Penguin GenderThe results are in—from a DNA test, that is: The rockhopper chick that hatched last June is a girl!

To those who don’t work with the penguins every day, these uniformly feathered birds appear identical down to the last detail. Of course, you can distinguish the rockhoppers from the Magellanics, but within each species, you won’t find any external characteristics to help you tell the boys from the girls.

You need to do a blood test for gender. Ken Ramirez, executive vice president of animal care and training, said there was no hurry to determine the chick’s gender, so his team waited until they were taking blood for her first full physical exam, typically done between 6 and 12 months, to include the genetic analysis. The test was done by an outside laboratory.

As in people, bird gender is determined by sex chromosomes, although they go by different names. Males have two Z chromosomes while females have a Z and a W.

Stop in to see the youngest rockhopper! You can spot her by her brand-new identification tag—two orange bands around one wing. You can also identify her by her lack of chrome yellow head plumes, but not for long—the yearling bird will sprout those soon.

Karen Furnweger, web editor