Birdie, help me out here. That web site shows Nocturnal migration. Call me ignorant, but I always thought that they flew in the day time. Do they fly at night and rest in the day, or do they fly day and night? I never really noticed migrating birds at night.
Not so much a need to rest, they don’t seem to need sleep the same way mammals do. Most songbirds migrate at night, presumably to reduce risk from hawks and falcons but also because it leaves the day free for refueling. For birds it’s all about body fat, they’ve figured out a songbird gets about 125 miles per gram of fat and they can lay on fat and burn it off equally quick.
Swallows and swifts migrate by day because they can feed as they fly. Robins gather up in wandering flocks in search of berries and migrate by day in the fall, dunno about the spring.
Other birds like waterfowl migrate both day and night.
Hummingbirds are believed to migrate mostly in daylight, just over the treetops so they can stop when they come across flowers. Yet they have been observed flying up and out of sight late afternoon. Those leaving the Gulf Coast in fall usually depart in the morning tho they prob’ly won’t make landfall on the Yucatán until the early hours of they following morning.
If they make it. Bird’s respiratory systems are so efficient they generally don’t fatigue like we do (pheasants, grouse and turkeys tire because of the white meat in their flight muscles) birds burn off all their fat and if they still ain’t made landfall they burn muscle until they become too weak to fly, this can happen inside 24 hours dependent upon the fat load at the start.
Blackpoll warblers, the size of a sparrow, are famous, because they fatten up on berries in New England before making a 72 hour nonstop flight over water to Brazil. The record is held by a pigeon-sized shorebird the leaves the Aleutians and shows up in New Zealand after a seven-day overwater flight,they can’t swim either.
