They derived from smaller birds that once could fly. This is possible in the creationist model. The wings have a function. It is a result of 'design economy' by the Creator. Humans use this with automobiles, for example.
All models have mounting points for air conditioning, power steering, etc.
Likewise, all models tend to use the same wiring harness, although not all features are implemented in any one model. In using the same embryological blueprint for all birds, all birds will have wings. No one has demonstrated this. Or perhaps the muscles attached to the extra toes give strength to the 'ankle' of the pig. Males have nipples because of the common embryological plan followed during early embryo development.