The first day of the long Independence Day weekend began at the box-office with a victory not for Transformers 2 and not for Public Enemies, the two films that were expected to be the primary contenders for first place. Instead, the hands-down winner was the 20th Century Fox animated 3D feature Ice Age: Dawn of the Dinosaurs, which grossed an estimated $14 million in its debut. Transformers -- last weekend's winner, which had also piled up huge grosses on Monday and Tuesday -- fell to $10 million on Wednesday, its eighth day of release. Universal's Public Enemies arrived with $8 million. Box office analysts, however, were issuing cautious predictions about the total five-day holiday, pointing out that kids were out of school for summer vacation on Wednesday, skewing the results. Moreover, the actual Fourth of July holiday this year comes on a Saturday -- ordinarily the week's busiest day at the box office -- when picnics and backyard barbecues are likely to draw audiences away from theaters.