Despite the arduous journeys involved, some 350 species of North American birds migrate long distances of several thousand miles.
The Dangers Migrating Birds Face
Long-distance migration is an effort that tests both the birds’ physical and mental capabilities. The physical stress of the trip, lack of adequate food supplies along the way, bad weather, and increased exposure to predators all add to the hazards of the journey.
In recent years migratory birds have been facing a growing threat from communication towers, tall buildings, and other aerial obstructions. It isn't just the buildings themselves – it also involves their lights. Birds are attracted to the lights of tall buildings and millions are killed each year in collisions with the structures. Click HERE to learn how you can alleviate this threat.
Light-dimming campaigns, such as the Fatal Light Awareness Program, are helping to raise awareness about this danger and educating people on how to make their windows safe for birds.
When you understand the nuances of weather patterns that trigger a bird’s instinct to migrate, you can start to make your own migration predictions. The above weather map by VENTUSKY offers a real-time map to help you make these predictions.
TIP: High-pressure systems rotate in a clockwise fashion and lows are counterclockwise. For example, the leading edge of a high or the trailing edge of a low has the southerly winds that favor a strong migratory southerly flight that night.
Why Do Birds Migrate at Night?
Migration can be triggered by a combination of changes in day length, lower temperatures, changes in food supplies, and genetic predisposition. While many types of birds — such as swallows, hawks, and hummingbirds — migrate during the day, the majority of birds travel at night. Although it would seem more difficult to fly when it's dark, there are good reasons for nighttime travel:
Birds do not have to worry about predator attacks from falcons or hawks.
The air in the atmosphere is usually less turbulent than during the day.
The air is cooler at night. A migrating bird produces a huge amount of excess heat that needs to be released. The colder the air temperature, the more quickly that heat can be released.
When Do Birds Migrate?
Migration patterns and routes are almost as varied as the birds themselves. The main migration routes of North American land birds are oriented north-south, partly because the coasts, major mountain ranges, and major river valleys tend to run in the north-south direction.
Northerly Migration (March through May)
steady southerly winds
clear moon-lit nights
a sudden increase in temperature
Southerly Migration (August through October)
steady northerly winds
clear moon-lit nights
a sudden decrease in temperature
Real-Time Migration Tools
Cornell scientists created a tool on their BirdCast website (with research funded by NSF, Leon Levy Foundation, Rose Postdoctoral Fellowship, and Marshall Aid Commission) that shows in near real-time the volume and direction of migratory birds traveling throughout the country. The migration forecast maps will keep you apprised of what to expect in the days (and nights) ahead. Bird migration forecast maps show predicted nocturnal migration 3 hours after local sunset and are updated every 6 hours.
