Can you sex mixed breeds

[mksauce23]

I’m a first-time Hatcher”, in the middle of hatching a few eggs from my backyard flock — I have a barred rock rooster and various hen breeds: Cuckoo Maran, Australorp, Buff Orpington, Sussex...

Ive read that a BR x BR you can sex by the size and shape of the spot on their head. I also read about how you can sex a barred rock hen mixed with a colored roo.

I’m new / unfamiliar with all of the mixing and sex linking. Will there be a way to determine with any of the mentioned crosses?

So far they’re all coming out of the eggs looking predominantly like a barred rock chick and all have fairly large spots on their heads...

The whole spot thing has me worried they’re all Roos so far... but if perhaps that is off the table because it’s not a pure cross that would be good to know!

 

[JacinLarkwell]

A barred rock male will throw chicks with barring, males and females

 

[Ridgerunner]

The first post in this thread takes you through how sex links work. You may have to study it and read it a few times but it's the best I have.

http://www.backyardchickens.com/forum/viewtopic.php?id=261208

Ive read that a BR x BR you can sex by the size and shape of the spot on their head.

That should work with a BR over a Cuckoo Marans too. But it's not always as easy as some people make it sound. Several years ago a forum member posted a thread where she talked about that and even showed photos. I can't remember who that was or find that thread. She was very experienced with it and still sometimes had trouble.

When both parents are barred, like BR, Cuckoo Marans, or Dominique, the boys get two barred genes, one from each parent. The girls get only one barred gene. The two barred genes creates a bigger spot on the head than one barred gene. That sounds simple. But the problem is that the colors can sort of bleed so you can't always tell what is part of that spot and what isn't. It really helps to have experience with it.

I also read about how you can sex a barred rock hen mixed with a colored roo.

If you read that post I referenced at the start, that is called a black sex link. The hen has to be barred and the rooster has to be not barred. The male offspring will have a spot and feather out barred. The female offspring will not have a spot and will not feather out barred. Also, you have to be able to see the spot. There are some color combinations where you will not be able to see the spot.

I’m new / unfamiliar with all of the mixing and sex linking. Will there be a way to determine with any of the mentioned crosses?

Other than the Cuckoo Marans, no. The hen has to be the one barred and the rooster has to be not barred. That does not work with a BR rooster.

So far they’re all coming out of the eggs looking predominantly like a barred rock chick and all have fairly large spots on their heads...

Them looking like BR chick is expected. I don't know what color or pattern your Sussex hens are but the black in the BR will probably overpower any other colors you have so they all have black down. Sometimes a Buff Orp crossed with a black will give you some yellow or even orange splotches in the down and feathers when they feather in but even those chicks should be mostly black. The BR rooster will give all his offspring a barred gene so they all (boys and girls) should have a spot. Since it is only one barred gene the spot should be on the smaller side whether they are a boy or a girl. Maybe that's a place where you can gain some experience in what the spots re supposed to look like.

The whole spot thing has me worried they’re all Roos so far... but if perhaps that is off the table because it’s not a pure cross that would be good to know!

It's off the table. Not because they are crosses but because the rooster was barred. If you had only hatched Cuckoo Marans eggs you might have a chance, but without a bit of experience even then it would be rough. When they feather out they should all be barred, boys and girls.

 

[mksauce23]

I don't know what color or pattern your Sussex hens are but the black in the BR will probably overpower any other colors you have so they all have black down.

She is a red speckled Sussex