An Inside Look at the Humble Sexlink Chicken
Sexlinks are one of the most common types of chickens out there, sold by most big hatcheries and in many feed stores that supply chicks. Their popularity is likely because production-oriented hatchery sexlinks are known to put out huge numbers of eggs per year, and extra large eggs at that! But the term sexlink doesn’t apply only to the common red and black stars found at the feed store. There are sexlinks in many colors, from the common red and black, to blue, and even chocolate! In fact, many backyard chickeners own a type of sexlink and don’t know it, as plenty of hatcheries have bred their birds toward a less obvious sex linked trait. The truth is, the term ‘sexlink’ comes, not from any common visual trait shared among all these birds, but from the genetic mechanism behind their unique appearances!
In this article, I will discuss some of the many types of sexlinked chickens available, how they are made, and even how they got their name! Sexlinks, particularly red sexlinks, are sold under many names, a topic which I will also touch upon within this article. But first, let’s start with the basics!
What is a Sexlink?
A sexlink chicken, contrary to popular belief, is NOT a breed, but a selective crossing of two breeds. Some refer to them as ‘hybrids’, which is not incorrect, but can be a bit misleading as the word ‘hybrid’ can also be used to describe a cross between two different species, such as a cross between a chicken and a Guinea fowl (something that is not impossible… but a topic for another article ). The term ‘sexlink’ comes from the fact that at least one prominent feature of an animal’s genetic code, usually something to do with their appearance in the case of chickens, is linked to the sex of the bird as a result of this selective crossing. This works in the same way that traits in humans can be sexlinked, such as colorblindness.
Sexlinked and Autosexing: What’s the Difference?
While reading around the forum, you might find references to both sexlinks and autosexing breeds, and perhaps see the terms used to define the same birds. Technically speaking, most sexlinked chickens are autosexing, and autosexing breeds do have sexlinked traits. The definition of autosexing is that a bird has been bred so that it is visually able to be sexed at hatch, and that's exactly what the sexlink chickens that this article focuses on are. The reason I say 'most' in the case of sexlinked birds, however, is because sexlinked traits DO exist that are NOT autosexing; that is, there are traits linked to the sex of a bird that are not visually apparent at hatch. Thus, 'autosexing' and 'sexlinked' truly are two different words with two different meanings. And, while technically there are characteristics of both terms in both sexlinks and autosexing breeds, using these terms interchangeably for these birds is considered incorrect. By most definitions in the poultry world, a sexlink is in essence a mixed breed, while an autosexing breed is just that, a pure breed. The major difference between them is that autosexing breeds work for generation after generation when kept pure bred, while sexlink crosses work only once; crossing a sexlink rooster to a sexlink hen of the same parentage WILL NOT produce more sexlinks!
Some examples of Autosexing breeds. On the left is a Cream Legbar, a fairly common autosexing breed. On the right is another autosexing breed, a Bielefelder. Both are hens.
The Mechanics of Sex Linkage
Now, I will not be exploring autosexing breeds any further on this article—that’s also a topic for another article —but I would like to explore a bit into the mechanisms behind how sexlinked traits work. Before I dive in any further here, however, I would like to give some warning to readers that this information gets a bit complicated. This is not an indication of how the rest of the article will be, and in fact is the most complex part of this page by far. You’re more than welcome to comment on this article or send me a private message with questions, and I will do my best to help you understand. I also wouldn’t blame anyone for scrolling right past this section, as I do understand how confusing this stuff can be! Ready? Here we go!
The sex of many animals is determined by what are called ‘sex chromosomes’. In humans, males are those that inherit an X and a Y chromosome from their parents, while females inherit two X chromosomes. In birds, this system is a little different; male birds inherit two of the same chromosome (in this case, two Z chromosomes) and females inherit two different chromosomes (a Z and a W chromosome). Each parent passes one of their chromosomes to their offspring, which determines the sex of that offspring. For example, a rooster can only pass on one of his Z chromosomes, and so depending on if the hen passes on a Z or a W chromosome, the offspring will be either male or female.
This simple chart shows this process in birds:
Sexlinked traits are genes that exist only on one of the two sex chromosomes; in humans, they are genes along the X chromosome, and in birds, along the Z chromosome. This means that, in birds, females can only carry one of any allele (or version) of these sexlinked genes and only on her Z chromosome because they don’t occur on her W chromosome. This is what causes slight color differences between males and females in certain breeds, such as Barred Rocks, whose males have more white than females of the same breed. The male has two copies of the allele for barring, and so has wider white bars over his underlying black coloration.
Left image: Kate the Barred Rock hen, my image; Right Image: Barred Plymouth Rock production strain cockerel by Lukas Ruetz, http://feathersite.com/Poultry/CGP/Rocks/BRKRocks.html
Sexlinked traits can work in one of two ways, depending on if the sexlinked gene is dominant or recessive to other genes present in the cross. The most commonly used sexlinked traits are dominant and create sexlinks when they are passed on by the parent with two different chromosomes (for example, a hen’s ZW chromosomes), while the parent with two of the same chromosomes (such as a rooster’s ZZ chromosomes) does not carry the gene. The chromosome carrying the trait is only passed on to offspring of one sex, and never to offspring of the other sex. This means that sexlinked traits in these crosses are only passed to a hen’s sons on her Z chromosome, and not to her daughters, simply because it does not exist on the W chromosome. These function in this way because they are dominant alleles and the presence of just one copy of them is enough for them to express in the appearance of the resulting chicks. Because the father in this type of sexlinked cross can only pass on a Z chromosome with the recessive allele, his contribution to his offspring is always the same, whether they are male or female.
An example of this is given below, using Barring as an example. It should be noted that a capital B indicates the dominant allele for barring, while a lowercase b indicates the recessive allele without barring. A plus sign shows the wild-type allele, the common allele in natural populations. In this case, wild-type is NOT barred. Finally, the dash indicates that the gene is nonexistent on that chromosome; this is the W chromosome.
Recessive sexlinked genes work in the opposite way. Recessive alleles are ‘covered’ by other, more dominant alleles, meaning if a dominant allele is present at all, even a single copy of it, then the recessive allele of the pair does not express. However, sexlinked recessive genes are only present along the Z chromosome and not on the W chromosome, just like sexlinked dominant traits. This means that females only need ONE copy of these sexlinked recessive alleles for them to express because there isn’t anywhere for the dominant version of the allele to be present and ‘cover up’ the expression of the recessive allele, but males need TWO copies in order for it to express because otherwise a dominant allele IS present to ‘cover up’ the recessive allele. Using a male with two copies of the recessive allele means that he will always pass on that allele to all of his offspring. However, if the mother is carrying the dominant allele, she will always pass it on to her sons, covering up that recessive trait that their father passed on to them, while not passing it to her daughters because it does not exist along the W chromosome. This means that only female offspring express the recessive gene.
The below image shows how this works, using Chocolate as the example trait. As with the barring example above, a capital letter (Ch) indicates the more dominant trait; in this case, this is the LACK of chocolate coloring. Chocolate coloring is instead indicated by a lowercase letter (ch) because it is recessive. If this gets too confusing with the capital and lowercase letters, just follow the plus sign—this shows the wild-type gene, which in this case is NOT chocolate. The dash still indicates the lack of the gene’s presence on the W chromosome.
Now, why do these only work in one generation? To put it simply, the birds have all the wrong alleles for this to work! Crossing, for example, the resulting barred males and non-barred females from the Barring example would simply result in a mix of both barred and non-barred offspring, not related to sex. The male in this case has one barring allele, and the female does not. Remember how the female always sends a Z chromosome to her sons and a W chromosome to her daughters? Well, the male’s contributed Z chromosomes, half of which will have a barring allele and half will not, are not selective, and so will be inherited equally by his male and female offspring. The below image shows what happens as a result.
Still with me? This is a lot of information, and I know it can be quite complicated! The rest of this article deals with the birds themselves, however, and so should be much easier to follow. Thanks for sticking it through! Now that you know a bit about what a sexlink is, let’s look at the different types of sexlinks, starting with the most commonly marketed, the red sexlink!
You may look at the above picture and think, ‘Hey, I have a bird that looks like that, but it was called a…’ Well, you wouldn’t be wrong in noticing that—red sexlinks are marketed under many, many different names! Many of those names are meant to apply to specific red sexlink crosses; that is, they are meant to apply only to the offspring of one breed in particular crossed to another breed in particular, without any substitutions allowed on either parent. However, often they are used interchangeably by flock owners across the country, and it’s difficult to know which name applies to which cross, especially when breeding sexlinks in a backyard setting. What they all have in common is that the females are primarily red-colored with some white accents, and the males are white, sometimes with brown shoulders or golden hackles. At hatch, females are reddish overall and males are white or yellow. Red sexlinks are created when a red or gold male is crossed with a silver female. There are many examples of this cross, but most commonly you will hear about Rhode Island red or New Hampshire roosters crossed with Delaware or Rhode Island White females. More examples of what can be crossed to produce red sexlinks can be found on this thread.
Red sexlinks may go by the following names:
And many more…
- Cinnamon Queen
- Bovans Brown
- Golden Buff
- Golden Comet
- Hyline Brown (Sometimes misheard or misspelled as ‘Highland Brown’)
- ISA Brown
- Lohmann Brown
- Red Comet
- Red Cross
- Red Star
Red Sexlink or Production Red?
Another term that is sometimes used for red sexlinks is ‘Production Red’. However, this is also a term used for production bred Rhode Island reds, New Hampshires, or non-sexlink crosses thereof, leading to some confusion. Visually, sometimes the two are quite similar, but there is one trait that can be used to tell one from the other. Red sexlinks have light colored down underneath their reddish feathers, while production quality birds of those other two breeds have down that is about the same color as their feathers, or sometimes darker. Below are two feathers, one from a Production Red and one from a Red Sexlink, side by side:
A side-by-side comparison of Production Red and red sexlink hens. Notice that the Production Red, on the left, has no white accents like the red sexlink, on the right, has.
A Black Sex Link Hen by Nature Whisperer, 2006. https://commons.wikimedia.org/wiki/File:Midnight1101.jpg
Black sexlinks are less common than red sexlinks and go by fewer names—in fact, Black Star and Black Rock are just about the only other names you see them going by! As the name implies, they are black rather than red. At hatch, pullets are pure black or black with a bit of reddishness around their faces, while cockerels are black with a white blotch on the back of their heads. As adults, the hens often have reddish or brown feathers in their hackles and down their front. The males are barred, but not like a purebred barred breed. Instead, male black sexlinks have darker barring like females of purebred barred breeds.
Left image: Black Sexlink cockerel by Jenny Simpson, http://feathersite.com/Poultry/CGP/Sex-links/BRKSexLink.html; Right Image: Barred Plymouth Rock production strain cockerel by Lukas Ruetz, http://feathersite.com/Poultry/CGP/Rocks/BRKRocks.html
Black sexlink hens can be somewhat similar to Black Copper Marans hens, but should not be confused. Some ways to tell them apart is by the Marans having copper only in her hackles and not on her chest, and by the Marans’ feathered legs, though these traits will depend on the quality of the Marans and the background of the sexlink.
Left image: Nadine the Black Copper Marans pullet, my image; Right image: Black Rock Hen ‘Blackie’ by Simon Springett, 2008. https://en.wikipedia.org/wiki/File:Black_Rock_Hen_'Blackie'.jpg CC BY 3.0 / Resized from original
Black sexlinks are fairly easy to make; just about any NON-barred male that is also not white crossed to just about any barred female (including Dominiques and Cuckoo Marans) will produce them! Most commonly, they are created by crossing Rhode Island Red roosters with Barred Plymouth Rock hens. See this thread for more examples of what can be crossed to make a black sexlink.
Other Sexlink Crosses
There are several genes that are also sexlinked, but some are less known or noticed. For instance, one very common sexlink cross is for feathering speed of chicks. Many hatcheries’ stock has been selected for this trait, allowing the chicks to be sexed by the feathering on their wings rather than vent sexing. That is why some might notice that their pullets feather out faster than their cockerels—but this is not the case in ALL chicks, and so cannot be relied on unless it’s known that the chicks were bred for it.
Another, but very uncommon production sexlink cross is called the Brown Sex Link, which, from all reports, produces females very similar to the Production Red hens mentioned above in the Red Sexlink section of this page. These sexlinks are so uncommon that not much information can be found about them. Ideal Poultry sells these, stating that they are a cross between Rhode Island red males and silver factor White Plymouth Rock females.
Sexlink crosses can be produced from any of the sexlinked genes that chickens may carry, such as the Chocolate gene mentioned in an above section, given the right conditions for the cross. To read up more about them, see the ‘links’ section below!
As for the blue sexlinks mentioned at the beginning of this article, I should explain that the blue gene is NOT sexlinked at all. Males and females can both carry either one or two copies of it. The chart below, from this thread, shows how blue is inherited. A simple matter of crossing a black Barred female, such as a Barred Rock or Cuckoo Marans, to a Splash male will produce sexlinked blue chicks. These chicks are, in essence, blue-colored Black Sexlinks.
Raising and Breeding Sexlinks: Advantages and Disadvantages
There are advantages and disadvantages to sexlinks no matter what your set up is, whether you intend to breed and sell them, or are only raising them for your own purposes. The primary advantage to sexlinks in a backyard setting is that you always know what you’re getting—there’s no ‘oopsie’ roosters that slip through when you’re looking at a stark color difference such as red versus white!
However, this comes with a disadvantage to those breeding sexlinks. It’s well known that the vast majority of people only want female chicks and definitely don’t want any roosters! In a pure, autosexing breed, it may be simple to just say you won’t sell anything but male-female pairs or even male-female-female trios, as these birds are compatible to continue breeding like any other pure breed, but in a cross like a sexlink, this simply doesn’t work out from a breeding standpoint. Not many would be interested in only buying pairs or trios of a production sexlink cross, just like not many are interested in buying any mixed breed rooster, except those few people only seeking pretty birds as pets. You may luck out and find that many people in your area are interested in roosters, if for nothing else than to raise them out for meat, but this is highly unlikely and shouldn’t be relied on. So, before deciding to breed sexlinks, one thing that should be planned for is what to do with extra roosters!
Another advantage to raising sexlinks, at least the high-production ones produced by hatcheries, is, well, their high production! Particularly, red sexlinks from hatcheries tend to have a very high output of eggs only rivaled by production-strain White Leghorns in many cases, and they start laying quite early, as early as 15-16 weeks in some cases! Now, egg production does dwindle after the first year or two, and so this egg production shouldn’t be relied on for years to come. However, often these high-production red sexlinks are also bred as a dual-purpose bird, meaning that these birds can be processed for a decent amount of meat once their laying drops off, too! This is an advantage of selecting them over Leghorns, as Leghorns tend not to be as meaty and so are of less value for processing. Sexlinks do tend to eat more than Leghorns, though, and so if feed conversion is a primary concern, Leghorns win out in the end.
Unfortunately, this high production does come at a cost to sexlinks, and that cost is their overall health and longevity. Red sexlinks particularly are prone to health issues related to their reproductive system, such as egg binding, internal laying, and cancers of the reproductive tract, particularly ovarian cancer. Of course, any hen can come down with any of these issues, but the productive nature of red sexlinks causes it to happen to them far more often. Many red sexlinks live only a few years as a result of this propensity, making them less than ideal to keep as pets due to the potential for heartbreak. This is compounded by their often friendly and curious (some might even say nosy) personalities. This is not to say that absolutely no production-bred red sexlink will have a long life, but it’s sadly not the case for many. As for non-production red sexlinks and other sexlink crosses, it’s likely that they will live just as long as any other chicken, as their bodies aren’t as taxed as high-production strains are.
So, what’s the bottom line?
All-in-all, sexlinks are nice backyard birds and will provide many, many eggs for their families, and potentially a decent meal in the end to boot.
- Sexlinks are useful for people who absolutely must be sure they are getting pullets.
- Breeding sexlinks on a small scale can lead to difficulties with extra roosters.
- In a setting where egg and meat production is of the greatest concern, red sexlinks in particular are quite ideal.
- As pets, production-bred red sexlinks might not be the best choice due to their reduced health and longevity, but other sexlinks are likely to do the job well.
(Not to be confused with sexlinks. )
Sex Linked Information – An excellent thread on the topic of sexlinked genes.
Sex Linked Breeding Examples – This thread shows inheritance of Chocolate and Barring. Just don’t get confused—Mottled, Blue, and Lavender are NOT sexlinked!
The Chicken Color Calculator – For those of you who may want to play around with color genetics and see what happens.
Genetics of Colors and Basics – A look at basic chicken color genetics, along with a section on sexlinked traits.
Backyard Chickens Reviews on Sexlinks, for more pictures and user reviews on these birds:
Black Sexlink - Blue Easter-Egger Sexlink - Cinnamon Queen - Gold Star - Golden Comet - Golden Sexlink - ISA Brown - Lohmann Brown - Red Cross - Red Sexlink (general) - Star (both Red and Black)
Backyard Chickens Reviews on Production Reds, for comparison.
Backyard Chickens Reviews of Autosexing Breeds:
Bielefelder - Cream Legbar - Another Legbar Page - Norwegian Jaerhon
Please note that these are not ALL the autosexing breeds, just the ones with review pages here on BYC at the time of writing this!