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Warning: All rights reserved. This article appeared in the Zebra Finch Society Bulletin and the NFSS Bulletin. Anyone wishing to reproduce this article for another bulletin, newsletter, article, journal, CD, or any other public forum needs express written consent of the NFSS and of the author michael@exoticfinches.com

The society finch has been cage bred for a longer time than any other finch species. Yet, until the mid 1980's there were no recorded sex-linked mutations. This seems amazing since sex-linked traits existed in so many other cage birds for so many years. But low and behold, on two different continents and at about the same time, two separate and very unique sex-linked mutations appeared in Lonchura striata. In Europe, the lovely ino or "creamino" mutation was discovered. This mutation is a single gene recessive sex-linked trait. Creamino changes the eye color to ruby red and turns the typical dark society finch into a much paler creamy color. In the chocolate background, (or European black brown) the ino mutation makes for a lovely deep creamy color with pinkish overtones. Although the gene works in combination with the color mutations "chestnut" and "fawn", it is not commonly bred into a double mutation with either chestnut or fawn since all that is accomplished is an overdilution of pigment resulting in a faded fawn color. Ino is sometimes combined with the modifying gene "gray" in a chocolate or black brown background to produce a very light gray rather than a cream color. This combination is called "grayino". The ino hens and males appear identical in color and sexing society finch inos is accomplished, as usual, by behavior rather than appearance unless the correct crosses are performed as you will see later.

The second sex-linked mutation was found in Japan. Among a group of chocolate pied birds in a pet shop, a notable Japanese breeder saw a chestnut-colored pied bird with the chestnut interrupted by patches of gray/silver sheen. The bird was purchased and was later determined to be a hen. With careful record keeping, the silvery trait was discovered to be, like creamino, a sex-linked recessive mutation. The mutation was worked into a chocolate self background for over ten years. With each generation, birds with increasing amounts of silver color were saved and paired to the darkest of chocolates. The new mutation was called the "pearl". Like the ino, it was discovered that in the pearl, a single gene controls the trait but unlike the ino the expression is extremely variable and somewhat unpredictable. It is by far the most unique pigment mutation in the society finch. It not only changes the dark chocolate color to a chestnut color but it also silverizes distinct portions of the bird classifying the mutation as a patterning gene. In modern pearls, the head is striking silver (especially impressive in crested birds), the wings and tail have a strong silver sheen, and if you are lucky the chest patch is dotted with a pearl necklace. We have noticed that with some of the better pearls (those expressing lots of silver), the hens tend to have a more washed out color with regard to the chestnut, and the silvering tends to blend into the background with less contrast. This is possibly caused by the fact that the male bird has two doses of the gene since it is sex-linked and the hen has only one dose. But this is just a thought and with time it may turn out that both sexes express the trait equally. Unlike creamino, where all inos are essentially alike, pearls are very variable ranging from hardly silver to almost completely silver. This can make for frustrating times when a nest box contains all "bad" pearls hardly distinguishable from chestnuts. But when a great one is seen in the nest box, you get goose bumps.

Pearl has been combined with the recessive gray gene to make gray pearls. These look like chestnut gray birds with a pearl silvery sheen. Several of these have been produced in Japan and a few of these have been produced in the USA. Both of us feel that the concept of this combination is more intriguing than the outcome. We both prefer a highly contrasting normal pearl to the gray pearl.

Having sex-linked color traits is a treat in a species where males and females are difficult to tell apart. By performing the correct pairing it is possible to sex babies in one specific case as will be seen later. Keep in mind that with sex-linked traits hens are either mutant or normal while males can be mutant, split, or normal.

Those with years of experience recommend not to breed creamino to creamino. Pearl to pearl can be done but eventually quality is lost. Lost quality can be regained by crossing pearls to very dark chocolates. It is important to understand the outcome of crosses using these sex-linked mutations. Remember that calculated ratios are for the "ideal" case and it would take many many offspring for the numbers to fall into place. After all, we all know human couples with three or four boys and no girls or vice versa when ideally it should be one to one.

The following pairings with their results are presented (note: the word 'pearl' can replace 'ino - they work the same since both are recessive sex-linked mutations).

1) normal hen x normal cock yields - 1:1 normal hens: normal cocks

2) normal hen x split to ino cock yields - 1:1:1:1 normal hens: ino hens: normal cocks: split to ino cocks

The above pairing results in some ino hens even though both parents look at face value to be normal chocolates. However, the male offspring will all look normal but half will actually be splits making it impossible to tell which of the males is split without doing more pairings to ino hens.

3) normal hen x ino cock yields - 1:1 ino hens and split to ino cocks

The above pairing let's you sex the all babies in the nest box and results in only one type of male!

4) ino hen x normal cock yields - 1:1 normal hens: split to ino cocks

5) ino hen x split to ino cock yields - 1:1:1:1 normal hens: ino hens: split to ino cocks: ino cocks

Just a few years ago there would have been no discussion in the society finch community in the USA about sex-linked traits. But then came the recent importations from Europe (Bob Rittmann) and Japan (Michael Marcotrigiano, Garrie Landry, Shempei Taniguchi). Now we are having a ball doing the pairings and obtaining beautiful offspring. Gee, I wonder what an ino pearl would look like?

Note: This article was written while MM was visiting GPL for Mardi Gras at an hour when only the insane are awake. We are in no way responsible for its contents since we were waited down by fried food and Mardi Gras beads and had been drinking tall glasses of fermented plant products.

For pictures of inos and pearls see our web pages at exoticfinches.com and societyfinches.com

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