A colony of Cliff Swallows has made a cliff it's home about 2 miles away from us. Even so, in the evening, they are soaring over our place ..capturing insects before their return home. What do they Swallow to make them sound that way? :)
Perhaps the most interesting adaptation of these birds, is rather than burrowing a hole in a cliff-side, they have the ability to build a mud hut! If you research a Navajo Hogan (hut), you'll find an amazing similarity!