4 top apps on the app store involve flying animals!

Have you noticed that the top 4 apps on the app store all involve flying animals? Number 1 is Air Penguin. This game involves a penguin jumping from iceberg to iceberg, doing flips while he does so. Sometimes, he uses his feet as propellers to make him fly. Number 2 and number 3 are Angry Birds Rio and Angry Birds, respectively. These involve flinging birds at pigs. Number 4 is Tiny Wings. This has a bird with tiny wings that you make fly by using hills as jumps. Is this pure coincidence, or do we like to play games involving flying animals for some reason?