Raptor migration soars on Web site

by Amy Olson

Farmington, Minn., Middle School teacher Steve Dibb was met with scoffs and sighs after he announced that the next unit in biology class would be birds of prey.
But after a University Raptor Center educator brought a few owls and hawks to the class, Dibb said his students were excited to study the birds and their migration routes on the center’s Web site.
Launched in 1994, the Raptor Center’s Web site includes information on birds of prey, also called raptors. Center staff members created classroom materials and put them on the World Wide Web, including a 16-day lesson plan to teach students about raptors.
The “Highway to the Tropics” site, www.raptor.cbm.umn.edu., monitors the birds’ migration routes, including two eagles and 18 osprey. Although the site was intended for classes, Mike Kennedy, assistant Raptor Center program director, said 133 of the 336 users log on from home to track the birds.
To track the osprey, Raptor Center staff trapped birds that nested on power line poles and outfitted them with satellite radio transmitters.
Mark Martell, the center’s senior scientist, said the researchers contacted the power company that owns the main power line running between North Dakota and Duluth to use the company’s equipment to reach the high nests.
The osprey are caught when they are seven weeks old, just before they are able to fly. They are outfitted with a one-ounce transmitter held on the bird’s back by four tiny straps sewn together to form a “backpack.”
The transmitter sends the bird’s location to a satellite, which beams the reports to the center daily. Kennedy said the Web site is updated each day during the migration period between August and mid-April.
Although scientists have studied migration routes using radio transmitters, Martell said the center has been using satellites to track the birds for less than two years.
Osprey live on all seven continents except Antarctica; since the birds consume only fish, they are found near lakes, rivers and seashores. They migrate to Central and South America for the winter.
Osprey weigh between 2 and 3 pounds and have a wingspan of 4.5 to 5.5 feet.
Like bald eagles and peregrine falcons, osprey populations were depleted throughout North America before the pesticide DDT was banned in 1973. Martell said osprey populations also dropped because of shootings and the loss of tall trees the birds prefer to nest in.
Martell said tracking enabled scientists to determine that osprey are territorial birds that return to the same area each year. While osprey return to the same nesting sites, Martell said scientists have not determined if they follow the same migration route or if they even migrate to the same place.
Martell said osprey populations have recovered in many areas. From 1984 to 1995, the center ran a program to relocate chicks to the Twin Cities from northern Minnesota where populations had been depleted. There are now 12 nests in the Twin Cities.
As part of his bird unit, Dibb assigned two students to track the osprey each day using the Web site.
Dibb said tracking the osprey quickly became an interdisciplinary subject because students mapped the birds’ routes and discussed how they were affected by forces outside the state. One teacher told him his students learned more geography by tracking the birds than they could have by memorizing a map.
Dibb said some of his students still check the Web site and have become “osprey vigilantes.”
While the students learned about birds, Dibb said the project taught them to think critically as they learned about multiple subjects.
“It was great,” Dibb said. “There were moments where there were lightning bolts flying all over the place.”