The fall landbird migration is peaking now.\u00a0 Most warblers have already passed south.\u00a0 Thrushes and sparrows will dominate the October migration.<\/p>\n
The fall migration is more leisurely than the spring migration for most birds.\u00a0 There is an urgency about the spring migration as birds are driven to arrive on the breeding grounds as early as possible to stake out good territories and find a mate.<\/p>\n
In some ways, the fall migration is even more impressive.\u00a0 This migration involves the spring migrants that survived the breeding season as well as all the young born in the summer.\u00a0 Ornithologists estimate that five billion birds migrate in North America alone each fall!<\/p>\n
Some species of birds migrate during the day.\u00a0 These include pelicans, hawks, falcons, hummingbirds, swifts, and swallows.\u00a0 All of these birds are strong fliers.\u00a0 The larger birds can take advantage of thermals that develop during the day.\u00a0 Swifts and swallows can feed on the wing during the day as they migrate.<\/p>\n
The majority of land birds migrate at night.\u00a0 These include cuckoos, flycatchers, warblers, vireos, thrushes, orioles and sparrows.\u00a0 Most of these birds are denizens of woods and other sheltered habitat.\u00a0 These birds are not extremely agile fliers so need dense habitat to avoid bird predators.<\/p>\n
Migration at night has at least three advantages.\u00a0 Birds do not have to worry about falcon or hawk attacks.\u00a0 Second, the air in the atmosphere is usually less turbulent than during the day.\u00a0 Lastly, the air is cooler at night.\u00a0 A migrating bird produces a huge amount of excess heat that needs to be released.\u00a0 Most of the heat is lost from the unfeathered legs.\u00a0 The colder the air temperature, the more quickly that heat can be dumped.<\/p>\n
Migrating birds wait for favorable winds before starting a migratory leg.\u00a0 Keep in mind that high pressure systems rotate in a clockwise fashion and lows are counterclockwise.\u00a0 So, the leading edge of a high or the trailing edge of a low have the southerly winds that favor a strong migratory flight that night.<\/p>\n
The evidence of a strong migration can be a fallout of many birds the following morning.\u00a0 But there are more direct ways to experience nocturnal migration.<\/p>\n
First, you can set up a spotting scope or use your binoculars and watch the face of the moon.\u00a0 It\u2019s very cool to watch migrating birds wing across the lighted surface.\u00a0\u00a0 Most nocturnal migrants start shortly after dusk and peak around midnight.<\/p>\n
Migrating birds can also be seen on radar.\u00a0 In the early days of radar, echoes of many, small targets were seen but poorly understood.\u00a0 These echoes were called \u201cangels\u201d.\u00a0 Now, we know that the angels are actually birds and sometimes bats.<\/p>\n
Radar is now used as a powerful tool to study nocturnal migration.\u00a0 Sid Gauthreaux of Clemson University is one of the pioneers of this field. Check out the radar image showing many angels at his website: http:\/\/virtual.clemson.edu\/groups\/birdrad\/COM4A.HTM<\/a><\/p>\n Yet one more way to appreciate nocturnal migration is to use your ears.\u00a0 Nocturnal migrants are noisy, regularly emitting short flight notes.\u00a0 In some cases, the flight notes are similar to the calls the birds give while they are on the ground.\u00a0 In many cases, however, the flight notes are only given during a nocturnal flight.<\/p>\n