Fun with Science Club®


			Scientists track traveling eagles Beth Tyler 05.03.01 Scientists tracking traveling eagles find that older eagles take shorter vacations. When the weather turns cold, many species of birds fly south. Scientists call this migration. During their flight, the birds need to stop to rest and get food before they can continue flying. Scientists call the places the migrating birds stop "migratory stopovers". A scientist named Marco Restani wanted to know why some bald eagles (Haliaeetus leucocephalus) stayed at the stopovers longer than others. Because young eagles aren't as strong as adult eagles and need to rest more, he predicted that the young eagles would stay at the stopovers longer than the adult eagles. To test his hypothesis, Restrani went to Montana, a state in the Western United States, where he knew bald eagles stopped on their 2000 kilometer (about 1200 miles) journey every year. The eagles stop here to catch and eat fish. Restrani set up traps to catch the eagles. The traps caught the eagle's foot so it couldn't fly away. Once caught, Restrani or one of his assistants weighed the eagle and put bands on the eagles' legs so they could identify him or her later. The scientists could also tell how old the eagle was by looking at his or her wings and eye color because both those features change as eagles age. Before letting the eagles fly away, the scientists glued radio tags to their wings. This instrument allowed Restrani to know where the eagle was even when he couldn't see him or her. Because of these tags, Restrani knew how long the eagle stayed at the stopover place. He then compared this time period with the eagle's age. As he had predicted, older eagles stayed at the stopover for less time than the young birds. A four-year old adult eagle stayed for about one and a half days, while a young one-year old eagle stayed for over two weeks.


			Restani, Marco. 2000. Age-specific stopover behavior of migrant bald eagles. Wilson Bulletin, 112(1): 28-34.