Does size almost always determine sex?

[bobsmith2002]

I bought four white silkie chicks from a feed store that were hatched on 7/23. Three of them are roughly the same size, but the fourth one is the smallest. Does this mean the small fourth one is a female and the three larger ones are males?

 

[SilverBirds]

Not really. It could be a few days younger than the others or just a bit runty. Silkies are notoriously hard to sex until they're a lot older and the best way to tell is by comb development.

 

[Ridgerunner]

Does this mean the small fourth one is a female and the three larger ones are males?

I once got 20 Buff Rock cockerels. One became my flock master and I ate the rest. By the time I ate them, some were twice the size of the others. They were a lot difference in size from the get-go. All were cockerels.

Cockerels "tend" to be larger than pullets after they have grown some. That does not mean all are, just that some are. At two weeks, size may be an indication of sex but it is also very possible it is not. If it were this easy it would be a lot easier.

If they hatched from a larger egg they may still be larger, say the difference in a pullet egg versus a hen egg. Some grow faster or slower than others, regardless of sex. Some may have thicker feathers or down so they look bigger. Some full sized Silkies are just bigger than others when they mature.

Personally I put very little faith in size at 2 weeks meaning much.