Not all penguin stories are equal in the public's mind.

"And Tango Makes Three," an award-winning children's book based on a true story about two male penguins who raised a baby penguin, topped the American Library Association's annual list of works attracting the most complaints from parents, library patrons and others.

Overall, the number of "challenged" books in 2006 jumped to 546, more than 30 percent higher than the previous year's total, 405, although still low compared to the mid-1990s, when challenges topped 750.

"We're still in ... the midrange in terms of how many challenges we get," Judith Krug, director of the ALA's Office for Intellectual Freedom, told The Associated Press during a recent interview.

"And Tango Makes Three," by Justin Richardson and Peter Parnell, was published in 2005 and named by the ALA as one of the year's best children's books. But parents and educators have complained that "Tango Makes Three" advocates homosexuality, with challenges reported in Southwick, Mass., Shiloh, Ill., and elsewhere.

The ALA defines a "challenge" as a "formal, written complaint filed with a library or school requesting that materials be removed because of content or appropriateness." For every challenge listed, about four to five go unreported, according to the library association. Krug said 30 books were actually banned last year.

"Books aren't banned nearly as much now as they used to be, because communities are much more active in fighting that," Krug said about the bans, which can lead to books being removed from school and public libraries.

Other books on the 2006 list include two by Nobel laureate Toni Morrison, "The Bluest Eye" and the Pulitzer Prize-winning "Beloved," both cited for language and sexual content; Cecily von Ziegesar's popular "Gossip Girls" series, criticized for sexual content and language; and Robert Cormier's "The Chocolate War," for language, violence and sexual content.

Krug said she has statistics for challenged books through the first few months of 2007, when there were widespread reports that librarians were banning Susan Patron's "The Higher Power of Lucky," the story of a 10-year-old's physical and spiritual journey and winner of the prestigious Newbery prize for the best children's book.

Librarians had complained on an Internet list serve, LM—Net, about the book's use of the word "scrotum." But in February, when The Associated Press contacted several librarians who had posted critical comments, all said they were either carrying "Higher Power" or hadn't decided.

Krug confirmed that the ALA had received no reports of "Higher Power" being banned, or even challenged. The publisher, Simon & Schuster, agreed, saying recently that it had not heard of any problems at libraries.