This job represents tens of thousand of pages of information. Fortunately, there are now high-tech approaches to studying birds. Aircraft radar has been discovered to record the passage of flying birds. Also, radio-transmitters attached to migrating birds can provide valuable research data. Both techniques have provided new ideas on how and where birds migrate.
Birds migrate for a variety of reasons.
They might need to escape approaching cold weather or look for more food sources. But knowning when to migrate and where to go is a complex issue. Even now all the answers are not known. Most scientist agree that the changing day length is a huge cue for migration. As days get shorter, migrating birds become anxious and restless.