Migratory Birds In Chicago:
Why do birds migrate? It is almost always about finding food. Usually, changes in daylight initiate brain signals in birds. The German term zugunruhe means migratory restlessness; birds begin to get antsy. It is the need for them to begin moving. For example, red-winged blackbirds coming back to New York come back within a two-week period. Typically, the males will migrate first. The adults leave first, then are followed by the juveniles. The bulk of migration happens at night because there are fewer predators. Since they cannot see much, they can detect the Earth's magnetic field. This is called magnetoreception. While it is still a mystery how magnetoreception works, scientists generally know that birds and other animals sense the Earth's magnetic field and use it to guide their paths. In the article "Unraveling the enigma of bird magnetoreception”, the author cites cryptochrome, which is found in the eyes, is what allows birds to see electromagnetic fields.[27]
Bird Banding to Keep Track of Bird Migration
Bird banding is a monitoring technique that has been used since the late 1500s.[28] The earliest record of a metal band attached to a bird’s leg was about 1595, when one of Henry IV's peregrine falcons was lost in France and then found in Malta about 1350 miles away only 24 hours later.[29] In 1803, John James Audubon, a French-American artist and ornithologist, began tying silver cords to the legs of eastern phoebes and was able to identify them when they returned the following year. Birds are usually banded by mist netting. Mist nets are made of fine black nylon or polyester mesh netting and are about 12 feet long and 8-10 feet high. They are placed between two poles and become nearly invisible to the birds. Once the bird is captured, it is gently handled by a bander who loosely places a band around a bird’s leg. Banding data are used in large-scale, long-term studies to track migratory movements and patterns, population size and demographics, morphology, and behavior, and to assess whether changes occur over time.[30]
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Bird captured with mist netting for banding
Migration Route: The Mississippi Flyway
The Mississippi Flyway is a migration route along the Mississippi, Missouri, and lower Ohio rivers. It is one of the four flyways in the United States. The others are Central, Pacific, and Atlantic. As one can see in the following illustration, Chicago lies along one of the main bird migratory routes in North America, the Mississippi Flyway. This bird migration corridor follows the Mississippi and the Missouri rivers. It is used by about 325 species of birds, about half of all North American birds. Most birds from the northern plains will probably winter on the Gulf Coast, using the Mississippi River as a visual cue. Over half of the birds that migrate rely on wetland habitats as they travel.[32]
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The Mississippi Flyway in blue
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