The changing picture of bird populations throughout the year intrigues those who are observant and who wish to know the source and destination of these birds.
Birds are the most mobile creatures on Earth.
Even man with his many vehicles of locomotion does not equal some birds in mobility. No human population moves each year as far as from the Arctic to the Antarctic and return. Yet the Arctic terns do-and without the aid of aircraft or compass. Birds are adapted in their body structure, as no other creatures, to life in the air. Their wings, tails, hollow bones, and internal air sacs all contribute to this great faculty.