The bald & the beautiful

The Detroit News Online carries this story on the progress the bald eagle has made in Michigan:

Thirty years ago, when Michigan's bald eagle nesting sites began to be inventoried by air, the numbers were depressing. There were fewer than 30 pairs of eagles in Michigan's Lower Peninsula, half as many as were hanging on in the more fertile eagle territory of Michigan's western Upper Peninsula. By 1979, the number had bottomed out: 84 nests, total, in the entire state.

The happy news almost three decades later is 1979's nadir has given way to about a 500 percent increase in bald eagles statewide. There were 427 nests in both peninsulas in 2004, the last year for which precise statewide data has been compiled.

This year, there are at least 303 nesting pairs in the Lower Peninsula, alone, which was the product of March's fly-over census conducted by Jerry Weinrich, a retired biologist from the Michigan Department of Natural Resources who lives in West Branch, and who annually oversees the Lower Peninsula count.

The increase can be traced to the same factor that sent numbers dwindling during the mid-to-late 1900s: industrial and chemical threats that killed birds and caused eggs to deteriorate began to be reined in with the 1970 ban on DDT, and with the 1972 Clean Water Act that helped restrict discharges of mercury, PCBs, and other toxins.

A tragic pattern of wildlife death and destruction has been reversed. It was from the Great Lakes shorelines that eagles first began disappearing when 20th century water ecology turned toxic. Now, the greatest number of renewed nesting sites exists along the Great Lakes, with the heaviest buildup along the Lower Peninsula shorelines from Lake Huron to Lake Michigan.

Bald eagles can live up to 25 years, and at about age 4 begin mating with a permanent partner. Most years, they return to the same nesting site and add another layer or level of construction to their nests, immense structures made from bases of tree limbs and branches that can be 2-3 inches in diameter. A bald eagle's nest can be 8 feet across and more than 10 feet deep.

They generally produce two eggs and hatchlings each spring, although one is relatively common, and three is not exceptional. The birds tend not to migrate in the conventional sense. They generally hang close to their nesting areas, although they will move to a home region's more food-rich areas if the cupboard is a bit too bare during winter.