GRADE LEVEL: 4-6
SUBJECTS: Language Arts, Science, Math, Geography
SKILLS: observation, inference, prediction
CORRELATION TO STATE GOALS FOR LEARNING: English language arts 3.C.2a; science 12.A.2b; social science
OBJECTIVE: Students will recognize why some birds migrate, describing the complex processes, and identify the hazards encountered during migration.
More than one-third of the world's birds migrate. Migration is a mechanism which allows birds to adapt to changes in the environment. Generally these changes are seasonal (weather, lack of food) and would make continuing to live in that habitat difficult. From the small ruby-throated hummingbird to the large bald eagle, birds move from the area where they raise young to their winter home. Migration is instinctive. Most birds migrate in flocks, even if they normally live alone. Migration in groups increases the chances for survival of individuals.
Migration moves birds from areas with dwindling food supplies to warmer winter feeding grounds with more abundant food. Only the fittest individuals will survive migration, insuring that the strongest birds are able to reproduce.
Some birds are diurnal migrators, others nocturnal. Daytime, or diurnal, migrators are generally larger (geese) and predatory species (hawks) that navigate by sight and have few, if any, predators. Many hawks begin their flight in mid-day taking advantage of rising warm air columns (thermals). Songbirds are nocturnal migrators, flying in darkness. Their daylight hours are spent searching for food and resting for the next leg of their trip.
The urge to migrate may be stimulated by a variety of factors. Changes in the angle and amount of light rays which occur seasonally may trigger migration. Low pressure areas in the fall trigger a southward migration, while high pressure areas in the spring encourage movement to the north. The lack of food sources in the fall and winter may also send birds toward areas where food supplies are more readily available.
The ability of birds to migrate great distances and return to the same general vicinity year after year is a subject which has fascinated people for centuries. Diurnal migrators fly along broad air routes established by physical features such as major rivers, coastlines, mountains and lakes. Many birds use the Mississippi River as a flyway. The position of the stars and moon and the earth's magnetic field are used by nocturnal migrators.
Birds encounter many hazards during their migration. Nocturnal and low-flying migrants risk flying into an assortment of humanmade objects such as tall buildings, power lines and towers, windows and aircraft. Hunting seasons are established for some species (ducks, geese, mourning doves) during the fall migration. Even though birds are harvested, hunting is within limits that a population can withstand. Predatory species, such as hawks, are often migrating at the same time that songbirds do. Habitat destruction and pollution are serious migrational hazards. Destruction and pollution of the northern breeding grounds affect spring migrations. Likewise, peoples' actions on southern feeding grounds, such as tropical deforestation, result in the death of untold numbers of birds. Late snow and ice storms and severe rain and lightning which occur on the spring breeding grounds also kill many migrants.
PROJECTS AND ACTIVITIES: Write a story or develop a journal entry with the author being a migrating bird. Include illustrations. Some suggested points to include are:
- the urge to fly
- numbers of birds preparing for migration; mostly young, inexperienced flyers that may not complete the migration
- eating like crazy to increase fat reserves
- waiting for proper weather (low pressure - rain and cold) to head south
- losses of flock before heading south due to predation, starvation, poisons, etc.
- cruising at heights around 4,000 feet and appearing on airport radar screens
- flying at speeds up to 30 mph and distances of 270 miles per day
- reviewing a map and selecting resting locations that include food and cover
- hazards encountered during flight such as power lines and ice storms
- arrival on the winter grounds (where; when; losses occurring due to starvation, loss of habitat, predation and hunting).
EVALUATION: In a written report, students will explain how and why birds migrate and the hazards encountered during the trip.
Research other migratory animals such as bats, monarch butterflies and salmon.
Compare why, when and how each migrates.
Complete some or all of the activities from the One Bird—Two Habitats unit. Complete the “Migration Mural” activity.
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