They try for all male but since the plants are harvested for shipment at an early stage now and then some female plants make it into the batch. You can just pull them if you wish or leave - either way works. If the females ended up being a large percentage of your order I'd contact the shipper for replacements.

Dave

It seems only to be 1 or 2 crowns out of 10. I'll probably just leave them. Whats the disadvantage of having female plants? Is it just smaller spears? Will having female plants reduce my yield? Does the plant "waste" energy in the berries and not put it into the crowns?

The Jersey Hybrids are supposed to be all-male without any culling necessary. So you could plant a whole row of asparagus and have all male plants. I'm not sure, but I think "all male" means like 90%. So 1 or 2 out of 10 would be about right, that is, if my 90% statement is correct.
For once, it's the male plant that produces more food.
The female plants spend alot of energy making seeds. The male plants just make little pollen bags. This leaves the males with alot more energy to produce lovely, fat, tender asparagus spears for you. Additionally, the female plants drop seeds which can become established and overcrowd the asparagus patch. I have read at least two authors claim that this is the typical demise of commercial asparagus patches forcing replanting.