By Rick LaFrombois
Wausau Daily Herald
Sunday, March 21, 2004

ANTIGO - It's mating season for eagles, and wildlife biologists will closely observe the behavior of three mateless eagles that recovered this winter from the West Nile virus at a rehabilitation center in Antigo.

The eagles were released in Prairie du Sac about two months ago and appear to be doing well. They are among the first birds known to have recovered from West Nile, a seasonal infection transmitted by mosquitoes.

Most eagles that have mates are back in their territories by now and have performed their annual courtship flights, said Marge Gibson, executive director of the Raptor Education Group in Antigo. She is curious to see how the three mateless eagles that she released will react to mating season.

Gibson and University of Wisconsin-Stevens Point graduate student Nick Derene have observed the eagles' movements with the use of satellite and radio transmitters strapped to the eagles' backs.

Two of the three eagles released - a 2-year-old female and 3-year-old male - are immature and will not seek mates until they are about 5 years old. But during mating season, immature eagles sometimes return to their roost to help their parents raise the next generation. Some explore new territories and interact with other immature eagles.

Derene, 23, said the female immature eagle flew north through Antigo last week on her way to the Upper Peninsula, where she was born. The male flew north from Prairie du Sac to Stevens Point, where he remained last week.

The third eagle, a 4-year-old sub-adult male, flew from the Rock River in Illinois to an island near the Mississippi River in Iowa. He appears to be heading north as the ice melts.

Derene, who rescued that eagle from Stevens Point last year and nursed it back from near death, has a special affinity for the bird. Seeing him thrive in the wild is "sort of an indescribable feeling," he said. "He was probably the sickest bird I've ever seen." An eagle must be in near-perfect condition mentally and physically to survive and reproduce in the wild. West Nile could have impaired the eagles' vision or vocal abilities, which are essential to hunt and successfully seek out a mate.

As a 4-year-old, the male eagle should be on the lookout for a mate this spring, Gibson said.

"He needs to start looking sharp; it's sort of his teenage years," she said. "He needs to play the field and figure out who he's attracted to and vice versa."

A pairing could last a lifetime or it could end soon, because eagles his age are looking for a mate but they're not necessarily ready to commit.

"Raptors are so incredibly like us - their social structure is more humanlike than some mammals."

Eagles, however, seek only to survive and reproduce during lives that can last 30 years or more in the wild.

The sub-adult male eagle has made significant progress since Derene brought him to Antigo as a floppy, half-conscious bird that weighed half his normal weight of 10 pounds.

"He took care of the staying alive part with our help, and he'll take care of the reproducing thing on his own," Derene said.

To reproduce, he will have to demonstrate to a female eagle that he has the capability to protect and provide for her while she sits on their eggs in a nest for up to 38 days.