Massachusetts Institute of Technology, Cambridge, Mass.

Perhaps no animal has been so often crossed with other
species, and even g-enera, as the domesticated canary
(Serinus canarius). Darwin (1885, I, p. 311) speaks of
“nine or ten” such crosses, but many more have un-
doubtedly been made. The hybrids resulting from these
crosses are usually, if not always, infertile, and hence
are popularly known as “mules.” In almost all of these
crosses the domesticated canary serves as the female and
the wild finch as the male, but bird fanciers occasionally
succeed in making- the reverse cross. The wild species
which is most commonly used for this “mule breeding”
is the European goldfinch, Carduelis carduelis Linnaeus. 1

This fringillid is one of the handsomest finches in ex-
istence, the plumage of the adults of both sexes being
made up of a beautiful combination of black, red, white,
yellow, and brown patches. The hybrids which result
when a yellow, or nearly yellow, canary is crossed with
this finch are chiefly interesting for two reasons: (1)
because they exhibit an apparently endless chain of
variability in coloration, and (2) because their plumage,
if dark, is conspicuously streaked, a character which is
lacking (as far as external appearance is concerned) in
both the yellow canary and the European goldfinch.

Concerning the first of these two points valuable data
have been published by Bechstein (1795), Hunefeld
(1864), Blakston (1880?), Klatt (1901), Davenport

i According to Chapman (1916, p. 383), this finch was introduced into
the United States at Hoboken, N. J. (in 1878), and Boston, and probably
still is a resident near both of these places.



(1908), and Gralloway (1909). According to these au-
thors, the hybrids between the yellow canary and the
European goldfinch may be: (a) completely dark, (b)
mottled (spotted), exhibiting an apparently endless
variation in color pattern, or (c) entirely white or yellow
(very rarely). 2

The streaking in the dark plumage of canary-Euro-
pean goldfinch hybrids has been variously explained as :
(a) “derived from the original wild canary” (Darwin,
1885, II, p. 15); (b) as reversion to the Serin finch,
Serinus hortulanus Koch (Klatt, 1901, p. 508) ; and (c)
as resulting from the latent streaking (visible in the
“green” variety of the domesticated canary) factor of
the yellow canary, plus the color factor of the European
goldfinch (Davenport, 1908, p. 20).

In 1914 the writer made several attempts to cross the
domesticated canary with some of our native American
finches, and some of the latter among themselves, ‘ since
such crosses, if made, seem to have never been recorded.
None of these experiments were successful. The work
was again taken up in the fall of 1918, and this second
attempt yielded several hybrids in 1919 and 1920. For
these latter experiments the writer had at his disposal
22 wild finches belonging to the following species : Ar-
kansas goldfinch (Astragalinus psaltria hesperophilus
Oberholser), willow goldfinch (Astragalinus tristis sali-
camans [Grinnell]), 3 California linnet (Carpodacus
mexicanus frontalis [Say]), and California purple finch
(Carpodacus purpureus calif ornicus Baird). Of these
22 wild finches, 5 were reared from eggs placed under

2 Galloway (1909, p. 4), who lias probably reared more canary-finch hy-
brids than any other breeder, reports the following proportions of self-
colored to variegated (mottled) individuals in the case of canary-European
gold-finch hybrids: (1) dark plumage (with no white or clear feathers), 172;
(2) slightly variegated (a few small white or clear spots in an otherwise
dark plumage), 74; (3) variegated (1/4 to 1/2 clear), 75; (4) lightly
variegated (1/2 clear to small ticks of dark in a,n otherwise clear plumage),
19; and (5) completely clear (total absence of dark feathers), 0.

3 A western sub-species of the American goldfinch (Astragalinus tristis
tristis Linnasus), popularly known as the “wild canary.”



[Vol. LVI

canary females and the remaining 17 were trapped
shortly before the breeding season. It is chiefly due to
this second fact that the number of hybrids obtained
was not larger. All of the experiments were carried out
in separate breeding cages. The matings which yielded
results were the following:





9 &







Yellow canary X California linnet

Yellow canary 4 X Willow goldfinch

Willow goldfinch X Arkansas goldfinch



The four hybrids resulting from cross No. 3 (willow
goldfinch ? X Arkansas goldfinch J 1 ) died a few days
after hatching, and the female could not be induced to
breed for a second time. These hybrids differed from
ordinary newly-hatched finches and from the eight hy-
brids obtained from crosses No. 1 and No. 2 in having
exceedingly large abdomens, a condition which was prob-
ably due to the fact that a large quantity of yolk had not
been assimilated.

Cross No. 1 (yellow canary ? X California linnet cf)
yielded three hybrids, one of which was accidentally
killed when nine days old. During the same summer
(1919) Mrs. L. V. Irelan of Berkeley, California, like-
wise succeeded in rearing a brood (2 males and 2 fe-
males) of canary-California linnet hybrids 5 which the
writer was able to compare with his own.

Before going into detail regarding the coloration of
these canary-California linnet hybrids, it seems desir-
able to refer briefly to the plumage color of the paternal
species, the California linnet. Both sexes of this finch
are grayish-brown in color, but, when about three months
old, the male turns rose pink, orange red, or scarlet about

* The same female which was used in cross No. 1.
s In this case the mother was also completely yellow.


the head, neck, breast and rump. These colors increase
in extent and brilliancy with each molt. Males reared
and kept in captivity never develop anything but a yel-
lowish-buff color in these regions, and if a mature wild
male is confined, its red color, during the molt, likewise
becomes yellowish-buff. Both adults and young are con-
spicuously streaked, especially the latter.

The six 6 canary-California linnet hybrids were all
completely dark (self-colored) until the first molt (fall
1919), and closely resembled young California linnets,
but their plumage was less intensely dark than that of
the latter. During the fall molt of 1919 all of the hybrids
became slightly “washed” (tinged) with yellow where
the California linnet S is red (or yellowish-buff). This
yellow tinge was more conspicuous in the males than in
the females and became somewhat more pronounced
during the fall molt of 1920.

All six canary-California linnet hybrids are streaked,
like the paternal and the “green” variety of the mater-
nal species. As regards size and shape, they differ very
little from the parents, both of which are similar in these
respects. Their notes are intermediate in timbre be-
tween those of the two parental species, the males hav-
ing a more powerful song than the canary.

In the spring of 1920 the writer paired two of these
canary-California linnet hybrids. Both showed an ar-
dent desire to breed and the female exhibited consider-
able skill in nest building. The first egg was laid on May
6, and several days later a second (May 10). Both of
these eggs were only about half the size of canary or
California linnet eggs 7 and were dark-blue in color, and
not speckled, while those of both parental species are
bluish-white and speckled. Both eggs were placed under
canary females, but proved to be infertile. The male

« The hybrid which was accidentally killed was identical in coloration
with these six.

T This corroborates similar observations by Bechstein (1795, IV, p. 469)
and Blakston (1880?, p. 265), both of whom compare the eggs of canary-
finch hybrids with peas.


used in this experiment was also mated with a yellow
canary, but, despite much treading, all eggs were clear.

From cross No. 2 (yellow canary 2 X willow goldfinch
cT) five 8 hybrids were obtained. A few years before, Dr.
H. C. Bryant of the California Fish and Game Commis-
sion also succeeded in rearing a canary-willow goldfinch
hybrid, concerning which he has been kind enough to
furnish the writer with complete information.

Before considering the plumage color of these canary-
willow goldfinch hybrids, it seems again desirable to
sketch briefly that of the wild finch. Both young and
adults of the’ willow goldfinch are chiefly olive-brown
and black in color, but the sexually mature male turns
canary-yellow during the summer, with the exception of
the wings, tail and a small patch on the head, which re-
main black. Neither young nor adults show any streak-
ing. 9

The three canary-willow goldfinch hybrids reared by
the writer are (January 6th, 1921) colored as follows:
No. 1, completely dark (self-colored) ; No. 2, likewise,
except for a few yellow feathers near the left eye; No.
3, dark, with a yellow band, about 5 mm. in width, run-
ning across the head; No. 4 (reared by Dr. Bryant), 10
dark, with some white feathers on the tail. All of the
hybrids reared by the writer are conspicuously streaked,
which, according to Dr. Bryant, was also true of hybrid
No. 4.

As regards size and shape, the writer’s canary-willow
goldfinch hybrids closely resemble the canary (this was
also true of hybrid No. 4), especially in shape of beak
and length of tail, in which respects there is a consider-
able difference between the two parental species. As in

s Two of these died shortly after hatching and hence furnished no re-
liable data as regards coloration.

9 This is also true of the remaining North American members of the
genus Astragalinus, the Arkansas and the Lawrence goldfinch {Astragalinus
lawrencei Cassin), except that in the ease of the latter, the lower parts of
the young are indistinctly streaked (ef. Bailey, 1912, pp. 322, 323).

10 The canary mother of this hybrid was also completely yellow.


the case of cross No. 1 (yellow canary ? X California
linnet <$), the notes of the hybrids are intermediate in timbre between those of the parents. "We now come to the question as to how these hybrids compare with other canary-finch hybrids, and in how far they conform with Mendel's laws of inheritance. It will be noticed that in the case of the canary-California linnet hybrids, as in many mammalian crosses, dark color is completely dominant over light color, but the number of offspring (7) is too small to warrant the con- clusion that this will always prove to be the case. On the other hand, as regards the canary-willow goldfinch hybrids, there is no complete dominance of one color, the hybrids in this case showing a similar variability to that of canary-European goldfinch hybrids. Davenport (1908, p. 23) believes that the variability in plumage color of canary-finch hybrids is entirely due to the "mottling factor" of the yellow canary. He says (p. 23): It [the yellow canary] carries a mottling factor. Consequently when the yellow canary is crossed with a pigmented canary or with a finch the hybrids. are mottled. In support of this hypothesis he makes the following statement : That it is the yellow canary which contains the mottling factor and is the source of the variability of the hybrids is shown by the fact that . (1) hybrids with the green canary do not vary in this fashion, and (2) hybrids between any two species of finches— of which many are bred by fanciers — are " cast in one mold." As regards the first of these two points, it may be said that one should not expect canary-finch hybrids from a "green" (self-colored) canary to show yellow markings as frequently as when a yellow canary is used. In regard to the second point, Davenport (1908) seems to have overlooked the fact that Blakston (1880?), on whose authority this statement was probably based, states only (p. 274) that all bullfinch-goldfinch "mules" are "cast- in one mould." In fact one of Blakston 's (1880?) re- 328 THE AMERICAN NATURALIST [Vol.LVI marks clearly indicates that this is not true of the hy- brids between all species of finches, for on the next page (275) he makes the following statement concerning the "much more common" greenfinch-goldfinch hybrid: It is not a very pretty bird, . . . partaking to a considerable extent of its [the greenfinch's] dull colour, though occasionally a more bril- liant example than usual, having a good deal of the Goldfinch char- acter about it, appears on the stage. Davenport's (1908) conclusion therefore does not seem to be very well founded. Eesults published by Galloway (1909) since the ap- pearance of Davenport's (1908) paper seem to throw some light on this question. As already stated, this author (Galloway) obtained 172 dark (self-colored) to 168 variegated (mottled) offspring from his canary- European goldfinch (Carduelis carduelis) crosses. How- ever, when he used the siskin (Carduelis spinus), a closely related but darker species, he obtained nearly three times as many (36 to 13) self-colored as mottled individuals, that is, almost a 3 to 1, instead of a 1 to 1 ratio. These results, supported by those set forth in this paper, suggest that the frequency of mottling in canary-finch hybrids is not solely due to the yellow canary," but probably also depends on the coloration of the wild finch. LITERATURE CITED Bailey, F. M. 1902. Handbook of Birds of the Western United States. The River- side Press, Cambridge. Beehstein, J. M. 1795. Gemeinniitzige Naturgesehichte Deutschlands nach alien drey Reiehen. Vol. 4. Siegfried Lebreeht Crusius, Leipzig. Blakston, W. A. 18801 The Illustrated Book of Canaries and Cage-birds. Cassell, London. 11 A similar problem exists in regard to the mottled seed-coat of the F t of certain pigmented-white bean crosses. Shull (1907) suggested that it is the white, and not the pigmented bean to which the mottling is due. How- ever, Tschermak (1904, 1912) has shown that in some cases it is the pig- mented bean which is the source of the mottling, a view which was later accepted by Shull (1908, pp. 437-439). No. 645] HYBRIDS OF TEE CANARY 329 Chapman, P. M. 1916. Handbook of the Birds of Eastern North America. D. Apple- ton & Co., New York and London. Darwin, C. 1885. The Variation of Animals and Plants Under Domestication. 2 Vols. John Murray, London. Davenport, C. B. 1908. Inheritance in Canaries. Carnegie Institute of Washington, Publication No. 95. Galloway, A. R. 1909. Canary Breeding. A Partial Analysis of Records from 1891- 1909. BiometriTca, Vol. 7, pp. 1-43, 5 figs., 5 pis. Hiinefeld, H. V. 1864. Ueber Bastardzucht zwischen Stieglitz und Canarienweibchen. Der Zool. Garten, Vol. 5, pp. 139-144. Klatt, G. T. 1901. Uber den Bastard von Stieglitz und Kanarienvogel. Arch. f. Entvyickelimgsmech. d. Organismen, Vol. 12, pp. 414-453 and 471-528, 1 pi. Shull, G. H. 1907. Some Latent Characters of a White Bean. Science, Vol. 25, pp. 828-832. 1908. A New Mendelian Ratio and Several Types of Latency. Amer. Naturalist, Vol. 42, pp. 433-451. Tschermak, E. v. 1904. Weitere Kreuzungsstudien an Erbsen, Levkojen und Bohnen. Zeitschr. f. d. landw. Versuchswesen. in Osterreich, Vol. 7, pp. 533-638. (After Shull.) 1912. Bastardierungsversuche an Levkojen, Erbsen und Bohnen mit Riieksieht auf die Faktorenlehre. Zeitschr. f. induM. Abstam- mungs- mid Vererbungslehre, Vol. 7, pp. 81-234, 12 figs.

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