Isn’t this Arctic Tern a stunning bird?
One distinctive feature of Arctic Terns is that they have incredibly short legs. It probably helps them to keep warm by leaving less of their body exposed. Over evolutionary time, the Arctic Terns with longer legs clearly raised fewer chicks than those with short legs.
Birds have a counter-current heat exchange mechanism in their legs where the heat from blood going to the toes warms the cold blood coming back from them. That means they lose less heat. Other species of bird stand on one leg to conserve heat. Arctic Terns have legs half the length, instead, to keep their bodies warm.
When flying, the feet are neatly tucked away into the most incredible aerodynamic shape. They have to fly the equivalent of three trips to the moon and back in a lifetime of migration. Any flapping feet trailing behind would soon reduce their breeding success and be eliminated from their gene pool.
Selection has produced beautiful birds which are fitted to their environment, beautifully, tiddly toes and all.