Is it their inelegant tottering, stubby wings or adorable corpulence?
All of the above?
Visitors stopping for a look at the National Aviary's two new penguin chicks during their introduction to the public Thursday had a hard time putting the flightless aquatic birds' appeal into words.
"Their actions are funny," said Maegen Snee, 21, visiting from Dallas with her mother and checking in on the chicks through a window into the aviary's "brooder room."
"They just kind of waddle around."
Katie Cullen, 20, and her brother Sean, 13, from Bradford Woods, made the trip expressly to see the new African penguins, the second pair of penguin chicks hatched at the North Side aviary.
"My dad saw this was the first day they were [on display]," Ms. Cullen said. "I love penguins. ... They're just interesting."
By 3 p.m., aviary staff said, about 600 people had filed into the aviary, many asking about the new arrivals, born Nov. 29 and Dec. 2.
"People just love penguins," said Teri Grendzinski, the aviary's supervisor of animal programs.
The chicks, which have yet to be named, are part of a cooperative captive breeding program with every other zoo in North America.
African penguins, native to the rocky coastlines of South Africa and Namibia, are an endangered species threatened by oil spills, habitat loss, overfishing and climate change, Ms. Grendzinski said, adding that the birds' population has plummeted about 90 percent in the past 100 years.
"Our goal is to have future generations for zoos," she said. "The plan for these guys is to keep them here and use them as educational animals."
To that end, the chicks will be hand-raised in the nursery to instill a bond with humans so they can take part in the aviary's array of educational programs, which aim to "inspire a respect for nature through an appreciation of birds," the aviary says.
"We have to have penguins that are used to people," said Robin Weber, the aviary's director of marketing and communications.
Growing up away from the rest of the penguin colony also protects the chicks from the rocky exhibit and the other 16 birds.
"They're naturally very aggressive with each other," said Ms. Grendzinski, who can testify to the strength of the penguins' beaks and has the bruises and bite marks to prove it. "People say penguins are cute and cuddly. ... I say they're cute."
The newest penguins will spend the next few weeks eating smelt and growing. The chicks are expected to add 10 percent of their body weight every day.
The penguins are expected to be fully grown -- about 18 inches tall and weighing up to 9 pounds -- in less than three months, so get a glimpse of the newborns quick.
"They're not going to be cute, fuzzy babies for long," Ms. Grendzinski said.
Robert Zullo: firstname.lastname@example.org or 412-263-3909.