He's a young guy and doesn't have hackle feathers yet. His saddle feathers are just starting to emerge.
With a bird this young you're better off sexing by color if you can, and for Barnevelders this color pattern is a dead give-away, since hens are laced and don't have green tails. Also, if you look closely you'll see dark red on the shoulders, and that's a cue that the bird is male no matter what the breed.
