bird animal alone walking at rock road

>For other uses, see Bird (disambiguation). Many - see section below. Birds are bipedal, warm-blooded, egg-laying vertebrates characterized primarily by feathers, forelimbs modified as wings, and hollow bones. Birds range in size from the tiny hummingbirds to the huge Ostrich and Emu. Depending on taxonomic viewpoint, there are about 8,800–10,200 living bird species (plus about 120–130 that have become extinct in the span of human history) in the world, making them the most diverse class of terrestrial vertebrates. See more at Wikipedia.org...

>For other uses, see Sand (disambiguation). Sand is an example of a class of materials called granular matter. Sand is a naturally occurring, finely divided rock, comprising particles or granules ranging in size from 1⁄16 to 2 millimeters. An individual particle in this range size is termed a sand grain. The next smaller size class in geology is silt: particles below 1⁄16 mm down to 1⁄256 mm (0.004 mm) in size. The next larger size class above sand is gravel, with particles ranging up to 64 mm (see grain size for standards in use). See more at Wikipedia.org...