Almost every part of a typical bird's anatomy is midified in some way that enhances flight.The bones have an internal structure that is honeycombe making them strong but light.The skeleton of a frigate bird for instance has a wingspan of more than 2 meters but weighs only about 113 grams.another adaptation reducing the weight of birds is the absence of some organs females for instance have only one ovary also modern birds are toothless an adaptation that trims the weight of the head.food is not chewed in the mouth but ground in the gizzard a digestive organ near the stomach crocodiles also have gizzards as did some dinosaurs.the bird's beak made of keratin.has proven to be very adaptable during avian evolution taking on a great variety of shapes suitable for different diets