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
The Bird That Drinks Tears Drinks Blood", and is entwined with many of the themes that run through two series. Because of this riddle, many people expect that Lee Yeongdo will write two more sequels to this Bird series, "The Bird That Drinks Poison" and "The Bird That Drinks Water". However, Lee Yeongdo has not yet confirmed this rumour and whether he would actually continue to finish all four birds is still unknown. The Bird That Drinks Tears The Bird That Drinks Tears (; abbreviated as ) is a series of Korean fantasy novels by Lee Yeongdo. A rare example of the genre Korean Fantasy,