Bird migration evidence. Seabirds fly low over water but gain altitude when crossing land, and the reverse pattern is seen in landbirds. However most bird migration is in the range of . Bird strike aviation records from the United States show most collisions occur below and almost none above . Bird migration is not limited to birds that can fly. Most species of penguin (Spheniscidae) migrate by swimming. These routes can cover over . Dusky grouse "Dendragapus obscurus" perform altitudinal migration mostly by walking. Emus "Dromaius novaehollandiae" in Australia have been observed to undertake long-distance movements on foot during droughts. While participating
What Bird is That? friends, together with the succinct but compendious descriptive information, will place within easy reach of the bird lover, a most valuable "vade mecum" of bird and bush lore for out of doors as well as a thing of beauty for the library." Cayley’s aim in creating this work was to make available a book that would encourage and help people to learn about and appreciate Australia’s remarkable and unique bird life. He saw and responded to a need for a simple book that was accessible to the non-specialist birdwatcher. Each species was illustrated in colour and the birds were organised