NOTES ON THE HYBRIDS BETWEEN THE CANARY AND TWO AMERICAN FINCHES

NOTES ON THE HYBRIDS BETWEEN THE CANARY AND TWO AMERICAN FINCHES

0. E. PLATH

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.

322

No. 645] HYBRIDS OF THE CANARY 323

(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.”

324

THE AMERICAN NATURALIST

[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:

TABLE I

Cross

No.

Year

9 &

No.

of

Offspring

1

2

1919
1920
1920

Yellow canary X California linnet

Yellow canary 4 X Willow goldfinch

Willow goldfinch X Arkansas goldfinch

3

■A

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.

No. 645] HYBBIDS OF THE CANARY 325

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.

326 THE AMERICAN NATURALIST [Vol.LVI

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.

No. 645] HYJ3BIDS OF THE CANARY 327

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.

Incubating and Hatching Eggs

Incubating and Hatching Eggs

This article has interesting information on storing eggs.

It’s often suggested to take the eggs from the sitting hen as they are laid and then replace them with artificial ones. The old advice is to store the eggs in seed and to turn them each day. Once all the eggs are produced, the artificial eggs are removed from the nest and the real ones returned. The idea is to have all the chicks hatch on the same day and so keep the last one or two from being runts.

I did this with my first few pair of canaries. Once I had more birds than that I stopped, as it just became too much of a chore. Honestly, I really didn’t notice any difference in the number of healthy chicks. As far as I know, none of the canary breeders I’ve met take eggs from the nest to regulate the hatching.

As for placing the eggs in seed, a moment’s thought reveals that not to be for the best. Seed absorbs moisture and that’s not good for the egg. Also, seed often has some dust and that too is a negative. The article below suggests using egg flats. These are made of cardboard.

The article states that eggs stored under 7 days don’t need to be turned.

Perhaps to maximize the production of rare canary varieties, egg storage might be a good idea? Here, more common hens can be used as fosters. This way, the more valuable birds will produce extra clutches.

Canary eggs hatched in an incubator

A bird farm in Formosa uses an incubator to hatch canary eggs. The chicks are put back into the nest to be raised by the adult.

Maintaining zebra finches

These notes are meant to complement
Proper Care, Husbandry, and Breeding Guide lines for the Zebra Finch, Taeniopygia guttata
Christopher R. Olson, Morgan Wirthlin, Peter V. Lovell, and Claudio V. Mello

A cage 18” X 18” X 24” is good for one breeding pair of zebra finches or a small group of immature birds. If space is at a premium, an 18” X 18”X 18” cage will suffice. A flight cage or aviary does reduce labor, but in a colony birds might get less exercise than when kept in an individual cage. Those housed privately can fly back and forth all day without any worries over aggression. In a flight, birds often stick to one spot so to defend their little “turf.” Pecking order pressures inevitably wear down the low little gals and guys on the totem pole. For those housed in a flight, reproductive odds will be tilted in favor of the winners of gang warfare. These birds are not necessarily suited for other purpose, like being good parents or easy to handle. Some other drawbacks of group housing are that there’s no way to determine parentage and all the birds need to be disturbed whenever one is to be handled. Do place multiple feeding and watering stations in a flight. This way, if a bully decides to monopolize one source of food or water, the rest of the flock won’t suffer.
. . .
Click HERE to read the complete article at SongBirdScience.com

Bird seed formulas

These are a vendor’s bird seed formulas

A scoop indicates a quantity of about a quart.

Nestling food
10 lbs meat and bone meal
20 lbs soy bean meal
10 lbs corn meal
5 lbs dry egg
4 scoops carrot granules
3 scoops celery granules
3 scoops spinach flakes
5 lbs white canary
1 scoop red millet
2 scoops poppy
3 scoops thistle
1 scoop dicalcium phosphate

Finch mix
25 lbs Siberian red millet
25 proso millet
25 canary
25 golden german millet
5 scoops corn meal
2 scoops soy bean meal
1 scoop thistle
2 scoops red millet
1 scoop hemp
1 scoop shelled sun
1 scoop flax
1 scoop dry egg
2 scoops oat groats
2 scoops cut oats
1 scoop sand
1 scoop oyster shell
1 scoop carrot granules
1 scoop spinach flakes
1 scoop dry celery
1 scoop coarse corn meal

Sunflower Parrot
50 lbs Jumbo sunflower seed
4 scoops Safflower
1 scoop Austrian peas
2 scoop pumpkin
2 scoop chili peppers
4 scoops peanut
2 scoops dry celery
1 scoop dry carrot
3 scoop wheat
3 scoop whole corn

Safflower parrot
50 lbs safflower
1 scoop peas
2 scoop dry celery
1 scoop dry carrot
3 scoops corn
2 scoops wheat
2 scoops chili peppers
2 scoops pumpkin
4 scoops peanuts

Cockatiel
50 lbs white canary
50 lbs white millet
5 scoops cracked corn
1 scoop buckwheat
1 scoop flax
4 scoops safflower
2 scoops groats
2 scoops red millet
1 scoop hemp
1 scoop thistle
12 scoops sunflower
5 scoops wheat
1 scoop dry carrot
1 scoop spinach flakes
1 scoop celery flake
1 scoop oyster shell
1 scoop sand

Parakeet and other Small Hookbill
50 lbs. White canary
50 lbs white millet
1 scoop dry egg
2 scoops red millet
1 scoop thistle
1 scoop hemp
1 scoops safflower
5 scoops wheat
5 scoops corn meal
2 scoops soy bean meal
1 scoop shelled sunflower
1 scoop flax
2 scoops oat groats
2 scoops steel cut oats
6 scoops golden german millet
1 scoop buckwheat
1 scoop carrot granules
1 scoop spinach flakes
1 scoop celery granules
1 scoop sand
1 scoop oyster shell
1 scoop buckwheat
1 scoop cracked corn

Canary Mix
50 lbs white canary
25 lbs rape
6 scoops golden german millet
1 scoop dry egg
2 scoops groats
2 scoops steel cut oats
1 scoop flax
2 scoops red millet
1 scoop hemp
4 scoops sesame
1 scoop poppy
1 scoop thistle
1 scoop coarse corn meal
2 scoops corn meal
1 scoop soybean meal
1 scoop dry celery
1 scoop dry spinach
1 scoop dry carrot
1 scoop shelled sunflower
4 scoop white millet

Belmont Keet
100 lbs white millet
50 lbs white canary
4 scoops oat groats
2 scoops red millet

Belmont Vitalizer
4 lbs Belmont Keet
2 lbs canary song
2 lbs groats
1 lb nestling

Soak seed
50 lbs rape
25 lbs w millet
25 white canary
2 scoops cracked corn
4 scoops wheat
1 scoop safflower
1 scoop buckwheat
1 scoop hemp
1 scoop poppy
1 scoop thistle
2 scoops red millet

Canary Song and Siskin
25 lbs thistle
5 scoops golden german millet
1 scoop hemp
1 scoop poppy
1 scoop flax
4 scoops sesame
3 scoops corn meal
2 scoops soybean meal
1 scoop carrot granules
1 scoop celery
1 scoop spinach flakes
1 scoop dry egg

Grit
150 lbs livestock sand
50 lbs fine oyster shell
1 scoop trace mineral salt
1 scoop charcoal

Dry Lori Diet
6 parts – Complete pancake mix
1 part – Gerber Rice Baby cereal
1 part – Confectioners’ sugar
1 part – Corn meal
1 part – Pollen (powdered)

Lories and Lorikeets

LIKE A RAINBOW

The many lories and lorikeets, with their striking colors, have long fascinated bird lovers. These birds possess unbounded energy. Constantly at play, they seem very much like feathered monkeys.

Seed or mynah bird pellets should not be fed. This sort of diet will eventually kill these special parrots. In nature, lories and lorikeets consume nectar and pollen from flowers. Fruits, greens, and insects are also included in the diet.

Since lories and lorikeets have such unusual dietary needs, for years they were not popular as pets. Now complete diets are available that simplify caring for them. A mix is sold that, added to water, provides complete nutrition. Powdered diets now are also prepared for lories. These are designed to be fed dry, with water available in a separate dish. The dry diets have the added advantage of making the bird’s droppings more solid. When given a liquid and fruit diet, these parrots will soil the area around their cage. With the powders, cleaning is not as much of a chore.

Soaked monkey chow is a terrible food. Monkey biscuit develops a high bacteria count as soon as it is moistened. This even takes place in the refrigerator. Many birds have been poisoned by rancid food.

Lories and lorikeets often enjoy mealworms. Only about five a day should be fed.

As these birds are bathing beauties, give them an opportunity to wash every day. A large ceramic dog dish makes a very good tub. The bird will jump in and splash about in obvious enjoyment. Remove the dish when the birds are done, so they don’t drink the dirty water.

Lories and lorikeets birds have very shrill voices. Nothing changes this fact. Do give the noise factor careful consideration before buying one. For a pet, only a hand raised bird will do. Wild caught Lories and Lorikeets, not only don’t become friendly, but will frequently attack humans. Their razor sharp beaks deliver especially painful bites.

Genetic variation and differentiation in captive and wild zebra finches (Taeniopygia guttata)

Genetic variation and differentiation in captive and wild zebra finches (Taeniopygia guttata).
Forstmeier W1, Segelbacher G, Mueller JC, Kempenaers B.

Abstract
The zebra finch (Taeniopygia guttata) is a small Australian grassland songbird that has been domesticated over the past two centuries. Because it is easy to breed in captivity, it has become a widely used study organism, especially in behavioural research. Most work has been conducted on domesticated populations maintained at numerous laboratories in Europe and North America. However, little is known about the extent to which, during the process of domestication, captive populations have gone through bottlenecks in population size, leading to inbred and potentially genetically differentiated study populations. This is an important issue, because (i) behavioural studies on captive populations might suffer from artefacts arising from high levels of inbreeding or lack of genetic variation in such populations, and (ii) it may hamper the comparability of research findings. To address this issue, we genotyped 1000 zebra finches from 18 captive and two wild populations at 10 highly variable microsatellite loci. We found that all captive populations have lost some of the genetic variability present in the wild, but there is no evidence that they have gone through a severe bottleneck, as the average captive population still showed a mean of 11.7 alleles per locus, compared to a mean of 19.3 alleles/locus for wild zebra finches. We found significant differentiation between the captive populations (F(ST) = 0.062). Patterns of genetic similarity closely match geographical relationships, so the most pronounced differences occur between the three continents: Australia, North America, and Europe. By providing a tree of the genetic similarity of the different captive populations, we hope to contribute to a better understanding of variation in research findings obtained by different laboratories.

Click HERE for the complete article.

Quick and healthy meals for small birds

By using a blender on a low setting, I grind shelled almonds, walnuts, cashews or brazil nuts. I mix the resulting meal with whole grain bread crumbs to make a nutritious meal for small birds.

I lightly toast a slice of whole grain bread and make the crumbs by grinding in the blender. This is the same bread that I eat. Each week, I buy a variety of kinds and brands.

You can grind firm tofu and mix that with whole wheat bread crumbs, too.

Birds like cooked brown rice (allowed to cool) with a little salt and olive oil. I alternate by every so often adding a bit of pancake syrup to the rice instead of the salt and oil.

The importance of color in Zebra Finches used in birdsong research

Dr. Cheryl F. Harding is a researcher in the Hunter College Department of Psychology notes the importance of color in Zebra Finches used in birdsong research.

In one study, the wild-type gray zebra finch did well, while other colors did not. Dr. Harding states that “It has been shown for rats that the fawn-hooded rats (light brown and white instead of black and white) have a very different serotonin system. We never looked into whether that was the problem with tan finches, but it seems possible. In addition, white birds’ visual connections are quite different from those of grays. So when you use multi-colored finches in your studies, you are adding a lot of variability. . . . In addition, we saw many behavioral differences between males with different plumage colors. In the end, we only used grays.”