I'm on my second batch of silver lace wyandotte and I wanted to make a few observations for anyone trying to sex their young SLWs. This may work for Wyandotte in general, but don't quote me on that.
A couple things to keep in mind.
1. I have read that not all wyandotte have the slow growing feather gene. I believe the two unrelated batches I have, do.
2. This is only my second batch and I'm open to constructive criticism, I'm far from an expert.
3. Sexing in this way was 100% accurate with my first batch. I will update on this batch when they are grown.
One male top of pic #1. Two females bottom of pic #1. The male was hatched 16 hours before the two females on the bottom. They are almost two weeks old here. Males wings are short, only half of his abdomen. At this point he shows no tail feather growth. The females wings reach to the end of the abdomen and they have a good start on their tail growth.
Pic #1 with comments
Pic #1 close up for detail. (You can click on images to make them bigger)
Picture #2 is arranged differently but with the same birds. I added it because it clearly shows the wing growth and tail growth of the female on the top left compared to the slower growing feathers of the male below her.