix it, make it nation-wide and carry with it clear
knowledge of the bird.
This, it seems to me, is one of the greatest needs for the spread of
bird knowledge in America today.
THE REALITY OF BIRD SPECIES.
BY LEVERETT MILLS LOOMIS.
In 1858, in volume IX of the ‘Reports of Explorations and Surveys ...
from the Mississippi River to the Pacific Ocean,’ _Ammodromus samuelis_
Baird and _Melospiza fallax_ Baird appear as full-fledged species.
In 1874, in ‘A History of North American Birds,’ Land Birds, volume
II, these so-called species are reduced in rank, being designated
respectively _Melospiza melodia_, var. _samuelis_, Baird and _Melospiza
melodia_, var. _fallax_, Baird. In 1886, in the first edition of the A.
O. U. ‘Check-List,’ these names are altered, in accordance with earlier
lists by Mr. Ridgway and Dr. Coues, to _Melospiza fasciata samuelis_
(Baird) and _Melospiza fasciata fallax_ (Baird), pure trinomials and
the term subspecies having come into vogue. In 1910, in the third
edition of the A. O. U. ‘Check-List,’ the two names are amended to
_Melospiza melodia samuelis_ (Baird) and _Melospiza melodia fallax_
(Baird).
Owing to his lack of knowledge of geographic variation, Professor
Baird gave to each of these geographic variations of the Song Sparrow
an entity which they did not possess, and this entity, having gained
a foothold in the literature, is perpetuated today in the subspecies
(‘incipient species’). As no one can foresee the future of these
variations of the Song Sparrow, it is not known whether they are the
beginnings of species or not. Nevertheless, it may be urged that bird
history repeats itself, and that the record of past events warrants
the conclusion that bird species are now in process of evolution
through geographic variation. Theorize as we may, the fact remains
that we do not know what part geographic variation or other agencies
played, or did not play, in the origin of existing bird species, the
_modus operandi_ of the evolution being unknown. But we do know that
geographic variation is one of the common variations occurring within
the bounds of a bird species of today, and that it is not the only
variation in which geography is a factor.
Independent of individualism, age, sex, season, or climatic conditions,
there exists a type of variation known as dichromatism, which perhaps
originated in mutations. It is well exemplified in the Jaegers,
Albatrosses and Petrels, Herons, Hawks, and Owls. In some species there
is a difference in the geographic range of the phases, but it does not
correlate with environment as in geographic variation. Instances to the
point are found in the Wedge-tailed Shearwater, Red-tailed Hawk, and
Screech Owl.
More than thirty years ago, when our knowledge of variation was far
less than it is now, Dr. Stejneger had the discernment to interpret
_Colaptes auratus_ (Linnæus), _Colaptes cafer_ (Gmelin), and _Colaptes
hybridus_ (Baird) to be dichromatic or trichromatic phases of one
species, and not two species that hybridize on a gigantic scale.[21]
None of the characteristics of dichromatism are wanting in these
extremes and intermediates. They are similar in general character to
the extremes and intermediates of well-known dichromatic species, of
the Wedge-tailed Shearwater, Neglected Petrel, and Rough-legged Hawk
for example. They are not individual and are not dependent upon age,
sex, season, or environmental conditions. Moreover, intermediates crop
out sporadically in the Eastern States, where the _auratus_ phase is
dominant. It is well to bear in mind that these variations of the
Flicker are not greater than certain other normal variations; as the
age variation of the Western Gull, the sexual variation of Williamson’s
Sapsucker, the seasonal variation of the Marbled Murrelet, and the
dichromatic variation of the Parasitic Jaeger.
The question naturally arises, whether dichromatism has often been
misinterpreted and made the basis of apocryphal species and their
supposed hybridization on a grand scale. In the alleged Junco species,
for instance, possibly dichromatism or polychromatism, originating in
mutations, obtains along with geographic variation.
_Vermivora leucobronchialis_ (Brewster) and _Vermivora lawrencei_
(Herrick) are not overlooked in this discussion. The evidence thus far
presented tends to prove that they are hybrids between two species
rather than intermediates of one dichromatic species.[22] Be this as
it may, hybridization between unquestionable species of birds is an
abnormal and relatively rare occurrence.
To affirm that bird species are concepts, is to ignore the facts in
the case. _Ammodromus samuelis_ Baird and _Melospiza fallax_ Baird are
concepts, but _Melospiza melodia_ with all its geographic variations
is a reality. It is absolutely separated from _Melospiza lincolni_ and
_Melospiza georgiana_ and all other existing bird species. _Colaptes
auratus_ is likewise a reality. In spite of its great dichromatic
variation, it does not intergrade with any other woodpecker. It is
confidently stated that the great majority of the A. O. U. ‘Check-List’
species are also realities, and the remainder time-honored concepts
based on inconstant variations, like _Fulmarus rodgersi_ Cassin, which
is merely an extreme white phase of _Fulmarus glacialis_ (Linnæus).[23]
In a word, absence of intergradation among birds results in a definite
entity, the existing bird species.
FOOTNOTES:
[21] Riverside Nat. Hist., Vol. IV, pp. 8, 9.
[22] Cf. Faxon, Mem. Mus. Comp. Zool., Vol. XL, 1911., pp. 57-78.
[23] Cf. Proc. Calif. Acad. Sci., 4th Ser., Vol. II, Pt. II, 1918, p.
88.
GEOGRAPHICAL VARIATION IN THE BLACK-THROATED LOONS.
BY A. C. BENT.
Dr. Jonathan Dwight’s interesting paper in ‘The Auk’ for April, 1918,
describing a new species of Loon from northeastern Siberia, has opened
up a subject to which I have given considerable study without having
been able to come to any satisfactory conclusion. After examining
directly or indirectly some seventy specimens of Black-throated Loons,
including the entire series in several of the largest collections in
this country, I came to the conclusion that the necessary material was
still lacking to settle satisfactorily the true status of this group.
I have long recognized the existence of a large, Green-throated Loon
in the Bering Sea region; but I have postponed publishing anything on
it until I could obtain enough breeding birds from somewhere in that
region, to establish a more or less definite breeding range in which
a more or less constant form is to be found. Now that Dr. Dwight has
seen fit to open up the subject, I feel called upon to publish what
incomplete data I have on the whole group.
It seems to me that there are only two alternative theories into which
the known facts may be made to fit. The first and most likely theory
is that there is but one circumpolar species, divided into three,
or possibly four, subspecies, as hereinafter designated. To support
this theory we need more material from Siberia and eastern Europe to
show complete intergradation between the two intermediate subspecies,
_arctica_ and _suschkini_, though what material we have seems to
indicate that such intergradation exists. An argument against this
theory is the fact that the two extreme subspecies, _viridigularis_ and
_pacifica_, apparently breed side by side in northeastern Siberia and
northwestern Alaska.
The second theory is that there are two species, _arctica_ in Europe,
with _viridigularis_ as a Siberian subspecies occupying a subarctic
area, and _pacifica_ in North America, with _suschkini_ as a Siberian
subspecies occupying the Arctic coast. This theory would explain the
breeding of the two extreme forms in the same or in contiguous areas;
but it would be upset by the discovery of more complete intergradation,
unless such intergrades could be regarded as hybrids. A final choice
between these two theories cannot be made until more material is
available showing the distribution and relationships of the forms to be
found in Siberia, a vast and little known region.
I will now attempt to state, roughly and in general terms, the main
known facts in this complicated case and let the reader judge for
himself how they fit in with the above theories. There are apparently
three or four fairly well marked subspecies of Black-throated Loons, as
follows:—
1. _Gavia arctica pacifica_ (Lawrence), the smallest of all, in which
the hind neck or nape is much lighter gray than the crown or forehead,
nearly white in some cases, the black throat patch terminates below
in a straight line and the metallic reflections of this patch almost
always appear purplish in any light. This form occupies a breeding area
which includes the whole of northern North America (which need not be
more definitely outlined here), the Arctic Islands west of Greenland
and the Arctic coast of Siberia for our unknown distance westward.
2. _Gavia arctica suschkini_ (Sarudny), intermediate in size between
_arctica_ and _pacifica_, but nearer the latter, in which the colors
are nearly as in _pacifica_, but with a slight tendency towards
_arctica_. This form probably has a breeding range somewhere on the
northern coast of Asia, but is known only from specimens taken in
winter or on migrations in the Ural and Turkestan regions.
3. _Gavia arctica arctica_ (Linnæus), intermediate in size, but nearer
_viridigularis_ than _pacifica_, in which the crown and nape are
uniform dark gray, the black throat patch terminates below in a point
and the reflections of this patch appear either purplish when held away
from the light and greenish when held towards it, or wholly purplish in
any light, with considerable individual variation. This form inhabits
northern Europe, and northern Asia for an unknown distance eastward and
southward in Siberia.
4. _Gavia arctica viridigularis_ (Dwight), the largest of all, but
intergrading perfectly with _arctica_, in which the crown and nape are
colored as in _arctica_, the black throat patch terminates below in
a point and the reflections of the throat are usually more greenish
than in the others. I have yet to see a specimen in which more or less
purple reflections could not be found. Even Dr. Dwight’s type shows
“slight purplish tints.” This form, if it is a good subspecies, has
no well defined habitat; but what specimens I have seen would seem to
indicate a breeding range on both sides of Bering Sea, which may extend
for a considerable distance westward into the interior of Siberia.
The above arrangement may appear satisfactory to the casual observer,
but the trouble with it is that all of the above characters,
particularly those on which Dr. Dwight bases his new species, are
decidedly variable and inconstant. Size is the most satisfactory
character but even this shows intergradation or overlapping and greater
individual variation in each group than the differences in averages
between the groups. The measurements, in inches, of the four forms,
which I have taken or had sent to me, are as follows:—
_Gavia arctica pacifica_ (Lawrence)
12 males from North America, east of the Mackenzie River,
average, bill 2.14 wing 11.65
largest, " 2.32 " 12.42
smallest, " 1.93 " 10.80
13 males from North America, west of the Mackenzie River,
average, bill 2.06 wing 11.66
largest, " 2.20 " 12.50
smallest, " 1.87 " 10.50
_Gavia arctica suschkini_ (Sarudny)
5 males from Turkestan,
average, bill 2.35 wing 12.40
largest, " 2.60 " 13.35
smallest, " 2.20 " 11.80
_Gavia arctica arctica_ (Linnæus)
6 males from Europe,
average, bill 2.44 wing 12.24
largest, " 2.62 " 12.75
smallest, " 2.30 " 12.
_Gavia arctica viridigularis_ (Dwight)
4 males from Bering Sea region,
average, bill 2.63 wing 12.69
largest, " 2.87 " 13.
smallest, " 2.50 " 12.
The other characters are equally confusing. The nape is lightest and
almost constantly so in North American _pacifica_; it is darkest in
_viridigularis_ and more or less intermediate in many specimens of the
other two forms.
The black throat patch terminates below in a straight line almost
invariably in North American _pacifica_; I have seen but one exception
to this rule; but in Siberian _pacifica_ this character is less
constant. In _viridigularis_ this patch terminates below in a decided
point, in all specimens that I have seen. In European _arctica_ about
half of the specimens I have seen have the patch decidedly pointed
below and the others have it nearly straight or only slightly pointed.
The colored reflections of the black throat-patch are the most variable
and inconstant of all the characters. In _viridigularis_ three of the
specimens examined show mainly greenish colors but even these show
some signs of purple; and in one, a bird in my own collection, the
colors are about equally divided. In European _arctica_ about half of
the specimens show mainly purplish reflections, while fully half show
both purplish and greenish. In North American _pacifica_ the purplish
reflections predominate, but five specimens out of twenty-two show
more or less greenish in certain lights. Mr. Waldron DeWitt Miller,
in sending me descriptions of Pacific Loons in the American Museum,
used the following terms in designating the colors of the throats;
greenish-blue, bluish-green, dark greenish-blue, violaceous and dark
violet. It can be easily seen from the above that the colors are very
variable.
Dr. Dwight says, in his diagnosis of _viridigularis_:—“The green
coloration of the throat is the essential character that sets this
species apart from _arctica_ and its races, which all have purple
throats.” In the light of the facts stated above this “essential
character” disappears and his new species must be reduced to the rank
of a subspecies at least. Even a subspecies must prove to be fairly
constant in a more or less definite range. The range of _viridigularis_
is very imperfectly known; the four specimens, referable to this form,
that I have seen were taken at Nijni Kolymsk, Siberia, St. George
Island, Bering Sea, Nome and Saint Michael, Alaska; Dr. Dwight’s
specimens all came from northeastern Siberia. The Nijni Kolymsk bird,
referred to above, is somewhat intermediate between _viridigularis_ and
_arctica_; if it had been taken in Europe it would probably be referred
to the latter. I also have a perfectly typical _pacifica_ from the
Kolyma River, Siberia.
I have seen birds from Victoria, B. C., from Finland and from Norway
which closely approach this new form, _viridigularis_, in size and
color characters. If we had a larger series of _arctica_ from Europe
and Asia available for comparison, we could perhaps match these birds
exactly and we could certainly show, if I have not already demonstrated
it, that _viridigularis_ is merely a subspecies of _arctica_. To use
Dr. Dwight’s own terms, the green throat seems to be a quantitative
rather than a qualitative character.
REASONS FOR DISCARDING A PROPOSED RACE OF THE GLAUCOUS GULL
(_LARUS HYPERBOREUS_).
BY JONATHAN DWIGHT, M. D.
In discussing the moults and plumages of the Glaucous Gull, a dozen
years ago I took occasion to bury “_Larus barrovianus_” among the
synonyms of _Larus hyperboreus_ (then known as _glaucus_) because
the alleged characters seemed to me to afford insufficient grounds
for recognizing even a subspecies (Auk, XXIII, 1906, p. 29). Later,
in the 1910 edition of the A. O. U. ‘Check-List,’ the Committee on
Nomenclature and Classification adopted my view of the case and
discarded “_barrovianus_”; but recently Dr. H. C. Oberholser has
seen fit to dig it up and it is revived, somewhat impressively, as a
subspecies of _hyperboreus_ (Auk, XXXV, 1918, p. 472).
If it were not for certain aspects of the matter I would merely
reaffirm my convictions of 1906; for it is a question whether Dr.
Oberholser has added anything new to the original claims made by the
describer, Mr. R. Ridgway (Auk, III, 1886, p. 330). This does not seem
to be the case, for his diagnosis is virtually a restatement of Mr.
Ridgway’s, except that a supposed character of the bill is discarded
on evidence I submitted in 1906. My measurements had shown that this
character, namely, “depth through the angle never less and usually
decidedly greater than through the base,” was not diagnostic, but this
was not my only “evident reason” then for rejecting “_barrovianus_”
as Dr. Oberholser now wrongly assumes. What I said was that this form
“is scarcely 3% smaller [than _glaucus_] in size and 4% smaller in
bill” and furthermore, I said; “It is true that the largest specimens
of _barrovianus_ never quite reach the dimensions of the largest
_glaucus_, but overlapping of size is so considerable even when careful
comparison of sexes is made that without first reading the labels
one cannot, except in a very few cases, tell whether a bird is from
Greenland or Alaska. The variation in the size and shape of the bill in
gulls is very great and a few millimeters difference in wings that are
as long as one’s arm is hardly ground on which to rest a subspecies,
much less a full species.”
These conclusions may be contrasted with Dr. Oberholser’s recent
diagnosis which reads, “Similar to _Larus hyperboreus hyperboreus_, but
smaller, the bill particularly so and relatively as well as actually
more slender; mantle decidedly darker; and the line of demarcation
between the white tips to the primaries and the pale grayish basal
portions usually more evident.” I would here call attention to the
fact that the “line of demarcation” is not a distinct character but
a corollary of the preceding, for the color of the mantle in the
Glaucous Gull regularly runs over, so to speak, into the wings, and a
darker mantle would mean darker bases of the primaries and therefore
greater contrast as a matter of course. Consequently, in the final
analysis there are two characters and only two on which “_barrovianus_”
rests,—(1) darker mantle and (2) smaller size, especially of the
bill. I will invite attention to a new estimate of the value of these
characters.
[Illustration: Fig. 1. Diagrams showing relative measurements in
millimeters of 31 adult specimens of _Larus hyperboreus_ and its
alleged race. Top line shows actual length in largest birds, middle
line shows average, and bottom line shows smallest of the series.]
1. As for the color of the mantle, which Mr. Ridgway calls “somewhat”
and Dr. Oberholser “decidedly” darker, I can only say that my series
fails to support either of these statements. I find that if comparison
of _like stages_ of plumage be made, birds from Greenland are quite as
dark as Alaska specimens and conversely Alaska birds are as pale as
those from Greenland. It is, perhaps, a matter of more than passing
interest that the majority of adult Greenland birds in the collections
I have seen are in worn faded plumage while most of the Alaska material
is in fresh dark plumage. One might easily get the impression that the
darker birds represent a race unless due allowance is made.
It may not be generally known that the adult Glaucous Gull moults twice
in the year, a complete postnuptial moult beginning toward the last of
July and extending over nearly two months and a prenuptial in March and
April which involves most of the body feathers but not the wings nor
the tail. Between moults the mantle fades and looks even paler than
it is in color because of the worn and whitened feather edges. There
is some individual variation in the depth of color in freshly moulted
specimens, whether from Greenland or Alaska, but both may be equally
dark and they may become equally pale after the lapse of a few months.
I have examined birds taken nearly every month in the year and I am at
a loss to understand how Dr. Oberholser finds a “decidedly darker” race
unless he has unwittingly compared birds of unlike stages of plumage.
2. As for size, this is a question of relative dimensions that permits
some latitude of opinion, so that a new presentation of the facts seems
desirable.
My early table of measurements (Auk, XXIII, 1906, p. 28) based on 31
adults (14 of them males and 17 females) is accepted by Dr. Oberholser
“except for dimensions of the bill which have been remeasured for
the present use.” I have reproduced all of these measurements by the
graphic method (Fig. 1) and anyone may see, almost at a glance, what
the variations of size in the Glaucous Gull actually are. The diagrams
are drawn to scale, the upper horizontal line representing the actual
size of the largest specimens, males and females, the middle line
the mean or average size and the lower line the smallest specimens.
The oblique solid lines represent _hyperboreus_, the broken lines
“_barrovianus_” and the dotted lines Dr. Oberholser’s remeasurements of
the bill. His “depth of bill” for “_barrovianus_” is the same as mine
and therefore cannot be separately plotted. He does not tell us from
what series he made the remeasurements that do not tally with mine,
but the figures suggest that it may have been a small one and with an
unusual proportion of very large and very small birds, possibly wrongly
sexed in some cases.
The original series that I measured was composed of breeding birds
from Greenland and from Alaska which formed a small part of the 200
specimens I had then gathered together for comparison. Although they
are now widely scattered, some of them (as well as new specimens)
are still either in my collection or in that of the American Museum
of Natural History. A reëxamination and remeasurement of them (68
in all, 39 being adults) confirms to a surprising degree my earlier
measurements and conclusions. Individual variation is greater than the
supposed subspecific values and the overlapping of size is marked.
Birds as large as these Gulls, it must be remembered, may not be
measured with unfailing accuracy, especially when different persons
attempt it, for specimens are often greatly worn, the wings or tail
are sometimes not quite grown and often the feathers are bent and
broken. It is not unusual to find a variation of five to ten or more
millimeters between the right and left wing of the same bird, due to
the make-up of the skin, while tarsi and toes of opposite legs may be
bent very much out of shape in drying. Where such variation exists, one
may to advantage measure each wing or foot separately and strike an
average as I have done in many cases.
Turning finally to the bill, I would call attention to the sketch (Fig.
2) which shows the average adult bill of the male of _hyperboreus_
contrasted with that of “_barrovianus_.” When one realizes that the
variation in the bills of all female gulls is much greater than that
of the males and that young birds only very slowly acquire adult
dimensions, it becomes evident that “_barrovianus_” is _not_ “very
readily recognizable by its usually smaller size and particularly
smaller bill.” One may guess cleverly that large birds belong to one
race and small ones to another, but without reference to the labels the
guesses may be astray by a continent’s width.
[Illustration: Fig. 2. Bill of average _Larus hyperboreus_, male, life
size, drawn to scale. The broken line shows the bill of the alleged
race.]