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
Bird feeder clean, and refreshed frequently with clean water to avoid mosquitoes. The birdbath should be placed where a frightened bird can fly up easily to an overhanging limb or resting place if disturbed or attacked. Squirrels may also help themselves to the contents of bird feeders, often not merely feeding, but carrying away the food to their hoard. There are various anti-squirrel techniques and devices available to thwart attempts by squirrels to raid bird feeders. Several manufacturers produce feeders with perches that collapse under the weight of anything heavier than a bird, or that use battery power to shock an intruder